Re: [PATCH] selftests/exec: Check if the syscall exists and bail if not

On Wed, 2015-01-21 at 10:22 +0000, David Drysdale wrote:

On Wed, Jan 21, 2015 at 7:41 AM, Michael Ellerman [off-list ref] wrote:

quoted

On systems which don't implement sys_execveat(), this test produces a
lot of output.

Add a check at the beginning to see if the syscall is present, and if
not just note one error and return.

Good point, thanks.

quoted

diff --git a/tools/testing/selftests/exec/execveat.c b/tools/testing/selftests/exec/execveat.c
index e238c9559caf..b87e4a843bea 100644
--- a/tools/testing/selftests/exec/execveat.c
+++ b/tools/testing/selftests/exec/execveat.c

@@ -234,6 +234,14 @@ static int run_tests(void)
        int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
        int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);

+       /* Check if we have execveat at all, and bail early if not */
+       errno = 0;
+       execveat_(-1, NULL, NULL, NULL, 0);
+       if (errno == -ENOSYS) {

Could we change this to ENOSYS (no minus) and also change
the execveat_() function similarly, so that a binary built where
__NR_execveat is available but running where it isn't also exits
early?  (My bad for having the minus sign in execveat_() in the
first place -- fingers too used to kernel mode.)

Ah yeah, me too, -ENOSYS just came naturally.

Will fix up and retest and resend.

cheers