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| author | Donglin Peng <dolinux.peng@gmail.com> | 2023-02-21 08:52:42 +0900 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2023-02-21 08:52:42 +0900 |
| commit | 8478cca1e3abd183f309cd9c2491f484acf5d377 (patch) | |
| tree | 22623d22350cc9f938a59ddc85b87da6bbb8ffdd /Documentation/trace | |
| parent | 96cd93af794cf3ef83ae1ad7291160029d7b525e (diff) | |
| download | linux-8478cca1e3abd183f309cd9c2491f484acf5d377.tar.gz | |
tracing/probe: add a char type to show the character value of traced arguments
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. I add a new type named 'char' to do it and a new test case
file named 'kprobe_args_char.tc' to do selftest for char type.
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[5]' > kprobe_events
we will get the following trace log:
... myprobe: (demo_func+0x0/0x29) arg1='A' arg2={'b','p','f','1',''}
Link: https://lore.kernel.org/all/20221219110613.367098-1-dolinux.peng@gmail.com/
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>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/kprobetrace.rst | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/Documentation/trace/kprobetrace.rst b/Documentation/trace/kprobetrace.rst index 08a2a6a3782f08..ef223b8ad6d506 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", "symbol", "symstr" + (x8/x16/x32/x64), "char", "string", "ustring", "symbol", "symstr" 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. |