When using the function_graph tracer to analyze system call failures,
it can be time-consuming to analyze the trace logs and locate the kernel
function that first returns an error. This change aims to simplify the
process by recording the function return value to the 'retval' member of
'ftrace_graph_ent' and printing it when outputing the trace log.
Note that even if a function's return type is void, a return value will
still be printed, so it should be ignored. If you care about this, the
BTF file can be used to obtain the details of function return type. We
can implement a tool to process the trace log and display the return
value based on its actual type.
Here is an example:
...
1) | cgroup_attach_task() {
1) | cgroup_migrate_add_src() {
1) 1.403 us | cset_cgroup_from_root(); /* = 0xffff93fc86f58010 */
1) 2.154 us | } /* cgroup_migrate_add_src = 0xffffb286c1297d00 */
1) ! 386.538 us | cgroup_migrate_prepare_dst(); /* = 0x0 */
1) | cgroup_migrate() {
1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
1) | cgroup_migrate_execute() {
1) | cpu_cgroup_can_attach() {
1) | cgroup_taskset_first() {
1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */
1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */
1) 4.369 us | } /* cgroup_migrate_execute = -22 */
1) 7.143 us | } /* cgroup_migrate = -22 */
1) | cgroup_migrate_finish() {
1) 0.411 us | put_css_set_locked(); /* = 0x8 */
1) + 62.397 us | put_css_set_locked(); /* = 0x80000001 */
1) + 64.742 us | } /* cgroup_migrate_finish = 0x80000000 */
1) ! 465.605 us | } /* cgroup_attach_task = -22 */
...
After processing the above trace logs using BTF information:
...
1) | cgroup_attach_task() {
1) | cgroup_migrate_add_src() {
1) 1.403 us | cset_cgroup_from_root(); /* = 0xffff93fc86f58010 */
1) 2.154 us | } /* cgroup_migrate_add_src */
1) ! 386.538 us | cgroup_migrate_prepare_dst(); /* = 0 */
1) | cgroup_migrate() {
1) 0.651 us | cgroup_migrate_add_task();
1) | cgroup_migrate_execute() {
1) | cpu_cgroup_can_attach() {
1) | cgroup_taskset_first() {
1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
1) 0.380 us | sched_rt_can_attach(); /* = 0 */
1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */
1) 4.369 us | } /* cgroup_migrate_execute = -22 */
1) 7.143 us | } /* cgroup_migrate = -22 */
1) | cgroup_migrate_finish() {
1) 0.411 us | put_css_set_locked();
1) + 62.397 us | put_css_set_locked();
1) + 64.742 us | } /* cgroup_migrate_finish */
1) ! 465.605 us | } /* cgroup_attach_task = -22 */
...
---
v9:
- Fix align issues in ARM asm code
- Fix align issues in LoongArch asm code
- Update commit messages
- Update comments for ftrace_return_to_handler
v8:
- Fix issues in ARM64 asm code
- Fix issues in selftest
- Add some comments on CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
- Make CONFIG_FUNCTION_GRAPH_RETVAL switable
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
v7:
- Rename trace option 'graph_retval_hex' to 'funcgraph-retval-hex'
- Introduce a new structure fgraph_ret_regs for each architecture to
hold return registers
- Separate each architecture modification info individual patches
- Add a test case for funcgraph-retval
- Update documentation description
- Support LoongArch
v6:
- Remove the conversion code for short and char types, because these
two types are rarely used to store an error code.
- Modify the limitations for funcgraph-retval
- Optimize the English expression
v5:
- Pass both the return values to ftrace_return_to_handler
- Modify the parameter sequence of ftrace_return_to_handler to
decrease the modification of assembly code, thanks to Russell King
- Wrap __ftrace_return_to_handler with ftrace_return_to_handler
for compatible
- Describe the limitations of funcgraph-retval
v4:
- Modify commit message
- Introduce new option graph_retval_hex to control display format
- Introduce macro CONFIG_FUNCTION_GRAPH_RETVAL and
CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
- Add related arch maintainers to review
v3:
- Modify the commit message: add trace logs processed with the btf tool
v2:
- Modify the commit message: use BTF to get the return type of function
Donglin Peng (8):
function_graph: Support recording and printing the return value of
function
tracing: Add documentation for funcgraph-retval and
funcgraph-retval-hex
ARM: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
riscv: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL
selftests/ftrace: Add funcgraph-retval test case
Documentation/trace/ftrace.rst | 74 +++++++++++++++
arch/arm/Kconfig | 1 +
arch/arm/include/asm/ftrace.h | 20 ++++
arch/arm/kernel/asm-offsets.c | 6 +-
arch/arm/kernel/entry-ftrace.S | 10 +-
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/ftrace.h | 20 ++++
arch/arm64/kernel/asm-offsets.c | 12 +++
arch/arm64/kernel/entry-ftrace.S | 27 +++---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/ftrace.h | 20 ++++
arch/loongarch/kernel/asm-offsets.c | 12 +++
arch/loongarch/kernel/mcount.S | 14 +--
arch/loongarch/kernel/mcount_dyn.S | 15 +--
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ftrace.h | 19 ++++
arch/riscv/kernel/mcount.S | 7 +-
arch/x86/Kconfig | 1 +
arch/x86/include/asm/ftrace.h | 18 ++++
arch/x86/kernel/ftrace_32.S | 8 +-
arch/x86/kernel/ftrace_64.S | 7 +-
include/linux/ftrace.h | 3 +
kernel/trace/Kconfig | 15 +++
kernel/trace/fgraph.c | 23 ++++-
kernel/trace/trace.h | 2 +
kernel/trace/trace_entries.h | 26 ++++++
kernel/trace/trace_functions_graph.c | 93 +++++++++++++++++--
.../ftrace/test.d/ftrace/fgraph-retval.tc | 39 ++++++++
28 files changed, 441 insertions(+), 54 deletions(-)
create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
--
2.25.1
Analyzing system call failures with the function_graph tracer can be a
time-consuming process, particularly when locating the kernel function
that first returns an error in the trace logs. This change aims to
simplify the process by recording the function return value to the
'retval' member of 'ftrace_graph_ent' and printing it when outputting
the trace log.
We have introduced new trace options: funcgraph-retval and
funcgraph-retval-hex. The former controls whether to display the return
value, while the latter controls the display format.
Please note that even if a function's return type is void, a return
value will still be printed. You can simply ignore it.
This patch only establishes the fundamental infrastructure. Subsequent
patches will make this feature available on some commonly used processor
architectures.
Here is an example:
I attempted to attach the demo process to a cpu cgroup, but it failed:
echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
-bash: echo: write error: Invalid argument
The strace logs indicate that the write system call returned -EINVAL(-22):
...
write(1, "273\n", 4) = -1 EINVAL (Invalid argument)
...
