From 39c6a356201ebbd7e1db5be53fbb46ef4bfc70a4 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Fri, 11 Oct 2024 16:10:01 -0300 Subject: [PATCH] perf trace: The return from 'write' isn't a pid When adding a explicit beautifier for the 'write' syscall when the BPF based buffer collector was introduced there was a cut'n'paste error that carried the syscall_fmt->errpid setting from a nearby syscall (waitid) that returns a pid. So the write return was being suppressed by the return pretty printer, remove that field, reverting it back to the default return handler, that prints positive numbers as-is and interpret negative values as errnos. I actually introduced the problem while making Howard's original patch work just with the 'write' syscall, as we couldn't just look for any buffers, the ones that are filled in by the kernel couldn't use the same sys_enter BPF collector. Fixes: b257fac12f38d7f5 ("perf trace: Pretty print buffer data") Reported-by: James Clark Link: https://lore.kernel.org/lkml/bcf50648-3c7e-4513-8717-0d14492c53b9@linaro.org Link: https://lore.kernel.org/all/Zt8jTfzDYgBPvFCd@x1/#t Cc: Adrian Hunter Cc: Alan Maguire Cc: Howard Chu Cc: Ian Rogers Cc: Jiri Olsa Cc: Kan Liang Cc: Namhyung Kim Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-trace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index f6e847529073..d3f11b90d025 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -1399,7 +1399,7 @@ static const struct syscall_fmt syscall_fmts[] = { .arg = { [2] = { .scnprintf = SCA_WAITID_OPTIONS, /* options */ }, }, }, { .name = "waitid", .errpid = true, .arg = { [3] = { .scnprintf = SCA_WAITID_OPTIONS, /* options */ }, }, }, - { .name = "write", .errpid = true, + { .name = "write", .arg = { [1] = { .scnprintf = SCA_BUF /* buf */, .from_user = true, }, }, }, };