hi,
sending additional fix for symbol resolving in kprobe multi link
requested by Alexei and Andrii [1].
This speeds up bpftrace kprobe attachment, when using pure symbols
(3344 symbols) to attach:
Before:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
After:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
v5 changes:
- added acks [Masami]
- workaround in selftest for RCU warning by filtering out several
functions to attach
v4 changes:
- fix compile issue [kernel test robot]
- added acks [Andrii]
v3 changes:
- renamed kallsyms_lookup_names to ftrace_lookup_symbols
and moved it to ftrace.c [Masami]
- added ack [Andrii]
- couple small test fixes [Andrii]
v2 changes (first version [2]):
- removed the 2 seconds check [Alexei]
- moving/forcing symbols sorting out of kallsyms_lookup_names function [Alexei]
- skipping one array allocation and copy_from_user [Andrii]
- several small fixes [Masami,Andrii]
- build fix [kernel test robot]
thanks,
jirka
[1] https://lore.kernel.org/bpf/CAEf4BzZtQaiUxQ-sm_hH2qKPRaqGHyOfEsW96DxtBHRaKLoL3Q@mail.gmail.com/
[2] https://lore.kernel.org/bpf/[email protected]/
---
Jiri Olsa (5):
kallsyms: Fully export kallsyms_on_each_symbol function
ftrace: Add ftrace_lookup_symbols function
fprobe: Resolve symbols with ftrace_lookup_symbols
bpf: Resolve symbols with ftrace_lookup_symbols for kprobe multi link
selftests/bpf: Add attach bench test
include/linux/ftrace.h | 6 ++++++
include/linux/kallsyms.h | 7 ++++++-
kernel/kallsyms.c | 3 +--
kernel/trace/bpf_trace.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----------------------------------------------
kernel/trace/fprobe.c | 32 ++++++++++++--------------------
kernel/trace/ftrace.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 143 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/progs/kprobe_multi_empty.c | 12 ++++++++++++
8 files changed, 308 insertions(+), 69 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
Using kallsyms_lookup_names function to speed up symbols lookup in
kprobe multi link attachment and replacing with it the current
kprobe_multi_resolve_syms function.
This speeds up bpftrace kprobe attachment:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
After:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
Acked-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
---
kernel/trace/bpf_trace.c | 112 +++++++++++++++++++++++----------------
1 file changed, 66 insertions(+), 46 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index f15b826f9899..7fd11c17558d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2229,6 +2229,59 @@ struct bpf_kprobe_multi_run_ctx {
unsigned long entry_ip;
};
+struct user_syms {
+ const char **syms;
+ char *buf;
+};
+
+static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt)
+{
+ unsigned long __user usymbol;
+ const char **syms = NULL;
+ char *buf = NULL, *p;
+ int err = -ENOMEM;
+ unsigned int i;
+
+ syms = kvmalloc(cnt * sizeof(*syms), GFP_KERNEL);
+ if (!syms)
+ goto error;
+
+ buf = kvmalloc(cnt * KSYM_NAME_LEN, GFP_KERNEL);
+ if (!buf)
+ goto error;
+
+ for (p = buf, i = 0; i < cnt; i++) {
+ if (__get_user(usymbol, usyms + i)) {
+ err = -EFAULT;
+ goto error;
+ }
+ err = strncpy_from_user(p, (const char __user *) usymbol, KSYM_NAME_LEN);
+ if (err == KSYM_NAME_LEN)
+ err = -E2BIG;
+ if (err < 0)
+ goto error;
+ syms[i] = p;
+ p += err + 1;
+ }
+
+ us->syms = syms;
+ us->buf = buf;
+ return 0;
+
+error:
+ if (err) {
+ kvfree(syms);
+ kvfree(buf);
+ }
+ return err;
+}
+
+static void free_user_syms(struct user_syms *us)
+{
+ kvfree(us->syms);
+ kvfree(us->buf);
+}
+
static void bpf_kprobe_multi_link_release(struct bpf_link *link)
{
struct bpf_kprobe_multi_link *kmulti_link;
@@ -2349,53 +2402,12 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long entry_ip,
kprobe_multi_link_prog_run(link, entry_ip, regs);
}
-static int
-kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt,
- unsigned long *addrs)