To capture trace logs during a write system call, use the following
commands:
cd /sys/kernel/debug/tracing/
echo 0 > tracing_on
echo > trace
echo *sys_write > set_graph_function
echo *spin* > set_graph_notrace
echo *rcu* >> set_graph_notrace
echo *alloc* >> set_graph_notrace
echo preempt* >> set_graph_notrace
echo kfree* >> set_graph_notrace
echo $$ > set_ftrace_pid
echo function_graph > current_tracer
echo 1 > options/funcgraph-retval
echo 0 > options/funcgraph-retval-hex
echo 1 > tracing_on
echo `pidof demo` > /sys/fs/cgroup/cpu/test/tasks
echo 0 > tracing_on
cat trace > ~/trace.log
To locate the root cause, search for error code -22 directly in the file
trace.log and identify the first function that returned -22. Once you
have identified this function, examine its code to determine the root
cause.
For example, in the trace log below, cpu_cgroup_can_attach
returned -22 first, so we can focus our analysis on this function to
identify the root cause.
...
1) | cgroup_migrate() {
1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
1) | cgroup_migrate_execute() {
1) | cpu_cgroup_can_attach() {
1) | cgroup_taskset_first() {
1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */
1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */
1) 4.369 us | } /* cgroup_migrate_execute = -22 */
1) 7.143 us | } /* cgroup_migrate = -22 */
...
Tested-by: Florian Kauer <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Update comments for ftrace_return_to_handler
v8:
- Add some comments on CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
- Make CONFIG_FUNCTION_GRAPH_RETVAL switable
v7:
- Rename trace option 'graph_retval_hex' to 'funcgraph-retval-hex'
- Separate each architecture modification info individual patches
- Introduce a new structure fgraph_ret_regs for each architecture to
hold return registers
v6:
- Remove the conversion code for short and char types, because these
two types are rarely used to store an error code.
v5:
- Pass both the return values to ftrace_return_to_handler
- Modify the parameter sequence of ftrace_return_to_handler to
decrease the modification of assembly code, thanks to Russell King
- Wrap __ftrace_return_to_handler with ftrace_return_to_handler
for compatible
v4:
- Modify commit message
- Introduce new option graph_retval_hex to control display format
- Introduce macro CONFIG_FUNCTION_GRAPH_RETVAL and
CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
- Add related arch maintainers to review
v3:
- Modify the commit message: add trace logs processed with the btf tool
v2:
- Modify the commit message: use BTF to get the return type of function
---
include/linux/ftrace.h | 3 +
kernel/trace/Kconfig | 15 +++++
kernel/trace/fgraph.c | 23 ++++++-
kernel/trace/trace.h | 2 +
kernel/trace/trace_entries.h | 26 ++++++++
kernel/trace/trace_functions_graph.c | 93 +++++++++++++++++++++++++---
6 files changed, 151 insertions(+), 11 deletions(-)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 366c730beaa3..be662a11cd13 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1032,6 +1032,9 @@ struct ftrace_graph_ent {
*/
struct ftrace_graph_ret {
unsigned long func; /* Current function */
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+ unsigned long retval;
+#endif
int depth;
/* Number of functions that overran the depth limit for current task */
unsigned int overrun;
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index a856d4a34c67..87de5964c81d 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -31,6 +31,9 @@ config HAVE_FUNCTION_GRAPH_TRACER
help
See Documentation/trace/ftrace-design.rst
+config HAVE_FUNCTION_GRAPH_RETVAL
+ bool
+
config HAVE_DYNAMIC_FTRACE
bool
help
@@ -227,6 +230,18 @@ config FUNCTION_GRAPH_TRACER
the return value. This is done by setting the current return
address on the current task structure into a stack of calls.
+config FUNCTION_GRAPH_RETVAL
+ bool "Function Graph Return Value"
+ depends on HAVE_FUNCTION_GRAPH_RETVAL
+ depends on FUNCTION_GRAPH_TRACER
+ default n
+ help
+ Support recording and printing the function return value when
+ using function graph tracer. It can be helpful to locate functions
+ that return errors. This feature is off by default, and you can
+ enable it via the trace option funcgraph-retval.
+ See Documentation/trace/ftrace.rst
+
config DYNAMIC_FTRACE
bool "enable/disable function tracing dynamically"
depends on FUNCTION_TRACER
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 218cd95bf8e4..170ec9429efb 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -240,12 +240,16 @@ static struct notifier_block ftrace_suspend_notifier = {
* Send the trace to the ring-buffer.
* @return the original return address.
*/
-unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
+static unsigned long __ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs,
+ unsigned long frame_pointer)
{
struct ftrace_graph_ret trace;
unsigned long ret;
ftrace_pop_return_trace(&trace, &ret, frame_pointer);
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+ trace.retval = fgraph_ret_regs_return_value(ret_regs);
+#endif
trace.rettime = trace_clock_local();
ftrace_graph_return(&trace);
/*
@@ -266,6 +270,23 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
return ret;
}
+/*
+ * After all architecures have selected HAVE_FUNCTION_GRAPH_RETVAL, we can
+ * leave only ftrace_return_to_handler(ret_regs).
