Re: [PATCH 3/3] s390x: Check HWCAP bits against compiler flags

[Stefan Liebler <stli@linux.ibm.com>]

On 06/05/2021 14:30, Florian Weimer via Libc-alpha wrote:
> When compiled with GCC 11.1 and -march=z14 -O3 build flags, running
> ld.so (or any dynamically linked program) prints:
> 
> Fatal glibc error: CPU lacks VXE support (z14 or later required)
> 
> Co-Authored-By: Stefan Liebler <stli@linux.ibm.com>
> ---
>  sysdeps/s390/s390-64/dl-hwcap-check.h | 40 +++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
>  create mode 100644 sysdeps/s390/s390-64/dl-hwcap-check.h
> 
> diff --git a/sysdeps/s390/s390-64/dl-hwcap-check.h b/sysdeps/s390/s390-64/dl-hwcap-check.h
> new file mode 100644
> index 0000000000..87e18be6bd
> --- /dev/null
> +++ b/sysdeps/s390/s390-64/dl-hwcap-check.h
> @@ -0,0 +1,40 @@
> +/* Check for hardware capabilities after HWCAP parsing.  S390 version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#ifndef _DL_HWCAP_CHECK_H
> +#define _DL_HWCAP_CHECK_H
> +
> +#include <ldsodefs.h>
> +
> +static inline void
> +dl_hwcap_check (void)
> +{
> +#if defined __ARCH__
> +# if __ARCH__ >= 13
> +  if (!(GLRO(dl_hwcap) & HWCAP_S390_VXRS_EXT2))
> +    _dl_fatal_printf ("\
> +Fatal glibc error: CPU lacks VXRS_EXT2 support (z15 or later required)\n");
> +# elif __ARCH__ >= 12
> +  if (!(GLRO(dl_hwcap) & HWCAP_S390_VXE))
> +    _dl_fatal_printf ("\
> +Fatal glibc error: CPU lacks VXE support (z14 or later required)\n");
> +# endif
> +#endif /* __ARCH__ */
> +}
> +
> +#endif /* _DL_HWCAP_CHECK_H */
> 

Hi Florian,

while running some tests, I got the messages as expected:
on z13:
- "-march=z13" => no message
- "-march=z14" => "z14 or later required"
- "-march=z15" => "z15 or later required"

on z14:
- "-march=z13" => no message
- "-march=z14" => no message
- "-march=z15" => "z15 or later required"

on z15:
- "-march=z13" => no message
- "-march=z14" => no message
- "-march=z15" => no message

Reviewed-by: Stefan Liebler <stli@linux.ibm.com>

Thanks,
Stefan