[PATCH 3.16 361/366] perf trace: Fix up fd -> pathname resolution

Ben Hutchings
2018-11-11T19:49:05Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit cdcd1e6bd8a92f8353fc2f37003c6eae2d1e6903 upstream.

There was a brown paper bag bug in the patch that introduced a reference
implementation on using 'perf probe' made wannabe tracepoints that broke fd ->
pathname resolution, fix it:

[root@zoo ~]# perf probe 'vfs_getname=getname_flags:65 pathname=result->name:string'
Added new event:
probe:vfs_getname (on getname_flags:65 with pathname=result->name:string)

You can now use it in all perf tools, such as:

perf record -e probe:vfs_getname -aR sleep 1

[root@zoo ~]

Before:

[acme@zoo linux]$ trace touch -e open,fstat /tmp/b
1.159 ( 0.007 ms): open(filename: 0x7fd73f2fe088, flags: CLOEXEC ) = 3
1.163 ( 0.002 ms): fstat(fd: 3, statbuf: 0x7fff1b25e610 ) = 0
1.192 ( 0.009 ms): open(filename: 0x7fd73f4fedb8, flags: CLOEXEC ) = 3
1.201 ( 0.002 ms): fstat(fd: 3, statbuf: 0x7fff1b25e660 ) = 0
1.501 ( 0.013 ms): open(filename: 0x7fd73f0a1610, flags: CLOEXEC ) = 3
1.505 ( 0.002 ms): fstat(fd: 3, statbuf: 0x7fd73f2ddb60 ) = 0
1.581 ( 0.011 ms): open(filename: 0x7fff1b2603da, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: 438) = 3
[acme@zoo linux]$

After:

[acme@zoo linux]$ trace touch -e open,fstat,dup2,mmap,close /tmp/b
1.105 ( 0.004 ms): mmap(len: 4096, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS, fd: -1 ) = 0x2fbf000
1.136 ( 0.008 ms): open(filename: 0x7f8902dbc088, flags: CLOEXEC ) = 3
1.140 ( 0.002 ms): fstat(fd: 3</etc/ld.so.cache>, statbuf: 0x7fff19889ef0 ) = 0
1.146 ( 0.004 ms): mmap(len: 86079, prot: READ, flags: PRIVATE, fd: 3</etc/ld.so.cache> ) = 0x2fa9000
1.149 ( 0.001 ms): close(fd: 3</etc/ld.so.cache> ) = 0
1.170 ( 0.010 ms): open(filename: 0x7f8902fbcdb8, flags: CLOEXEC ) = 3
1.178 ( 0.002 ms): fstat(fd: 3</lib64/libc.so.6>, statbuf: 0x7fff19889f40 ) = 0
1.188 ( 0.006 ms): mmap(len: 3924576, prot: EXEC|READ, flags: PRIVATE|DENYWRITE, fd: 3</lib64/libc.so.6>) = 0x29e2000
1.207 ( 0.007 ms): mmap(addr: 0x7f8902d96000, len: 24576, prot: READ|WRITE, flags: PRIVATE|DENYWRITE|FIXED, fd: 3</lib64/libc.so.6>, off: 1785856) = 0x2d96000
1.217 ( 0.004 ms): mmap(addr: 0x7f8902d9c000, len: 16992, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS|FIXED, fd: -1) = 0x2d9c000
1.228 ( 0.002 ms): close(fd: 3</lib64/libc.so.6> ) = 0
1.243 ( 0.003 ms): mmap(len: 4096, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS, fd: -1 ) = 0x2fa8000
1.250 ( 0.003 ms): mmap(len: 8192, prot: READ|WRITE, flags: PRIVATE|ANONYMOUS, fd: -1 ) = 0x2fa6000
1.452 ( 0.010 ms): open(filename: 0x7f8902b5f610, flags: CLOEXEC ) = 3
1.455 ( 0.002 ms): fstat(fd: 3</usr/lib/locale/locale-archive>, statbuf: 0x7f8902d9bb60 ) = 0
1.461 ( 0.004 ms): mmap(len: 106070960, prot: READ, flags: PRIVATE, fd: 3</usr/lib/locale/locale-archive>) = 0xfc4b9000
1.469 ( 0.002 ms): close(fd: 3</usr/lib/locale/locale-archive> ) = 0
1.528 ( 0.010 ms): open(filename: 0x7fff1988c3da, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: 438) = 3
1.532 ( 0.002 ms): dup2(oldfd: 3</tmp/b> ) = 0
1.535 ( 0.001 ms): close(fd: 3</tmp/b> ) = 0
1.544 ( 0.001 ms): close( ) = 0
1.555 ( 0.001 ms): close(fd: 1 ) = 0
1.558 ( 0.001 ms): close(fd: 2 ) = 0
[acme@zoo linux]$

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-vcm22xpjxc3j4hbyuzjzf7ik@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
tools/perf/builtin-trace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -1276,11 +1276,11 @@ static const char *thread__fd_path(struc
if (fd < 0)
return NULL;

- if ((fd > ttrace->paths.max || ttrace->paths.table[fd] == NULL))
+ if ((fd > ttrace->paths.max || ttrace->paths.table[fd] == NULL)) {
if (!trace->live)
return NULL;
++trace->stats.proc_getname;
- if (thread__read_fd_path(thread, fd)) {
+ if (thread__read_fd_path(thread, fd))
return NULL;
}