+ */
+#ifdef CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
+unsigned long ftrace_return_to_handler(struct fgraph_ret_regs *ret_regs)
+{
+ return __ftrace_return_to_handler(ret_regs,
+ fgraph_ret_regs_frame_pointer(ret_regs));
+}
+#else
+unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
+{
+ return __ftrace_return_to_handler(NULL, frame_pointer);
+}
+#endif
+
/**
* ftrace_graph_get_ret_stack - return the entry of the shadow stack
* @task: The task to read the shadow stack from
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 616e1aa1c4da..0a3c4582df10 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -831,6 +831,8 @@ static __always_inline bool ftrace_hash_empty(struct ftrace_hash *hash)
#define TRACE_GRAPH_PRINT_TAIL 0x100
#define TRACE_GRAPH_SLEEP_TIME 0x200
#define TRACE_GRAPH_GRAPH_TIME 0x400
+#define TRACE_GRAPH_PRINT_RETVAL 0x800
+#define TRACE_GRAPH_PRINT_RETVAL_HEX 0x1000
#define TRACE_GRAPH_PRINT_FILL_SHIFT 28
#define TRACE_GRAPH_PRINT_FILL_MASK (0x3 << TRACE_GRAPH_PRINT_FILL_SHIFT)
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index cd41e863b51c..340b2fa98218 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -86,6 +86,30 @@ FTRACE_ENTRY_PACKED(funcgraph_entry, ftrace_graph_ent_entry,
);
/* Function return entry */
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+
+FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
+
+ TRACE_GRAPH_RET,
+
+ F_STRUCT(
+ __field_struct( struct ftrace_graph_ret, ret )
+ __field_packed( unsigned long, ret, func )
+ __field_packed( unsigned long, ret, retval )
+ __field_packed( int, ret, depth )
+ __field_packed( unsigned int, ret, overrun )
+ __field_packed( unsigned long long, ret, calltime)
+ __field_packed( unsigned long long, ret, rettime )
+ ),
+
+ F_printk("<-- %ps (%d) (start: %llx end: %llx) over: %d retval: %lx",
+ (void *)__entry->func, __entry->depth,
+ __entry->calltime, __entry->rettime,
+ __entry->depth, __entry->retval)
+);
+
+#else
+
FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
TRACE_GRAPH_RET,
@@ -105,6 +129,8 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
__entry->depth)
);
+#endif
+
/*
* Context switch trace entry - which task (and prio) we switched from/to:
*
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 203204cadf92..c35fbaab2a47 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -58,6 +58,12 @@ static struct tracer_opt trace_opts[] = {
{ TRACER_OPT(funcgraph-irqs, TRACE_GRAPH_PRINT_IRQS) },
/* Display function name after trailing } */
{ TRACER_OPT(funcgraph-tail, TRACE_GRAPH_PRINT_TAIL) },
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+ /* Display function return value ? */
+ { TRACER_OPT(funcgraph-retval, TRACE_GRAPH_PRINT_RETVAL) },
+ /* Display function return value in hexadecimal format ? */
+ { TRACER_OPT(funcgraph-retval-hex, TRACE_GRAPH_PRINT_RETVAL_HEX) },
+#endif
/* Include sleep time (scheduled out) between entry and return */
{ TRACER_OPT(sleep-time, TRACE_GRAPH_SLEEP_TIME) },
@@ -619,6 +625,56 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
trace_seq_puts(s, "| ");
}
+#ifdef CONFIG_FUNCTION_GRAPH_RETVAL
+
+#define __TRACE_GRAPH_PRINT_RETVAL TRACE_GRAPH_PRINT_RETVAL
+
+static void print_graph_retval(struct trace_seq *s, unsigned long retval,
+ bool leaf, void *func, bool hex_format)
+{
+ unsigned long err_code = 0;
+
+ if (retval == 0 || hex_format)
+ goto done;
+
+ /* Check if the return value matches the negative format */
+ if (IS_ENABLED(CONFIG_64BIT) && (retval & BIT(31)) &&
+ (((u64)retval) >> 32) == 0) {
+ /* sign extension */
+ err_code = (unsigned long)(s32)retval;
+ } else {
+ err_code = retval;
+ }
+
+ if (!IS_ERR_VALUE(err_code))
+ err_code = 0;
+
+done:
+ if (leaf) {
+ if (hex_format || (err_code == 0))
+ trace_seq_printf(s, "%ps(); /* = 0x%lx */\n",
+ func, retval);
+ else
+ trace_seq_printf(s, "%ps(); /* = %ld */\n",
+ func, err_code);
+ } else {
+ if (hex_format || (err_code == 0))
+ trace_seq_printf(s, "} /* %ps = 0x%lx */\n",
+ func, retval);
+ else
+ trace_seq_printf(s, "} /* %ps = %ld */\n",
+ func, err_code);
+ }
+}
+
+#else
+
+#define __TRACE_GRAPH_PRINT_RETVAL 0
+
+#define print_graph_retval(_seq, _retval, _leaf, _func, _format) do {} while (0)
+
+#endif
+
/* Case of a leaf function on its call entry */
static enum print_line_t
print_graph_entry_leaf(struct trace_iterator *iter,
@@ -663,7 +719,15 @@ print_graph_entry_leaf(struct trace_iterator *iter,
for (i = 0; i < call->depth * TRACE_GRAPH_INDENT; i++)
trace_seq_putc(s, ' ');
- trace_seq_printf(s, "%ps();\n", (void *)call->func);
+ /*
+ * Write out the function return value if the option function-retval is
+ * enabled.
+ */
+ if (flags & __TRACE_GRAPH_PRINT_RETVAL)
+ print_graph_retval(s, graph_ret->retval, true, (void *)call->func,
+ !!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX));
+ else
+ trace_seq_printf(s, "%ps();\n", (void *)call->func);
print_graph_irq(iter, graph_ret->func, TRACE_GRAPH_RET,
cpu, iter->ent->pid, flags);
@@ -942,16 +1006,25 @@ print_graph_return(struct ftrace_graph_ret *trace, struct trace_seq *s,
trace_seq_putc(s, ' ');
/*
- * If the return function does not have a matching entry,
- * then the entry was lost. Instead of just printing
- * the '}' and letting the user guess what function this
- * belongs to, write out the function name. Always do
- * that if the funcgraph-tail option is enabled.
+ * Always write out the function name and its return value if the
+ * function-retval option is enabled.
*/
- if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
- trace_seq_puts(s, "}\n");
- else
- trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
+ if (flags & __TRACE_GRAPH_PRINT_RETVAL) {
+ print_graph_retval(s, trace->retval, false, (void *)trace->func,
+ !!(flags & TRACE_GRAPH_PRINT_RETVAL_HEX));
+ } else {
+ /*
+ * If the return function does not have a matching entry,
+ * then the entry was lost. Instead of just printing
+ * the '}' and letting the user guess what function this
+ * belongs to, write out the function name. Always do
+ * that if the funcgraph-tail option is enabled.
+ */
+ if (func_match && !(flags & TRACE_GRAPH_PRINT_TAIL))
+ trace_seq_puts(s, "}\n");
+ else
+ trace_seq_printf(s, "} /* %ps */\n", (void *)trace->func);
+ }
/* Overrun */
if (flags & TRACE_GRAPH_PRINT_OVERRUN)
--
2.25.1
The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the RISC-V platform.
We introduce a new structure called fgraph_ret_regs for the RISC-V
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address to
the function ftrace_return_to_handler to record the return value.
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Update the commit message
v8:
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
arch/riscv/Kconfig | 1 +
arch/riscv/include/asm/ftrace.h | 19 +++++++++++++++++++
arch/riscv/kernel/mcount.S | 7 +------
3 files changed, 21 insertions(+), 6 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c5e42cc37604..a616af85defb 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -138,6 +138,7 @@ config RISCV
select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && MMU && $(cc-option,-fpatchable-function-entry=8)
select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
+ select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER if !XIP_KERNEL && !PREEMPTION
diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h
index d47d87c2d7e3..8e1b9cfc0619 100644
--- a/arch/riscv/include/asm/ftrace.h
+++ b/arch/riscv/include/asm/ftrace.h
@@ -111,4 +111,23 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec);
#endif /* CONFIG_DYNAMIC_FTRACE */
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+ unsigned long a1;
+ unsigned long a0;
+ unsigned long s0;
+ unsigned long ra;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->a0;
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->s0;
+}
+#endif
+
#endif /* _ASM_RISCV_FTRACE_H */
diff --git a/arch/riscv/kernel/mcount.S b/arch/riscv/kernel/mcount.S
index 30102aadc4d7..8a6e5a9e842a 100644
--- a/arch/riscv/kernel/mcount.S
+++ b/arch/riscv/kernel/mcount.S
@@ -65,13 +65,8 @@ ENTRY(return_to_handler)
* So alternatively we check the *old* frame pointer position, that is, the
* value stored in -16(s0) on entry, and the s0 on return.
