Hello, On Thu, Feb 08, 2018 at 04:13:20PM +0800, [email protected] wrote: > From: Changbin Du <[email protected]> > > The terminal character '\0' should take into account into 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. If usersapce writes a non-terminated string, the kernel > side will always return success but actually no filter applied. > > As discussed before, the kernel now support '\0' to mark the end of string: > https://lkml.org/lkml/2018/1/16/116 > > After this fix in userspace, the perf will report correct error state. Also > let it print an error if reset_tracing_files() fails.
But what about old kernels? IIRC there was an error with this change. Thanks, Namhyung > > The problem: > $ 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. The expected error is hidden. > > Signed-off-by: Changbin Du <[email protected]> > --- > tools/perf/builtin-ftrace.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c > index 25a42ac..a87e9b3 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]; > > @@ -280,8 +280,10 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int > argc, const char **argv) > signal(SIGCHLD, sig_handler); > signal(SIGPIPE, sig_handler); > > - if (reset_tracing_files(ftrace) < 0) > + if (reset_tracing_files(ftrace) < 0) { > + pr_err("failed to reset ftrace\n"); > goto out; > + } > > /* reset ftrace buffer */ > if (write_tracing_file("trace", "0") < 0) > -- > 2.7.4 >
