linux: Consolidate sigaction implementation

This patch consolidates all Linux sigaction implementations on the default
sysdeps/unix/sysv/linux/sigaction.c.  The idea is remove redundant code
and simplify new ports addition by following the current generic
Linux User API (UAPI).

The UAPI for new ports defines a generic extensible sigaction struct as:

  struct sigaction
  {
    __sighandler_t sa_handler;
    unsigned long sa_flags;
  #ifdef SA_RESTORER
    void (*sa_restorer) (void);
  #endif
    sigset_t sa_mask;
  };

Where SA_RESTORER is just placed for compatibility reasons (news ports
should not add it).  A similar definition is used on generic
kernel_sigaction.h.

The user exported sigaction definition is not changed, so for most
architectures it requires an adjustment to kernel expected one for the
syscall.

The main changes are:

  - All architectures now define and use a kernel_sigaction struct meant
    for the syscall, even for the architectures where the user sigaction
    has the same layout of the kernel expected one (s390-64 and ia64).
    Although it requires more work for these architectures, it simplifies
    the generic implementation. Also, sigaction is hardly a hotspot where
    micro optimization would play an important role.

  - The generic kernel_sigaction definition is now aligned with expected
    UAPI one for newer ports, where SA_RESTORER and sa_restorer are not
    expected to be defined.  This means adding kernel_sigaction for
    current architectures that does define it (m68k, nios2, powerpc, s390,
    sh, sparc, and tile) and which rely on previous generic definition.

  - Remove old MIPS usage of sa_restorer.  This was removed since 2.6.27
    (2957c9e61ee9c - "[MIPS] IRIX: Goodbye and thanks for all the fish").

  - The remaining arch-specific sigaction.c are to handle ABI idiosyncrasies
    (like SPARC kernel ABI for rt_sigaction that requires an additional
    stub argument).

So for new ports the generic implementation should work if its uses
Linux UAPI.  If SA_RESTORER is still required (due some architecture
limitation), it should define its own kernel_sigaction.h, define it and
include generic header (assuming it still uses the default generic kernel
layout).

Checked on x86_64-linux-gnu, i686-linux-gnu, arm-linux-gnueabihf,
aarch64-linux-gnu, sparc64-linux-gnu, sparcv9-linux-gnu, powerpc-linux-gnu,
powerpc64-linux-gnu, ia64-linux-gnu and alpha-linux-gnu.  I also checked the
build on all remaining affected ABIs.

	* sysdeps/unix/sysv/linux/aarch64/sigaction.c: Use default Linux version
	as base implementation.
	* sysdeps/unix/sysv/linux/arm/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/alpha/kernel_sigaction.h: Add include guards,
	remove unrequired definitions and update comments.
	* sysdeps/unix/sysv/linux/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/ia64/kernel_sigaction.h: New file.
	* sysdeps/unix/sysv/linux/m68k/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/nios2/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/kernel_sigaction: Likewise.
	* sysdeps/unix/sysv/linux/s390/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/sh/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/tile/kernel_sigaction.h: Likewise.
	* sysdeps/unix/sysv/linux/ia64/sigaction.c: Remove file.
	* sysdeps/unix/sysv/linux/mips/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/sigaction.c: Likewise.
	* sysdeps/unix/sysv/linux/sigaction.c: Add STUB, SET_SA_RESTORER,
	and RESET_SA_RESTORER hooks.

2 files changed, 10 insertions, 154 deletions

diff --git a/sysdeps/unix/sysv/linux/mips/kernel_sigaction.h b/sysdeps/unix/sysv/linux/mips/kernel_sigaction.h
index b6f52cc9c9..beef976cc3 100644
--- a/sysdeps/unix/sysv/linux/mips/kernel_sigaction.h
+++ b/sysdeps/unix/sysv/linux/mips/kernel_sigaction.h
@@ -1,40 +1,12 @@
-/* This is the sigaction structure from the Linux 2.1.24 kernel.  */
-
-#include <sgidefs.h>
-
-#define HAVE_SA_RESTORER
-
-struct old_kernel_sigaction {
-	unsigned int	sa_flags;
-	__sighandler_t	k_sa_handler;
-	unsigned long	sa_mask;
-	unsigned int    __pad0[3]; /* reserved, keep size constant */
-
-	/* Abi says here follows reserved int[2] */
-	void		(*sa_restorer)(void);
-#if (_MIPS_SZPTR < 64)
-	/*
-	 * For 32 bit code we have to pad struct sigaction to get
-	 * constant size for the ABI
-	 */
-	int		pad1[1]; /* reserved */
-#endif
+#ifndef _KERNEL_SIGACTION_H
+# define _KERNEL_SIGACTION_H
+
+/* This is the sigaction structure from the Linux 3.2 kernel.  */
+struct kernel_sigaction
+{
+  unsigned int    sa_flags;
+  __sighandler_t  k_sa_handler;
+  sigset_t        sa_mask;
 };
 
