Hi,
Here is the 2nd version of RFC series to use ftrace_regs instead of pt_regs.
But this includes the generic part and minimum modifications of arch
dependent code. (e.g. not including rethook for arm64.) This series is based
on the discussion at
https://lore.kernel.org/all/[email protected]/
This version includes 1 patch to expose ftrace_regs. so
- Simply replace pt_regs in fprobe_entry_handler with ftrace_regs.
- Expose ftrace_regs even if CONFIG_FUNCTION_TRACER=n.
- Replace pt_regs in rethook and fprobe_exit_handler with ftrace_regs. This
introduce a new HAVE_PT_REGS_COMPAT_FTRACE_REGS which means ftrace_regs is
just a wrapper of pt_regs (except for arm64, other architectures do this)
- Update fprobe-events to use ftrace_regs natively.
- Introduce ftrace_partial_regs(). (This changes ARM64 which needs a custom
implementation)
- Update bpf multi-kprobe handler use ftrace_partial_regs().
Florent, feel free to add your rethook for arm64, but please do not remove
kretprobe trampoline yet. It is another discussion point. We may be possible
to use ftrace_regs for kretprobe by ftrace_partial_regs() but kretprobe
allows nest probe. (maybe we can skip that case?)
This series can also be found below branch.
https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/log/?h=topic/fprobe-ftrace-regs
Thank you,
---
Masami Hiramatsu (Google) (6):
fprobe: Use fprobe_regs in fprobe entry handler
tracing: Expose ftrace_regs regardless of CONFIG_FUNCTION_TRACER
fprobe: rethook: Use fprobe_regs in fprobe exit handler and rethook
tracing/fprobe: Enable fprobe events with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
ftrace: Add ftrace_partial_regs() for converting ftrace_regs to pt_regs
bpf: Enable kprobe_multi feature if CONFIG_FPROBE is enabled
arch/Kconfig | 1 +
arch/arm64/include/asm/ftrace.h | 11 ++++++
arch/loongarch/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/kernel/rethook.c | 9 +++--
include/linux/fprobe.h | 4 +-
include/linux/ftrace.h | 56 ++++++++++++++++++-----------
include/linux/rethook.h | 11 +++---
kernel/kprobes.c | 9 ++++-
kernel/trace/Kconfig | 9 ++++-
kernel/trace/bpf_trace.c | 14 +++++--
kernel/trace/fprobe.c | 8 ++--
kernel/trace/rethook.c | 16 ++++----
kernel/trace/trace_fprobe.c | 76 ++++++++++++++++++++++++---------------
kernel/trace/trace_probe_tmpl.h | 2 +
lib/test_fprobe.c | 10 +++--
samples/fprobe/fprobe_example.c | 4 +-
18 files changed, 154 insertions(+), 89 deletions(-)
--
Masami Hiramatsu (Google) <[email protected]>
From: Masami Hiramatsu (Google) <[email protected]>
This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
on arm64.
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
include/linux/fprobe.h | 2 +-
kernel/trace/Kconfig | 3 ++-
kernel/trace/bpf_trace.c | 10 +++++++---
kernel/trace/fprobe.c | 2 +-
kernel/trace/trace_fprobe.c | 6 +++++-
lib/test_fprobe.c | 4 ++--
samples/fprobe/fprobe_example.c | 2 +-
7 files changed, 19 insertions(+), 10 deletions(-)
diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 3e03758151f4..36c0595f7b93 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -35,7 +35,7 @@ struct fprobe {
int nr_maxactive;
int (*entry_handler)(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
unsigned long ret_ip, struct pt_regs *regs,
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 61c541c36596..976fd594b446 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -287,7 +287,7 @@ config DYNAMIC_FTRACE_WITH_ARGS
config FPROBE
bool "Kernel Function Probe (fprobe)"
depends on FUNCTION_TRACER
- depends on DYNAMIC_FTRACE_WITH_REGS
+ depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
depends on HAVE_RETHOOK
select RETHOOK
default n
@@ -672,6 +672,7 @@ config FPROBE_EVENTS
select TRACING
select PROBE_EVENTS
select DYNAMIC_EVENTS
+ depends on DYNAMIC_FTRACE_WITH_REGS
default y
help
This allows user to add tracing events on the function entry and
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 5f2dcabad202..51573eaa04c4 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void)
fs_initcall(bpf_event_init);
#endif /* CONFIG_MODULES */
-#ifdef CONFIG_FPROBE
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
struct bpf_kprobe_multi_link {
struct bpf_link link;
struct fprobe fp;
@@ -2652,10 +2652,14 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
static int
kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *data)
{
struct bpf_kprobe_multi_link *link;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return 0;
link = container_of(fp, struct bpf_kprobe_multi_link, fp);
kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
@@ -2910,7 +2914,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
kvfree(cookies);
return err;
}
-#else /* !CONFIG_FPROBE */
+#else /* !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
return -EOPNOTSUPP;
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 3b21f4063258..15a2aef92733 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -46,7 +46,7 @@ static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
}
if (fp->entry_handler)
- ret = fp->entry_handler(fp, ip, parent_ip, ftrace_get_regs(fregs), entry_data);
+ ret = fp->entry_handler(fp, ip, parent_ip, fregs, entry_data);
/* If entry_handler returns !0, nmissed is not counted. */
if (rh) {
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index dfe2e546acdc..4d3ae79f036e 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -320,12 +320,16 @@ NOKPROBE_SYMBOL(fexit_perf_func);
#endif /* CONFIG_PERF_EVENTS */
static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
+ struct pt_regs *regs = ftrace_get_regs(fregs);
int ret = 0;
+ if (!regs)
+ return 0;
+
if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
fentry_trace_func(tf, entry_ip, regs);
#ifdef CONFIG_PERF_EVENTS
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index 24de0e5ff859..ff607babba18 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c
@@ -40,7 +40,7 @@ static noinline u32 fprobe_selftest_nest_target(u32 value, u32 (*nest)(u32))
static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
/* This can be called on the fprobe_selftest_target and the fprobe_selftest_target2 */
@@ -81,7 +81,7 @@ static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
return 0;
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 64e715e7ed11..1545a1aac616 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -50,7 +50,7 @@ static void show_backtrace(void)
static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
if (use_trace)
/*
From: Masami Hiramatsu (Google) <[email protected]>
Allow fprobe events to be enabled with CONFIG_DYNAMIC_FTRACE_WITH_ARGS.
With this change, fprobe events mostly use ftrace_regs instead of pt_regs.
Note that if the arch doesn't enable HAVE_PT_REGS_COMPAT_FTRACE_REGS,
fprobe events will not be able to use from perf.
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
kernel/trace/Kconfig | 1 -
kernel/trace/trace_fprobe.c | 72 ++++++++++++++++++++++-----------------
kernel/trace/trace_probe_tmpl.h | 2 +
3 files changed, 41 insertions(+), 34 deletions(-)
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 7d6abb5bd861..e9b7bd88cf9e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -679,7 +679,6 @@ config FPROBE_EVENTS
select TRACING
select PROBE_EVENTS
select DYNAMIC_EVENTS
- depends on DYNAMIC_FTRACE_WITH_REGS
default y
help
This allows user to add tracing events on the function entry and
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index f440c97e050f..4e9c250dbd19 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -132,25 +132,30 @@ static int
process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
void *base)
{
- struct pt_regs *regs = rec;
- unsigned long val;
+ struct ftrace_regs *fregs = rec;
+ unsigned long val, *stackp;
int ret;
retry:
/* 1st stage: get value from context */
switch (code->op) {
case FETCH_OP_STACK:
- val = regs_get_kernel_stack_nth(regs, code->param);
+ stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
+ if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
+ ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
+ val = *(stackp + code->param);
+ else
+ val = 0;
break;
case FETCH_OP_STACKP:
- val = kernel_stack_pointer(regs);
+ val = ftrace_regs_get_stack_pointer(fregs);
break;
case FETCH_OP_RETVAL:
- val = regs_return_value(regs);
+ val = ftrace_regs_return_value(fregs);
break;
#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
case FETCH_OP_ARG:
- val = regs_get_kernel_argument(regs, code->param);
+ val = ftrace_regs_get_argument(fregs, code->param);
break;
#endif
case FETCH_NOP_SYMBOL: /* Ignore a place holder */
@@ -170,7 +175,7 @@ NOKPROBE_SYMBOL(process_fetch_insn)
/* function entry handler */
static nokprobe_inline void
__fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs,
+ struct ftrace_regs *fregs,
struct trace_event_file *trace_file)
{
struct fentry_trace_entry_head *entry;
@@ -184,36 +189,36 @@ __fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (trace_trigger_soft_disabled(trace_file))
return;
- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, fregs);
entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
if (!entry)
return;
- fbuffer.regs = regs;
+ fbuffer.regs = ftrace_get_regs(fregs);
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->ip = entry_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, sizeof(*entry), dsize);
trace_event_buffer_commit(&fbuffer);
}
static void
fentry_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs)
{
struct event_file_link *link;
trace_probe_for_each_link_rcu(link, &tf->tp)
- __fentry_trace_func(tf, entry_ip, regs, link->file);
+ __fentry_trace_func(tf, entry_ip, fregs, link->file);
}
NOKPROBE_SYMBOL(fentry_trace_func);
/* Kretprobe handler */
static nokprobe_inline void
__fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
struct trace_event_file *trace_file)
{
struct fexit_trace_entry_head *entry;
@@ -227,37 +232,37 @@ __fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (trace_trigger_soft_disabled(trace_file))
return;
- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, fregs);
entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + tf->tp.size + dsize);
if (!entry)
return;
- fbuffer.regs = regs;
+ fbuffer.regs = ftrace_get_regs(fregs);
entry = fbuffer.entry = ring_buffer_event_data(fbuffer.event);
entry->func = entry_ip;
entry->ret_ip = ret_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, sizeof(*entry), dsize);
trace_event_buffer_commit(&fbuffer);
}
static void
fexit_trace_func(struct trace_fprobe *tf, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct ftrace_regs *fregs)
{
struct event_file_link *link;
trace_probe_for_each_link_rcu(link, &tf->tp)
- __fexit_trace_func(tf, entry_ip, ret_ip, regs, link->file);
+ __fexit_trace_func(tf, entry_ip, ret_ip, fregs, link->file);
}
NOKPROBE_SYMBOL(fexit_trace_func);
#ifdef CONFIG_PERF_EVENTS
static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs, struct pt_regs *regs)
{
struct trace_event_call *call = trace_probe_event_call(&tf->tp);
struct fentry_trace_entry_head *entry;
@@ -269,7 +274,7 @@ static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (hlist_empty(head))
return 0;
- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, fregs);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -280,7 +285,7 @@ static int fentry_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
entry->ip = entry_ip;
memset(&entry[1], 0, dsize);
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
return 0;
@@ -289,7 +294,8 @@ NOKPROBE_SYMBOL(fentry_perf_func);
static void
fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct ftrace_regs *fregs,
+ struct pt_regs *regs)
{
struct trace_event_call *call = trace_probe_event_call(&tf->tp);
struct fexit_trace_entry_head *entry;
@@ -301,7 +307,7 @@ fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
if (hlist_empty(head))
return;
- dsize = __get_data_size(&tf->tp, regs);
+ dsize = __get_data_size(&tf->tp, fregs);
__size = sizeof(*entry) + tf->tp.size + dsize;
size = ALIGN(__size + sizeof(u32), sizeof(u64));
size -= sizeof(u32);
@@ -312,7 +318,7 @@ fexit_perf_func(struct trace_fprobe *tf, unsigned long entry_ip,
entry->func = entry_ip;
entry->ret_ip = ret_ip;
- store_trace_args(&entry[1], &tf->tp, regs, sizeof(*entry), dsize);
+ store_trace_args(&entry[1], &tf->tp, fregs, sizeof(*entry), dsize);
perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs,
head, NULL);
}
@@ -327,14 +333,15 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
struct pt_regs *regs = ftrace_get_regs(fregs);
int ret = 0;
+ if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
+ fentry_trace_func(tf, entry_ip, fregs);
+
+#ifdef CONFIG_PERF_EVENTS
if (!regs)
return 0;
- if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
- fentry_trace_func(tf, entry_ip, regs);
-#ifdef CONFIG_PERF_EVENTS
if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE))
- ret = fentry_perf_func(tf, entry_ip, regs);
+ ret = fentry_perf_func(tf, entry_ip, fregs, regs);
#endif
return ret;
}
@@ -347,14 +354,15 @@ static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip,
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
struct pt_regs *regs = ftrace_get_regs(fregs);
+ if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
+ fexit_trace_func(tf, entry_ip, ret_ip, fregs);
+
+#ifdef CONFIG_PERF_EVENTS
if (!regs)
return;
- if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
- fexit_trace_func(tf, entry_ip, ret_ip, regs);
-#ifdef CONFIG_PERF_EVENTS
if (trace_probe_test_flag(&tf->tp, TP_FLAG_PROFILE))
- fexit_perf_func(tf, entry_ip, ret_ip, regs);
+ fexit_perf_func(tf, entry_ip, ret_ip, fregs, regs);
#endif
}
NOKPROBE_SYMBOL(fexit_dispatcher);
diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 3935b347f874..05445a745a07 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -232,7 +232,7 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
/* Sum up total data length for dynamic arrays (strings) */
static nokprobe_inline int
-__get_data_size(struct trace_probe *tp, struct pt_regs *regs)
+__get_data_size(struct trace_probe *tp, void *regs)
{
struct probe_arg *arg;
int i, len, ret = 0;
From: Masami Hiramatsu (Google) <[email protected]>
Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
converted from ftrace_regs by ftrace_partial_regs(), thus some registers
may always returns 0. But it should be enough for function entry (access
arguments) and exit (access return value).
