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.

1 files changed, 16 insertions, 12 deletions

diff --git a/sysdeps/unix/sysv/linux/sigaction.c b/sysdeps/unix/sysv/linux/sigaction.c
index 40a311a3b3..0e6851a148 100644
--- a/sysdeps/unix/sysv/linux/sigaction.c
+++ b/sysdeps/unix/sysv/linux/sigaction.c
@@ -22,11 +22,19 @@
 #include <sysdep.h>
 #include <sys/syscall.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.  */
+/* New ports should not define the obsolete SA_RESTORER, however some
+   architecture requires for compat mode and/or due old ABI.  */
 #include <kernel_sigaction.h>
 
+#ifndef SA_RESTORER
+# define SET_SA_RESTORER(kact, act)
+# define RESET_SA_RESTORER(act, kact)
+#endif
+
+/* SPARC passes the restore function as an argument to rt_sigaction.  */
+#ifndef STUB
+# define STUB(act)
+#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.  */
@@ -42,25 +50,21 @@ __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
       kact.k_sa_handler = act->sa_handler;
       memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
       kact.sa_flags = act->sa_flags;
-#ifdef HAVE_SA_RESTORER
-      kact.sa_restorer = act->sa_restorer;
-#endif
+      SET_SA_RESTORER (&kact, act);
     }
 
   /* 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, _NSIG / 8);
+  result = INLINE_SYSCALL_CALL (rt_sigaction, sig,
+				act ? &kact : NULL,
+				oact ? &koact : NULL, STUB(act) _NSIG / 8);
 
   if (oact && result >= 0)
     {
       oact->sa_handler = koact.k_sa_handler;
       memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
       oact->sa_flags = koact.sa_flags;
-#ifdef HAVE_SA_RESTORER
-      oact->sa_restorer = koact.sa_restorer;
-#endif
+      RESET_SA_RESTORER (oact, &koact);
     }
   return result;
 }