text: /* Set thread_state for sighandler, and sigcontext to recover.  i386 version.
     Copyright (C) 1994, 95, 96, 97, 98, 99 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, write to the Free
     Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
     02111-1307 USA.  */
  
  #include <hurd/signal.h>
  #include <hurd/userlink.h>
  #include "thread_state.h"
  #include <assert.h>
  #include <errno.h>
  #include "hurdfault.h"
  #include "intr-msg.h"
  
  
  struct sigcontext *
  _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
  			int signo, struct hurd_signal_detail *detail,
  			volatile int rpc_wait,
  			struct machine_thread_all_state *state)
  {
    void trampoline (void);
    void rpc_wait_trampoline (void);
    void firewall (void);
    extern const void _hurd_intr_rpc_msg_in_trap;
    extern const void _hurd_intr_rpc_msg_cx_sp;
    extern const void _hurd_intr_rpc_msg_sp_restored;
    void *volatile sigsp;
    struct sigcontext *scp;
    struct
      {
        int signo;
        long int sigcode;
        struct sigcontext *scp;	/* Points to ctx, below.  */
        void *sigreturn_addr;
        void *sigreturn_returns_here;
        struct sigcontext *return_scp; /* Same; arg to sigreturn.  */
        struct sigcontext ctx;
        struct hurd_userlink link;
      } *stackframe;
  
    if (ss->context)
      {
        /* We have a previous sigcontext that sigreturn was about
  	 to restore when another signal arrived.  We will just base
  	 our setup on that.  */
        if (! _hurdsig_catch_memory_fault (ss->context))
  	{
  	  memcpy (&state->basic, &ss->context->sc_i386_thread_state,
  		  sizeof (state->basic));
  	  memcpy (&state->fpu, &ss->context->sc_i386_float_state,
  		  sizeof (state->fpu));
  	  state->set |= (1 << i386_THREAD_STATE) | (1 << i386_FLOAT_STATE);
  	}
      }
  
    if (! machine_get_basic_state (ss->thread, state))
      return NULL;
  
    /* Save the original SP in the gratuitous `esp' slot.
       We may need to reset the SP (the `uesp' slot) to avoid clobbering an
       interrupted RPC frame.  */
    state->basic.esp = state->basic.uesp;
  
    if ((ss->actions[signo].sa_flags & SA_ONSTACK) &&
        !(ss->sigaltstack.ss_flags & (SS_DISABLE|SS_ONSTACK)))
      {
        sigsp = ss->sigaltstack.ss_sp + ss->sigaltstack.ss_size;
        ss->sigaltstack.ss_flags |= SS_ONSTACK;
        /* XXX need to set up base of new stack for
  	 per-thread variables, cthreads.  */
      }
    /* This code has intimate knowledge of the special mach_msg system call
       done in intr-msg.c; that code does (see intr-msg.h):
  					movl %esp, %ecx
  					leal ARGS, %esp
  	_hurd_intr_rpc_msg_cx_sp:	movl $-25, %eax
  	_hurd_intr_rpc_msg_do_trap:	lcall $7, $0
  	_hurd_intr_rpc_msg_in_trap:	movl %ecx, %esp
  	_hurd_intr_rpc_msg_sp_restored:
       We must check for the window during which %esp points at the
       mach_msg arguments.  The space below until %ecx is used by
       the _hurd_intr_rpc_mach_msg frame, and must not be clobbered.  */
    else if (state->basic.eip >= (int) &_hurd_intr_rpc_msg_cx_sp &&
  	   state->basic.eip < (int) &_hurd_intr_rpc_msg_sp_restored)
      /* The SP now points at the mach_msg args, but there is more stack
         space used below it.  The real SP is saved in %ecx; we must push the
         new frame below there, and restore that value as the SP on
         sigreturn.  */
      sigsp = (char *) (state->basic.uesp = state->basic.ecx);
    else
      sigsp = (char *) state->basic.uesp;
  
    /* Push the arguments to call `trampoline' on the stack.  */
    sigsp -= sizeof (*stackframe);
    stackframe = sigsp;
  
    if (_hurdsig_catch_memory_fault (stackframe))
      {
        /* We got a fault trying to write the stack frame.
  	 We cannot set up the signal handler.
  	 Returning NULL tells our caller, who will nuke us with a SIGILL.  */
        return NULL;
      }
    else
      {
        int ok;
  
        extern void _hurdsig_longjmp_from_handler (void *, jmp_buf, int);
  
        /* Add a link to the thread's active-resources list.  We mark this as
  	 the only user of the "resource", so the cleanup function will be
  	 called by any longjmp which is unwinding past the signal frame.
  	 The cleanup function (in sigunwind.c) will make sure that all the
  	 appropriate cleanups done by sigreturn are taken care of.  */
        stackframe->link.cleanup = &_hurdsig_longjmp_from_handler;
        stackframe->link.cleanup_data = &stackframe->ctx;
        stackframe->link.resource.next = NULL;
        stackframe->link.resource.prevp = NULL;
        stackframe->link.thread.next = ss->active_resources;
        stackframe->link.thread.prevp = &ss->active_resources;
        if (stackframe->link.thread.next)
  	stackframe->link.thread.next->thread.prevp
  	  = &stackframe->link.thread.next;
        ss->active_resources = &stackframe->link;
  