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
kernel/trace/bpf_trace.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 99c5f95360f9..0725272a3de2 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void)
fs_initcall(bpf_event_init);
#endif /* CONFIG_MODULES */
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#ifdef CONFIG_FPROBE
struct bpf_kprobe_multi_link {
struct bpf_link link;
struct fprobe fp;
@@ -2482,6 +2482,8 @@ struct user_syms {
char *buf;
};
+static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
+
static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
{
unsigned long __user usymbol;
@@ -2623,13 +2625,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
static int
kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
- unsigned long entry_ip, struct pt_regs *regs)
+ unsigned long entry_ip, struct ftrace_regs *fregs)
{
struct bpf_kprobe_multi_run_ctx run_ctx = {
.link = link,
.entry_ip = entry_ip,
};
struct bpf_run_ctx *old_run_ctx;
+ struct pt_regs *regs;
int err;
if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
@@ -2639,6 +2642,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
migrate_disable();
rcu_read_lock();
+ regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));
old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
err = bpf_prog_run(link->link.prog, regs);
bpf_reset_run_ctx(old_run_ctx);
@@ -2656,13 +2660,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
void *data)
{
struct bpf_kprobe_multi_link *link;
- struct pt_regs *regs = ftrace_get_regs(fregs);
-
- if (!regs)
- return 0;
link = container_of(fp, struct bpf_kprobe_multi_link, fp);
- kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
+ kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
return 0;
}
@@ -2672,13 +2672,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
void *data)
{
struct bpf_kprobe_multi_link *link;
- struct pt_regs *regs = ftrace_get_regs(fregs);
-
- if (!regs)
- return;
link = container_of(fp, struct bpf_kprobe_multi_link, fp);
- kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
+ kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
}
static int symbols_cmp_r(const void *a, const void *b, const void *priv)
@@ -2918,7 +2914,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
kvfree(cookies);
return err;
}
-#else /* !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
+#else /* !CONFIG_FPROBE */
int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
{
return -EOPNOTSUPP;
From: Masami Hiramatsu (Google) <[email protected]>
Add ftrace_partial_regs() which converts the ftrace_regas to pt_regs.
If the architecture defines its own ftrace_regs, this copies partial
registers to pt_regs and returns it. If not, ftrace_regs is the same as
pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
arch/arm64/include/asm/ftrace.h | 11 +++++++++++
include/linux/ftrace.h | 11 +++++++++++
2 files changed, 22 insertions(+)
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index ab158196480c..b108cd6718cf 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -137,6 +137,17 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs)
fregs->pc = fregs->lr;
}
+static __always_inline struct pt_regs *
+ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
+{
+ memcpy(regs->regs, fregs->regs, sizeof(u64) * 10);
+ regs->sp = fregs->sp;
+ regs->pc = fregs->pc;
+ regs->x[29] = fregs->fp;
+ regs->x[30] = fregs->lr;
+ return regs;
+}
+
int ftrace_regs_query_register_offset(const char *name);
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 3fb94a1a2461..7f45654441b7 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -155,6 +155,17 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
return arch_ftrace_get_regs(fregs);
}
+#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \
+ defined(CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS)
+
+static __always_inline struct pt_regs *
+ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
+{
+ return arch_ftrace_get_regs((struct ftrace_regs *)fregs);
+}
+
+#endif /* !CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS || CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS */
+
/*
* When true, the ftrace_regs_{get,set}_*() functions may be used on fregs.
* Note: this can be true even when ftrace_get_regs() cannot provide a pt_regs.
From: Masami Hiramatsu (Google) <[email protected]>
In order to be able to use ftrace_regs even from features unrelated to
function tracer (e.g. kretprobe), expose ftrace_regs structures and
APIs even if the CONFIG_FUNCTION_TRACER=n.
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
include/linux/ftrace.h | 45 ++++++++++++++++++++++++---------------------
1 file changed, 24 insertions(+), 21 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index ce156c7704ee..3fb94a1a2461 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
}
#endif
-#ifdef CONFIG_FUNCTION_TRACER
-
-extern int ftrace_enabled;
-
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
+/*
+ * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
+ * tracer, define the default(pt_regs compatible) ftrace_regs.
+ */
+#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
struct ftrace_regs {
struct pt_regs regs;
@@ -129,6 +129,22 @@ struct ftrace_regs {
* HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports live kernel patching.
*/
#define ftrace_regs_set_instruction_pointer(fregs, ip) do { } while (0)
+
+#define ftrace_regs_get_instruction_pointer(fregs) \
+ instruction_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_get_argument(fregs, n) \
+ regs_get_kernel_argument(ftrace_get_regs(fregs), n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+ kernel_stack_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_return_value(fregs) \
+ regs_return_value(ftrace_get_regs(fregs))
+#define ftrace_regs_set_return_value(fregs, ret) \
+ regs_set_return_value(ftrace_get_regs(fregs), ret)
+#define ftrace_override_function_with_return(fregs) \
+ override_function_with_return(ftrace_get_regs(fregs))
+#define ftrace_regs_query_register_offset(name) \
+ regs_query_register_offset(name)
+
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)
@@ -151,22 +167,9 @@ static __always_inline bool ftrace_regs_has_args(struct ftrace_regs *fregs)
return ftrace_get_regs(fregs) != NULL;
}
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
-#define ftrace_regs_get_instruction_pointer(fregs) \
- instruction_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_get_argument(fregs, n) \
- regs_get_kernel_argument(ftrace_get_regs(fregs), n)
-#define ftrace_regs_get_stack_pointer(fregs) \
- kernel_stack_pointer(ftrace_get_regs(fregs))
-#define ftrace_regs_return_value(fregs) \
- regs_return_value(ftrace_get_regs(fregs))
-#define ftrace_regs_set_return_value(fregs, ret) \
- regs_set_return_value(ftrace_get_regs(fregs), ret)
-#define ftrace_override_function_with_return(fregs) \
- override_function_with_return(ftrace_get_regs(fregs))
-#define ftrace_regs_query_register_offset(name) \
- regs_query_register_offset(name)
-#endif
+#ifdef CONFIG_FUNCTION_TRACER
+
+extern int ftrace_enabled;
typedef void (*ftrace_func_t)(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct ftrace_regs *fregs);
From: Masami Hiramatsu (Google) <[email protected]>
Change the fprobe exit handler and rethook to use ftrace_regs data structure
instead of pt_regs. This also introduce HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
which means the ftrace_regs is equal to the pt_regs so that those are
compatible. Only if it is enabled, kretprobe will use rethook since kretprobe
requires pt_regs for backward compatibility.
This means the archs which currently implement rethook for kretprobes needs to
set that flag and it must ensure struct ftrace_regs is same as pt_regs.
If not, it must be either disabling kretprobe or implementing kretprobe
trampoline separately from rethook trampoline.
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
---
arch/Kconfig | 1 +
arch/loongarch/Kconfig | 1 +
arch/s390/Kconfig | 1 +
arch/x86/Kconfig | 1 +
arch/x86/kernel/rethook.c | 9 ++++++---
include/linux/fprobe.h | 2 +-
include/linux/rethook.h | 11 ++++++-----
kernel/kprobes.c | 9 +++++++--
kernel/trace/Kconfig | 7 +++++++
kernel/trace/bpf_trace.c | 6 +++++-
kernel/trace/fprobe.c | 6 +++---
kernel/trace/rethook.c | 16 ++++++++--------
kernel/trace/trace_fprobe.c | 6 +++++-
lib/test_fprobe.c | 6 +++---
samples/fprobe/fprobe_example.c | 2 +-
15 files changed, 56 insertions(+), 28 deletions(-)
diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af2..e321bdb8b22b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
def_bool y
depends on HAVE_RETHOOK
depends on KRETPROBES
+ depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
select RETHOOK
config USER_RETURN_NOTIFIER
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index e55511af4c77..93a4336b0a94 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -102,6 +102,7 @@ config LOONGARCH
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_COMPAT_FTRACE_REGS
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 5b39918b7042..299ba17d3316 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -165,6 +165,7 @@ config S390
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_PT_REGS_COMPAT_FTRACE_REGS
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7422db409770..df1b7a2791e8 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -207,6 +207,7 @@ config X86
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
+ select HAVE_PT_REGS_COMPAT_FTRACE_REGS if X86_64
select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
index 8a1c0111ae79..79a52bfde562 100644
--- a/arch/x86/kernel/rethook.c
+++ b/arch/x86/kernel/rethook.c
@@ -83,7 +83,8 @@ __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
* arch_rethook_fixup_return() which called from this
* rethook_trampoline_handler().
*/
- rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
+ rethook_trampoline_handler((struct ftrace_regs *)regs,
+ (unsigned long)frame_pointer);
/*
* Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()
@@ -104,9 +105,10 @@ NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
/* This is called from rethook_trampoline_handler(). */
-void arch_rethook_fixup_return(struct pt_regs *regs,
+void arch_rethook_fixup_return(struct ftrace_regs *fregs,
unsigned long correct_ret_addr)
{
+ struct pt_regs *regs = ftrace_get_regs(fregs);
unsigned long *frame_pointer = (void *)(regs + 1);
/* Replace fake return address with real one. */
@@ -114,8 +116,9 @@ void arch_rethook_fixup_return(struct pt_regs *regs,
}
NOKPROBE_SYMBOL(arch_rethook_fixup_return);
-void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+void arch_rethook_prepare(struct rethook_node *rh, struct ftrace_regs *fregs, bool mcount)
{
+ struct pt_regs *regs = ftrace_get_regs(fregs);
unsigned long *stack = (unsigned long *)regs->sp;
rh->ret_addr = stack[0];
diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
index 36c0595f7b93..b9c0c216dedb 100644
--- a/include/linux/fprobe.h
+++ b/include/linux/fprobe.h
@@ -38,7 +38,7 @@ struct fprobe {
unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *entry_data);
};
diff --git a/include/linux/rethook.h b/include/linux/rethook.h
index 26b6f3c81a76..138d64c8b67b 100644
--- a/include/linux/rethook.h
+++ b/include/linux/rethook.h
@@ -7,6 +7,7 @@
#include <linux/compiler.h>
#include <linux/freelist.h>
+#include <linux/ftrace.h>
#include <linux/kallsyms.h>
#include <linux/llist.h>
#include <linux/rcupdate.h>
@@ -14,7 +15,7 @@
struct rethook_node;
-typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
+typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct ftrace_regs *);
/**
* struct rethook - The rethook management data structure.
