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perf trace: Avoid garbage when not printing a syscall's arguments

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syscall__scnprintf_args may not place anything in the output buffer
(e.g., because the arguments are all zero). If that happened in
trace__fprintf_sys_enter, its fprintf would receive an unitialized
buffer leading to garbage output.

Fix the problem by passing the (possibly zero) bounds of the argument
buffer to the output fprintf.

Fixes: a98392bb1e ("perf trace: Use beautifiers on syscalls:sys_enter_ handlers")
Signed-off-by: Benjamin Peterson <benjamin@engflow.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Howard Chu <howardchu95@gmail.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241107232128.108981-2-benjamin@engflow.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Benjamin Peterson 2024-11-07 23:21:27 +00:00 committed by Arnaldo Carvalho de Melo
parent 3fd7c36973
commit 1302e352b2
1 changed files with 3 additions and 2 deletions
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5
tools/perf/builtin-trace.c
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@ -2702,6 +2702,7 @@ static int trace__fprintf_sys_enter(struct trace *trace, struct evsel *evsel,
char msg[1024]; char msg[1024];
void *args, *augmented_args = NULL; void *args, *augmented_args = NULL;
int augmented_args_size; int augmented_args_size;
size_t printed = 0;
if (sc == NULL) if (sc == NULL)
return -1; return -1;
@ -2717,8 +2718,8 @@ static int trace__fprintf_sys_enter(struct trace *trace, struct evsel *evsel,
args = perf_evsel__sc_tp_ptr(evsel, args, sample); args = perf_evsel__sc_tp_ptr(evsel, args, sample);
augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls_args_size); augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls_args_size);
syscall__scnprintf_args(sc, msg, sizeof(msg), args, augmented_args, augmented_args_size, trace, thread); printed += syscall__scnprintf_args(sc, msg, sizeof(msg), args, augmented_args, augmented_args_size, trace, thread);
fprintf(trace->output, "%s", msg); fprintf(trace->output, "%.*s", (int)printed, msg);
err = 0; err = 0;
out_put: out_put:
thread__put(thread); thread__put(thread);