@@ -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.
@@ -5615,7 +5615,7 @@ static const char readme_msg[] =
"\t $stack<index>, $stack, $retval, $comm,\n"
#endif
"\t +|-[u]<offset>(<fetcharg>), \\imm-value, \\\"imm-string\"\n"
- "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
+ "\t type: s8/16/32/64, u8/16/32/64, x8/16/32/64, char, string, symbol,\n"
"\t b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
"\t <type>\\[<array-size>\\]\n"
#ifdef CONFIG_HIST_TRIGGERS
@@ -50,6 +50,7 @@ DEFINE_BASIC_PRINT_TYPE_FUNC(x8, u8, "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x16, u16, "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x32, u32, "0x%x")
DEFINE_BASIC_PRINT_TYPE_FUNC(x64, u64, "0x%Lx")
+DEFINE_BASIC_PRINT_TYPE_FUNC(char, u8, "\'%c\'")
int PRINT_TYPE_FUNC_NAME(symbol)(struct trace_seq *s, void *data, void *ent)
{
@@ -93,6 +94,7 @@ static const struct fetch_type probe_fetch_types[] = {
ASSIGN_FETCH_TYPE_ALIAS(x16, u16, u16, 0),
ASSIGN_FETCH_TYPE_ALIAS(x32, u32, u32, 0),
ASSIGN_FETCH_TYPE_ALIAS(x64, u64, u64, 0),
+ ASSIGN_FETCH_TYPE_ALIAS(char, u8, u8, 0),
ASSIGN_FETCH_TYPE_ALIAS(symbol, ADDR_FETCH_TYPE, ADDR_FETCH_TYPE, 0),
ASSIGN_FETCH_TYPE_END
@@ -164,6 +164,7 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(x16);
DECLARE_BASIC_PRINT_TYPE_FUNC(x32);
DECLARE_BASIC_PRINT_TYPE_FUNC(x64);
+DECLARE_BASIC_PRINT_TYPE_FUNC(char);
DECLARE_BASIC_PRINT_TYPE_FUNC(string);
DECLARE_BASIC_PRINT_TYPE_FUNC(symbol);
new file mode 100644
@@ -0,0 +1,47 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Kprobe event char type argument
+# requires: kprobe_events
+
+case `uname -m` in
+x86_64)
+ ARG1=%di
+;;
+i[3456]86)
+ ARG1=%ax
+;;
+aarch64)
+ ARG1=%x0
+;;
+arm*)
+ ARG1=%r0
+;;
+ppc64*)
+ ARG1=%r3
+;;
+ppc*)
+ ARG1=%r3
+;;
+s390*)
+ ARG1=%r2
+;;
+mips*)
+ ARG1=%r4
+;;
+*)
+ echo "Please implement other architecture here"
+ exit_untested
+esac
+
+: "Test get argument (1)"
+echo "p:testprobe tracefs_create_dir arg1=+0(${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
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 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