@@ -64,12 +65,12 @@ void rethook_free(struct rethook *rh);
void rethook_add_node(struct rethook *rh, struct rethook_node *node);
struct rethook_node *rethook_try_get(struct rethook *rh);
void rethook_recycle(struct rethook_node *node);
-void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+void rethook_hook(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
struct llist_node **cur);
/* Arch dependent code must implement arch_* and trampoline code */
-void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
+void arch_rethook_prepare(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
void arch_rethook_trampoline(void);
/**
@@ -84,11 +85,11 @@ static inline bool is_rethook_trampoline(unsigned long addr)
}
/* If the architecture needs to fixup the return address, implement it. */
-void arch_rethook_fixup_return(struct pt_regs *regs,
+void arch_rethook_fixup_return(struct ftrace_regs *regs,
unsigned long correct_ret_addr);
/* Generic trampoline handler, arch code must prepare asm stub */
-unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+unsigned long rethook_trampoline_handler(struct ftrace_regs *regs,
unsigned long frame);
#ifdef CONFIG_RETHOOK
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1fc6095d502d..ccbe41c961c3 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2120,7 +2120,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
if (rp->entry_handler && rp->entry_handler(ri, regs))
rethook_recycle(rhn);
else
- rethook_hook(rhn, regs, kprobe_ftrace(p));
+ rethook_hook(rhn, (struct ftrace_regs *)regs, kprobe_ftrace(p));
return 0;
}
@@ -2128,12 +2128,17 @@ NOKPROBE_SYMBOL(pre_handler_kretprobe);
static void kretprobe_rethook_handler(struct rethook_node *rh, void *data,
unsigned long ret_addr,
- struct pt_regs *regs)
+ struct ftrace_regs *fregs)
{
struct kretprobe *rp = (struct kretprobe *)data;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
struct kretprobe_instance *ri;
struct kprobe_ctlblk *kcb;
+ /* This is bug because this depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS */
+ if (WARN_ON_ONCE(!regs))
+ return;
+
/* The data must NOT be null. This means rethook data structure is broken. */
if (WARN_ON_ONCE(!data) || !rp->handler)
return;
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 976fd594b446..7d6abb5bd861 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -57,6 +57,13 @@ config HAVE_DYNAMIC_FTRACE_WITH_ARGS
This allows for use of ftrace_regs_get_argument() and
ftrace_regs_get_stack_pointer().
+config HAVE_PT_REGS_COMPAT_FTRACE_REGS
+ bool
+ help
+ If this is set, the ftrace_regs data structure is compatible
+ with the pt_regs. So it is possible to be converted by
+ ftrace_get_regs().
+
config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
bool
help
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 51573eaa04c4..99c5f95360f9 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2668,10 +2668,14 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
static void
kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *data)
{
struct bpf_kprobe_multi_link *link;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return;
link = container_of(fp, struct bpf_kprobe_multi_link, fp);
kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 15a2aef92733..70b9c493e52d 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -53,7 +53,7 @@ static inline void __fprobe_handler(unsigned long ip, unsigned long parent_ip,
if (ret)
rethook_recycle(rh);
else
- rethook_hook(rh, ftrace_get_regs(fregs), true);
+ rethook_hook(rh, fregs, true);
}
}
@@ -120,7 +120,7 @@ static void fprobe_kprobe_handler(unsigned long ip, unsigned long parent_ip,
}
static void fprobe_exit_handler(struct rethook_node *rh, void *data,
- unsigned long ret_ip, struct pt_regs *regs)
+ unsigned long ret_ip, struct ftrace_regs *fregs)
{
struct fprobe *fp = (struct fprobe *)data;
struct fprobe_rethook_node *fpr;
@@ -141,7 +141,7 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
return;
}
- fp->exit_handler(fp, fpr->entry_ip, ret_ip, regs,
+ fp->exit_handler(fp, fpr->entry_ip, ret_ip, fregs,
fp->entry_data_size ? (void *)fpr->data : NULL);
ftrace_test_recursion_unlock(bit);
}
diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index 5eb9b598f4e9..7c5cf9d5910c 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -189,7 +189,7 @@ NOKPROBE_SYMBOL(rethook_try_get);
/**
* rethook_hook() - Hook the current function return.
* @node: The struct rethook node to hook the function return.
- * @regs: The struct pt_regs for the function entry.
+ * @fregs: The struct ftrace_regs for the function entry.
* @mcount: True if this is called from mcount(ftrace) context.
*
* Hook the current running function return. This must be called when the
@@ -199,9 +199,9 @@ NOKPROBE_SYMBOL(rethook_try_get);
* from the real function entry (e.g. kprobes) @mcount must be set false.
* This is because the way to hook the function return depends on the context.
*/
-void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount)
+void rethook_hook(struct rethook_node *node, struct ftrace_regs *fregs, bool mcount)
{
- arch_rethook_prepare(node, regs, mcount);
+ arch_rethook_prepare(node, fregs, mcount);
__llist_add(&node->llist, ¤t->rethooks);
}
NOKPROBE_SYMBOL(rethook_hook);
@@ -269,7 +269,7 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame
}
NOKPROBE_SYMBOL(rethook_find_ret_addr);
-void __weak arch_rethook_fixup_return(struct pt_regs *regs,
+void __weak arch_rethook_fixup_return(struct ftrace_regs *fregs,
unsigned long correct_ret_addr)
{
/*
@@ -281,7 +281,7 @@ void __weak arch_rethook_fixup_return(struct pt_regs *regs,
}
/* This function will be called from each arch-defined trampoline. */
-unsigned long rethook_trampoline_handler(struct pt_regs *regs,
+unsigned long rethook_trampoline_handler(struct ftrace_regs *fregs,
unsigned long frame)
{
struct llist_node *first, *node = NULL;
@@ -295,7 +295,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
BUG_ON(1);
}
- instruction_pointer_set(regs, correct_ret_addr);
+ ftrace_regs_set_instruction_pointer(fregs, correct_ret_addr);
/*
* These loops must be protected from rethook_free_rcu() because those
@@ -315,7 +315,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
handler = READ_ONCE(rhn->rethook->handler);
if (handler)
handler(rhn, rhn->rethook->data,
- correct_ret_addr, regs);
+ correct_ret_addr, fregs);
if (first == node)
break;
@@ -323,7 +323,7 @@ unsigned long rethook_trampoline_handler(struct pt_regs *regs,
}
/* Fixup registers for returning to correct address. */
- arch_rethook_fixup_return(regs, correct_ret_addr);
+ arch_rethook_fixup_return(fregs, correct_ret_addr);
/* Unlink used shadow stack */
first = current->rethooks.first;
diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
index 4d3ae79f036e..f440c97e050f 100644
--- a/kernel/trace/trace_fprobe.c
+++ b/kernel/trace/trace_fprobe.c
@@ -341,10 +341,14 @@ static int fentry_dispatcher(struct fprobe *fp, unsigned long entry_ip,
NOKPROBE_SYMBOL(fentry_dispatcher);
static void fexit_dispatcher(struct fprobe *fp, unsigned long entry_ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *fregs,
void *entry_data)
{
struct trace_fprobe *tf = container_of(fp, struct trace_fprobe, fp);
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+
+ if (!regs)
+ return;
if (trace_probe_test_flag(&tf->tp, TP_FLAG_TRACE))
fexit_trace_func(tf, entry_ip, ret_ip, regs);
diff --git a/lib/test_fprobe.c b/lib/test_fprobe.c
index ff607babba18..d1e80653bf0c 100644
--- a/lib/test_fprobe.c
+++ b/lib/test_fprobe.c
@@ -59,9 +59,9 @@ static notrace int fp_entry_handler(struct fprobe *fp, unsigned long ip,
static notrace void fp_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
- unsigned long ret = regs_return_value(regs);
+ unsigned long ret = ftrace_regs_return_value(fregs);
KUNIT_EXPECT_FALSE(current_test, preemptible());
if (ip != target_ip) {
@@ -89,7 +89,7 @@ static notrace int nest_entry_handler(struct fprobe *fp, unsigned long ip,
static notrace void nest_exit_handler(struct fprobe *fp, unsigned long ip,
unsigned long ret_ip,
- struct pt_regs *regs, void *data)
+ struct ftrace_regs *fregs, void *data)
{
KUNIT_EXPECT_FALSE(current_test, preemptible());
KUNIT_EXPECT_EQ(current_test, ip, target_nest_ip);
diff --git a/samples/fprobe/fprobe_example.c b/samples/fprobe/fprobe_example.c
index 1545a1aac616..d476d1f07538 100644
--- a/samples/fprobe/fprobe_example.c
+++ b/samples/fprobe/fprobe_example.c
@@ -67,7 +67,7 @@ static int sample_entry_handler(struct fprobe *fp, unsigned long ip,
}
static void sample_exit_handler(struct fprobe *fp, unsigned long ip,
- unsigned long ret_ip, struct pt_regs *regs,
+ unsigned long ret_ip, struct ftrace_regs *regs,
void *data)
{
unsigned long rip = ret_ip;
On Mon, Aug 07, 2023 at 03:49:33PM +0900, Masami Hiramatsu (Google) wrote:
> From: Masami Hiramatsu (Google) <[email protected]>
>
> Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
> converted from ftrace_regs by ftrace_partial_regs(), thus some registers
> may always returns 0. But it should be enough for function entry (access
> arguments) and exit (access return value).
>
> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> ---
> kernel/trace/bpf_trace.c | 22 +++++++++-------------
> 1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 99c5f95360f9..0725272a3de2 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void)
> fs_initcall(bpf_event_init);
> #endif /* CONFIG_MODULES */
>
> -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> +#ifdef CONFIG_FPROBE
> struct bpf_kprobe_multi_link {
> struct bpf_link link;
> struct fprobe fp;
> @@ -2482,6 +2482,8 @@ struct user_syms {
> char *buf;
> };
>
> +static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
> +
> static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
> {
> unsigned long __user usymbol;
> @@ -2623,13 +2625,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
>
> static int
> kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> - unsigned long entry_ip, struct pt_regs *regs)
> + unsigned long entry_ip, struct ftrace_regs *fregs)
> {
> struct bpf_kprobe_multi_run_ctx run_ctx = {
> .link = link,
> .entry_ip = entry_ip,
> };
> struct bpf_run_ctx *old_run_ctx;
> + struct pt_regs *regs;
> int err;
>
> if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
> @@ -2639,6 +2642,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
>
> migrate_disable();
> rcu_read_lock();
> + regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));
you did check for !regs when returned from ftrace_get_regs, why don't we need
to check it in here? both ftrace_partial_regs and ftrace_get_regs call
arch_ftrace_get_regs on x86
also also I can't find the place ensuring fregs->regs.cs != 0 for FL_SAVE_REGS
flag as stated in arch_ftrace_get_regs, any hint?
thanks,
jirka
> old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> err = bpf_prog_run(link->link.prog, regs);
> bpf_reset_run_ctx(old_run_ctx);
> @@ -2656,13 +2660,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> void *data)
> {
> struct bpf_kprobe_multi_link *link;
> - struct pt_regs *regs = ftrace_get_regs(fregs);
> -
> - if (!regs)
> - return 0;
>
> link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> return 0;
> }
>
> @@ -2672,13 +2672,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
> void *data)
> {
> struct bpf_kprobe_multi_link *link;
> - struct pt_regs *regs = ftrace_get_regs(fregs);
> -
> - if (!regs)
> - return;
>
> link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> }
>
> static int symbols_cmp_r(const void *a, const void *b, const void *priv)
> @@ -2918,7 +2914,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
> kvfree(cookies);
> return err;
> }
> -#else /* !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> +#else /* !CONFIG_FPROBE */
> int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> {
> return -EOPNOTSUPP;
>
On Tue, 8 Aug 2023 16:29:27 +0200
Florent Revest <[email protected]> wrote:
> On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> >
> > Florent, feel free to add your rethook for arm64, but please do not remove
> > kretprobe trampoline yet. It is another discussion point. We may be possible
> > to use ftrace_regs for kretprobe by ftrace_partial_regs() but kretprobe
> > allows nest probe. (maybe we can skip that case?)
