[v3,1/6] hurd: Implement sigreturn for x86_64

  Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
This incorporates back the fix made to the i386 version: we do need to call
_hurd_self_sigstate () once after all.

 sysdeps/mach/hurd/x86_64/sigreturn.c | 162 +++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 sysdeps/mach/hurd/x86_64/sigreturn.c
  

Applied, thanks!

Sergey Bugaev, le sam. 29 avril 2023 23:18:17 +0300, a ecrit:
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
> This incorporates back the fix made to the i386 version: we do need to call
> _hurd_self_sigstate () once after all.
> 
>  sysdeps/mach/hurd/x86_64/sigreturn.c | 162 +++++++++++++++++++++++++++
>  1 file changed, 162 insertions(+)
>  create mode 100644 sysdeps/mach/hurd/x86_64/sigreturn.c
> 
> diff --git a/sysdeps/mach/hurd/x86_64/sigreturn.c b/sysdeps/mach/hurd/x86_64/sigreturn.c
> new file mode 100644
> index 00000000..82247e3c
> --- /dev/null
> +++ b/sysdeps/mach/hurd/x86_64/sigreturn.c
> @@ -0,0 +1,162 @@
> +/* Copyright (C) 1991-2023 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/>.  */
> +
> +#include <hurd.h>
> +#include <hurd/signal.h>
> +#include <hurd/msg.h>
> +#include <stdlib.h>
> +
> +/* This is run on the thread stack after restoring it, to be able to
> +   unlock SS off sigstack.  */
> +void
> +__sigreturn2 (struct hurd_sigstate *ss, uintptr_t *usp,
> +              struct sigcontext *scp)
> +{
> +  mach_port_t reply_port;
> +  _hurd_sigstate_unlock (ss);
> +
> +  /* Destroy the MiG reply port used by the signal handler, and restore the
> +     reply port in use by the thread when interrupted.
> +
> +     We cannot use the original reply port for our RPCs that we do here, since
> +     we could unexpectedly receive/consume a reply message meant for the user
> +     (in particular, msg_sig_post_reply), and also since we would deallocate
> +     the port if *our* RPC fails, which we don't want to do since the user
> +     still has the old name.  And so, temporarily set MACH_PORT_DEAD as our
> +     reply name, and make sure destroying the port is the very last RPC we
> +     do.  */
> +  reply_port = THREAD_GETMEM (THREAD_SELF, reply_port);
> +  THREAD_SETMEM (THREAD_SELF, reply_port, MACH_PORT_DEAD);
> +  if (__glibc_likely (MACH_PORT_VALID (reply_port)))
> +    (void) __mach_port_mod_refs (__mach_task_self (), reply_port,
> +                                 MACH_PORT_RIGHT_RECEIVE, -1);
> +  THREAD_SETMEM (THREAD_SELF, reply_port, scp->sc_reply_port);
> +
> +  asm volatile (
> +                /* Point the stack to the register dump.  */
> +                "movq %0, %%rsp\n"
> +                /* Pop off the registers.  */
> +                "popq %%r8\n"
> +                "popq %%r9\n"
> +                "popq %%r10\n"
> +                "popq %%r11\n"
> +                "popq %%r12\n"
> +                "popq %%r13\n"
> +                "popq %%r14\n"
> +                "popq %%r15\n"
> +                "popq %%rdi\n"
> +                "popq %%rsi\n"
> +                "popq %%rbp\n"
> +                "popq %%rbx\n"
> +                "popq %%rdx\n"
> +                "popq %%rcx\n"
> +                "popq %%rax\n"
> +                "popfq\n"
> +                /* Restore %rip and %rsp with a single instruction.  */
> +                "retq $128" :
> +                : "rm" (usp));
> +  __builtin_unreachable ();
> +}
> +
> +int
> +__sigreturn (struct sigcontext *scp)
> +{
> +  struct hurd_sigstate *ss;
> +  struct hurd_userlink *link = (void *) &scp[1];
> +
> +  if (__glibc_unlikely (scp == NULL || (scp->sc_mask & _SIG_CANT_MASK)))
> +    {
> +      errno = EINVAL;
> +      return -1;
> +    }
> +
> +  ss = _hurd_self_sigstate ();
> +  _hurd_sigstate_lock (ss);
> +
> +  /* Remove the link on the `active resources' chain added by
> +     _hurd_setup_sighandler.  Its purpose was to make sure
> +     that we got called; now we have, it is done.  */
> +  _hurd_userlink_unlink (link);
> +
> +  /* Restore the set of blocked signals, and the intr_port slot.  */
> +  ss->blocked = scp->sc_mask;
> +  ss->intr_port = scp->sc_intr_port;
> +
> +  /* Check for pending signals that were blocked by the old set.  */
> +  if (_hurd_sigstate_pending (ss) & ~ss->blocked)
> +    {
> +      /* There are pending signals that just became unblocked.  Wake up the
> +	 signal thread to deliver them.  But first, squirrel away SCP where
> +	 the signal thread will notice it if it runs another handler, and
> +	 arrange to have us called over again in the new reality.  */
> +      ss->context = scp;
> +      _hurd_sigstate_unlock (ss);
> +      __msg_sig_post (_hurd_msgport, 0, 0, __mach_task_self ());
> +      /* If a pending signal was handled, sig_post never returned.
> +	 If it did return, the pending signal didn't run a handler;
> +	 proceed as usual.  */
> +      _hurd_sigstate_lock (ss);
> +      ss->context = NULL;
> +    }
> +
> +  if (scp->sc_onstack)
> +    ss->sigaltstack.ss_flags &= ~SS_ONSTACK;
> +
> +  if (scp->sc_fpused)
> +    /* Restore the FPU state.  Mach conveniently stores the state
> +       in the format the i387 `frstor' instruction uses to restore it.  */
> +    asm volatile ("frstor %0" : : "m" (scp->sc_fpsave));
> +
> +  {
> +    /* There are convenient instructions to pop state off the stack, so we
> +       copy the registers onto the user's stack, switch there, pop and
> +       return.  */
> +
> +    uintptr_t *usp = (uintptr_t *) scp->sc_ursp - 128;
> +
> +    *--usp = scp->sc_rip;
> +    *--usp = scp->sc_rfl;
> +    *--usp = scp->sc_rax;
> +    *--usp = scp->sc_rcx;
> +    *--usp = scp->sc_rdx;
> +    *--usp = scp->sc_rbx;
> +    *--usp = scp->sc_rbp;
> +    *--usp = scp->sc_rsi;
> +    *--usp = scp->sc_rdi;
> +    *--usp = scp->sc_r15;
> +    *--usp = scp->sc_r14;
> +    *--usp = scp->sc_r13;
> +    *--usp = scp->sc_r12;
> +    *--usp = scp->sc_r11;
> +    *--usp = scp->sc_r10;
> +    *--usp = scp->sc_r9;
> +    *--usp = scp->sc_r8;
> +
> +    /* Switch to the user's stack that we have just prepared, and call
> +       __sigreturn2.  Clobber "memory" to make sure GCC flushes the stack
> +       setup to actual memory.  We align the stack as per the ABI, but pass
> +       the original usp to __sigreturn2 as an argument.  */
> +    asm volatile ("movq %1, %%rsp\n"
> +                  "andq $-16, %%rsp\n"
> +                  "call __sigreturn2" :
> +                  : "D" (ss), "S" (usp), "d" (scp)
> +                  : "memory");
> +    __builtin_unreachable ();
> +  }
> +}
> +
> +weak_alias (__sigreturn, sigreturn)
> -- 
> 2.40.1
>