*/
-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
- mv t6, s0
-#endif
SAVE_RET_ABI_STATE
-#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
- mv a0, t6
-#endif
+ mv a0, sp
call ftrace_return_to_handler
mv a2, a0
RESTORE_RET_ABI_STATE
--
2.25.1
The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the LoongArch platform.
We introduce a new structure called fgraph_ret_regs for the LoongArch
platform to hold return registers and the frame pointer. We then fill
its content in the return_to_handler and pass its address to the
function ftrace_return_to_handler to record the return value.
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Fix stack pointer align issues
- Update the commit message
v8:
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/include/asm/ftrace.h | 20 ++++++++++++++++++++
arch/loongarch/kernel/asm-offsets.c | 12 ++++++++++++
arch/loongarch/kernel/mcount.S | 14 ++++++++------
arch/loongarch/kernel/mcount_dyn.S | 15 ++++++++-------
5 files changed, 49 insertions(+), 13 deletions(-)
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 7fd51257e0ed..4bf60132869b 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -99,6 +99,7 @@ config LOONGARCH
select HAVE_FAST_GUP
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_ARG_ACCESS_API
+ select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GENERIC_VDSO
diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
index 3418d32d4fc7..01e7f92de03c 100644
--- a/arch/loongarch/include/asm/ftrace.h
+++ b/arch/loongarch/include/asm/ftrace.h
@@ -63,4 +63,24 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
#endif /* CONFIG_FUNCTION_TRACER */
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+ /* a0 - a1 */
+ unsigned long regs[2];
+
+ unsigned long fp;
+ unsigned long __unused;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->fp;
+}
+#endif
+
#endif /* _ASM_LOONGARCH_FTRACE_H */
diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 4bdb203fc66e..fab5bcddeb23 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -12,6 +12,7 @@
#include <asm/cpu-info.h>
#include <asm/ptrace.h>
#include <asm/processor.h>
+#include <asm/ftrace.h>
void output_ptreg_defines(void)
{
@@ -60,6 +61,17 @@ void output_ptreg_defines(void)
BLANK();
}
+
+void output_fgraph_ret_regs_defines(void)
+{
+ COMMENT(" LoongArch fgraph_ret_regs offsets. ");
+ OFFSET(FGRET_REGS_A0, fgraph_ret_regs, regs[0]);
+ OFFSET(FGRET_REGS_A1, fgraph_ret_regs, regs[1]);
+ OFFSET(FGRET_REGS_FP, fgraph_ret_regs, fp);
+ DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
+ BLANK();
+}
+
void output_task_defines(void)
{
COMMENT("LoongArch task_struct offsets.");
diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
index 8cdc1563cd33..cb8e5803de4b 100644
--- a/arch/loongarch/kernel/mcount.S
+++ b/arch/loongarch/kernel/mcount.S
@@ -79,18 +79,20 @@ SYM_FUNC_START(ftrace_graph_caller)
SYM_FUNC_END(ftrace_graph_caller)
SYM_FUNC_START(return_to_handler)
- PTR_ADDI sp, sp, -2 * SZREG
- PTR_S a0, sp, 0
- PTR_S a1, sp, SZREG
+ PTR_ADDI sp, sp, -FGRET_REGS_SIZE
+ PTR_S a0, sp, FGRET_REGS_A0
+ PTR_S a1, sp, FGRET_REGS_A1
+ PTR_S zero, sp, FGRET_REGS_FP
+ move a0, sp
bl ftrace_return_to_handler
/* Restore the real parent address: a0 -> ra */
move ra, a0
- PTR_L a0, sp, 0
- PTR_L a1, sp, SZREG
- PTR_ADDI sp, sp, 2 * SZREG
+ PTR_L a0, sp, FGRET_REGS_A0
+ PTR_L a1, sp, FGRET_REGS_A1
+ PTR_ADDI sp, sp, FGRET_REGS_SIZE
jr ra
SYM_FUNC_END(return_to_handler)
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
index bbabf06244c2..ec24ae1de741 100644
--- a/arch/loongarch/kernel/mcount_dyn.S
+++ b/arch/loongarch/kernel/mcount_dyn.S
@@ -131,18 +131,19 @@ SYM_CODE_END(ftrace_graph_caller)
SYM_CODE_START(return_to_handler)
/* Save return value regs */
- PTR_ADDI sp, sp, -2 * SZREG
- PTR_S a0, sp, 0
- PTR_S a1, sp, SZREG
+ PTR_ADDI sp, sp, -FGRET_REGS_SIZE
+ PTR_S a0, sp, FGRET_REGS_A0
+ PTR_S a1, sp, FGRET_REGS_A1
+ PTR_S zero, sp, FGRET_REGS_FP
- move a0, zero
+ move a0, sp
bl ftrace_return_to_handler
move ra, a0
/* Restore return value regs */
- PTR_L a0, sp, 0
- PTR_L a1, sp, SZREG
- PTR_ADDI sp, sp, 2 * SZREG
+ PTR_L a0, sp, FGRET_REGS_A0
+ PTR_L a1, sp, FGRET_REGS_A1
+ PTR_ADDI sp, sp, FGRET_REGS_SIZE
jr ra
SYM_CODE_END(return_to_handler)
--
2.25.1
The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the ARM64 platform.
We introduce a new structure called fgraph_ret_regs for the ARM64
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address to
the function ftrace_return_to_handler to record the return value.
