[thirdparty/glibc.git] / sysdeps / mach / hurd / i386 / trampoline.c

/* Set thread_state for sighandler, and sigcontext to recover.  i386 version.
   Copyright (C) 1994-2015 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 <hurd/signal.h>
#include <hurd/userlink.h>
#include <thread_state.h>
#include <mach/machine/eflags.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;

  /* The x86 ABI says the DF bit is clear on entry to any function.  */
  state->basic.efl &= ~EFL_DF;

  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");
Commit	Line	Data
28f540f4	1	/* Set thread_state for sighandler, and sigcontext to recover. i386 version.
b168057a	2	Copyright (C) 1994-2015 Free Software Foundation, Inc.
478b92f0	3	This file is part of the GNU C Library.
28f540f4	4
478b92f0	5	The GNU C Library is free software; you can redistribute it and/or
41bdb6e2 AJ	6	modify it under the terms of the GNU Lesser General Public
	7	License as published by the Free Software Foundation; either
	8	version 2.1 of the License, or (at your option) any later version.
28f540f4	9
478b92f0 UD	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
41bdb6e2	13	Lesser General Public License for more details.
28f540f4	14
41bdb6e2	15	You should have received a copy of the GNU Lesser General Public
59ba27a6 PE	16	License along with the GNU C Library; if not, see
59ba27a6 PE	17	<http://www.gnu.org/licenses/>. */
28f540f4 RM	18
28f540f4 RM	19	#include <hurd/signal.h>
e607b492	20	#include <hurd/userlink.h>
8f480b4b	21	#include <thread_state.h>
d2ea0b96	22	#include <mach/machine/eflags.h>
28f540f4 RM	23	#include <assert.h>
	24	#include <errno.h>
	25	#include "hurdfault.h"
8f480b4b	26	#include <intr-msg.h>
28f540f4	27
7974fe21	28
28f540f4 RM	29	struct sigcontext *
28f540f4 RM	30	_hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
0e3426bb	31	int signo, struct hurd_signal_detail *detail,
28f540f4 RM	32	volatile int rpc_wait,
	33	struct machine_thread_all_state *state)
	34	{
83ddec31 RM	35	void trampoline (void);
	36	void rpc_wait_trampoline (void);
	37	void firewall (void);
3fe9de0d RM	38	extern const void _hurd_intr_rpc_msg_in_trap;
	39	extern const void _hurd_intr_rpc_msg_cx_sp;
	40	extern const void _hurd_intr_rpc_msg_sp_restored;
28f540f4 RM	41	void *volatile sigsp;
28f540f4 RM	42	struct sigcontext *scp;
7974fe21	43	struct
28f540f4 RM	44	{
	45	int signo;
	46	long int sigcode;
	47	struct sigcontext scp; / Points to ctx, below. */
f0bf9cb9 RM	48	void *sigreturn_addr;
f0bf9cb9 RM	49	void *sigreturn_returns_here;
28f540f4 RM	50	struct sigcontext return_scp; / Same; arg to sigreturn. */
28f540f4 RM	51	struct sigcontext ctx;
e607b492	52	struct hurd_userlink link;
28f540f4 RM	53	} *stackframe;
	54
	55	if (ss->context)
	56	{
	57	/* We have a previous sigcontext that sigreturn was about
	58	to restore when another signal arrived. We will just base
	59	our setup on that. */
7974fe21	60	if (! _hurdsig_catch_memory_fault (ss->context))
28f540f4 RM	61	{
	62	memcpy (&state->basic, &ss->context->sc_i386_thread_state,
	63	sizeof (state->basic));
	64	memcpy (&state->fpu, &ss->context->sc_i386_float_state,
	65	sizeof (state->fpu));
421f82e5	66	state->set \|= (1 << i386_THREAD_STATE) \| (1 << i386_FLOAT_STATE);
28f540f4	67	}
28f540f4	68	}
421f82e5 RM	69
421f82e5 RM	70	if (! machine_get_basic_state (ss->thread, state))
28f540f4 RM	71	return NULL;
28f540f4 RM	72
3fe9de0d RM	73	/* Save the original SP in the gratuitous `esp' slot.
	74	We may need to reset the SP (the `uesp' slot) to avoid clobbering an
	75	interrupted RPC frame. */
	76	state->basic.esp = state->basic.uesp;
	77
28f540f4	78	if ((ss->actions[signo].sa_flags & SA_ONSTACK) &&
7ce241a0	79	!(ss->sigaltstack.ss_flags & (SS_DISABLE\|SS_ONSTACK)))
28f540f4 RM	80	{
28f540f4 RM	81	sigsp = ss->sigaltstack.ss_sp + ss->sigaltstack.ss_size;
7ce241a0	82	ss->sigaltstack.ss_flags \|= SS_ONSTACK;
28f540f4 RM	83	/* XXX need to set up base of new stack for
	84	per-thread variables, cthreads. */
	85	}
3fe9de0d	86	/* This code has intimate knowledge of the special mach_msg system call
4ca84cff	87	done in intr-msg.c; that code does (see intr-msg.h):
3fe9de0d RM	88	movl %esp, %ecx
	89	leal ARGS, %esp
	90	_hurd_intr_rpc_msg_cx_sp: movl $-25, %eax
	91	_hurd_intr_rpc_msg_do_trap: lcall $7, $0
	92	_hurd_intr_rpc_msg_in_trap: movl %ecx, %esp
478b92f0	93	_hurd_intr_rpc_msg_sp_restored:
3fe9de0d RM	94	We must check for the window during which %esp points at the
	95	mach_msg arguments. The space below until %ecx is used by
	96	the _hurd_intr_rpc_mach_msg frame, and must not be clobbered. */
