Messages in this thread Patch in this message | | | From | Donglin Peng <> | Subject | [PATCH v4] tracing/probe: add a char type to show the character value of traced arguments | Date | Thu, 15 Dec 2022 01:13:46 -0800 |
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There are scenes that we want to show the character value of traced arguments other than a decimal or hexadecimal or string value for debug convinience. Add a new type named 'char' to do it.
For example:
The to be traced function is 'void demo_func(char type, char *name);', we can add a kprobe event as follows to show argument values as we want:
echo 'p:myprobe demo_func $arg1:char +0($arg2):char[2]' > kprobe_events
we will get the following trace log:
... 95.451350: myprobe: (demo_func+0x0/0x29) arg1=A arg2={b,p}
Signed-off-by: Donglin Peng <dolinux.peng@gmail.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reported-by: kernel test robot <lkp@intel.com> --- Changes in v4: - update the example in the commit log
Changes in v3: - update readme_msg
Changes in v2: - fix build warnings reported by kernel test robot - modify commit log --- Documentation/trace/kprobetrace.rst | 3 ++- kernel/trace/trace.c | 2 +- kernel/trace/trace_probe.c | 2 ++ kernel/trace/trace_probe.h | 1 + 4 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index 4274cc6a2f94..007972a3c5c4 100644 --- a/Documentation/trace/kprobetrace.rst +++ b/Documentation/trace/kprobetrace.rst @@ -58,7 +58,7 @@ Synopsis of kprobe_events NAME=FETCHARG : Set NAME as the argument name of FETCHARG. FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types - (x8/x16/x32/x64), "string", "ustring" and bitfield + (x8/x16/x32/x64), "char", "string", "ustring" and bitfield are supported. (\*1) only for the probe on function entry (offs == 0). @@ -80,6 +80,7 @@ E.g. 'x16[4]' means an array of x16 (2bytes hex) with 4 elements. Note that the array can be applied to memory type fetchargs, you can not apply it to registers/stack-entries etc. (for example, '$stack1:x8[8]' is wrong, but '+8($stack):x8[8]' is OK.) +Char type can be used to show the character value of traced arguments. String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container has been paged out. "ustring" type is an alternative of string for user-space. diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5cfc95a52bc3..a64e206f94e6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5615,7 +5615,7 @@ static const char readme_msg[] = "\t $stack<index>, $stack, $retval, $comm,\n" #endif "\t +|-[u]<offset>(<fetcharg>), \\imm-value, \\\"imm-string\"\n" - "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n" + "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, char, string, symbol,\n" "\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n" "\t <type>\\[<array-size>\\]\n" #ifdef CONFIG_HIST_TRIGGERS diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 36dff277de46..a4abf7f6c295 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -50,6 +50,7 @@ DEFINE_BASIC_PRINT_TYPE_FUNC(x8, u8, "0x%x") DEFINE_BASIC_PRINT_TYPE_FUNC(x16, u16, "0x%x") DEFINE_BASIC_PRINT_TYPE_FUNC(x32, u32, "0x%x") DEFINE_BASIC_PRINT_TYPE_FUNC(x64, u64, "0x%Lx") +DEFINE_BASIC_PRINT_TYPE_FUNC(char, u8, "%c") int PRINT_TYPE_FUNC_NAME(symbol)(struct trace_seq *s, void *data, void *ent) { @@ -93,6 +94,7 @@ static const struct fetch_type probe_fetch_types[] = { ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0), ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0), ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0), + ASSIGN_FETCH_TYPE_ALIAS(char, u8, u8, 0), ASSIGN_FETCH_TYPE_ALIAS(symbol, ADDR_FETCH_TYPE, ADDR_FETCH_TYPE, 0), ASSIGN_FETCH_TYPE_END diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index de38f1c03776..8c86aaa8b0c9 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -164,6 +164,7 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(x16); DECLARE_BASIC_PRINT_TYPE_FUNC(x32); DECLARE_BASIC_PRINT_TYPE_FUNC(x64); +DECLARE_BASIC_PRINT_TYPE_FUNC(char); DECLARE_BASIC_PRINT_TYPE_FUNC(string); DECLARE_BASIC_PRINT_TYPE_FUNC(symbol); -- 2.25.1
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