lkml.org 
[lkml]   [2017]   [Dec]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] perf ftrace: Fix the buffer size in __write_tracing_file
Date
From: Changbin Du <changbin.du@intel.com>

The terminal character '\0' should take into account as size of the string
buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and
'--trace-funcs' options didn't work as expected when the <func> doesn't
exist.

I didn't dive into kernel ftrace fops, but strace shows that if usersapce
writes a non-terminated string, the kernel side will return success but
no filter applied. After this fix in userspace, the kernel will return an
error.

$ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg
0) 0.140 us | rcu_all_qs();
3) 0.304 us | mutex_unlock();
0) 0.153 us | find_vma();
3) 0.088 us | __fsnotify_parent();
0) 6.145 us | handle_mm_fault();
3) 0.089 us | fsnotify();
3) 0.161 us | __sb_end_write();
3) 0.710 us | SyS_close();
3) 7.848 us | exit_to_usermode_loop();

On above example, I specified function filter 'abcdefg' but all functions
are enabled.

Signed-off-by: Changbin Du <changbin.du@intel.com>
---
tools/perf/builtin-ftrace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 25a42ac..2604a64 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
{
char *file;
int fd, ret = -1;
- ssize_t size = strlen(val);
+ ssize_t size = strlen(val) + 1;
int flags = O_WRONLY;
char errbuf[512];

--
2.7.4
\
 
 \ /
  Last update: 2017-12-26 10:36    [W:0.063 / U:2.864 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site