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SubjectRe: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file
On Mon, Jan 08, 2018 at 11:05:12AM +0800, Du, Changbin wrote:
> Hi Olsa,
> What about this fix now? Thanks!
>
> On Tue, Dec 26, 2017 at 05:26:56PM +0800, changbin.du@intel.com wrote:
> > 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.

hum, haven't checked, but looks like the filter is not working at all now:

[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs proc_sys_read
write ' ' to tracing/set_ftrace_pid failed: Invalid argument
[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs SyS_read
write ' ' to tracing/set_ftrace_pid failed: Invalid argument
[root@krava perf]# ./perf ftrace -vv -a --graph-depth 1 --graph-funcs fsnotify
write ' ' to tracing/set_ftrace_pid failed: Invalid argument

jirka

> >
> > 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
> >
>
> --
> Thanks,
> Changbin Du

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