[tip:perf/urgent] perf trace: Auto bump rlimit(MEMLOCK) for eBPF maps sake

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  c3e78a3403dabcb7115c2fb7b538a1095d168cd5
Gitweb:     https://git.kernel.org/tip/c3e78a3403dabcb7115c2fb7b538a1095d168cd5
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Tue, 9 Jul 2019 16:36:45 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 9 Jul 2019 16:36:45 -0300

perf trace: Auto bump rlimit(MEMLOCK) for eBPF maps sake

Circa v5.2 this started to fail:

  # perf trace -e /wb/augmented_raw_syscalls.o
  event syntax error: '/wb/augmented_raw_syscalls.o'
                       \___ Operation not permitted

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf trace [<options>] [<command>]
      or: perf trace [<options>] -- <command> [<options>]
      or: perf trace record [<options>] [<command>]
      or: perf trace record [<options>] -- <command> [<options>]

      -e, --event <event>   event/syscall selector. use 'perf list' to list available events
  #

In verbose mode we some -EPERM when creating a BPF map:

  # perf trace -v -e /wb/augmented_raw_syscalls.o
  <SNIP>
  libbpf: failed to create map (name: '__augmented_syscalls__'): Operation not permitted
  libbpf: failed to load object '/wb/augmented_raw_syscalls.o'
  bpf: load objects failed: err=-1: (Operation not permitted)
  event syntax error: '/wb/augmented_raw_syscalls.o'
                       \___ Operation not permitted

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf trace [<options>] [<command>]
      or: perf trace [<options>] -- <command> [<options>]
      or: perf trace record [<options>] [<command>]
      or: perf trace record [<options>] -- <command> [<options>]

      -e, --event <event>   event/syscall selector. use 'perf list' to list available events
  #

If we bumped 'ulimit -l 128' to get it from the 64k default to double that, it
worked, so use the recently added rlimit__bump_memlock() helper:

  # perf trace -e /wb/augmented_raw_syscalls.o -e open*,*sleep sleep 1
       0.000 ( 0.007 ms): sleep/28042 openat(dfd: CWD, filename: "/etc/ld.so.cache", flags: RDONLY|CLOEXEC) = 3
       0.022 ( 0.004 ms): sleep/28042 openat(dfd: CWD, filename: "/lib64/libc.so.6", flags: RDONLY|CLOEXEC) = 3
       0.201 ( 0.007 ms): sleep/28042 openat(dfd: CWD, filename: "", flags: RDONLY|CLOEXEC)                 = 3
       0.241 (1000.421 ms): sleep/28042 nanosleep(rqtp: 0x7ffd6c3e6ed0)                                       = 0
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-j6f2ioa6hj9dinzpjvlhcjoc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/builtin-trace.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index 1aa2ed096f65..4f0bbffee05f 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -19,6 +19,7 @@
 #include <api/fs/tracing_path.h>
 #include <bpf/bpf.h>
 #include "util/bpf_map.h"
+#include "util/rlimit.h"
 #include "builtin.h"
 #include "util/cgroup.h"
 #include "util/color.h"
@@ -3864,6 +3865,15 @@ int cmd_trace(int argc, const char **argv)
 		goto out;
 	}
 
+	/*
+	 * Parsing .perfconfig may entail creating a BPF event, that may need
+	 * to create BPF maps, so bump RLIM_MEMLOCK as the default 64K setting
+	 * is too small. This affects just this process, not touching the
+	 * global setting. If it fails we'll get something in 'perf trace -v'
+	 * to help diagnose the problem.
+	 */
+	rlimit__bump_memlock();
+
 	err = perf_config(trace__config, &trace);
 	if (err)
 		goto out;