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perf trace: avoid garbage when not printing a trace event's arguments

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[ Upstream commit 5fb8e56542a3cf469fdf25d77f50e21cbff3ae7e ]

trace__fprintf_tp_fields may not print any tracepoint arguments. E.g., if the
argument values are all zero. Previously, this would result in a totally
uninitialized buffer being passed to fprintf, which could lead to garbage on the
console. Fix the problem by passing the number of initialized bytes fprintf.

Fixes: f11b2803bb88 ("perf trace: Allow choosing how to augment the tracepoint arguments")
Signed-off-by: Benjamin Peterson <benjamin@engflow.com>
Tested-by: Howard Chu <howardchu95@gmail.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20241103204816.7834-1-benjamin@engflow.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Benjamin Peterson 2024-11-03 20:48:16 +00:00 • committed by Ksawlii
parent da70f85ef9
commit 5496bf6890
1 changed files with 1 additions and 1 deletions
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2
tools/perf/builtin-trace.c
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@ -2748,7 +2748,7 @@ static size_t trace__fprintf_tp_fields(struct trace *trace, struct evsel *evsel,
printed += syscall_arg_fmt__scnprintf_val(arg, bf + printed, size - printed, &syscall_arg, val); printed += syscall_arg_fmt__scnprintf_val(arg, bf + printed, size - printed, &syscall_arg, val);
} }
return printed + fprintf(trace->output, "%s", bf); return printed + fprintf(trace->output, "%.*s", (int)printed, bf);
} }
static int trace__event_handler(struct trace *trace, struct evsel *evsel, static int trace__event_handler(struct trace *trace, struct evsel *evsel,