+static int symbols_cmp(const void *a, const void *b)
{
- unsigned long addr, size;
- const char __user **syms;
- int err = -ENOMEM;
- unsigned int i;
- char *func;
-
- size = cnt * sizeof(*syms);
- syms = kvzalloc(size, GFP_KERNEL);
- if (!syms)
- return -ENOMEM;
+ const char **str_a = (const char **) a;
+ const char **str_b = (const char **) b;
- func = kmalloc(KSYM_NAME_LEN, GFP_KERNEL);
- if (!func)
- goto error;
-
- if (copy_from_user(syms, usyms, size)) {
- err = -EFAULT;
- goto error;
- }
-
- for (i = 0; i < cnt; i++) {
- err = strncpy_from_user(func, syms[i], KSYM_NAME_LEN);
- if (err == KSYM_NAME_LEN)
- err = -E2BIG;
- if (err < 0)
- goto error;
- err = -EINVAL;
- addr = kallsyms_lookup_name(func);
- if (!addr)
- goto error;
- if (!kallsyms_lookup_size_offset(addr, &size, NULL))
- goto error;
- addr = ftrace_location_range(addr, addr + size - 1);
- if (!addr)
- goto error;
- addrs[i] = addr;
- }
-
- err = 0;
-error:
- kvfree(syms);
- kfree(func);
- return err;
+ return strcmp(*str_a, *str_b);
}
int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)
@@ -2441,7 +2453,15 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr
goto error;
}
} else {
- err = kprobe_multi_resolve_syms(usyms, cnt, addrs);
+ struct user_syms us;
+
+ err = copy_user_syms(&us, usyms, cnt);
+ if (err)
+ goto error;
+
+ sort(us.syms, cnt, sizeof(*us.syms), symbols_cmp, NULL);
+ err = ftrace_lookup_symbols(us.syms, cnt, addrs);
+ free_user_syms(&us);
if (err)
goto error;
}
--
2.35.1
Adding test that reads all functions from ftrace available_filter_functions
file and attach them all through kprobe_multi API.
It also prints stats info with -v option, like on my setup:
test_bench_attach: found 48712 functions
test_bench_attach: attached in 1.069s
test_bench_attach: detached in 0.373s
Acked-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
---
.../bpf/prog_tests/kprobe_multi_test.c | 143 ++++++++++++++++++
.../selftests/bpf/progs/kprobe_multi_empty.c | 12 ++
2 files changed, 155 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
index c56db65d4c15..816eacededd1 100644
--- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
+++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c
@@ -2,6 +2,9 @@
#include <test_progs.h>
#include "kprobe_multi.skel.h"
#include "trace_helpers.h"
+#include "kprobe_multi_empty.skel.h"
+#include "bpf/libbpf_internal.h"
+#include "bpf/hashmap.h"
static void kprobe_multi_test_run(struct kprobe_multi *skel, bool test_return)
{
@@ -301,6 +304,144 @@ static void test_attach_api_fails(void)
kprobe_multi__destroy(skel);
}
+static inline __u64 get_time_ns(void)
+{
+ struct timespec t;
+
+ clock_gettime(CLOCK_MONOTONIC, &t);
+ return (__u64) t.tv_sec * 1000000000 + t.tv_nsec;
+}
+
+static size_t symbol_hash(const void *key, void *ctx __maybe_unused)
+{
+ return str_hash((const char *) key);
+}
+
+static bool symbol_equal(const void *key1, const void *key2, void *ctx __maybe_unused)
+{
+ return strcmp((const char *) key1, (const char *) key2) == 0;
+}
+
+static int get_syms(char ***symsp, size_t *cntp)
+{
+ size_t cap = 0, cnt = 0, i;
+ char *name, **syms = NULL;
+ struct hashmap *map;
+ char buf[256];
+ FILE *f;
+ int err;
+
+ /*
+ * The available_filter_functions contains many duplicates,
+ * but other than that all symbols are usable in kprobe multi
+ * interface.
+ * Filtering out duplicates by using hashmap__add, which won't
+ * add existing entry.
+ */
+ f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r");
+ if (!f)
+ return -EINVAL;
+
+ map = hashmap__new(symbol_hash, symbol_equal, NULL);
+ if (IS_ERR(map))
+ goto error;
+
+ while (fgets(buf, sizeof(buf), f)) {
+ /* skip modules */
+ if (strchr(buf, '['))
+ continue;
+ if (sscanf(buf, "%ms$*[^\n]\n", &name) != 1)
+ continue;
+ /*
+ * We attach to almost all kernel functions and some of them
+ * will cause 'suspicious RCU usage' when fprobe is attached
+ * to them. Filter out the current culprits - arch_cpu_idle
+ * and rcu_* functions.
