[v2] nptl: Add <thread_pointer.h> for defining __thread_pointer

<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.

---
v2: Handle fewer architectures.  Always use an inline function.

 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(+)

----- On Dec 6, 2021, at 2:56 PM, Florian Weimer fweimer@redhat.com 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.

What list did you use to select which architectures to prune ? I notice that
e.g. m68k implements sys_rseq, but has been removed from the list. Likewise
for many other architectures.

Thanks,

Mathieu

> 
> ---
> v2: Handle fewer architectures.  Always use an inline function.
> 
> 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(+)
> 
> 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 */

* Mathieu Desnoyers:

> ----- On Dec 6, 2021, at 2:56 PM, Florian Weimer fweimer@redhat.com 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.
>
> What list did you use to select which architectures to prune ? I notice that
> e.g. m68k implements sys_rseq, but has been removed from the list. Likewise
> for many other architectures.

Availability of RSEQ_SIG.

$ python3 sysdeps/unix/sysv/linux/glibcsyscalls.py query-syscall rseq
rseq: defined on all architectures

So that's no real simplification/ 8-)

Thanks,
Florian