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Update the commit message
v8:
- Fix issues in ARM64 asm code
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/ftrace.h | 20 ++++++++++++++++++++
arch/arm64/kernel/asm-offsets.c | 12 ++++++++++++
arch/arm64/kernel/entry-ftrace.S | 27 ++++++++++++++-------------
4 files changed, 47 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1023e896d46b..48856d230800 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -195,6 +195,7 @@ config ARM64
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_TRACER
select HAVE_FUNCTION_ERROR_INJECTION
+ select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_GCC_PLUGINS
select HAVE_HW_BREAKPOINT if PERF_EVENTS
diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
index 1c2672bbbf37..5d2fb57e8a5f 100644
--- a/arch/arm64/include/asm/ftrace.h
+++ b/arch/arm64/include/asm/ftrace.h
@@ -170,4 +170,24 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
}
#endif /* ifndef __ASSEMBLY__ */
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+ /* x0 - x7 */
+ unsigned long regs[8];
+
+ unsigned long fp;
+ unsigned long __unused;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->regs[0];
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->fp;
+}
+#endif
+
#endif /* __ASM_FTRACE_H */
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index ae345b06e9f7..f4f774e9a11f 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -198,5 +198,17 @@ int main(void)
#ifdef CONFIG_FUNCTION_TRACER
DEFINE(FTRACE_OPS_FUNC, offsetof(struct ftrace_ops, func));
#endif
+ BLANK();
+ DEFINE(FGRET_REGS_X0, offsetof(struct fgraph_ret_regs, regs[0]));
+ DEFINE(FGRET_REGS_X1, offsetof(struct fgraph_ret_regs, regs[1]));
+ DEFINE(FGRET_REGS_X2, offsetof(struct fgraph_ret_regs, regs[2]));
+ DEFINE(FGRET_REGS_X3, offsetof(struct fgraph_ret_regs, regs[3]));
+ DEFINE(FGRET_REGS_X4, offsetof(struct fgraph_ret_regs, regs[4]));
+ DEFINE(FGRET_REGS_X5, offsetof(struct fgraph_ret_regs, regs[5]));
+ DEFINE(FGRET_REGS_X6, offsetof(struct fgraph_ret_regs, regs[6]));
+ DEFINE(FGRET_REGS_X7, offsetof(struct fgraph_ret_regs, regs[7]));
+ DEFINE(FGRET_REGS_FP, offsetof(struct fgraph_ret_regs, fp));
+ DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
+ BLANK();
return 0;
}
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 350ed81324ac..da1443bcf776 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -270,22 +270,23 @@ SYM_FUNC_END(ftrace_stub_graph)
*/
SYM_CODE_START(return_to_handler)
/* save return value regs */
- sub sp, sp, #64
- stp x0, x1, [sp]
- stp x2, x3, [sp, #16]
- stp x4, x5, [sp, #32]
- stp x6, x7, [sp, #48]
+ sub sp, sp, #FGRET_REGS_SIZE
+ stp x0, x1, [sp, #FGRET_REGS_X0]
+ stp x2, x3, [sp, #FGRET_REGS_X2]
+ stp x4, x5, [sp, #FGRET_REGS_X4]
+ stp x6, x7, [sp, #FGRET_REGS_X6]
+ str x29, [sp, #FGRET_REGS_FP] // parent's fp
- mov x0, x29 // parent's fp
- bl ftrace_return_to_handler// addr = ftrace_return_to_hander(fp);
- mov x30, x0 // restore the original return address
+ mov x0, sp
+ bl ftrace_return_to_handler // addr = ftrace_return_to_hander(regs);
+ mov x30, x0 // restore the original return address
/* restore return value regs */
- ldp x0, x1, [sp]
- ldp x2, x3, [sp, #16]
- ldp x4, x5, [sp, #32]
- ldp x6, x7, [sp, #48]
- add sp, sp, #64
+ ldp x0, x1, [sp, #FGRET_REGS_X0]
+ ldp x2, x3, [sp, #FGRET_REGS_X2]
+ ldp x4, x5, [sp, #FGRET_REGS_X4]
+ ldp x6, x7, [sp, #FGRET_REGS_X6]
+ add sp, sp, #FGRET_REGS_SIZE
ret
SYM_CODE_END(return_to_handler)
--
2.25.1
Add documentation for the two newly introduced options for the
function_graph tracer. The funcgraph-retval option is used to
control whether or not to display the return value, while the
funcgraph-retval-hex option is used to control the display
format of the return value.
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Update limitation description
v7:
- Rename trace option 'graph_retval_hex' to 'funcgraph-retval-hex'
- Update documentation description
v6:
- Modify the limitations for funcgraph-retval
- Optimize the English expression
v5:
- Describe the limitations of funcgraph-retval
---
Documentation/trace/ftrace.rst | 74 ++++++++++++++++++++++++++++++++++
1 file changed, 74 insertions(+)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index b927fb2b94dc..f572ae419219 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -1328,6 +1328,19 @@ Options for function_graph tracer:
only a closing curly bracket "}" is displayed for
the return of a function.
+ funcgraph-retval
+ When set, the return value of each traced function
+ will be printed after an equal sign "=". By default
+ this is off.
+
+ funcgraph-retval-hex
+ When set, the return value will always be printed
+ in hexadecimal format. If the option is not set and
+ the return value is an error code, it will be printed
+ in signed decimal format; otherwise it will also be
+ printed in hexadecimal format. By default, this option
+ is off.
+
sleep-time
When running function graph tracer, to include
the time a task schedules out in its function.
@@ -2673,6 +2686,67 @@ It is default disabled.
0) 1.757 us | } /* kmem_cache_free() */
0) 2.861 us | } /* putname() */
+The return value of each traced function can be displayed after
+an equal sign "=". When encountering system call failures, it
+can be verfy helpful to quickly locate the function that first
+returns an error code.
+
+ - hide: echo nofuncgraph-retval > trace_options
+ - show: echo funcgraph-retval > trace_options
+
+ Example with funcgraph-retval::
+
+ 1) | cgroup_migrate() {
+ 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
+ 1) | cgroup_migrate_execute() {
+ 1) | cpu_cgroup_can_attach() {
+ 1) | cgroup_taskset_first() {
+ 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
+ 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
+ 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */
+ 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */
+ 1) 4.369 us | } /* cgroup_migrate_execute = -22 */
+ 1) 7.143 us | } /* cgroup_migrate = -22 */
+
+The above example shows that the function cpu_cgroup_can_attach
+returned the error code -22 firstly, then we can read the code
+of this function to get the root cause.
+
+When the option funcgraph-retval-hex is not set, the return value can
+be displayed in a smart way. Specifically, if it is an error code,
+it will be printed in signed decimal format, otherwise it will
+printed in hexadecimal format.
+
+ - smart: echo nofuncgraph-retval-hex > trace_options
+ - hexadecimal always: echo funcgraph-retval-hex > trace_options
+
+ Example with funcgraph-retval-hex::
+
+ 1) | cgroup_migrate() {
+ 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */
+ 1) | cgroup_migrate_execute() {
+ 1) | cpu_cgroup_can_attach() {
+ 1) | cgroup_taskset_first() {
+ 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */
+ 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */
+ 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */
+ 1) 2.335 us | } /* cpu_cgroup_can_attach = 0xffffffea */
+ 1) 4.369 us | } /* cgroup_migrate_execute = 0xffffffea */
+ 1) 7.143 us | } /* cgroup_migrate = 0xffffffea */
+
+At present, there are some limitations when using the funcgraph-retval
+option, and these limitations will be eliminated in the future:
+
+- Even if the function return type is void, a return value will still
+ be printed, and you can just ignore it.
+
+- Even if return values are stored in multiple registers, only the
+ value contained in the first register will be recorded and printed.
+ To illustrate, in the x86 architecture, eax and edx are used to store
+ a 64-bit return value, with the lower 32 bits saved in eax and the
+ upper 32 bits saved in edx. However, only the value stored in eax
+ will be recorded and printed.
+
You can put some comments on specific functions by using
trace_printk() For example, if you want to put a comment inside
the __might_sleep() function, you just have to include
--
2.25.1
The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the x86 platform.
We introduce a new structure called fgraph_ret_regs for the x86
platform to hold return registers and the frame pointer. We then
fill its content in the return_to_handler and pass its address
to the function ftrace_return_to_handler to record the return
value.
