[PATCH v3 1/2] perf-probe: Replace unacceptable characters when generating event name

Masami Hiramatsu (Google)
2024-11-13T00:21:25Z

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Replace unacceptable characters with '_' when generating event name from
the probing function name. This is not for C program. For the C program,
it will continue to remove suffixes.
Note that this language checking depends on the debuginfo. So without the
debuginfo, perf probe will always replaces unacceptable characters with
'_'.

For example.

$ ./perf probe -x cro3 -D \"cro3::cmd::servo::run_show\"
p:probe_cro3/cro3_cmd_servo_run_show /work/cro3/target/x86_64-unknown-linux-gnu/debug/cro3:0x197530

$ ./perf probe -x /work/go/example/outyet/main -D 'main.(*Server).poll'
p:probe_main/main_Server_poll /work/go/example/outyet/main:0x353040

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
Changes in v3:
- Update for the latest perf-tools.
Changes in v2:
- Check dwarf language instead of checking wildcards.
---
tools/perf/util/probe-event.c | 32 +++++++++++++++++++++++++-------
tools/perf/util/probe-event.h | 3 ++-
tools/perf/util/probe-finder.c | 15 +++++++++++++++
tools/perf/util/probe-finder.h | 5 +++++
4 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 1d5184697871..a5e42055a2f4 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2774,7 +2774,7 @@ int show_perf_probe_events(struct strfilter *filter)

static int get_new_event_name(char *buf, size_t len, const char *base,
struct strlist *namelist, bool ret_event,
- bool allow_suffix)
+ bool allow_suffix, bool not_C_symname)
{
int i, ret;
char *p, *nbase;
@@ -2785,10 +2785,24 @@ static int get_new_event_name(char *buf, size_t len, const char *base,
if (!nbase)
return -ENOMEM;

- /* Cut off the dot suffixes (e.g. .const, .isra) and version suffixes */
- p = strpbrk(nbase, ".@");
- if (p && p != nbase)
- *p = '\0';
+ if (not_C_symname) {
+ /* Replace non-alnum with '_' */
+ char *s, *d;
+
+ s = d = nbase;
+ do {
+ if (*s && !isalnum(*s)) {
+ if (d != nbase && *(d - 1) != '_')
+ *d++ = '_';
+ } else
+ *d++ = *s;
+ } while (*s++);
+ } else {
+ /* Cut off the dot suffixes (e.g. .const, .isra) and version suffixes */
+ p = strpbrk(nbase, ".@");
+ if (p && p != nbase)
+ *p = '\0';
+ }

/* Try no suffix number */
ret = e_snprintf(buf, len, "%s%s", nbase, ret_event ? "__return" : "");
@@ -2883,6 +2897,7 @@ static int probe_trace_event__set_name(struct probe_trace_event *tev,
bool allow_suffix)
{
const char *event, *group;
+ bool not_C_symname = true;
char buf[MAX_EVENT_NAME_LEN];
int ret;

@@ -2897,8 +2912,10 @@ static int probe_trace_event__set_name(struct probe_trace_event *tev,
(strncmp(pev->point.function, "0x", 2) != 0) &&
!strisglob(pev->point.function))
event = pev->point.function;
- else
+ else {
event = tev->point.realname;
+ not_C_symname = !is_known_C_lang(tev->lang);
+ }
}
if (pev->group && !pev->sdt)
group = pev->group;
@@ -2915,7 +2932,8 @@ static int probe_trace_event__set_name(struct probe_trace_event *tev,

/* Get an unused new event name */
ret = get_new_event_name(buf, sizeof(buf), event, namelist,
- tev->point.retprobe, allow_suffix);
+ tev->point.retprobe, allow_suffix,
+ not_C_symname);
if (ret < 0)
return ret;

diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index 4850e52f274e..ab9d07034170 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -57,7 +57,8 @@ struct probe_trace_event {
char *event; /* Event name */
char *group; /* Group name */
struct probe_trace_point point; /* Trace point */
- int nargs; /* Number of args */
+ int nargs; /* Number of args */
+ int lang; /* Dwarf language code */
bool uprobes; /* uprobes only */
struct probe_trace_arg *args; /* Arguments */
};
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 7f2ee0cb43ca..863147c4b7d6 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -35,6 +35,19 @@
/* Kprobe tracer basic type is up to u64 */
#define MAX_BASIC_TYPE_BITS 64

+bool is_known_C_lang(int lang)
+{
+ switch (lang) {
+ case DW_LANG_C89:
+ case DW_LANG_C:
+ case DW_LANG_C99:
+ case DW_LANG_C11:
+ return true;
+ default:
+ return false;
+ }
+}
+
/*
* Probe finder related functions
*/
@@ -1269,6 +1282,8 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
ret = -ENOMEM;
goto end;
}
+ tev->lang = dwarf_srclang(dwarf_diecu(sc_die, &pf->cu_die,
+ NULL, NULL));

pr_debug("Probe point found: %s+%lu\n", tev->point.symbol,
tev->point.offset);
diff --git a/tools/perf/util/probe-finder.h b/tools/perf/util/probe-finder.h
index be7b46ea2460..dcf6cc1e1cbe 100644
--- a/tools/perf/util/probe-finder.h
+++ b/tools/perf/util/probe-finder.h
@@ -26,6 +26,9 @@ static inline int is_c_varname(const char *name)
#include "dwarf-aux.h"
#include "debuginfo.h"

+/* Check the language code is known C */
+bool is_known_C_lang(int lang);
+
/* Find probe_trace_events specified by perf_probe_event from debuginfo */
int debuginfo__find_trace_events(struct debuginfo *dbg,
struct perf_probe_event *pev,
@@ -103,6 +106,8 @@ struct line_finder {
int found;
};

+#else
+#define is_known_C_lang(lang) (false)
#endif /* HAVE_LIBDW_SUPPORT */

#endif /*_PROBE_FINDER_H */