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tracing/probes: Treating longer symbol name on event comparation

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MAX_COMMON_HEAD_LEN (63) was used to allocate a temporary buffer for
formatting command heads in trace_kprobe_match_command_head() and
trace_uprobe_match_command_head(). However, the buffer size is too
short for some longer symbols. Especially, with rust code, the symbol
can be mangled and become very long.

Refactor trace_kprobe_match_command_head() to perform direct string
comparisons using strcmp() and strncmp(), eliminating the need for a
temporary buffer and removing the MAX_COMMON_HEAD_LEN string length
restriction on probe symbol names.

For trace_uprobe_match_command_head(), since tu->filename is already
matched via strncmp(), use a fixed 64-byte stack buffer solely for
formatting offset and ref_ctr_offset (which requires at most 39 bytes).

With all users converted, remove the MAX_COMMON_HEAD_LEN definition from
trace_probe.h.

Link: https://lore.kernel.org/all/178521361102.34226.9650586522488974115.stgit@devnote2/

Reported-by: Zhan Xusheng <zhanxusheng1024@gmail.com>
Link: https://lore.kernel.org/all/20260724023317.624074-1-zhanxusheng@xiaomi.com/
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Masami Hiramatsu (Google) 2026-07-28 13:40:11 +09:00
parent d0d7dc1a70
commit c00e735410
3 changed files with 17 additions and 10 deletions
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24
kernel/trace/trace_kprobe.c
View File

@ -149,20 +149,28 @@ static bool trace_kprobe_is_busy(struct dyn_event *ev)
static bool trace_kprobe_match_command_head(struct trace_kprobe *tk,
int argc, const char **argv)
{
char buf[MAX_COMMON_HEAD_LEN + 1];
char buf[32];
int len;
if (!argc)
return true;
if (!tk->symbol)
if (!tk->symbol) {
snprintf(buf, sizeof(buf), "0x%p", tk->rp.kp.addr);
else if (tk->rp.kp.offset)
snprintf(buf, sizeof(buf), "%s+%u",
trace_kprobe_symbol(tk), tk->rp.kp.offset);
else
snprintf(buf, sizeof(buf), "%s", trace_kprobe_symbol(tk));
if (strcmp(buf, argv[0]))
if (strcmp(buf, argv[0]))
return false;
} else if (tk->rp.kp.offset) {
len = strlen(trace_kprobe_symbol(tk));
if (strncmp(trace_kprobe_symbol(tk), argv[0], len) ||
argv[0][len] != '+')
return false;
snprintf(buf, sizeof(buf), "%u", tk->rp.kp.offset);
if (strcmp(buf, &argv[0][len + 1]))
return false;
} else if (strcmp(trace_kprobe_symbol(tk), argv[0]))
return false;
argc--; argv++;
return trace_probe_match_command_args(&tk->tp, argc, argv);

1
kernel/trace/trace_probe.h
View File

@ -33,7 +33,6 @@
#define MAX_TRACE_ARGS 128
#define MAX_ARGSTR_LEN 255
#define MAX_COMMON_HEAD_LEN 63
#define MAX_ARRAY_LEN 64
#define MAX_ARG_NAME_LEN 32
#define MAX_BTF_ARGS_LEN 128

2
kernel/trace/trace_uprobe.c
View File

@ -281,7 +281,7 @@ static bool trace_uprobe_is_busy(struct dyn_event *ev)
static bool trace_uprobe_match_command_head(struct trace_uprobe *tu,
int argc, const char **argv)
{
char buf[MAX_COMMON_HEAD_LEN + 1];
char buf[64];
int len;
if (!argc)