[tip:perf/core] perf jit: memset() variable 'st' using the correct size

tip-bot for Colin Ian King
2016-04-23T13:05:03Z

Commit-ID: f56ebf20d0f535f5da7cfcf0000ab3e0af133f81
Gitweb: http://git.kernel.org/tip/f56ebf20d0f535f5da7cfcf0000ab3e0af133f81
Author: Colin Ian King <colin.king@canonical.com>
AuthorDate: Tue, 19 Apr 2016 00:07:18 +0100
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 19 Apr 2016 12:37:01 -0300

perf jit: memset() variable 'st' using the correct size

The current code is memsetting the 'struct stat' variable 'st' with the size of
'stat' (which turns out to be 1 byte) rather than the size of variable 'sz'.

Committer notes:

sizeof(function) isn't valid, the result depends on the compiler used, with
gcc, enabling pedantic warnings we get:

$ cat sizeof_function.c
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>

int main(void)
{
printf("sizeof(stat)=%zd, stat=%p\n", sizeof(stat), stat);
return 0;
}
$ readelf -sW sizeof_function | grep -w stat
49: 0000000000400630 16 FUNC WEAK HIDDEN 13 stat
$ cc -pedantic sizeof_function.c -o sizeof_function
sizeof_function.c: In function ‘main’:
sizeof_function.c:8:46: warning: invalid application of ‘sizeof’ to a function type [-Wpointer-arith]
printf("sizeof(stat)=%zd, stat=%p\n", sizeof(stat), stat);
^
$ ./sizeof_function
sizeof(stat)=1, stat=0x400630
$

Standard C, section 6.5.3.4:

"The sizeof operator shall not be applied to an expression that has function
type or an incomplete type, to the parenthesized name of such a type,
or to an expression that designates a bit-field member."

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Fixes: 9b07e27f88b9 ("perf inject: Add jitdump mmap injection support")
Link: http://lkml.kernel.org/r/1461020838-9260-1-git-send-email-colin.king@canonical.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/jitdump.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index 52fcef3..86afe96 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -412,7 +412,7 @@ static int jit_repipe_code_load(struct jit_buf_desc *jd, union jr_entry *jr)
return -1;
}
if (stat(filename, &st))
- memset(&st, 0, sizeof(stat));
+ memset(&st, 0, sizeof(st));

event->mmap2.header.type = PERF_RECORD_MMAP2;
event->mmap2.header.misc = PERF_RECORD_MISC_USER;
@@ -500,7 +500,7 @@ static int jit_repipe_code_move(struct jit_buf_desc *jd, union jr_entry *jr)
size++; /* for \0 */

if (stat(filename, &st))
- memset(&st, 0, sizeof(stat));
+ memset(&st, 0, sizeof(st));

size = PERF_ALIGN(size, sizeof(u64));