>
> Ack :)
>
> > arch/Kconfig | 1 +
> > arch/arm64/include/asm/ftrace.h | 11 ++++++
> > arch/loongarch/Kconfig | 1 +
> > arch/s390/Kconfig | 1 +
> > arch/x86/Kconfig | 1 +
> > arch/x86/kernel/rethook.c | 9 +++--
> > include/linux/fprobe.h | 4 +-
> > include/linux/ftrace.h | 56 ++++++++++++++++++-----------
> > include/linux/rethook.h | 11 +++---
> > kernel/kprobes.c | 9 ++++-
> > kernel/trace/Kconfig | 9 ++++-
> > kernel/trace/bpf_trace.c | 14 +++++--
> > kernel/trace/fprobe.c | 8 ++--
> > kernel/trace/rethook.c | 16 ++++----
> > kernel/trace/trace_fprobe.c | 76 ++++++++++++++++++++++++---------------
> > kernel/trace/trace_probe_tmpl.h | 2 +
> > lib/test_fprobe.c | 10 +++--
> > samples/fprobe/fprobe_example.c | 4 +-
>
> I believe that Documentation/trace/fprobe.rst should also be modified
> following the API change
Indeed. Let me update it.
Thanks!
--
Masami Hiramatsu (Google) <[email protected]>
On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
>
> Florent, feel free to add your rethook for arm64, but please do not remove
> kretprobe trampoline yet. It is another discussion point. We may be possible
> to use ftrace_regs for kretprobe by ftrace_partial_regs() but kretprobe
> allows nest probe. (maybe we can skip that case?)
Ack :)
> arch/Kconfig | 1 +
> arch/arm64/include/asm/ftrace.h | 11 ++++++
> arch/loongarch/Kconfig | 1 +
> arch/s390/Kconfig | 1 +
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/rethook.c | 9 +++--
> include/linux/fprobe.h | 4 +-
> include/linux/ftrace.h | 56 ++++++++++++++++++-----------
> include/linux/rethook.h | 11 +++---
> kernel/kprobes.c | 9 ++++-
> kernel/trace/Kconfig | 9 ++++-
> kernel/trace/bpf_trace.c | 14 +++++--
> kernel/trace/fprobe.c | 8 ++--
> kernel/trace/rethook.c | 16 ++++----
> kernel/trace/trace_fprobe.c | 76 ++++++++++++++++++++++++---------------
> kernel/trace/trace_probe_tmpl.h | 2 +
> lib/test_fprobe.c | 10 +++--
> samples/fprobe/fprobe_example.c | 4 +-
I believe that Documentation/trace/fprobe.rst should also be modified
following the API change
On Tue, 8 Aug 2023 00:08:11 +0200
Jiri Olsa <[email protected]> wrote:
> On Mon, Aug 07, 2023 at 03:49:33PM +0900, Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > Enable kprobe_multi feature if CONFIG_FPROBE is enabled. The pt_regs is
> > converted from ftrace_regs by ftrace_partial_regs(), thus some registers
> > may always returns 0. But it should be enough for function entry (access
> > arguments) and exit (access return value).
> >
> > Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> > ---
> > kernel/trace/bpf_trace.c | 22 +++++++++-------------
> > 1 file changed, 9 insertions(+), 13 deletions(-)
> >
> > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> > index 99c5f95360f9..0725272a3de2 100644
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void)
> > fs_initcall(bpf_event_init);
> > #endif /* CONFIG_MODULES */
> >
> > -#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> > +#ifdef CONFIG_FPROBE
> > struct bpf_kprobe_multi_link {
> > struct bpf_link link;
> > struct fprobe fp;
> > @@ -2482,6 +2482,8 @@ struct user_syms {
> > char *buf;
> > };
> >
> > +static DEFINE_PER_CPU(struct pt_regs, bpf_kprobe_multi_pt_regs);
> > +
> > static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
> > {
> > unsigned long __user usymbol;
> > @@ -2623,13 +2625,14 @@ static u64 bpf_kprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
> >
> > static int
> > kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> > - unsigned long entry_ip, struct pt_regs *regs)
> > + unsigned long entry_ip, struct ftrace_regs *fregs)
> > {
> > struct bpf_kprobe_multi_run_ctx run_ctx = {
> > .link = link,
> > .entry_ip = entry_ip,
> > };
> > struct bpf_run_ctx *old_run_ctx;
> > + struct pt_regs *regs;
> > int err;
> >
> > if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
> > @@ -2639,6 +2642,7 @@ kprobe_multi_link_prog_run(struct bpf_kprobe_multi_link *link,
> >
> > migrate_disable();
> > rcu_read_lock();
> > + regs = ftrace_partial_regs(fregs, this_cpu_ptr(&bpf_kprobe_multi_pt_regs));
>
> you did check for !regs when returned from ftrace_get_regs, why don't we need
> to check it in here? both ftrace_partial_regs and ftrace_get_regs call
> arch_ftrace_get_regs on x86
Good catch! I think ftrace_partial_regs must not return NULL (unless getting
invalid parameter, e.g. fregs == NULL).
>
> also also I can't find the place ensuring fregs->regs.cs != 0 for FL_SAVE_REGS
> flag as stated in arch_ftrace_get_regs, any hint?
Oops, I misread that part. Maybe ftrace_partial_regs must forcibly return
ftrace_regs::regs if HAVE_PT_REGS_COMPAT_FTRACE_REGS=y because it does not
care the regs is partial or not.
Thank you!
>
> thanks,
> jirka
>
>
> > old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> > err = bpf_prog_run(link->link.prog, regs);
> > bpf_reset_run_ctx(old_run_ctx);
> > @@ -2656,13 +2660,9 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> > void *data)
> > {
> > struct bpf_kprobe_multi_link *link;
> > - struct pt_regs *regs = ftrace_get_regs(fregs);
> > -
> > - if (!regs)
> > - return 0;
> >
> > link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> > - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> > + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> > return 0;
> > }
> >
> > @@ -2672,13 +2672,9 @@ kprobe_multi_link_exit_handler(struct fprobe *fp, unsigned long fentry_ip,
> > void *data)
> > {
> > struct bpf_kprobe_multi_link *link;
> > - struct pt_regs *regs = ftrace_get_regs(fregs);
> > -
> > - if (!regs)
> > - return;
> >
> > link = container_of(fp, struct bpf_kprobe_multi_link, fp);
> > - kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), regs);
> > + kprobe_multi_link_prog_run(link, get_entry_ip(fentry_ip), fregs);
> > }
> >
> > static int symbols_cmp_r(const void *a, const void *b, const void *priv)
> > @@ -2918,7 +2914,7 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
> > kvfree(cookies);
> > return err;
> > }
> > -#else /* !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
> > +#else /* !CONFIG_FPROBE */
> > int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
> > {
> > return -EOPNOTSUPP;
> >
--
Masami Hiramatsu (Google) <[email protected]>
On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
>
> From: Masami Hiramatsu (Google) <[email protected]>
>
> Allow fprobe events to be enabled with CONFIG_DYNAMIC_FTRACE_WITH_ARGS.
> With this change, fprobe events mostly use ftrace_regs instead of pt_regs.
> Note that if the arch doesn't enable HAVE_PT_REGS_COMPAT_FTRACE_REGS,
> fprobe events will not be able to use from perf.
nit: "to be used from perf" ?
> --- a/kernel/trace/trace_fprobe.c
> +++ b/kernel/trace/trace_fprobe.c
> @@ -132,25 +132,30 @@ static int
> process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> void *base)
> {
> - struct pt_regs *regs = rec;
> - unsigned long val;
> + struct ftrace_regs *fregs = rec;
> + unsigned long val, *stackp;
> int ret;
>
> retry:
> /* 1st stage: get value from context */
> switch (code->op) {
> case FETCH_OP_STACK:
> - val = regs_get_kernel_stack_nth(regs, code->param);
> + stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
> + if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
> + ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
Maybe it'd be worth extracting a local
"ftrace_regs_get_kernel_stack_nth_addr" helper function and/or
"ftrace_regs_within_kernel_stack" ?
On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
>
> From: Masami Hiramatsu (Google) <[email protected]>
>
> This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> on arm64.
This patch lets fprobe code build on configs WITH_ARGS and !WITH_REGS
but fprobe wouldn't run on these builds because fprobe still registers
to ftrace with FTRACE_OPS_FL_SAVE_REGS, which would fail on
!WITH_REGS. Shouldn't we also let the fprobe_init callers decide
whether they want REGS or not ?
> static int
> kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> - unsigned long ret_ip, struct pt_regs *regs,
> + unsigned long ret_ip, struct ftrace_regs *fregs,
> void *data)
> {
> struct bpf_kprobe_multi_link *link;
> + struct pt_regs *regs = ftrace_get_regs(fregs);
> +
> + if (!regs)
> + return 0;
(with the above comment addressed) this means that BPF multi_kprobe
would successfully attach on builds WITH_ARGS but the programs would
never actually run because here regs would be 0. This is a confusing
failure mode for the user. I think that if multi_kprobe won't work
(because we don't have a pt_regs conversion path yet), the user should
be notified at attachment time that they won't be getting any events.
That's why I think kprobe_multi should inform fprobe_init that it
wants FTRACE_OPS_FL_SAVE_REGS and fail if that's not possible (no
trampoline for it for example)
The title says "Use fprobe_regs", I think you meant ftrace_regs (we
have enough problems with two regs structs already! :o) ) same comment
for patch 1
On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
>
> From: Masami Hiramatsu (Google) <[email protected]>
>
> Change the fprobe exit handler and rethook to use ftrace_regs data structure
> instead of pt_regs. This also introduce HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
The macro name in the patch description doesn't match the one in the
patch (HAVE_PT_REGS_COMPAT_FTRACE_REGS)
> which means the ftrace_regs is equal to the pt_regs so that those are
> compatible. Only if it is enabled, kretprobe will use rethook since kretprobe
> requires pt_regs for backward compatibility.
>
> This means the archs which currently implement rethook for kretprobes needs to
> set that flag and it must ensure struct ftrace_regs is same as pt_regs.
nit: I'm a bit confused when you say that these structures are "the
same". Let's take x86 as an example, ftrace_regs is "the same" as
pt_regs in the sense that they use the same space in memory and have
the same fields alignment but my understanding of ftrace_regs is that
it can either be a full pt_regs or a sparse pt_regs. If the trampoline
doesn't go through ftrace_regs_caller_op_ptr, registers like CS will
be missing and ftrace_get_regs will return NULL, I don't call it being
"the same". I guess what you mean here is that a pt_regs can be casted
back into a ftrace_regs. Maybe HAVE_PT_REGS_TO_FTRACE_REGS_CAST would
be a clearer name ?
> If not, it must be either disabling kretprobe or implementing kretprobe
> trampoline separately from rethook trampoline.