        /* Set up the arguments for the signal handler.  */
        stackframe->signo = signo;
        stackframe->sigcode = detail->code;
        stackframe->scp = stackframe->return_scp = scp = &stackframe->ctx;
        stackframe->sigreturn_addr = &__sigreturn;
        stackframe->sigreturn_returns_here = firewall; /* Crash on return.  */
  
        /* Set up the sigcontext from the current state of the thread.  */
  
        scp->sc_onstack = ss->sigaltstack.ss_flags & SS_ONSTACK ? 1 : 0;
  
        /* struct sigcontext is laid out so that starting at sc_gs mimics a
  	 struct i386_thread_state.  */
        memcpy (&scp->sc_i386_thread_state,
  	      &state->basic, sizeof (state->basic));
  
        /* struct sigcontext is laid out so that starting at sc_fpkind mimics
  	 a struct i386_float_state.  */
        ok = machine_get_state (ss->thread, state, i386_FLOAT_STATE,
  			      &state->fpu, &scp->sc_i386_float_state,
  			      sizeof (state->fpu));
  
        _hurdsig_end_catch_fault ();
  
        if (! ok)
  	return NULL;
      }
  
    /* Modify the thread state to call the trampoline code on the new stack.  */
    if (rpc_wait)
      {
        /* The signalee thread was blocked in a mach_msg_trap system call,
  	 still waiting for a reply.  We will have it run the special
  	 trampoline code which retries the message receive before running
  	 the signal handler.
  
  	 To do this we change the OPTION argument on its stack to enable only
  	 message reception, since the request message has already been
  	 sent.  */
  
        struct mach_msg_trap_args *args = (void *) state->basic.esp;
  
        if (_hurdsig_catch_memory_fault (args))
  	{
  	  /* Faulted accessing ARGS.  Bomb.  */
  	  return NULL;
  	}
  
        assert (args->option & MACH_RCV_MSG);
        /* Disable the message-send, since it has already completed.  The
  	 calls we retry need only wait to receive the reply message.  */
        args->option &= ~MACH_SEND_MSG;
  
        /* Limit the time to receive the reply message, in case the server
  	 claimed that `interrupt_operation' succeeded but in fact the RPC
  	 is hung.  */
        args->option |= MACH_RCV_TIMEOUT;
        args->timeout = _hurd_interrupted_rpc_timeout;
  
        _hurdsig_end_catch_fault ();
  
        state->basic.eip = (int) rpc_wait_trampoline;
        /* The reply-receiving trampoline code runs initially on the original
  	 user stack.  We pass it the signal stack pointer in %ebx.  */
        state->basic.uesp = state->basic.esp; /* Restore mach_msg syscall SP.  */
        state->basic.ebx = (int) sigsp;
        /* After doing the message receive, the trampoline code will need to
  	 update the %eax value to be restored by sigreturn.  To simplify
  	 the assembly code, we pass the address of its slot in SCP to the
  	 trampoline code in %ecx.  */
        state->basic.ecx = (int) &scp->sc_eax;
      }
    else
      {
        state->basic.eip = (int) trampoline;
        state->basic.uesp = (int) sigsp;
      }
    /* We pass the handler function to the trampoline code in %edx.  */
    state->basic.edx = (int) handler;
  
    return scp;
  }
  
  /* The trampoline code follows.  This used to be located inside
     _hurd_setup_sighandler, but was optimized away by gcc 2.95.  */
  
  asm ("rpc_wait_trampoline:\n");
    /* This is the entry point when we have an RPC reply message to receive
       before running the handler.  The MACH_MSG_SEND bit has already been
       cleared in the OPTION argument on our stack.  The interrupted user
       stack pointer has not been changed, so the system call can find its
       arguments; the signal stack pointer is in %ebx.  For our convenience,
       %ecx points to the sc_eax member of the sigcontext.  */
  asm (/* Retry the interrupted mach_msg system call.  */
       "movl $-25, %eax\n"	/* mach_msg_trap */
       "lcall $7, $0\n"
       /* When the sigcontext was saved, %eax was MACH_RCV_INTERRUPTED.  But
  	now the message receive has completed and the original caller of
  	the RPC (i.e. the code running when the signal arrived) needs to
  	see the final return value of the message receive in %eax.  So
  	store the new %eax value into the sc_eax member of the sigcontext
  	(whose address is in %ecx to make this code simpler).  */
       "movl %eax, (%ecx)\n"
       /* Switch to the signal stack.  */
       "movl %ebx, %esp\n");
  
   asm ("trampoline:\n");
    /* Entry point for running the handler normally.  The arguments to the
       handler function are already on the top of the stack:
  
         0(%esp)	SIGNO
         4(%esp)	SIGCODE
         8(%esp)	SCP
       */
  asm ("call *%edx\n"		/* Call the handler function.  */
       "addl $12, %esp\n"		/* Pop its args.  */
       /* The word at the top of stack is &__sigreturn; following are a dummy
  	word to fill the slot for the address for __sigreturn to return to,
  	and a copy of SCP for __sigreturn's argument.  "Return" to calling
  	__sigreturn (SCP); this call never returns.  */
       "ret");
  
  asm ("firewall:\n"
       "hlt");
  