From 6a648b534d3d4f6532241fd9b97c0dab7b0c3f89 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Thu, 2 Aug 2018 10:30:08 -0300 Subject: [PATCH] perf trace: Associate vfs_getname()'ed pathname with fd returned from 'openat' When the vfs_getname() wannabe tracepoint is in place: # perf probe -l probe:vfs_getname (on getname_flags:73@acme/git/linux/fs/namei.c with pathname) # 'perf trace' will use it to get the pathname when it is copied from userspace to the kernel, right after syscalls:sys_enter_open, copied in the 'probe:vfs_getname', stash it somewhere and then, at syscalls:sys_exit_open time, if the 'open' return is not -1, i.e. a successfull open syscall, associate that pathname to this return, i.e. the fd. We were not doing this for the 'openat' syscall, which would cause 'perf trace' to fallback to using /proc to get the fd, change it so that we use what we got from probe:vfs_getname, reducing the 'openat' beautification process cost, ditching the syscalls performed to read procfs state and avoiding some possible races in the process. Cc: Adrian Hunter Cc: David Ahern Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-xnp44ao3bkb6ejeczxfnjwsh@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-trace.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c index 88561eed7950..2a85f5198da0 100644 --- a/tools/perf/builtin-trace.c +++ b/tools/perf/builtin-trace.c @@ -121,7 +121,6 @@ struct trace { bool force; bool vfs_getname; int trace_pgfaults; - int open_id; }; struct tp_field { @@ -805,12 +804,17 @@ static struct syscall_fmt *syscall_fmt__find(const char *name) return bsearch(name, syscall_fmts, nmemb, sizeof(struct syscall_fmt), syscall_fmt__cmp); } +/* + * is_exit: is this "exit" or "exit_group"? + * is_open: is this "open" or "openat"? To associate the fd returned in sys_exit with the pathname in sys_enter. + */ struct syscall { struct event_format *tp_format; int nr_args; + bool is_exit; + bool is_open; struct format_field *args; const char *name; - bool is_exit; struct syscall_fmt *fmt; struct syscall_arg_fmt *arg_fmt; }; @@ -1299,6 +1303,7 @@ static int trace__read_syscall_info(struct trace *trace, int id) } sc->is_exit = !strcmp(name, "exit_group") || !strcmp(name, "exit"); + sc->is_open = !strcmp(name, "open") || !strcmp(name, "openat"); return syscall__set_arg_fmts(sc); } @@ -1722,7 +1727,7 @@ static int trace__sys_exit(struct trace *trace, struct perf_evsel *evsel, ret = perf_evsel__sc_tp_uint(evsel, ret, sample); - if (id == trace->open_id && ret >= 0 && ttrace->filename.pending_open) { + if (sc->is_open && ret >= 0 && ttrace->filename.pending_open) { trace__set_fd_pathname(thread, ret, ttrace->filename.name); ttrace->filename.pending_open = false; ++trace->stats.vfs_getname; @@ -3205,8 +3210,6 @@ int cmd_trace(int argc, const char **argv) } } - trace.open_id = syscalltbl__id(trace.sctbl, "open"); - err = target__validate(&trace.opts.target); if (err) { target__strerror(&trace.opts.target, err, bf, sizeof(bf)); -- 2.11.0