[PATCH 4/7] perf probe: Fix bug with global variables handling

From: Arnaldo Carvalho de Melo
Date: Mon Apr 27 2015 - 13:06:56 EST

From: He Kuang <hekuang@xxxxxxxxxx>

There are missing curly braces which causes find_variable() return wrong
value when probing with global variables.

This problem can be reproduced as following:

$ perf probe -v --add='generic_perform_write global_variable_for_test'
Try to find probe point from debuginfo.
Probe point found: generic_perform_write+0
Searching 'global_variable_for_test' variable in context.
An error occurred in debuginfo analysis (-2).
Error: Failed to add events. Reason: No such file or directory (Code: -2)

After this patch:

$ perf probe -v --add='generic_perform_write global_variable_for_test'
Converting variable global_variable_for_test into trace event.
global_variable_for_test type is int.
Found 1 probe_trace_events.
Opening /sys/kernel/debug/tracing/kprobe_events write=1
Added new event:
Writing event: p:probe/generic_perform_write _stext+1237464
probe:generic_perform_write (on generic_perform_write with

You can now use it in all perf tools, such as:

perf record -e probe:generic_perform_write -aR sleep 1

Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1429949338-18678-1-git-send-email-hekuang@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
tools/perf/util/probe-finder.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 44554c3c2220..1c3cc07937d5 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -578,10 +578,12 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
/* Search child die for local variables and parameters. */
if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
/* Search again in global variables */
- if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
+ if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
+ 0, &vr_die)) {
pr_warning("Failed to find '%s' in this function.\n",
ret = -ENOENT;
+ }
if (ret >= 0)
ret = convert_variable(&vr_die, pf);

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