[PATCH v3 4/5] perf tools: [uclibc] don't rely on glibc malloc working for sz 0

Vineet Gupta
2015-01-13T13:44:23Z

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 <------
}
}

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
tools/perf/util/evsel.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 1e90c8557ede..1d826d63bc20 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -797,6 +797,9 @@ int perf_evsel__enable(struct perf_evsel *evsel, int ncpus, int nthreads)

int perf_evsel__alloc_id(struct perf_evsel *evsel, int ncpus, int nthreads)
{
+ if (ncpus == 0 || nthreads == 0)
+ return 0;
+
if (evsel->system_wide)
nthreads = 1;

--
1.9.1