+ */
+ if (!strcmp(name, "arch_cpu_idle"))
+ continue;
+ if (!strncmp(name, "rcu_", 4))
+ continue;
+ err = hashmap__add(map, name, NULL);
+ if (err) {
+ free(name);
+ if (err == -EEXIST)
+ continue;
+ goto error;
+ }
+ err = libbpf_ensure_mem((void **) &syms, &cap,
+ sizeof(*syms), cnt + 1);
+ if (err) {
+ free(name);
+ goto error;
+ }
+ syms[cnt] = name;
+ cnt++;
+ }
+
+ *symsp = syms;
+ *cntp = cnt;
+
+error:
+ fclose(f);
+ hashmap__free(map);
+ if (err) {
+ for (i = 0; i < cnt; i++)
+ free(syms[cnt]);
+ free(syms);
+ }
+ return err;
+}
+
+static void test_bench_attach(void)
+{
+ LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+ struct kprobe_multi_empty *skel = NULL;
+ long attach_start_ns, attach_end_ns;
+ long detach_start_ns, detach_end_ns;
+ double attach_delta, detach_delta;
+ struct bpf_link *link = NULL;
+ char **syms = NULL;
+ size_t cnt, i;
+
+ if (!ASSERT_OK(get_syms(&syms, &cnt), "get_syms"))
+ return;
+
+ skel = kprobe_multi_empty__open_and_load();
+ if (!ASSERT_OK_PTR(skel, "kprobe_multi_empty__open_and_load"))
+ goto cleanup;
+
+ opts.syms = (const char **) syms;
+ opts.cnt = cnt;
+
+ attach_start_ns = get_time_ns();
+ link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_empty,
+ NULL, &opts);
+ attach_end_ns = get_time_ns();
+
+ if (!ASSERT_OK_PTR(link, "bpf_program__attach_kprobe_multi_opts"))
+ goto cleanup;
+
+ detach_start_ns = get_time_ns();
+ bpf_link__destroy(link);
+ detach_end_ns = get_time_ns();
+
+ attach_delta = (attach_end_ns - attach_start_ns) / 1000000000.0;
+ detach_delta = (detach_end_ns - detach_start_ns) / 1000000000.0;
+
+ printf("%s: found %lu functions\n", __func__, cnt);
+ printf("%s: attached in %7.3lfs\n", __func__, attach_delta);
+ printf("%s: detached in %7.3lfs\n", __func__, detach_delta);
+
+cleanup:
+ kprobe_multi_empty__destroy(skel);
+ if (syms) {
+ for (i = 0; i < cnt; i++)
+ free(syms[i]);
+ free(syms);
+ }
+}
+
void test_kprobe_multi_test(void)
{
if (!ASSERT_OK(load_kallsyms(), "load_kallsyms"))
@@ -320,4 +461,6 @@ void test_kprobe_multi_test(void)
test_attach_api_syms();
if (test__start_subtest("attach_api_fails"))
test_attach_api_fails();
+ if (test__start_subtest("bench_attach"))
+ test_bench_attach();
}
diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
new file mode 100644
index 000000000000..e76e499aca39
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+SEC("kprobe.multi/")
+int test_kprobe_empty(struct pt_regs *ctx)
+{
+ return 0;
+}
--
2.35.1
Fully exporting kallsyms_on_each_symbol function, so it can be used
in following changes.
Rather than adding another ifdef option let's export the function
completely (when CONFIG_KALLSYMS option is defined).
Cc: Christoph Hellwig <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
---
include/linux/kallsyms.h | 7 ++++++-
kernel/kallsyms.c | 2 --
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index ce1bd2fbf23e..89f063651192 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -65,11 +65,11 @@ static inline void *dereference_symbol_descriptor(void *ptr)
return ptr;
}
+#ifdef CONFIG_KALLSYMS
int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
unsigned long),
void *data);
-#ifdef CONFIG_KALLSYMS
/* Lookup the address for a symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name);
@@ -163,6 +163,11 @@ static inline bool kallsyms_show_value(const struct cred *cred)
return false;
}
+static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, unsigned long),
+ void *data)
+{
+ return -EOPNOTSUPP;
+}
#endif /*CONFIG_KALLSYMS*/
static inline void print_ip_sym(const char *loglvl, unsigned long ip)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 79f2eb617a62..fdfd308bebc4 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -228,7 +228,6 @@ unsigned long kallsyms_lookup_name(const char *name)
return module_kallsyms_lookup_name(name);
}
-#ifdef CONFIG_LIVEPATCH
/*
* Iterate over all symbols in vmlinux. For symbols from modules use
* module_kallsyms_on_each_symbol instead.
