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

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Date:	Fri, 23 Jan 2015 17:01:26 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	David Drysdale <drysdale@...gle.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux API <linux-api@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Shuah Khan <shuahkh@....samsung.com>, davej@...emonkey.org.uk
Subject: 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 <mpe@...erman.id.au> wrote:
> > 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.
> 
> > 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


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