>
> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> ---
> arch/Kconfig | 1 +
> arch/loongarch/Kconfig | 1 +
> arch/s390/Kconfig | 1 +
> arch/x86/Kconfig | 1 +
> arch/x86/kernel/rethook.c | 9 ++++++---
> include/linux/fprobe.h | 2 +-
> include/linux/rethook.h | 11 ++++++-----
> kernel/kprobes.c | 9 +++++++--
> kernel/trace/Kconfig | 7 +++++++
> kernel/trace/bpf_trace.c | 6 +++++-
> kernel/trace/fprobe.c | 6 +++---
> kernel/trace/rethook.c | 16 ++++++++--------
> kernel/trace/trace_fprobe.c | 6 +++++-
> lib/test_fprobe.c | 6 +++---
> samples/fprobe/fprobe_example.c | 2 +-
> 15 files changed, 56 insertions(+), 28 deletions(-)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index aff2746c8af2..e321bdb8b22b 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
> def_bool y
> depends on HAVE_RETHOOK
> depends on KRETPROBES
> + depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
> select RETHOOK
>
> config USER_RETURN_NOTIFIER
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index e55511af4c77..93a4336b0a94 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -102,6 +102,7 @@ config LOONGARCH
> select HAVE_DMA_CONTIGUOUS
> select HAVE_DYNAMIC_FTRACE
> select HAVE_DYNAMIC_FTRACE_WITH_ARGS
> + select HAVE_PT_REGS_COMPAT_FTRACE_REGS
> select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> select HAVE_DYNAMIC_FTRACE_WITH_REGS
> select HAVE_EBPF_JIT
> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> index 5b39918b7042..299ba17d3316 100644
> --- a/arch/s390/Kconfig
> +++ b/arch/s390/Kconfig
> @@ -165,6 +165,7 @@ config S390
> select HAVE_DMA_CONTIGUOUS
> select HAVE_DYNAMIC_FTRACE
> select HAVE_DYNAMIC_FTRACE_WITH_ARGS
> + select HAVE_PT_REGS_COMPAT_FTRACE_REGS
> select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> select HAVE_DYNAMIC_FTRACE_WITH_REGS
> select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 7422db409770..df1b7a2791e8 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -207,6 +207,7 @@ config X86
> select HAVE_DYNAMIC_FTRACE
> select HAVE_DYNAMIC_FTRACE_WITH_REGS
> select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
> + select HAVE_PT_REGS_COMPAT_FTRACE_REGS if X86_64
> select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
> select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
> diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
> index 8a1c0111ae79..79a52bfde562 100644
> --- a/arch/x86/kernel/rethook.c
> +++ b/arch/x86/kernel/rethook.c
> @@ -83,7 +83,8 @@ __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
> * arch_rethook_fixup_return() which called from this
> * rethook_trampoline_handler().
> */
> - rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
> + rethook_trampoline_handler((struct ftrace_regs *)regs,
> + (unsigned long)frame_pointer);
>
> /*
> * Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()
> @@ -104,9 +105,10 @@ NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
> STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
>
> /* This is called from rethook_trampoline_handler(). */
> -void arch_rethook_fixup_return(struct pt_regs *regs,
> +void arch_rethook_fixup_return(struct ftrace_regs *fregs,
> unsigned long correct_ret_addr)
> {
> + struct pt_regs *regs = ftrace_get_regs(fregs);
> unsigned long *frame_pointer = (void *)(regs + 1);
>
> /* Replace fake return address with real one. */
> @@ -114,8 +116,9 @@ void arch_rethook_fixup_return(struct pt_regs *regs,
> }
> NOKPROBE_SYMBOL(arch_rethook_fixup_return);
>
> -void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
> +void arch_rethook_prepare(struct rethook_node *rh, struct ftrace_regs *fregs, bool mcount)
> {
> + struct pt_regs *regs = ftrace_get_regs(fregs);
> unsigned long *stack = (unsigned long *)regs->sp;
>
> rh->ret_addr = stack[0];
> diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
> index 36c0595f7b93..b9c0c216dedb 100644
> --- a/include/linux/fprobe.h
> +++ b/include/linux/fprobe.h
> @@ -38,7 +38,7 @@ struct fprobe {
> unsigned long ret_ip, struct ftrace_regs *regs,
> void *entry_data);
> void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
> - unsigned long ret_ip, struct pt_regs *regs,
> + unsigned long ret_ip, struct ftrace_regs *regs,
> void *entry_data);
> };
>
> diff --git a/include/linux/rethook.h b/include/linux/rethook.h
> index 26b6f3c81a76..138d64c8b67b 100644
> --- a/include/linux/rethook.h
> +++ b/include/linux/rethook.h
> @@ -7,6 +7,7 @@
>
> #include <linux/compiler.h>
> #include <linux/freelist.h>
> +#include <linux/ftrace.h>
> #include <linux/kallsyms.h>
> #include <linux/llist.h>
> #include <linux/rcupdate.h>
> @@ -14,7 +15,7 @@
>
> struct rethook_node;
>
> -typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
> +typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct ftrace_regs *);
>
> /**
> * struct rethook - The rethook management data structure.
> @@ -64,12 +65,12 @@ void rethook_free(struct rethook *rh);
> void rethook_add_node(struct rethook *rh, struct rethook_node *node);
> struct rethook_node *rethook_try_get(struct rethook *rh);
> void rethook_recycle(struct rethook_node *node);
> -void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
> +void rethook_hook(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
> unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
> struct llist_node **cur);
>
> /* Arch dependent code must implement arch_* and trampoline code */
> -void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
> +void arch_rethook_prepare(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
> void arch_rethook_trampoline(void);
>
> /**
> @@ -84,11 +85,11 @@ static inline bool is_rethook_trampoline(unsigned long addr)
> }
>
> /* If the architecture needs to fixup the return address, implement it. */
> -void arch_rethook_fixup_return(struct pt_regs *regs,
> +void arch_rethook_fixup_return(struct ftrace_regs *regs,
> unsigned long correct_ret_addr);
>
> /* Generic trampoline handler, arch code must prepare asm stub */
> -unsigned long rethook_trampoline_handler(struct pt_regs *regs,
> +unsigned long rethook_trampoline_handler(struct ftrace_regs *regs,
> unsigned long frame);
>
> #ifdef CONFIG_RETHOOK
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 1fc6095d502d..ccbe41c961c3 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2120,7 +2120,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
> if (rp->entry_handler && rp->entry_handler(ri, regs))
> rethook_recycle(rhn);
> else
> - rethook_hook(rhn, regs, kprobe_ftrace(p));
> + rethook_hook(rhn, (struct ftrace_regs *)regs, kprobe_ftrace(p));
I think there are two things that can be meant with "rethook uses ftrace_regs":
- rethook callbacks receive a ftrace_regs (that's what you do further down)
- rethook can hook to a traced function using a ftrace_regs (that's
what you use in fprobe now)
But I think the second proposition shouldn't imply that rethook_hook
can _only_ hook to ftrace_regs. For the kprobe use case, I think there
should also be a rethook_hook_pt_regs() that operates on a pt_regs. We
could have a default implementation of rethook_hook that calls into
the other (or vice versa) on HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
but I think it's good to separate these two APIs
On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index ce156c7704ee..3fb94a1a2461 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
> }
> #endif
>
> -#ifdef CONFIG_FUNCTION_TRACER
> -
> -extern int ftrace_enabled;
> -
> -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> +/*
> + * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
nit: disables*
> + * tracer, define the default(pt_regs compatible) ftrace_regs.
> + */
> +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
I wonder if we should make things simpler with:
#if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
And remove the ftrace_regs definitions that are copy-pastes of this
block in arch specific headers. Then we can enforce in a single point
that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
Maybe that's a question for Steven ?
On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
<[email protected]> wrote:
>
> From: Masami Hiramatsu (Google) <[email protected]>
>
> Add ftrace_partial_regs() which converts the ftrace_regas to pt_regs.
ftrace_regs*
> If the architecture defines its own ftrace_regs, this copies partial
> registers to pt_regs and returns it. If not, ftrace_regs is the same as
> pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.
>
> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> ---
> arch/arm64/include/asm/ftrace.h | 11 +++++++++++
> include/linux/ftrace.h | 11 +++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index ab158196480c..b108cd6718cf 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -137,6 +137,17 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs)
> fregs->pc = fregs->lr;
> }
>
> +static __always_inline struct pt_regs *
> +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> +{
> + memcpy(regs->regs, fregs->regs, sizeof(u64) * 10);
Are you intentionally copying that tenth value (fregs.direct_tramp)
into pt_regs.regs[9] ? This seems wrong and it looks like it will bite
us back one day. Isn't it one of these cases where we can simply use
sizeof(fregs->regs) ?
> + regs->sp = fregs->sp;
> + regs->pc = fregs->pc;
> + regs->x[29] = fregs->fp;
> + regs->x[30] = fregs->lr;
> + return regs;
> +}
> +
> int ftrace_regs_query_register_offset(const char *name);
>
> int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index 3fb94a1a2461..7f45654441b7 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -155,6 +155,17 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
> return arch_ftrace_get_regs(fregs);
> }
>
> +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \
> + defined(CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS)
> +
> +static __always_inline struct pt_regs *
> +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> +{
> + return arch_ftrace_get_regs((struct ftrace_regs *)fregs);
> +}
I don't think this works. Suppose you are on x86, WITH_ARGS, and with
HAVE_PT_REGS_COMPAT_FTRACE_REGS. If you register to ftrace without
FTRACE_OPS_FL_SAVE_REGS you will receive a ftrace_regs from the light
ftrace pre-trampoline that has a CS register equal to 0 and
arch_ftrace_get_regs will return NULL here, which should never happen.
Have you tested your series without registering as FTRACE_OPS_FL_SAVE_REGS ?
On Wed, 9 Aug 2023 12:30:47 +0200
Florent Revest <[email protected]> wrote:
> The title says "Use fprobe_regs", I think you meant ftrace_regs (we
> have enough problems with two regs structs already! :o) ) same comment
> for patch 1
Oops! thanks!
>
> On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> >
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > Change the fprobe exit handler and rethook to use ftrace_regs data structure
> > instead of pt_regs. This also introduce HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
>
> The macro name in the patch description doesn't match the one in the
> patch (HAVE_PT_REGS_COMPAT_FTRACE_REGS)
Ah, sorry, that is also a typo, it was the old macro name.
(but since it too long, I changed that)
>
> > which means the ftrace_regs is equal to the pt_regs so that those are
> > compatible. Only if it is enabled, kretprobe will use rethook since kretprobe
> > requires pt_regs for backward compatibility.
> >
> > This means the archs which currently implement rethook for kretprobes needs to
> > set that flag and it must ensure struct ftrace_regs is same as pt_regs.
>
> nit: I'm a bit confused when you say that these structures are "the
> same". Let's take x86 as an example, ftrace_regs is "the same" as
> pt_regs in the sense that they use the same space in memory and have
> the same fields alignment but my understanding of ftrace_regs is that
> it can either be a full pt_regs or a sparse pt_regs.
Yes, you're right. it must be changed that it means ftrace_regs is
just a wrapper of pt_regs, so the memory layout is the same.
> If the trampoline
> doesn't go through ftrace_regs_caller_op_ptr, registers like CS will
> be missing and ftrace_get_regs will return NULL, I don't call it being
> "the same". I guess what you mean here is that a pt_regs can be casted
> back into a ftrace_regs. Maybe HAVE_PT_REGS_TO_FTRACE_REGS_CAST would
> be a clearer name ?
Ok, let me change the name.
>
> > If not, it must be either disabling kretprobe or implementing kretprobe
> > trampoline separately from rethook trampoline.
