Re: [PATCH 1/8] nptl: Add <thread_pointer.h> for defining __thread_pointer

[Szabolcs Nagy <szabolcs.nagy@arm.com>]

The 12/07/2021 14:00, Florian Weimer via Libc-alpha wrote:
> <tls.h> already contains a definition that is quite similar,
> but it is not consistent across architectures.
> 
> Only architectures for which rseq support is added are covered.

This looks ok.

It's an annoying gcc bug that __builtin_thread_pointer
does not work consistently across targets.

Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>

> ---
> v2: As posted before.
> 
>  sysdeps/nptl/thread_pointer.h         | 28 ++++++++++++++++++++
>  sysdeps/powerpc/nptl/thread_pointer.h | 33 +++++++++++++++++++++++
>  sysdeps/x86/nptl/thread_pointer.h     | 38 +++++++++++++++++++++++++++
>  3 files changed, 99 insertions(+)
>  create mode 100644 sysdeps/nptl/thread_pointer.h
>  create mode 100644 sysdeps/powerpc/nptl/thread_pointer.h
>  create mode 100644 sysdeps/x86/nptl/thread_pointer.h
> 
> diff --git a/sysdeps/nptl/thread_pointer.h b/sysdeps/nptl/thread_pointer.h
> new file mode 100644
> index 0000000000..92f2f3093e
> --- /dev/null
> +++ b/sysdeps/nptl/thread_pointer.h
> @@ -0,0 +1,28 @@
> +/* __thread_pointer definition.  Generic 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 _SYS_THREAD_POINTER_H
> +#define _SYS_THREAD_POINTER_H
> +
> +static inline void *
> +__thread_pointer (void)
> +{
> +  return __builtin_thread_pointer ();
> +}
> +
> +#endif /* _SYS_THREAD_POINTER_H */
> diff --git a/sysdeps/powerpc/nptl/thread_pointer.h b/sysdeps/powerpc/nptl/thread_pointer.h
> new file mode 100644
> index 0000000000..8fd5ba671f
> --- /dev/null
> +++ b/sysdeps/powerpc/nptl/thread_pointer.h
> @@ -0,0 +1,33 @@
> +/* __thread_pointer definition.  powerpc 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 _SYS_THREAD_POINTER_H
> +#define _SYS_THREAD_POINTER_H
> +
> +static inline void *
> +__thread_pointer (void)
> +{
> +#ifdef __powerpc64__
> +  register void *__result asm ("r13");
> +#else
> +  register void *__result asm ("r2");
> +#endif
> +  return __result;
> +}
> +
> +#endif /* _SYS_THREAD_POINTER_H */
> diff --git a/sysdeps/x86/nptl/thread_pointer.h b/sysdeps/x86/nptl/thread_pointer.h
> new file mode 100644
> index 0000000000..6b71b6f7e1
> --- /dev/null
> +++ b/sysdeps/x86/nptl/thread_pointer.h
> @@ -0,0 +1,38 @@
> +/* __thread_pointer definition.  x86 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 _SYS_THREAD_POINTER_H
> +#define _SYS_THREAD_POINTER_H
> +
> +static inline void *
> +__thread_pointer (void)
> +{
> +#if __GNUC_PREREQ (11, 1)
> +  return __builtin_thread_pointer ();
> +#else
> +  void *__result;
> +# ifdef __x86_64__
> +  __asm__ ("mov %%fs:0, %0" : "=r" (__result));
> +# else
> +  __asm__ ("mov %%gs:0, %0" : "=r" (__result));
> +# endif
> +  return __result;
> +#endif /* !GCC 11 */
> +}
> +
> +#endif /* _SYS_THREAD_POINTER_H */
> -- 
> 2.33.1
> 
>