[tip:perf/urgent] perf data: Fix 'strncat may truncate' build failure with recent gcc

From: tip-bot for Shawn Landden
Date: Tue May 28 2019 - 17:25:57 EST


Commit-ID: 97acec7df172cd1e450f81f5e293c0aa145a2797
Gitweb: https://git.kernel.org/tip/97acec7df172cd1e450f81f5e293c0aa145a2797
Author: Shawn Landden <shawn@xxxxxxx>
AuthorDate: Sat, 18 May 2019 15:32:38 -0300
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 28 May 2019 09:49:03 -0300

perf data: Fix 'strncat may truncate' build failure with recent gcc

This strncat() is safe because the buffer was allocated with zalloc(),
however gcc doesn't know that. Since the string always has 4 non-null
bytes, just use memcpy() here.

CC /home/shawn/linux/tools/perf/util/data-convert-bt.o
In file included from /usr/include/string.h:494,
from /home/shawn/linux/tools/lib/traceevent/event-parse.h:27,
from util/data-convert-bt.c:22:
In function âstrncatâ,
inlined from âstring_set_valueâ at util/data-convert-bt.c:274:4:
/usr/include/powerpc64le-linux-gnu/bits/string_fortified.h:136:10: error: â__builtin_strncatâ output may be truncated copying 4 bytes from a string of length 4 [-Werror=stringop-truncation]
136 | return __builtin___strncat_chk (__dest, __src, __len, __bos (__dest));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Shawn Landden <shawn@xxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
LPU-Reference: 20190518183238.10954-1-shawn@xxxxxxx
Link: https://lkml.kernel.org/n/tip-289f1jice17ta7tr3tstm9jm@xxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/data-convert-bt.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/data-convert-bt.c b/tools/perf/util/data-convert-bt.c
index e0311c9750ad..9097543a818b 100644
--- a/tools/perf/util/data-convert-bt.c
+++ b/tools/perf/util/data-convert-bt.c
@@ -271,7 +271,7 @@ static int string_set_value(struct bt_ctf_field *field, const char *string)
if (i > 0)
strncpy(buffer, string, i);
}
- strncat(buffer + p, numstr, 4);
+ memcpy(buffer + p, numstr, 4);
p += 3;
}
}