@@ -251,7 +250,6 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
}
return 0;
}
-#endif /* CONFIG_LIVEPATCH */
static unsigned long get_symbol_pos(unsigned long addr,
unsigned long *symbolsize,
--
2.35.1
Using ftrace_lookup_symbols to speed up symbols lookup
in register_fprobe_syms API.
Acked-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
---
kernel/trace/fprobe.c | 32 ++++++++++++--------------------
1 file changed, 12 insertions(+), 20 deletions(-)
diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 89d9f994ebb0..aac63ca9c3d1 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -85,39 +85,31 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data,
}
NOKPROBE_SYMBOL(fprobe_exit_handler);
+static int symbols_cmp(const void *a, const void *b)
+{
+ const char **str_a = (const char **) a;
+ const char **str_b = (const char **) b;
+
+ return strcmp(*str_a, *str_b);
+}
+
/* Convert ftrace location address from symbols */
static unsigned long *get_ftrace_locations(const char **syms, int num)
{
- unsigned long addr, size;
unsigned long *addrs;
- int i;
/* Convert symbols to symbol address */
addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
if (!addrs)
return ERR_PTR(-ENOMEM);
- for (i = 0; i < num; i++) {
- addr = kallsyms_lookup_name(syms[i]);
- if (!addr) /* Maybe wrong symbol */
- goto error;
-
- /* Convert symbol address to ftrace location. */
- if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
- goto error;
+ /* ftrace_lookup_symbols expects sorted symbols */
+ sort(syms, num, sizeof(*syms), symbols_cmp, NULL);
- addr = ftrace_location_range(addr, addr + size - 1);
- if (!addr) /* No dynamic ftrace there. */
- goto error;
+ if (!ftrace_lookup_symbols(syms, num, addrs))
+ return addrs;
- addrs[i] = addr;
- }
-
- return addrs;
-
-error:
kfree(addrs);
-
return ERR_PTR(-ENOENT);
}
--
2.35.1
I'm not sure how I'm supposed to review just a patch 1 out of 5
without the rest.
What I can ѕay without the rest is that the subject line is wrong
as nothing is exported, and that you are adding an overly long line.
On Mon, May 09, 2022 at 08:01:04AM +0200, Christoph Hellwig wrote:
> I'm not sure how I'm supposed to review just a patch 1 out of 5
> without the rest.
sorry, I did not think the rest was needed, full patchset is in here:
https://lore.kernel.org/bpf/[email protected]/
I'll cc you on full patchset in next version
>
> What I can ѕay without the rest is that the subject line is wrong
> as nothing is exported, and that you are adding an overly long line.
right, how about the change below?
thanks,
jirka
---
Subject: [PATCH] kallsyms: Make kallsyms_on_each_symbol generally available
Making kallsyms_on_each_symbol generally available, so it can be
used outside CONFIG_LIVEPATCH option in following changes.
Rather than adding another ifdef option let's make the function
generally available (when CONFIG_KALLSYMS option is defined).
Cc: Christoph Hellwig <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Jiri Olsa <[email protected]>
---
include/linux/kallsyms.h | 7 ++++++-
kernel/kallsyms.c | 2 --
2 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index ce1bd2fbf23e..ad39636e0c3f 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -65,11 +65,11 @@ static inline void *dereference_symbol_descriptor(void *ptr)
return ptr;
}
+#ifdef CONFIG_KALLSYMS
int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
unsigned long),
void *data);
-#ifdef CONFIG_KALLSYMS
/* Lookup the address for a symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name);
@@ -163,6 +163,11 @@ static inline bool kallsyms_show_value(const struct cred *cred)
return false;
}
+static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
+ unsigned long), void *data)
+{
+ return -EOPNOTSUPP;
+}
#endif /*CONFIG_KALLSYMS*/
static inline void print_ip_sym(const char *loglvl, unsigned long ip)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 79f2eb617a62..fdfd308bebc4 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -228,7 +228,6 @@ unsigned long kallsyms_lookup_name(const char *name)
return module_kallsyms_lookup_name(name);
}
-#ifdef CONFIG_LIVEPATCH
/*
* Iterate over all symbols in vmlinux. For symbols from modules use
* module_kallsyms_on_each_symbol instead.
@@ -251,7 +250,6 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
}
return 0;
}
-#endif /* CONFIG_LIVEPATCH */
static unsigned long get_symbol_pos(unsigned long addr,
unsigned long *symbolsize,
--
2.35.3