With a suitably defined "probe:vfs_getname" probe, 'perf trace' can "beautify" its output, so syscalls like open() or openat() can print the "filename" argument instead of just its hex address, like: $ perf trace -e open -- touch /dev/null [...] 0.590 ( 0.014 ms): touch/18063 open(filename: /dev/null, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3 [...] The output without such beautifier looks like: 0.529 ( 0.011 ms): touch/18075 open(filename: 0xc78cf288, flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3 However, when the vfs_getname probe expands to multiple probes and it is not the first one that is hit, the beautifier fails, as following: 0.326 ( 0.010 ms): touch/18072 open(filename: , flags: CREAT|NOCTTY|NONBLOCK|WRONLY, mode: IRUGO|IWUGO) = 3 Fix it by hooking into all the expanded probes (inlines), now, for instance: [root@quaco ~]# perf probe -l probe:vfs_getname (on getname_flags:73@fs/namei.c with pathname) probe:vfs_getname_1 (on getname_flags:73@fs/namei.c with pathname) [root@quaco ~]# perf trace -e open* sleep 1 0.010 ( 0.005 ms): sleep/5588 openat(dfd: CWD, filename: /etc/ld.so.cache, flags: RDONLY|CLOEXEC) = 3 0.029 ( 0.006 ms): sleep/5588 openat(dfd: CWD, filename: /lib64/libc.so.6, flags: RDONLY|CLOEXEC) = 3 0.194 ( 0.008 ms): sleep/5588 openat(dfd: CWD, filename: /usr/lib/locale/locale-archive, flags: RDONLY|CLOEXEC) = 3 [root@quaco ~]# Works, further verified with: [root@quaco ~]# perf test vfs 65: Use vfs_getname probe to get syscall args filenames : Ok 66: Add vfs_getname probe to get syscall args filenames : Ok 67: Check open filename arg using perf trace + vfs_getname: Ok [root@quaco ~]#
Unified · Split
| @@ -2514,19 +2514,30 @@ static size_t trace__fprintf_thread_summary(struct trace *trace, FILE *fp); · 2513 unmodified lines | ||
| 2514 | 2514 | |
| 2515 | 2515 | static bool perf_evlist__add_vfs_getname(struct perf_evlist *evlist) |
| 2516 | 2516 | { |
| 2517 | − struct perf_evsel *evsel = perf_evsel__newtp("probe", "vfs_getname"); | |
| 2517 | + bool found = false; | |
| 2518 | + struct perf_evsel *evsel, *tmp; | |
| 2519 | + struct parse_events_error err = { .idx = 0, }; | |
| 2520 | + int ret = parse_events(evlist, "probe:vfs_getname*", &err); | |
| 2518 | 2521 | |
| 2519 | − if (IS_ERR(evsel)) | |
| 2522 | + if (ret) | |
| 2520 | 2523 | return false; |
| 2521 | 2524 | |
| 2522 | − if (perf_evsel__field(evsel, "pathname") == NULL) { | |
| 2525 | + evlist__for_each_entry_safe(evlist, evsel, tmp) { | |
| 2526 | + if (!strstarts(perf_evsel__name(evsel), "probe:vfs_getname")) | |
| 2527 | + continue; | |
| 2528 | + | |
| 2529 | + if (perf_evsel__field(evsel, "pathname")) { | |
| 2530 | + evsel->handler = trace__vfs_getname; | |
| 2531 | + found = true; | |
| 2532 | + continue; | |
| 2533 | + } | |
| 2534 | + | |
| 2535 | + list_del_init(&evsel->node); | |
| 2536 | + evsel->evlist = NULL; | |
| 2523 | 2537 | perf_evsel__delete(evsel); |
| 2524 | − return false; | |
| 2525 | 2538 | } |
| 2526 | 2539 | |
| 2527 | − evsel->handler = trace__vfs_getname; | |
| 2528 | − perf_evlist__add(evlist, evsel); | |
| 2529 | − return true; | |
| 2540 | + return found; | |
| 2530 | 2541 | } |
| 2531 | 2542 | |
| 2532 | 2543 | static struct perf_evsel *perf_evsel__new_pgfault(u64 config) |