Signed-off-by: Donglin Peng <[email protected]>
---
v9:
- Update the commit message
v8:
- Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/ftrace.h | 18 ++++++++++++++++++
arch/x86/kernel/ftrace_32.S | 8 +++++---
arch/x86/kernel/ftrace_64.S | 7 ++++---
4 files changed, 28 insertions(+), 6 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a825bf031f49..956cc988bdf9 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -214,6 +214,7 @@ config X86
select HAVE_FAST_GUP
select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE
select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_GRAPH_TRACER if X86_32 || (X86_64 && DYNAMIC_FTRACE)
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 5061ac98ffa1..0b7cda39f29b 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -147,4 +147,22 @@ static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
#endif /* !COMPILE_OFFSETS */
#endif /* !__ASSEMBLY__ */
+#ifndef __ASSEMBLY__
+struct fgraph_ret_regs {
+ unsigned long ax;
+ unsigned long dx;
+ unsigned long bp;
+};
+
+static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->ax;
+}
+
+static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
+{
+ return ret_regs->bp;
+}
+#endif
+
#endif /* _ASM_X86_FTRACE_H */
diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
index a0ed0e4a2c0c..5a9cc723f81f 100644
--- a/arch/x86/kernel/ftrace_32.S
+++ b/arch/x86/kernel/ftrace_32.S
@@ -182,12 +182,14 @@ SYM_CODE_END(ftrace_graph_caller)
.globl return_to_handler
return_to_handler:
- pushl %eax
+ pushl $0
pushl %edx
- movl $0, %eax
+ pushl %eax
+ movl %esp, %eax
call ftrace_return_to_handler
movl %eax, %ecx
- popl %edx
popl %eax
+ popl %edx
+ addl $4, %esp # skip ebp
JMP_NOSPEC ecx
#endif
diff --git a/arch/x86/kernel/ftrace_64.S b/arch/x86/kernel/ftrace_64.S
index fb4f1e01b64a..ef78c0bbae62 100644
--- a/arch/x86/kernel/ftrace_64.S
+++ b/arch/x86/kernel/ftrace_64.S
@@ -344,12 +344,13 @@ STACK_FRAME_NON_STANDARD_FP(__fentry__)
SYM_CODE_START(return_to_handler)
UNWIND_HINT_EMPTY
ANNOTATE_NOENDBR
- subq $16, %rsp
+ subq $24, %rsp
/* Save the return values */
movq %rax, (%rsp)
movq %rdx, 8(%rsp)
- movq %rbp, %rdi
+ movq %rbp, 16(%rsp)
+ movq %rsp, %rdi
call ftrace_return_to_handler
@@ -357,7 +358,7 @@ SYM_CODE_START(return_to_handler)
movq 8(%rsp), %rdx
movq (%rsp), %rax
- addq $16, %rsp
+ addq $24, %rsp
/*
* Jump back to the old return address. This cannot be JMP_NOSPEC rdi
* since IBT would demand that contain ENDBR, which simply isn't so for
--
2.25.1
Add a test case for the funcgraph-retval and funcgraph-retval-hex
trace options.
Signed-off-by: Donglin Peng <[email protected]>
---
v8:
- Fix issues in selftest
---
.../ftrace/test.d/ftrace/fgraph-retval.tc | 39 +++++++++++++++++++
1 file changed, 39 insertions(+)
create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
new file mode 100644
index 000000000000..ac6d0183e4d9
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc
@@ -0,0 +1,39 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: ftrace - function graph print function return value
+# requires: set_graph_function options/funcgraph-retval options/funcgraph-retval-hex function_graph:tracer
+
+# Make sure that funcgraph-retval works
+
+fail() { # msg
+ echo $1
+ exit_fail
+}
+
+echo proc_reg_write > set_graph_function
+echo function_graph > current_tracer
+echo funcgraph-retval > trace_options
+
+enable_tracing
+
+set +e
+echo > /proc/interrupts
+set -e
+
+disable_tracing
+
+: "Test printing the error code in signed decimal format"
+echo nofuncgraph-retval-hex > trace_options
+count=`cat trace | grep 'proc_reg_write' | grep '= -5' | wc -l`
+if [ $count -eq 0 ]; then
+ fail "Return value can not be printed in signed decimal format"
+fi
+
+: "Test printing the error code in hexadecimal format"
+echo funcgraph-retval-hex > trace_options
+count=`cat trace | grep 'proc_reg_write' | grep 'fffffffb' | wc -l`
+if [ $count -eq 0 ]; then
+ fail "Return value can not be printed in hexadecimal format"
+fi
+
+exit 0
--
2.25.1
Hi, Donglin,
On Thu, Mar 30, 2023 at 7:39 PM Donglin Peng <[email protected]> wrote:
>
> The previous patch ("function_graph: Support recording and printing
> the return value of function") has laid the groundwork for the for
> the funcgraph-retval, and this modification makes it available on
> the LoongArch platform.
>
> We introduce a new structure called fgraph_ret_regs for the LoongArch
> platform to hold return registers and the frame pointer. We then fill
> its content in the return_to_handler and pass its address to the
> function ftrace_return_to_handler to record the return value.
>
> Signed-off-by: Donglin Peng <[email protected]>
> ---
> v9:
> - Fix stack pointer align issues
> - Update the commit message
>
> v8:
> - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/ftrace.h | 20 ++++++++++++++++++++
> arch/loongarch/kernel/asm-offsets.c | 12 ++++++++++++
> arch/loongarch/kernel/mcount.S | 14 ++++++++------
> arch/loongarch/kernel/mcount_dyn.S | 15 ++++++++-------
> 5 files changed, 49 insertions(+), 13 deletions(-)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 7fd51257e0ed..4bf60132869b 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -99,6 +99,7 @@ config LOONGARCH
> select HAVE_FAST_GUP
> select HAVE_FTRACE_MCOUNT_RECORD
> select HAVE_FUNCTION_ARG_ACCESS_API
> + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_FUNCTION_GRAPH_TRACER
> select HAVE_FUNCTION_TRACER
> select HAVE_GENERIC_VDSO
> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
> index 3418d32d4fc7..01e7f92de03c 100644
> --- a/arch/loongarch/include/asm/ftrace.h
> +++ b/arch/loongarch/include/asm/ftrace.h
> @@ -63,4 +63,24 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>
> #endif /* CONFIG_FUNCTION_TRACER */
>
> +#ifndef __ASSEMBLY__
> +struct fgraph_ret_regs {
> + /* a0 - a1 */
> + unsigned long regs[2];
> +
> + unsigned long fp;
> + unsigned long __unused;
> +};
> +
> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
> +{
> + return ret_regs->regs[0];
> +}
> +
> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
> +{
> + return ret_regs->fp;
> +}
> +#endif
> +
> #endif /* _ASM_LOONGARCH_FTRACE_H */
> diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
> index 4bdb203fc66e..fab5bcddeb23 100644
> --- a/arch/loongarch/kernel/asm-offsets.c
> +++ b/arch/loongarch/kernel/asm-offsets.c
> @@ -12,6 +12,7 @@
> #include <asm/cpu-info.h>
> #include <asm/ptrace.h>
> #include <asm/processor.h>
> +#include <asm/ftrace.h>
>
> void output_ptreg_defines(void)
> {
> @@ -60,6 +61,17 @@ void output_ptreg_defines(void)
> BLANK();
> }
>
> +
> +void output_fgraph_ret_regs_defines(void)
> +{
> + COMMENT(" LoongArch fgraph_ret_regs offsets. ");
No space needed at the beginning, and I prefer to move this function
to the end of this file.
