From 11fd3eb874e73ee8069bcfd54e3c16fa7ce56fe6 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Fri, 10 Jul 2020 22:11:13 +0900 Subject: perf probe: Fix wrong variable warning when the probe point is not found Fix a wrong "variable not found" warning when the probe point is not found in the debuginfo. Since the debuginfo__find_probes() can return 0 even if it does not find given probe point in the debuginfo, fill_empty_trace_arg() can be called with tf.ntevs == 0 and it can emit a wrong warning. To fix this, reject ntevs == 0 in fill_empty_trace_arg(). E.g. without this patch; # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di" Failed to find the location of the '%di' variable at this address. Perhaps it has been optimized out. Use -V with the --range option to show '%di' location range. Added new events: probe_libc:memcpy (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di) probe_libc:memcpy (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di) You can now use it in all perf tools, such as: perf record -e probe_libc:memcpy -aR sleep 1 With this; # perf probe -x /lib64/libc-2.30.so -a "memcpy arg1=%di" Added new events: probe_libc:memcpy (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di) probe_libc:memcpy (on memcpy in /usr/lib64/libc-2.30.so with arg1=%di) You can now use it in all perf tools, such as: perf record -e probe_libc:memcpy -aR sleep 1 Fixes: cb4027308570 ("perf probe: Trace a magic number if variable is not found") Reported-by: Andi Kleen Signed-off-by: Masami Hiramatsu Reviewed-by: Srikar Dronamraju Tested-by: Andi Kleen Cc: Oleg Nesterov Cc: stable@vger.kernel.org Link: http://lore.kernel.org/lkml/159438667364.62703.2200642186798763202.stgit@devnote2 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/probe-finder.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'tools/perf/util/probe-finder.c') diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 55924255c535..9963e4e8ea20 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -1408,6 +1408,9 @@ static int fill_empty_trace_arg(struct perf_probe_event *pev, char *type; int i, j, ret; + if (!ntevs) + return -ENOENT; + for (i = 0; i < pev->nargs; i++) { type = NULL; for (j = 0; j < ntevs; j++) { -- cgit v1.2.3-59-g8ed1b