[PATCH 4/5] perf tools: [uclibc] don't rely on glibc malloc working for sz 0

From: Vineet Gupta
Date: Tue Jan 06 2015 - 08:53:16 EST


When running perf on ARC (uClibc based userspace), ran into this issue
------------->8----------------
[ARCLinux]$ ./perf record ls
bin etc perf sys
debug init perf.data tmp
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.001 MB perf.data (~24 samples) ]

[ARCLinux]$ ./perf report
incompatible file format (rerun with -v to learn more)
------------->8----------------

The problem happens in the following call stack when zalloc is called
with size zero

glibc default / uClibc with MALLOC_GLIBC_COMPAT are OK, but not if that
config option is not enabled.

cmd_report
perf_session__new
perf_session__open
perf_session__read_header
read_attr(fd, header, &f_attr)
nr_ids = f_attr.ids.size / sizeof(u64); <-- 0
perf_evsel__alloc_id(vsel, 1, nr_ids)
zalloc(ncpus * nthreads * sizeof(u64)) <-- 0

header.c: read_attr()

(gdb) p *f_attr
$17 = {
attr = {
type = 0,
size = 96,
config = 0,
{
sample_period = 4000,
sample_freq = 4000
},
...
ids = {
offset = 104,
size = 0 <------
}
}

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
tools/perf/util/header.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index b20e40c74468..43671068ce75 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2532,7 +2532,7 @@ int perf_session__read_header(struct perf_session *session)
*/
perf_evlist__add(session->evlist, evsel);

- nr_ids = f_attr.ids.size / sizeof(u64);
+ nr_ids = f_attr.ids.size / sizeof(u64) ? : 1;
/*
* We don't have the cpu and thread maps on the header, so
* for allocating the perf_sample_id table we fake 1 cpu and
--
1.9.1

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