-
-#define _KERNEL_NSIG	       128
-#define _KERNEL_NSIG_BPW       _MIPS_SZLONG
-#define _KERNEL_NSIG_WORDS     (_KERNEL_NSIG / _KERNEL_NSIG_BPW)
-
-typedef struct {
-	unsigned long sig[_KERNEL_NSIG_WORDS];
-} kernel_sigset_t;
-
-/* This is the sigaction structure from the Linux 2.1.68 kernel.  */
-struct kernel_sigaction {
-	unsigned int	sa_flags;
-	__sighandler_t	k_sa_handler;
-	kernel_sigset_t	sa_mask;
-	void		(*sa_restorer)(void);
-	int		s_resv[1]; /* reserved */
-};
+#endif
diff --git a/sysdeps/unix/sysv/linux/mips/sigaction.c b/sysdeps/unix/sysv/linux/mips/sigaction.c
deleted file mode 100644
index 008b688977..0000000000
--- a/sysdeps/unix/sysv/linux/mips/sigaction.c
+++ /dev/null
@@ -1,116 +0,0 @@
-/* Copyright (C) 1997-2018 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
-   <http://www.gnu.org/licenses/>.  */
-
-#include <errno.h>
-#include <sgidefs.h>
-#include <signal.h>
-#include <string.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-#include <sgidefs.h>
-
-/* The difference here is that the sigaction structure used in the
-   kernel is not the same as we use in the libc.  Therefore we must
-   translate it here.  */
-#include <kernel_sigaction.h>
-
-#if _MIPS_SIM != _ABIO32
-
-# ifdef __NR_rt_sigreturn
-static void restore_rt (void) asm ("__restore_rt");
-# endif
-# ifdef __NR_sigreturn
-static void restore (void) asm ("__restore");
-# endif
-#endif
-
-/* If ACT is not NULL, change the action for SIG to *ACT.
-   If OACT is not NULL, put the old action for SIG in *OACT.  */
-int
-__libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
-{
-  int result;
-
-  struct kernel_sigaction kact, koact;
-
-  if (act)
-    {
-      kact.k_sa_handler = act->sa_handler;
-      memcpy (&kact.sa_mask, &act->sa_mask, sizeof (kernel_sigset_t));
-      kact.sa_flags = act->sa_flags;
-#ifdef HAVE_SA_RESTORER
-# if _MIPS_SIM == _ABIO32
-      kact.sa_restorer = act->sa_restorer;
-# else
-      kact.sa_restorer = &restore_rt;
-# endif
-#endif
-    }
-
-  /* XXX The size argument hopefully will have to be changed to the
-     real size of the user-level sigset_t.	*/
-  result = INLINE_SYSCALL (rt_sigaction, 4, sig,
-			   act ? &kact : NULL,
-			   oact ? &koact : NULL,
-			   sizeof (kernel_sigset_t));
-
-  if (oact && result >= 0)
-    {
-      oact->sa_handler = koact.k_sa_handler;
-      memcpy (&oact->sa_mask, &koact.sa_mask,
-	      sizeof (kernel_sigset_t));
-      oact->sa_flags = koact.sa_flags;
-#ifdef HAVE_SA_RESTORER
-      oact->sa_restorer = koact.sa_restorer;
-#endif
-    }
-  return result;
-}
-libc_hidden_def (__libc_sigaction)
-
-#include <nptl/sigaction.c>
-
-
-/* NOTE: Please think twice before making any changes to the bits of
-   code below.  GDB needs some intimate knowledge about it to
-   recognize them as signal trampolines, and make backtraces through
-   signal handlers work right.  Important are both the names
-   (__restore_rt) and the exact instruction sequence.
-   If you ever feel the need to make any changes, please notify the
-   appropriate GDB maintainer.  */
-
-#define RESTORE(name, syscall) RESTORE2 (name, syscall)
-#define RESTORE2(name, syscall) \
-asm						\
-  (						\
-   ".align 4\n"					\
-   "__" #name ":\n"				\
-   "	li $2, " #syscall "\n"			\
-   "	syscall\n"				\
-   );
-
-/* The return code for realtime-signals.  */
-#if _MIPS_SIM != _ABIO32
-# ifdef __NR_rt_sigreturn
-RESTORE (restore_rt, __NR_rt_sigreturn)
-# endif
-# ifdef __NR_sigreturn
-RESTORE (restore, __NR_sigreturn)
-# endif
-#endif