> >
> > Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> > ---
> > arch/Kconfig | 1 +
> > arch/loongarch/Kconfig | 1 +
> > arch/s390/Kconfig | 1 +
> > arch/x86/Kconfig | 1 +
> > arch/x86/kernel/rethook.c | 9 ++++++---
> > include/linux/fprobe.h | 2 +-
> > include/linux/rethook.h | 11 ++++++-----
> > kernel/kprobes.c | 9 +++++++--
> > kernel/trace/Kconfig | 7 +++++++
> > kernel/trace/bpf_trace.c | 6 +++++-
> > kernel/trace/fprobe.c | 6 +++---
> > kernel/trace/rethook.c | 16 ++++++++--------
> > kernel/trace/trace_fprobe.c | 6 +++++-
> > lib/test_fprobe.c | 6 +++---
> > samples/fprobe/fprobe_example.c | 2 +-
> > 15 files changed, 56 insertions(+), 28 deletions(-)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index aff2746c8af2..e321bdb8b22b 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
> > def_bool y
> > depends on HAVE_RETHOOK
> > depends on KRETPROBES
> > + depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > select RETHOOK
> >
> > config USER_RETURN_NOTIFIER
> > diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> > index e55511af4c77..93a4336b0a94 100644
> > --- a/arch/loongarch/Kconfig
> > +++ b/arch/loongarch/Kconfig
> > @@ -102,6 +102,7 @@ config LOONGARCH
> > select HAVE_DMA_CONTIGUOUS
> > select HAVE_DYNAMIC_FTRACE
> > select HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > + select HAVE_PT_REGS_COMPAT_FTRACE_REGS
> > select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > select HAVE_DYNAMIC_FTRACE_WITH_REGS
> > select HAVE_EBPF_JIT
> > diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
> > index 5b39918b7042..299ba17d3316 100644
> > --- a/arch/s390/Kconfig
> > +++ b/arch/s390/Kconfig
> > @@ -165,6 +165,7 @@ config S390
> > select HAVE_DMA_CONTIGUOUS
> > select HAVE_DYNAMIC_FTRACE
> > select HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > + select HAVE_PT_REGS_COMPAT_FTRACE_REGS
> > select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > select HAVE_DYNAMIC_FTRACE_WITH_REGS
> > select HAVE_EBPF_JIT if HAVE_MARCH_Z196_FEATURES
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index 7422db409770..df1b7a2791e8 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -207,6 +207,7 @@ config X86
> > select HAVE_DYNAMIC_FTRACE
> > select HAVE_DYNAMIC_FTRACE_WITH_REGS
> > select HAVE_DYNAMIC_FTRACE_WITH_ARGS if X86_64
> > + select HAVE_PT_REGS_COMPAT_FTRACE_REGS if X86_64
> > select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
> > select HAVE_SAMPLE_FTRACE_DIRECT if X86_64
> > select HAVE_SAMPLE_FTRACE_DIRECT_MULTI if X86_64
> > diff --git a/arch/x86/kernel/rethook.c b/arch/x86/kernel/rethook.c
> > index 8a1c0111ae79..79a52bfde562 100644
> > --- a/arch/x86/kernel/rethook.c
> > +++ b/arch/x86/kernel/rethook.c
> > @@ -83,7 +83,8 @@ __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
> > * arch_rethook_fixup_return() which called from this
> > * rethook_trampoline_handler().
> > */
> > - rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
> > + rethook_trampoline_handler((struct ftrace_regs *)regs,
> > + (unsigned long)frame_pointer);
> >
> > /*
> > * Copy FLAGS to 'pt_regs::ss' so that arch_rethook_trapmoline()
> > @@ -104,9 +105,10 @@ NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
> > STACK_FRAME_NON_STANDARD_FP(arch_rethook_trampoline);
> >
> > /* This is called from rethook_trampoline_handler(). */
> > -void arch_rethook_fixup_return(struct pt_regs *regs,
> > +void arch_rethook_fixup_return(struct ftrace_regs *fregs,
> > unsigned long correct_ret_addr)
> > {
> > + struct pt_regs *regs = ftrace_get_regs(fregs);
> > unsigned long *frame_pointer = (void *)(regs + 1);
> >
> > /* Replace fake return address with real one. */
> > @@ -114,8 +116,9 @@ void arch_rethook_fixup_return(struct pt_regs *regs,
> > }
> > NOKPROBE_SYMBOL(arch_rethook_fixup_return);
> >
> > -void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
> > +void arch_rethook_prepare(struct rethook_node *rh, struct ftrace_regs *fregs, bool mcount)
> > {
> > + struct pt_regs *regs = ftrace_get_regs(fregs);
> > unsigned long *stack = (unsigned long *)regs->sp;
> >
> > rh->ret_addr = stack[0];
> > diff --git a/include/linux/fprobe.h b/include/linux/fprobe.h
> > index 36c0595f7b93..b9c0c216dedb 100644
> > --- a/include/linux/fprobe.h
> > +++ b/include/linux/fprobe.h
> > @@ -38,7 +38,7 @@ struct fprobe {
> > unsigned long ret_ip, struct ftrace_regs *regs,
> > void *entry_data);
> > void (*exit_handler)(struct fprobe *fp, unsigned long entry_ip,
> > - unsigned long ret_ip, struct pt_regs *regs,
> > + unsigned long ret_ip, struct ftrace_regs *regs,
> > void *entry_data);
> > };
> >
> > diff --git a/include/linux/rethook.h b/include/linux/rethook.h
> > index 26b6f3c81a76..138d64c8b67b 100644
> > --- a/include/linux/rethook.h
> > +++ b/include/linux/rethook.h
> > @@ -7,6 +7,7 @@
> >
> > #include <linux/compiler.h>
> > #include <linux/freelist.h>
> > +#include <linux/ftrace.h>
> > #include <linux/kallsyms.h>
> > #include <linux/llist.h>
> > #include <linux/rcupdate.h>
> > @@ -14,7 +15,7 @@
> >
> > struct rethook_node;
> >
> > -typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct pt_regs *);
> > +typedef void (*rethook_handler_t) (struct rethook_node *, void *, unsigned long, struct ftrace_regs *);
> >
> > /**
> > * struct rethook - The rethook management data structure.
> > @@ -64,12 +65,12 @@ void rethook_free(struct rethook *rh);
> > void rethook_add_node(struct rethook *rh, struct rethook_node *node);
> > struct rethook_node *rethook_try_get(struct rethook *rh);
> > void rethook_recycle(struct rethook_node *node);
> > -void rethook_hook(struct rethook_node *node, struct pt_regs *regs, bool mcount);
> > +void rethook_hook(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
> > unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame,
> > struct llist_node **cur);
> >
> > /* Arch dependent code must implement arch_* and trampoline code */
> > -void arch_rethook_prepare(struct rethook_node *node, struct pt_regs *regs, bool mcount);
> > +void arch_rethook_prepare(struct rethook_node *node, struct ftrace_regs *regs, bool mcount);
> > void arch_rethook_trampoline(void);
> >
> > /**
> > @@ -84,11 +85,11 @@ static inline bool is_rethook_trampoline(unsigned long addr)
> > }
> >
> > /* If the architecture needs to fixup the return address, implement it. */
> > -void arch_rethook_fixup_return(struct pt_regs *regs,
> > +void arch_rethook_fixup_return(struct ftrace_regs *regs,
> > unsigned long correct_ret_addr);
> >
> > /* Generic trampoline handler, arch code must prepare asm stub */
> > -unsigned long rethook_trampoline_handler(struct pt_regs *regs,
> > +unsigned long rethook_trampoline_handler(struct ftrace_regs *regs,
> > unsigned long frame);
> >
> > #ifdef CONFIG_RETHOOK
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 1fc6095d502d..ccbe41c961c3 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -2120,7 +2120,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
> > if (rp->entry_handler && rp->entry_handler(ri, regs))
> > rethook_recycle(rhn);
> > else
> > - rethook_hook(rhn, regs, kprobe_ftrace(p));
> > + rethook_hook(rhn, (struct ftrace_regs *)regs, kprobe_ftrace(p));
>
> I think there are two things that can be meant with "rethook uses ftrace_regs":
>
> - rethook callbacks receive a ftrace_regs (that's what you do further down)
> - rethook can hook to a traced function using a ftrace_regs (that's
> what you use in fprobe now)
>
> But I think the second proposition shouldn't imply that rethook_hook
> can _only_ hook to ftrace_regs. For the kprobe use case, I think there
> should also be a rethook_hook_pt_regs() that operates on a pt_regs. We
> could have a default implementation of rethook_hook that calls into
> the other (or vice versa) on HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
> but I think it's good to separate these two APIs
Yeah, so for simplying the 2nd case, I added this dependency.
diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af2..e321bdb8b22b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
def_bool y
depends on HAVE_RETHOOK
depends on KRETPROBES
+ depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
select RETHOOK
This is the point why I said that "do not remove kretprobe trampoline".
If there is arch dependent kretprobe trampoline, kretprobe does not use
the rethook for hooking return. And eventually I would like to remove
kretprobe itself (replace it with fprobe + rethook). If so, I don't want
to pay more efforts on this part, and keep kretprobe on rethook as it is.
Thank you,
--
Masami Hiramatsu (Google) <[email protected]>
Hi Florent,
On Wed, 9 Aug 2023 12:28:38 +0200
Florent Revest <[email protected]> wrote:
> On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> >
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> > instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> > on arm64.
>
> This patch lets fprobe code build on configs WITH_ARGS and !WITH_REGS
> but fprobe wouldn't run on these builds because fprobe still registers
> to ftrace with FTRACE_OPS_FL_SAVE_REGS, which would fail on
> !WITH_REGS. Shouldn't we also let the fprobe_init callers decide
> whether they want REGS or not ?
Ah, I think you meant FPROBE_EVENTS? Yes I forgot to add the dependency
on it. But fprobe itself can work because fprobe just pass the ftrace_regs
to the handlers. (Note that exit callback may not work until next patch)
>
> > static int
> > kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> > - unsigned long ret_ip, struct pt_regs *regs,
> > + unsigned long ret_ip, struct ftrace_regs *fregs,
> > void *data)
> > {
> > struct bpf_kprobe_multi_link *link;
> > + struct pt_regs *regs = ftrace_get_regs(fregs);
> > +
> > + if (!regs)
> > + return 0;
>
> (with the above comment addressed) this means that BPF multi_kprobe
> would successfully attach on builds WITH_ARGS but the programs would
> never actually run because here regs would be 0. This is a confusing
> failure mode for the user. I think that if multi_kprobe won't work
> (because we don't have a pt_regs conversion path yet), the user should
> be notified at attachment time that they won't be getting any events.
Yes, so I changed it will not be compiled in that case.
@@ -2460,7 +2460,7 @@ static int __init bpf_event_init(void)
fs_initcall(bpf_event_init);
#endif /* CONFIG_MODULES */
-#ifdef CONFIG_FPROBE
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
struct bpf_kprobe_multi_link {
struct bpf_link link;
struct fprobe fp;
> That's why I think kprobe_multi should inform fprobe_init that it
> wants FTRACE_OPS_FL_SAVE_REGS and fail if that's not possible (no
> trampoline for it for example)
Yeah, that's another possibility, but in the previous thread we
discussed and agreed to introduce the ftrace_partial_regs() which
will copy the partial registers from ftrace_regs to pt_regs.
Thank you,
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, 9 Aug 2023 12:29:13 +0200
Florent Revest <[email protected]> wrote:
> On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index ce156c7704ee..3fb94a1a2461 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -112,11 +112,11 @@ static inline int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *val
> > }
> > #endif
> >
> > -#ifdef CONFIG_FUNCTION_TRACER
> > -
> > -extern int ftrace_enabled;
> > -
> > -#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > +/*
> > + * If the architecture doesn't support FTRACE_WITH_ARGS or disable function
>
> nit: disables*
Thanks!
>
> > + * tracer, define the default(pt_regs compatible) ftrace_regs.
> > + */
> > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
>
> I wonder if we should make things simpler with:
>
> #if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
>
> And remove the ftrace_regs definitions that are copy-pastes of this
> block in arch specific headers. Then we can enforce in a single point
> that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
Here, the "HAVE_PT_REGS_COMPAT_FTRACE_REGS" does not mean that the
ftrace_regs is completely compatible with pt_regs, but on the memory
it wraps struct pt_regs (thus we can just cast the type).
- CONFIG_DYNAMIC_FTRACE_WITH_REGS
ftrace_regs is completely compatible with pt_regs
- CONFIG_DYNAMIC_FTRACE_WITH_ARGS
| ftrace_regs may not compatible with pt_regs
|
+- CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS
but on memory image, ftrace_regs includes pt_regs.
Thank you,
>
> Maybe that's a question for Steven ?
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, 9 Aug 2023 12:31:00 +0200
Florent Revest <[email protected]> wrote:
> On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> >
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > Allow fprobe events to be enabled with CONFIG_DYNAMIC_FTRACE_WITH_ARGS.
> > With this change, fprobe events mostly use ftrace_regs instead of pt_regs.
> > Note that if the arch doesn't enable HAVE_PT_REGS_COMPAT_FTRACE_REGS,
> > fprobe events will not be able to use from perf.
