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Subject[tip: perf/urgent] perf tests: Avoid raising SEGV using an obvious NULL dereference
The following commit has been merged into the perf/urgent branch of tip:

Commit-ID: e3e2cf3d5b1fe800b032e14c0fdcd9a6fb20cf3b
Gitweb: https://git.kernel.org/tip/e3e2cf3d5b1fe800b032e14c0fdcd9a6fb20cf3b
Author: Ian Rogers <irogers@google.com>
AuthorDate: Wed, 25 Sep 2019 12:59:24 -07:00
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitterDate: Fri, 27 Sep 2019 09:26:14 -03:00

perf tests: Avoid raising SEGV using an obvious NULL dereference

An optimized build such as:

make -C tools/perf CLANG=1 CC=clang EXTRA_CFLAGS="-O3

will turn the dereference operation into a ud2 instruction, raising a
SIGILL rather than a SIGSEGV. Use raise(..) for correctness and clarity.

Similar issues were addressed in Numfor Mbiziwo-Tiapo's patch:

https://lkml.org/lkml/2019/7/8/1234

Committer testing:

Before:

[root@quaco ~]# perf test hooks
55: perf hooks : Ok
[root@quaco ~]# perf test -v hooks
55: perf hooks :
--- start ---
test child forked, pid 17092
SIGSEGV is observed as expected, try to recover.
Fatal error (SEGFAULT) in perf hook 'test'
test child finished with 0
---- end ----
perf hooks: Ok
[root@quaco ~]#

After:

[root@quaco ~]# perf test hooks
55: perf hooks : Ok
[root@quaco ~]# perf test -v hooks
55: perf hooks :
--- start ---
test child forked, pid 17909
SIGSEGV is observed as expected, try to recover.
Fatal error (SEGFAULT) in perf hook 'test'
test child finished with 0
---- end ----
perf hooks: Ok
[root@quaco ~]#

Fixes: a074865e60ed ("perf tools: Introduce perf hooks")
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lore.kernel.org/lkml/20190925195924.152834-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/tests/perf-hooks.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tools/perf/tests/perf-hooks.c b/tools/perf/tests/perf-hooks.c
index dbc2719..dd865e0 100644
--- a/tools/perf/tests/perf-hooks.c
+++ b/tools/perf/tests/perf-hooks.c
@@ -19,12 +19,11 @@ static void sigsegv_handler(int sig __maybe_unused)
static void the_hook(void *_hook_flags)
{
int *hook_flags = _hook_flags;
- int *p = NULL;

*hook_flags = 1234;

/* Generate a segfault, test perf_hooks__recover */
- *p = 0;
+ raise(SIGSEGV);
}

int test__perf_hooks(struct test *test __maybe_unused, int subtest __maybe_unused)
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