Re: [LTP] [PATCH] containers: Use raw setns syscall for versions of glibc that don't include it

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Hangbin Liu" <liuhangbin@gmail.com>
> To: "LTP List" <ltp-list@lists.sourceforge.net>
> Sent: Tuesday, 30 June, 2015 8:18:45 AM
> Subject: [LTP] [PATCH] containers: Use raw setns syscall for versions of	glibc that don't include it
> 
> On RHEL6.6, the kernel support setns syscall, but glibc(2.12) does not
> support
> this syscall. Thus ltp build failed with "userns04.c:58: undefined reference
> to `setns'". Use raw setns syscall to make ltp build pass.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
> ---
>  testcases/kernel/containers/userns/userns_helper.h | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/testcases/kernel/containers/userns/userns_helper.h
> b/testcases/kernel/containers/userns/userns_helper.h
> index da03bae..9107886 100644
> --- a/testcases/kernel/containers/userns/userns_helper.h
> +++ b/testcases/kernel/containers/userns/userns_helper.h
> @@ -15,6 +15,19 @@
>  #include "test.h"
>  #include "safe_macros.h"
>  
> +/*
> + * Use raw setns syscall for versions of glibc that don't include it (namely
> + * glibc-2.12)
> + */
> +#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 14
> +#ifdef SYS_setns
> +int setns(int fd, int nstype)
> +{
> +	return syscall(SYS_setns, fd, nstype);
> +}
> +#endif
> +#endif
> +

This will still fail if SYS_setns is not defined.

We have ltp_syscall and "linux_syscall_numbers.h", which can guaruantee
that __NR_setns will be defined and ltp_syscall will break with TCONF
in case you get ENOSYS.

So if you add dummy call to setns in setup():
  ltp_syscall(__NR_setns, -1, 0);
you can stop the testcase quite early with TCONF if setns is not supported.

Regards,
Jan

>  static int dummy_child(void *v)
>  {
>  	(void) v;
> --
> 1.9.3
> 
> 
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