>
> nit: "to be used from perf" ?
OK.
>
> > --- a/kernel/trace/trace_fprobe.c
> > +++ b/kernel/trace/trace_fprobe.c
> > @@ -132,25 +132,30 @@ static int
> > process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> > void *base)
> > {
> > - struct pt_regs *regs = rec;
> > - unsigned long val;
> > + struct ftrace_regs *fregs = rec;
> > + unsigned long val, *stackp;
> > int ret;
> >
> > retry:
> > /* 1st stage: get value from context */
> > switch (code->op) {
> > case FETCH_OP_STACK:
> > - val = regs_get_kernel_stack_nth(regs, code->param);
> > + stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
> > + if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
> > + ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
>
> Maybe it'd be worth extracting a local
> "ftrace_regs_get_kernel_stack_nth_addr" helper function and/or
> "ftrace_regs_within_kernel_stack" ?
Yeah, maybe we can make it a generic inline function in linux/ftrace.h.
Thank you!
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, 9 Aug 2023 12:31:27 +0200
Florent Revest <[email protected]> wrote:
> On Mon, Aug 7, 2023 at 8:49 AM Masami Hiramatsu (Google)
> <[email protected]> wrote:
> >
> > From: Masami Hiramatsu (Google) <[email protected]>
> >
> > Add ftrace_partial_regs() which converts the ftrace_regas to pt_regs.
>
> ftrace_regs*
Oops, thanks.
>
> > If the architecture defines its own ftrace_regs, this copies partial
> > registers to pt_regs and returns it. If not, ftrace_regs is the same as
> > pt_regs and ftrace_partial_regs() will return ftrace_regs::regs.
> >
> > Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> > ---
> > arch/arm64/include/asm/ftrace.h | 11 +++++++++++
> > include/linux/ftrace.h | 11 +++++++++++
> > 2 files changed, 22 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> > index ab158196480c..b108cd6718cf 100644
> > --- a/arch/arm64/include/asm/ftrace.h
> > +++ b/arch/arm64/include/asm/ftrace.h
> > @@ -137,6 +137,17 @@ ftrace_override_function_with_return(struct ftrace_regs *fregs)
> > fregs->pc = fregs->lr;
> > }
> >
> > +static __always_inline struct pt_regs *
> > +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> > +{
> > + memcpy(regs->regs, fregs->regs, sizeof(u64) * 10);
>
> Are you intentionally copying that tenth value (fregs.direct_tramp)
> into pt_regs.regs[9] ? This seems wrong and it looks like it will bite
> us back one day. Isn't it one of these cases where we can simply use
> sizeof(fregs->regs) ?
Ah, sorry, it was my mistake. It should be "sizeof(u64) * 9".
I would like to know how can I handle the 'direct_tramp' thing?
Can I just ignore it?
>
> > + regs->sp = fregs->sp;
> > + regs->pc = fregs->pc;
> > + regs->x[29] = fregs->fp;
> > + regs->x[30] = fregs->lr;
> > + return regs;
> > +}
> > +
> > int ftrace_regs_query_register_offset(const char *name);
> >
> > int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 3fb94a1a2461..7f45654441b7 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -155,6 +155,17 @@ static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs
> > return arch_ftrace_get_regs(fregs);
> > }
> >
> > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || \
> > + defined(CONFIG_HAVE_PT_REGS_COMPAT_FTRACE_REGS)
> > +
> > +static __always_inline struct pt_regs *
> > +ftrace_partial_regs(const struct ftrace_regs *fregs, struct pt_regs *regs)
> > +{
> > + return arch_ftrace_get_regs((struct ftrace_regs *)fregs);
> > +}
>
> I don't think this works. Suppose you are on x86, WITH_ARGS, and with
> HAVE_PT_REGS_COMPAT_FTRACE_REGS. If you register to ftrace without
> FTRACE_OPS_FL_SAVE_REGS you will receive a ftrace_regs from the light
> ftrace pre-trampoline that has a CS register equal to 0 and
> arch_ftrace_get_regs will return NULL here, which should never happen.
Yes, Jiri also pointed it. So I simply made it (also remove 'const' from fregs)
return &fregs->regs;
Thank you,
>
> Have you tested your series without registering as FTRACE_OPS_FL_SAVE_REGS ?
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, Aug 9, 2023 at 4:45 PM Masami Hiramatsu <[email protected]> wrote:
> > > --- a/kernel/trace/trace_fprobe.c
> > > +++ b/kernel/trace/trace_fprobe.c
> > > @@ -132,25 +132,30 @@ static int
> > > process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> > > void *base)
> > > {
> > > - struct pt_regs *regs = rec;
> > > - unsigned long val;
> > > + struct ftrace_regs *fregs = rec;
> > > + unsigned long val, *stackp;
> > > int ret;
> > >
> > > retry:
> > > /* 1st stage: get value from context */
> > > switch (code->op) {
> > > case FETCH_OP_STACK:
> > > - val = regs_get_kernel_stack_nth(regs, code->param);
> > > + stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
> > > + if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
> > > + ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
> >
> > Maybe it'd be worth extracting a local
> > "ftrace_regs_get_kernel_stack_nth_addr" helper function and/or
> > "ftrace_regs_within_kernel_stack" ?
>
> Yeah, maybe we can make it a generic inline function in linux/ftrace.h.
Or even just above this function if there are low chances it would get
used elsewhere :)
On Wed, Aug 9, 2023 at 4:43 PM Masami Hiramatsu <[email protected]> wrote:
>
> > I think there are two things that can be meant with "rethook uses ftrace_regs":
> >
> > - rethook callbacks receive a ftrace_regs (that's what you do further down)
> > - rethook can hook to a traced function using a ftrace_regs (that's
> > what you use in fprobe now)
> >
> > But I think the second proposition shouldn't imply that rethook_hook
> > can _only_ hook to ftrace_regs. For the kprobe use case, I think there
> > should also be a rethook_hook_pt_regs() that operates on a pt_regs. We
> > could have a default implementation of rethook_hook that calls into
> > the other (or vice versa) on HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
> > but I think it's good to separate these two APIs
>
> Yeah, so for simplying the 2nd case, I added this dependency.
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index aff2746c8af2..e321bdb8b22b 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
> def_bool y
> depends on HAVE_RETHOOK
> depends on KRETPROBES
> + depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
> select RETHOOK
>
> This is the point why I said that "do not remove kretprobe trampoline".
> If there is arch dependent kretprobe trampoline, kretprobe does not use
> the rethook for hooking return. And eventually I would like to remove
> kretprobe itself (replace it with fprobe + rethook). If so, I don't want
> to pay more efforts on this part, and keep kretprobe on rethook as it is.
What are your thoughts on kprobe + rethook though ?
If that's something you think is worth having, then in this case, it
seems that having a rethook_hook_pt_regs() API would help users.
If that's a frankenstein use case you don't want to support then I
agree we can live without this API and get away with the cast
protected by the depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS...
On Wed, Aug 9, 2023 at 4:10 PM Masami Hiramatsu <[email protected]> wrote:
>
> Hi Florent,
>
> On Wed, 9 Aug 2023 12:28:38 +0200
> Florent Revest <[email protected]> wrote:
>
> > On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> > <[email protected]> wrote:
> > >
> > > From: Masami Hiramatsu (Google) <[email protected]>
> > >
> > > This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> > > instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> > > on arm64.
> >
> > This patch lets fprobe code build on configs WITH_ARGS and !WITH_REGS
> > but fprobe wouldn't run on these builds because fprobe still registers
> > to ftrace with FTRACE_OPS_FL_SAVE_REGS, which would fail on
> > !WITH_REGS. Shouldn't we also let the fprobe_init callers decide
> > whether they want REGS or not ?
>
> Ah, I think you meant FPROBE_EVENTS? Yes I forgot to add the dependency
> on it. But fprobe itself can work because fprobe just pass the ftrace_regs
> to the handlers. (Note that exit callback may not work until next patch)
No, I mean that fprobe still registers its ftrace ops with the
FTRACE_OPS_FL_SAVE_REGS flag:
https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/fprobe.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n185
Which means that __register_ftrace_function will return -EINVAL on
builds !WITH_REGS:
https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/ftrace.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n338
As documented here:
https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/include/linux/ftrace.h?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n188
There are two parts to using sparse pt_regs. One is "static": having
WITH_ARGS in the config, the second one is "dynamic": a ftrace ops
needs to specify that it doesn't want to go through the ftrace
trampoline that saves a full pt_regs, by not giving
FTRACE_OPS_FL_SAVE_REGS. If we want fprobe to work on builds
!WITH_REGS then we should both remove Kconfig dependencies to
WITH_REGS (like you've done) but also stop passing this ftrace ops
flag.
> >
> > > static int
> > > kprobe_multi_link_handler(struct fprobe *fp, unsigned long fentry_ip,
> > > - unsigned long ret_ip, struct pt_regs *regs,
> > > + unsigned long ret_ip, struct ftrace_regs *fregs,
> > > void *data)
> > > {
> > > struct bpf_kprobe_multi_link *link;
> > > + struct pt_regs *regs = ftrace_get_regs(fregs);
> > > +
> > > + if (!regs)
> > > + return 0;
> >
> > (with the above comment addressed) this means that BPF multi_kprobe
> > would successfully attach on builds WITH_ARGS but the programs would
> > never actually run because here regs would be 0. This is a confusing
> > failure mode for the user. I think that if multi_kprobe won't work
> > (because we don't have a pt_regs conversion path yet), the user should
> > be notified at attachment time that they won't be getting any events.
>
> Yes, so I changed it will not be compiled in that case.
Ah ok I missed the CONFIG_DYNAMIC_FTRACE_WITH_REGS guard that you keep
between patch 1 and 6 to avoid this case. (after patch 6, it's no
longer an issue) then that's fine.
On Wed, Aug 9, 2023 at 6:09 PM Florent Revest <[email protected]> wrote:
>
> On Wed, Aug 9, 2023 at 4:10 PM Masami Hiramatsu <[email protected]> wrote:
> >
> > Hi Florent,
> >
> > On Wed, 9 Aug 2023 12:28:38 +0200
> > Florent Revest <[email protected]> wrote:
> >
> > > On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> > > <[email protected]> wrote:
> > > >
> > > > From: Masami Hiramatsu (Google) <[email protected]>
> > > >
> > > > This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> > > > instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> > > > on arm64.
> > >
> > > This patch lets fprobe code build on configs WITH_ARGS and !WITH_REGS
> > > but fprobe wouldn't run on these builds because fprobe still registers
> > > to ftrace with FTRACE_OPS_FL_SAVE_REGS, which would fail on
> > > !WITH_REGS. Shouldn't we also let the fprobe_init callers decide
> > > whether they want REGS or not ?
> >
> > Ah, I think you meant FPROBE_EVENTS? Yes I forgot to add the dependency
> > on it. But fprobe itself can work because fprobe just pass the ftrace_regs
> > to the handlers. (Note that exit callback may not work until next patch)
>
> No, I mean that fprobe still registers its ftrace ops with the
> FTRACE_OPS_FL_SAVE_REGS flag:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/fprobe.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n185
>
> Which means that __register_ftrace_function will return -EINVAL on
> builds !WITH_REGS:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/ftrace.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n338
>
> As documented here:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/include/linux/ftrace.h?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n188
>
> There are two parts to using sparse pt_regs. One is "static": having
> WITH_ARGS in the config, the second one is "dynamic": a ftrace ops
> needs to specify that it doesn't want to go through the ftrace
> trampoline that saves a full pt_regs, by not giving
> FTRACE_OPS_FL_SAVE_REGS. If we want fprobe to work on builds
> !WITH_REGS then we should both remove Kconfig dependencies to
> WITH_REGS (like you've done) but also stop passing this ftrace ops
> flag.
