Looking back at emails that happened when I was off ;-)
Masami, what's you thoughts about this patch?
-- Steve
On Mon, 19 Dec 2022 03:06:13 -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. 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',''}
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 v6:
- change "'%c'" to "'%c'" in trace_probe.c
Changes in v5:
- wrap the output character with single quotes
- add a test case named kprobe_args_char.tc to do selftest
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 + .../ftrace/test.d/kprobe/kprobe_args_char.tc | 47 +++++++++++++++++++ 5 files changed, 53 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc
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(*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 6d7ef130f57e..c602081e64c8 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 bb2f95d7175c..794a21455396 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); diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc new file mode 100644 index 000000000000..285b4770efad --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_args_char.tc @@ -0,0 +1,47 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: Kprobe event char type argument +# requires: kprobe_events
+case `uname -m` in +x86_64)
- ARG1=%di
+;; +i[3456]86)
- ARG1=%ax
+;; +aarch64)
- ARG1=%x0
+;; +arm*)
- ARG1=%r0
+;; +ppc64*)
- ARG1=%r3
+;; +ppc*)
- ARG1=%r3
+;; +s390*)
- ARG1=%r2
+;; +mips*)
- ARG1=%r4
+;; +*)
- echo "Please implement other architecture here"
- exit_untested
+esac
+: "Test get argument (1)" +echo "p:testprobe tracefs_create_dir arg1=+0(${ARG1}):char" > kprobe_events +echo 1 > events/kprobes/testprobe/enable +echo "p:test $FUNCTION_FORK" >> kprobe_events +grep -qe "testprobe.* arg1='t'" trace
+echo 0 > events/kprobes/testprobe/enable +: "Test get argument (2)" +echo "p:testprobe tracefs_create_dir arg1=+0(${ARG1}):char arg2=+0(${ARG1}):char[4]" > kprobe_events +echo 1 > events/kprobes/testprobe/enable +echo "p:test $FUNCTION_FORK" >> kprobe_events +grep -qe "testprobe.* arg1='t' arg2={'t','e','s','t'}" trace