Messages in this thread |  | | Date | Sun, 18 Dec 2022 10:39:07 +0900 | From | Masami Hiramatsu (Google) <> | Subject | Re: [PATCH v4] tracing/probe: add a char type to show the character value of traced arguments |
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Hi Donglin,
Thanks for updating you patch. And can you also send a test code update (tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_type.tc)?
Thank you,
On Thu, 15 Dec 2022 01:13:46 -0800 Donglin Peng <dolinux.peng@gmail.com> wrote:
> 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 >
-- Masami Hiramatsu (Google) <mhiramat@kernel.org>
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