Said in a different way: there are arches that support both WITH_ARGS
and WITH_REGS (like x86 actually). They have two ftrace trampolines
compiled in: ftrace_caller and ftrace_regs_caller, one for each
usecase. If you register to ftrace with the FTRACE_OPS_FL_SAVE_REGS
flag you are telling it that what you want is a pt_regs. If you are
trying to move away from pt_regs and support ftrace_regs in the more
general case (meaning, in the case where it can contain a sparse
pt_regs) then you should stop passing that flag so you go through the
lighter, faster trampoline and test your code in the circumstances
where ftrace_regs isn't just a regular pt_regs but an actually sparse
or light data structure.
I hope that makes my thoughts clearer? It's a hairy topic ahah
On Wed, Aug 9, 2023 at 4:16 PM Masami Hiramatsu <[email protected]> wrote:
>
> On Wed, 9 Aug 2023 12:29:13 +0200
> Florent Revest <[email protected]> wrote:
> > > + * tracer, define the default(pt_regs compatible) ftrace_regs.
> > > + */
> > > +#if !defined(CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS) || !defined(CONFIG_FUNCTION_TRACER)
> >
> > I wonder if we should make things simpler with:
> >
> > #if defined(HAVE_PT_REGS_COMPAT_FTRACE_REGS) || !defined(CONFIG_FUNCTION_TRACER)
> >
> > And remove the ftrace_regs definitions that are copy-pastes of this
> > block in arch specific headers. Then we can enforce in a single point
> > that HAVE_PT_REGS_COMPAT_FTRACE_REGS holds.
>
> Here, the "HAVE_PT_REGS_COMPAT_FTRACE_REGS" does not mean that the
> ftrace_regs is completely compatible with pt_regs, but on the memory
> it wraps struct pt_regs (thus we can just cast the type).
But in practice I think that all architectures that chose to wrap a
pt_regs in their ftrace_regs also do:
+#define ftrace_regs_get_instruction_pointer(fregs) \
+ instruction_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_get_argument(fregs, n) \
+ regs_get_kernel_argument(ftrace_get_regs(fregs), n)
+#define ftrace_regs_get_stack_pointer(fregs) \
+ kernel_stack_pointer(ftrace_get_regs(fregs))
+#define ftrace_regs_return_value(fregs) \
+ regs_return_value(ftrace_get_regs(fregs))
+#define ftrace_regs_set_return_value(fregs, ret) \
+ regs_set_return_value(ftrace_get_regs(fregs), ret)
+#define ftrace_override_function_with_return(fregs) \
+ override_function_with_return(ftrace_get_regs(fregs))
+#define ftrace_regs_query_register_offset(name) \
+ regs_query_register_offset(name)
And are just careful to populate the fields that let these macros
work. So maybe these could be factorized... But anyway, I'm not
particularly a super fan of the idea and I don't think it should
necessarily fit in that series. It's just something that crossed my
mind, if you're not a fan then we should probably not do it ;)
On Wed, 9 Aug 2023 18:17:47 +0200
Florent Revest <[email protected]> wrote:
> On Wed, Aug 9, 2023 at 6:09 PM Florent Revest <[email protected]> wrote:
> >
> > On Wed, Aug 9, 2023 at 4:10 PM Masami Hiramatsu <[email protected]> wrote:
> > >
> > > Hi Florent,
> > >
> > > On Wed, 9 Aug 2023 12:28:38 +0200
> > > Florent Revest <[email protected]> wrote:
> > >
> > > > On Mon, Aug 7, 2023 at 8:48 AM Masami Hiramatsu (Google)
> > > > <[email protected]> wrote:
> > > > >
> > > > > From: Masami Hiramatsu (Google) <[email protected]>
> > > > >
> > > > > This allows fprobes to be available with CONFIG_DYNAMIC_FTRACE_WITH_ARGS
> > > > > instead of CONFIG_DYNAMIC_FTRACE_WITH_REGS, then we can enable fprobe
> > > > > on arm64.
> > > >
> > > > This patch lets fprobe code build on configs WITH_ARGS and !WITH_REGS
> > > > but fprobe wouldn't run on these builds because fprobe still registers
> > > > to ftrace with FTRACE_OPS_FL_SAVE_REGS, which would fail on
> > > > !WITH_REGS. Shouldn't we also let the fprobe_init callers decide
> > > > whether they want REGS or not ?
> > >
> > > Ah, I think you meant FPROBE_EVENTS? Yes I forgot to add the dependency
> > > on it. But fprobe itself can work because fprobe just pass the ftrace_regs
> > > to the handlers. (Note that exit callback may not work until next patch)
> >
> > No, I mean that fprobe still registers its ftrace ops with the
> > FTRACE_OPS_FL_SAVE_REGS flag:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/fprobe.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n185
> >
> > Which means that __register_ftrace_function will return -EINVAL on
> > builds !WITH_REGS:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/kernel/trace/ftrace.c?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n338
> >
> > As documented here:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/tree/include/linux/ftrace.h?h=topic/fprobe-ftrace-regs&id=2ca022b2753ae0d2a2513c95f7ed5b5b727fb2c4#n188
> >
> > There are two parts to using sparse pt_regs. One is "static": having
> > WITH_ARGS in the config, the second one is "dynamic": a ftrace ops
> > needs to specify that it doesn't want to go through the ftrace
> > trampoline that saves a full pt_regs, by not giving
> > FTRACE_OPS_FL_SAVE_REGS. If we want fprobe to work on builds
> > !WITH_REGS then we should both remove Kconfig dependencies to
> > WITH_REGS (like you've done) but also stop passing this ftrace ops
> > flag.
>
> Said in a different way: there are arches that support both WITH_ARGS
> and WITH_REGS (like x86 actually). They have two ftrace trampolines
> compiled in: ftrace_caller and ftrace_regs_caller, one for each
> usecase. If you register to ftrace with the FTRACE_OPS_FL_SAVE_REGS
> flag you are telling it that what you want is a pt_regs. If you are
> trying to move away from pt_regs and support ftrace_regs in the more
> general case (meaning, in the case where it can contain a sparse
> pt_regs) then you should stop passing that flag so you go through the
> lighter, faster trampoline and test your code in the circumstances
> where ftrace_regs isn't just a regular pt_regs but an actually sparse
> or light data structure.
>
> I hope that makes my thoughts clearer? It's a hairy topic ahah
Ah, I see your point.
static void fprobe_init(struct fprobe *fp)
{
fp->nmissed = 0;
if (fprobe_shared_with_kprobes(fp))
fp->ops.func = fprobe_kprobe_handler;
else
fp->ops.func = fprobe_handler;
fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS; <---- This flag!
}
So it should be FTRACE_OPS_FL_ARGS. Let me fix that.
Thank you!
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, 9 Aug 2023 17:45:29 +0200
Florent Revest <[email protected]> wrote:
> On Wed, Aug 9, 2023 at 4:43 PM Masami Hiramatsu <[email protected]> wrote:
> >
> > > I think there are two things that can be meant with "rethook uses ftrace_regs":
> > >
> > > - rethook callbacks receive a ftrace_regs (that's what you do further down)
> > > - rethook can hook to a traced function using a ftrace_regs (that's
> > > what you use in fprobe now)
> > >
> > > But I think the second proposition shouldn't imply that rethook_hook
> > > can _only_ hook to ftrace_regs. For the kprobe use case, I think there
> > > should also be a rethook_hook_pt_regs() that operates on a pt_regs. We
> > > could have a default implementation of rethook_hook that calls into
> > > the other (or vice versa) on HAVE_FTRACE_REGS_COMPATIBLE_WITH_PT_REGS
> > > but I think it's good to separate these two APIs
> >
> > Yeah, so for simplying the 2nd case, I added this dependency.
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index aff2746c8af2..e321bdb8b22b 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -201,6 +201,7 @@ config KRETPROBE_ON_RETHOOK
> > def_bool y
> > depends on HAVE_RETHOOK
> > depends on KRETPROBES
> > + depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS || !HAVE_DYNAMIC_FTRACE_WITH_ARGS
> > select RETHOOK
> >
> > This is the point why I said that "do not remove kretprobe trampoline".
> > If there is arch dependent kretprobe trampoline, kretprobe does not use
> > the rethook for hooking return. And eventually I would like to remove
> > kretprobe itself (replace it with fprobe + rethook). If so, I don't want
> > to pay more efforts on this part, and keep kretprobe on rethook as it is.
>
> What are your thoughts on kprobe + rethook though ?
Isn't it KRETPROBE_ON_RETHOOK?
> If that's something you think is worth having, then in this case, it
> seems that having a rethook_hook_pt_regs() API would help users.
>
> If that's a frankenstein use case you don't want to support then I
> agree we can live without this API and get away with the cast
> protected by the depends on HAVE_PT_REGS_COMPAT_FTRACE_REGS...
Yeah, it needs to introduce arch_rethook_prepare_pt_regs() for each
arch too.
BTW, I found that I have to update the implementation of
arch_rethook_prepare() for x86. (Use ftrace_get_stack_pointer())
Thank you!
--
Masami Hiramatsu (Google) <[email protected]>
On Wed, 9 Aug 2023 17:38:00 +0200
Florent Revest <[email protected]> wrote:
> On Wed, Aug 9, 2023 at 4:45 PM Masami Hiramatsu <[email protected]> wrote:
> > > > --- a/kernel/trace/trace_fprobe.c
> > > > +++ b/kernel/trace/trace_fprobe.c
> > > > @@ -132,25 +132,30 @@ static int
> > > > process_fetch_insn(struct fetch_insn *code, void *rec, void *dest,
> > > > void *base)
> > > > {
> > > > - struct pt_regs *regs = rec;
> > > > - unsigned long val;
> > > > + struct ftrace_regs *fregs = rec;
> > > > + unsigned long val, *stackp;
> > > > int ret;
> > > >
> > > > retry:
> > > > /* 1st stage: get value from context */
> > > > switch (code->op) {
> > > > case FETCH_OP_STACK:
> > > > - val = regs_get_kernel_stack_nth(regs, code->param);
> > > > + stackp = (unsigned long *)ftrace_regs_get_stack_pointer(fregs);
> > > > + if (((unsigned long)(stackp + code->param) & ~(THREAD_SIZE - 1)) ==
> > > > + ((unsigned long)stackp & ~(THREAD_SIZE - 1)))
> > >
> > > Maybe it'd be worth extracting a local
> > > "ftrace_regs_get_kernel_stack_nth_addr" helper function and/or
> > > "ftrace_regs_within_kernel_stack" ?
> >
> > Yeah, maybe we can make it a generic inline function in linux/ftrace.h.
>
> Or even just above this function if there are low chances it would get
> used elsewhere :)
Thanks, but since regs_get_kernel_stack_nth() is defined in asm/ptrace.h,
I think ftrace_regs_get_kernel_stack_nth() is better defined in
linux/ftrace.h. :)
Thank you!
--
Masami Hiramatsu (Google) <[email protected]>
On Thu, 10 Aug 2023 09:38:45 +0900
Masami Hiramatsu (Google) <[email protected]> wrote:
> > Or even just above this function if there are low chances it would get
> > used elsewhere :)
>
> Thanks, but since regs_get_kernel_stack_nth() is defined in asm/ptrace.h,
> I think ftrace_regs_get_kernel_stack_nth() is better defined in
> linux/ftrace.h. :)
I agree with Masami.
Thanks,
-- Steve
On Thu, 10 Aug 2023 07:13:30 +0900
Masami Hiramatsu (Google) <[email protected]> wrote:
> >
> > I hope that makes my thoughts clearer? It's a hairy topic ahah
>
> Ah, I see your point.
>
> static void fprobe_init(struct fprobe *fp)
> {
> fp->nmissed = 0;
> if (fprobe_shared_with_kprobes(fp))
> fp->ops.func = fprobe_kprobe_handler;
> else
> fp->ops.func = fprobe_handler;
> fp->ops.flags |= FTRACE_OPS_FL_SAVE_REGS; <---- This flag!
> }
>
> So it should be FTRACE_OPS_FL_ARGS. Let me fix that.
Yes, this was the concern that I was bringing up, where I did not see an
advantage of fprobes over kprobes using ftrace, because they both were
saving all registers.
-- Steve