Huacai
> + OFFSET(FGRET_REGS_A0, fgraph_ret_regs, regs[0]);
> + OFFSET(FGRET_REGS_A1, fgraph_ret_regs, regs[1]);
> + OFFSET(FGRET_REGS_FP, fgraph_ret_regs, fp);
> + DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
> + BLANK();
> +}
> +
> void output_task_defines(void)
> {
> COMMENT("LoongArch task_struct offsets.");
> diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
> index 8cdc1563cd33..cb8e5803de4b 100644
> --- a/arch/loongarch/kernel/mcount.S
> +++ b/arch/loongarch/kernel/mcount.S
> @@ -79,18 +79,20 @@ SYM_FUNC_START(ftrace_graph_caller)
> SYM_FUNC_END(ftrace_graph_caller)
>
> SYM_FUNC_START(return_to_handler)
> - PTR_ADDI sp, sp, -2 * SZREG
> - PTR_S a0, sp, 0
> - PTR_S a1, sp, SZREG
> + PTR_ADDI sp, sp, -FGRET_REGS_SIZE
> + PTR_S a0, sp, FGRET_REGS_A0
> + PTR_S a1, sp, FGRET_REGS_A1
> + PTR_S zero, sp, FGRET_REGS_FP
>
> + move a0, sp
> bl ftrace_return_to_handler
>
> /* Restore the real parent address: a0 -> ra */
> move ra, a0
>
> - PTR_L a0, sp, 0
> - PTR_L a1, sp, SZREG
> - PTR_ADDI sp, sp, 2 * SZREG
> + PTR_L a0, sp, FGRET_REGS_A0
> + PTR_L a1, sp, FGRET_REGS_A1
> + PTR_ADDI sp, sp, FGRET_REGS_SIZE
> jr ra
> SYM_FUNC_END(return_to_handler)
> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
> diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
> index bbabf06244c2..ec24ae1de741 100644
> --- a/arch/loongarch/kernel/mcount_dyn.S
> +++ b/arch/loongarch/kernel/mcount_dyn.S
> @@ -131,18 +131,19 @@ SYM_CODE_END(ftrace_graph_caller)
>
> SYM_CODE_START(return_to_handler)
> /* Save return value regs */
> - PTR_ADDI sp, sp, -2 * SZREG
> - PTR_S a0, sp, 0
> - PTR_S a1, sp, SZREG
> + PTR_ADDI sp, sp, -FGRET_REGS_SIZE
> + PTR_S a0, sp, FGRET_REGS_A0
> + PTR_S a1, sp, FGRET_REGS_A1
> + PTR_S zero, sp, FGRET_REGS_FP
>
> - move a0, zero
> + move a0, sp
> bl ftrace_return_to_handler
> move ra, a0
>
> /* Restore return value regs */
> - PTR_L a0, sp, 0
> - PTR_L a1, sp, SZREG
> - PTR_ADDI sp, sp, 2 * SZREG
> + PTR_L a0, sp, FGRET_REGS_A0
> + PTR_L a1, sp, FGRET_REGS_A1
> + PTR_ADDI sp, sp, FGRET_REGS_SIZE
>
> jr ra
> SYM_CODE_END(return_to_handler)
> --
> 2.25.1
>
On 2023/3/30 20:48, Huacai Chen wrote:
> Hi, Donglin,
>
> On Thu, Mar 30, 2023 at 7:39 PM Donglin Peng <[email protected]> wrote:
>>
>> The previous patch ("function_graph: Support recording and printing
>> the return value of function") has laid the groundwork for the for
>> the funcgraph-retval, and this modification makes it available on
>> the LoongArch platform.
>>
>> We introduce a new structure called fgraph_ret_regs for the LoongArch
>> platform to hold return registers and the frame pointer. We then fill
>> its content in the return_to_handler and pass its address to the
>> function ftrace_return_to_handler to record the return value.
>>
>> Signed-off-by: Donglin Peng <[email protected]>
>> ---
>> v9:
>> - Fix stack pointer align issues
>> - Update the commit message
>>
>> v8:
>> - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
>> ---
>> arch/loongarch/Kconfig | 1 +
>> arch/loongarch/include/asm/ftrace.h | 20 ++++++++++++++++++++
>> arch/loongarch/kernel/asm-offsets.c | 12 ++++++++++++
>> arch/loongarch/kernel/mcount.S | 14 ++++++++------
>> arch/loongarch/kernel/mcount_dyn.S | 15 ++++++++-------
>> 5 files changed, 49 insertions(+), 13 deletions(-)
>>
>> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
>> index 7fd51257e0ed..4bf60132869b 100644
>> --- a/arch/loongarch/Kconfig
>> +++ b/arch/loongarch/Kconfig
>> @@ -99,6 +99,7 @@ config LOONGARCH
>> select HAVE_FAST_GUP
>> select HAVE_FTRACE_MCOUNT_RECORD
>> select HAVE_FUNCTION_ARG_ACCESS_API
>> + select HAVE_FUNCTION_GRAPH_RETVAL if HAVE_FUNCTION_GRAPH_TRACER
>> select HAVE_FUNCTION_GRAPH_TRACER
>> select HAVE_FUNCTION_TRACER
>> select HAVE_GENERIC_VDSO
>> diff --git a/arch/loongarch/include/asm/ftrace.h b/arch/loongarch/include/asm/ftrace.h
>> index 3418d32d4fc7..01e7f92de03c 100644
>> --- a/arch/loongarch/include/asm/ftrace.h
>> +++ b/arch/loongarch/include/asm/ftrace.h
>> @@ -63,4 +63,24 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
>>
>> #endif /* CONFIG_FUNCTION_TRACER */
>>
>> +#ifndef __ASSEMBLY__
>> +struct fgraph_ret_regs {
>> + /* a0 - a1 */
>> + unsigned long regs[2];
>> +
>> + unsigned long fp;
>> + unsigned long __unused;
>> +};
>> +
>> +static inline unsigned long fgraph_ret_regs_return_value(struct fgraph_ret_regs *ret_regs)
>> +{
>> + return ret_regs->regs[0];
>> +}
>> +
>> +static inline unsigned long fgraph_ret_regs_frame_pointer(struct fgraph_ret_regs *ret_regs)
>> +{
>> + return ret_regs->fp;
>> +}
>> +#endif
>> +
>> #endif /* _ASM_LOONGARCH_FTRACE_H */
>> diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
>> index 4bdb203fc66e..fab5bcddeb23 100644
>> --- a/arch/loongarch/kernel/asm-offsets.c
>> +++ b/arch/loongarch/kernel/asm-offsets.c
>> @@ -12,6 +12,7 @@
>> #include <asm/cpu-info.h>
>> #include <asm/ptrace.h>
>> #include <asm/processor.h>
>> +#include <asm/ftrace.h>
>>
>> void output_ptreg_defines(void)
>> {
>> @@ -60,6 +61,17 @@ void output_ptreg_defines(void)
>> BLANK();
>> }
>>
>> +
>> +void output_fgraph_ret_regs_defines(void)
>> +{
>> + COMMENT(" LoongArch fgraph_ret_regs offsets. ");
> No space needed at the beginning, and I prefer to move this function
> to the end of this file.
