perf_evlist__mmap_ex() can fail without setting errno (for example,
fail in condition checking. In this case all syscall is success).
If this happen, record__open() incorrectly returns 0. Force setting
rc is a quick way to avoid this problem, or we have to follow all
possible code path in perf_evlist__mmap_ex() to make sure there's
at least one system call before returning an error.

Signed-off-by: Wang Nan <wangn...@huawei.com>
Signed-off-by: He Kuang <heku...@huawei.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Jiri Olsa <jo...@kernel.org>
Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Zefan Li <lize...@huawei.com>
Cc: pi3or...@163.com
---
 tools/perf/builtin-record.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a2de15b..fa16099 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -363,7 +363,10 @@ try_again:
                } else {
                        pr_err("failed to mmap with %d (%s)\n", errno,
                                strerror_r(errno, msg, sizeof(msg)));
-                       rc = -errno;
+                       if (errno)
+                               rc = -errno;
+                       else
+                               rc = -EINVAL;
                }
                goto out;
        }
-- 
1.8.3.4

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