>
Yes, I will fix it. I copy it from output_pbe_defines, and it has a
space at the beginning, so I will fix it too.
> Huacai
>> + OFFSET(FGRET_REGS_A0, fgraph_ret_regs, regs[0]);
>> + OFFSET(FGRET_REGS_A1, fgraph_ret_regs, regs[1]);
>> + OFFSET(FGRET_REGS_FP, fgraph_ret_regs, fp);
>> + DEFINE(FGRET_REGS_SIZE, sizeof(struct fgraph_ret_regs));
>> + BLANK();
>> +}
>> +
>> void output_task_defines(void)
>> {
>> COMMENT("LoongArch task_struct offsets.");
>> diff --git a/arch/loongarch/kernel/mcount.S b/arch/loongarch/kernel/mcount.S
>> index 8cdc1563cd33..cb8e5803de4b 100644
>> --- a/arch/loongarch/kernel/mcount.S
>> +++ b/arch/loongarch/kernel/mcount.S
>> @@ -79,18 +79,20 @@ SYM_FUNC_START(ftrace_graph_caller)
>> SYM_FUNC_END(ftrace_graph_caller)
>>
>> SYM_FUNC_START(return_to_handler)
>> - PTR_ADDI sp, sp, -2 * SZREG
>> - PTR_S a0, sp, 0
>> - PTR_S a1, sp, SZREG
>> + PTR_ADDI sp, sp, -FGRET_REGS_SIZE
>> + PTR_S a0, sp, FGRET_REGS_A0
>> + PTR_S a1, sp, FGRET_REGS_A1
>> + PTR_S zero, sp, FGRET_REGS_FP
>>
>> + move a0, sp
>> bl ftrace_return_to_handler
>>
>> /* Restore the real parent address: a0 -> ra */
>> move ra, a0
>>
>> - PTR_L a0, sp, 0
>> - PTR_L a1, sp, SZREG
>> - PTR_ADDI sp, sp, 2 * SZREG
>> + PTR_L a0, sp, FGRET_REGS_A0
>> + PTR_L a1, sp, FGRET_REGS_A1
>> + PTR_ADDI sp, sp, FGRET_REGS_SIZE
>> jr ra
>> SYM_FUNC_END(return_to_handler)
>> #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
>> diff --git a/arch/loongarch/kernel/mcount_dyn.S b/arch/loongarch/kernel/mcount_dyn.S
>> index bbabf06244c2..ec24ae1de741 100644
>> --- a/arch/loongarch/kernel/mcount_dyn.S
>> +++ b/arch/loongarch/kernel/mcount_dyn.S
>> @@ -131,18 +131,19 @@ SYM_CODE_END(ftrace_graph_caller)
>>
>> SYM_CODE_START(return_to_handler)
>> /* Save return value regs */
>> - PTR_ADDI sp, sp, -2 * SZREG
>> - PTR_S a0, sp, 0
>> - PTR_S a1, sp, SZREG
>> + PTR_ADDI sp, sp, -FGRET_REGS_SIZE
>> + PTR_S a0, sp, FGRET_REGS_A0
>> + PTR_S a1, sp, FGRET_REGS_A1
>> + PTR_S zero, sp, FGRET_REGS_FP
>>
>> - move a0, zero
>> + move a0, sp
>> bl ftrace_return_to_handler
>> move ra, a0
>>
>> /* Restore return value regs */
>> - PTR_L a0, sp, 0
>> - PTR_L a1, sp, SZREG
>> - PTR_ADDI sp, sp, 2 * SZREG
>> + PTR_L a0, sp, FGRET_REGS_A0
>> + PTR_L a1, sp, FGRET_REGS_A1
>> + PTR_ADDI sp, sp, FGRET_REGS_SIZE
>>
>> jr ra
>> SYM_CODE_END(return_to_handler)
>> --
>> 2.25.1
>>
On Thu, Mar 30, 2023 at 04:39:07AM -0700, Donglin Peng wrote:
> v9:
> - Fix align issues in ARM asm code
> - Fix align issues in LoongArch asm code
> - Update commit messages
> - Update comments for ftrace_return_to_handler
>
> v8:
> - Fix issues in ARM64 asm code
> - Fix issues in selftest
> - Add some comments on CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
> - Make CONFIG_FUNCTION_GRAPH_RETVAL switable
> - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL
Please control your spamming:
From: Documentation/process/submitting-patches.rst
Don't get discouraged - or impatient
------------------------------------
After you have submitted your change, be patient and wait. Reviewers are
busy people and may not get to your patch right away.
Once upon a time, patches used to disappear into the void without comment,
but the development process works more smoothly than that now. You should
receive comments within a week or so; if that does not happen, make sure
that you have sent your patches to the right place. Wait for a minimum of
^^^^^^^^^^^^^^^^^^^^^
one week before resubmitting or pinging reviewers - possibly longer during
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
busy times like merge windows.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Thu, 30 Mar 2023 15:59:48 +0200
Borislav Petkov <[email protected]> wrote:
> Please control your spamming:
>
> From: Documentation/process/submitting-patches.rst
>
> Don't get discouraged - or impatient
> ------------------------------------
>
> After you have submitted your change, be patient and wait. Reviewers are
> busy people and may not get to your patch right away.
>
> Once upon a time, patches used to disappear into the void without comment,
> but the development process works more smoothly than that now. You should
> receive comments within a week or so; if that does not happen, make sure
> that you have sent your patches to the right place. Wait for a minimum of
> ^^^^^^^^^^^^^^^^^^^^^
>
> one week before resubmitting or pinging reviewers - possibly longer during
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> busy times like merge windows.
To be fair, this isn't a ping or a resend. It's addressing comments that
were given in v8 that was sent out on Tuesday.
This isn't v1, where I would agree with waiting a week for comments. v1 was
sent back in 3/6. I do not expect (nor want) someone to wait a week on v8
for all feedback to come in, unless it was a redesign of the code. But it's
now starting to settle, and that "week waiting" period isn't necessary for
fixing up minor suggestions by the reviewers.
I was hoping this would be good to go by the end of the week, so I could
get it into linux-next by next week.
-- Steve