7974fe21	97	else if (state->basic.eip >= (int) &_hurd_intr_rpc_msg_cx_sp &&
3fe9de0d RM	98	state->basic.eip < (int) &_hurd_intr_rpc_msg_sp_restored)
	99	/* The SP now points at the mach_msg args, but there is more stack
	100	space used below it. The real SP is saved in %ecx; we must push the
	101	new frame below there, and restore that value as the SP on
	102	sigreturn. */
	103	sigsp = (char *) (state->basic.uesp = state->basic.ecx);
28f540f4 RM	104	else
	105	sigsp = (char *) state->basic.uesp;
	106
	107	/* Push the arguments to call `trampoline' on the stack. */
	108	sigsp -= sizeof (*stackframe);
	109	stackframe = sigsp;
	110
7974fe21	111	if (_hurdsig_catch_memory_fault (stackframe))
28f540f4	112	{
28f540f4 RM	113	/* We got a fault trying to write the stack frame.
	114	We cannot set up the signal handler.
	115	Returning NULL tells our caller, who will nuke us with a SIGILL. */
	116	return NULL;
	117	}
	118	else
	119	{
	120	int ok;
	121
e607b492 RM	122	extern void _hurdsig_longjmp_from_handler (void *, jmp_buf, int);
	123
	124	/* Add a link to the thread's active-resources list. We mark this as
	125	the only user of the "resource", so the cleanup function will be
	126	called by any longjmp which is unwinding past the signal frame.
	127	The cleanup function (in sigunwind.c) will make sure that all the
	128	appropriate cleanups done by sigreturn are taken care of. */
	129	stackframe->link.cleanup = &_hurdsig_longjmp_from_handler;
	130	stackframe->link.cleanup_data = &stackframe->ctx;
	131	stackframe->link.resource.next = NULL;
	132	stackframe->link.resource.prevp = NULL;
	133	stackframe->link.thread.next = ss->active_resources;
	134	stackframe->link.thread.prevp = &ss->active_resources;
	135	if (stackframe->link.thread.next)
	136	stackframe->link.thread.next->thread.prevp
	137	= &stackframe->link.thread.next;
	138	ss->active_resources = &stackframe->link;
	139
28f540f4 RM	140	/* Set up the arguments for the signal handler. */
28f540f4 RM	141	stackframe->signo = signo;
0e3426bb	142	stackframe->sigcode = detail->code;
28f540f4	143	stackframe->scp = stackframe->return_scp = scp = &stackframe->ctx;
f0bf9cb9	144	stackframe->sigreturn_addr = &__sigreturn;
83ddec31	145	stackframe->sigreturn_returns_here = firewall; /* Crash on return. */
28f540f4 RM	146
	147	/* Set up the sigcontext from the current state of the thread. */
	148
7ce241a0	149	scp->sc_onstack = ss->sigaltstack.ss_flags & SS_ONSTACK ? 1 : 0;
28f540f4 RM	150
	151	/* struct sigcontext is laid out so that starting at sc_gs mimics a
	152	struct i386_thread_state. */
	153	memcpy (&scp->sc_i386_thread_state,
	154	&state->basic, sizeof (state->basic));
	155
	156	/* struct sigcontext is laid out so that starting at sc_fpkind mimics
	157	a struct i386_float_state. */
	158	ok = machine_get_state (ss->thread, state, i386_FLOAT_STATE,
	159	&state->fpu, &scp->sc_i386_float_state,
	160	sizeof (state->fpu));
	161
	162	_hurdsig_end_catch_fault ();
	163
	164	if (! ok)
	165	return NULL;
	166	}
	167
	168	/* Modify the thread state to call the trampoline code on the new stack. */
	169	if (rpc_wait)
	170	{
	171	/* The signalee thread was blocked in a mach_msg_trap system call,
	172	still waiting for a reply. We will have it run the special
	173	trampoline code which retries the message receive before running
	174	the signal handler.
7974fe21	175
28f540f4 RM	176	To do this we change the OPTION argument on its stack to enable only
	177	message reception, since the request message has already been
	178	sent. */
	179
3fe9de0d	180	struct mach_msg_trap_args args = (void ) state->basic.esp;
28f540f4	181
7974fe21	182	if (_hurdsig_catch_memory_fault (args))
28f540f4	183	{
28f540f4 RM	184	/* Faulted accessing ARGS. Bomb. */
	185	return NULL;
	186	}
	187
	188	assert (args->option & MACH_RCV_MSG);
	189	/* Disable the message-send, since it has already completed. The
	190	calls we retry need only wait to receive the reply message. */
	191	args->option &= ~MACH_SEND_MSG;
	192
54da5be3 RM	193	/* Limit the time to receive the reply message, in case the server
	194	claimed that `interrupt_operation' succeeded but in fact the RPC
	195	is hung. */
	196	args->option \|= MACH_RCV_TIMEOUT;
	197	args->timeout = _hurd_interrupted_rpc_timeout;
	198
28f540f4 RM	199	_hurdsig_end_catch_fault ();
28f540f4 RM	200
83ddec31	201	state->basic.eip = (int) rpc_wait_trampoline;
28f540f4 RM	202	/* The reply-receiving trampoline code runs initially on the original
28f540f4 RM	203	user stack. We pass it the signal stack pointer in %ebx. */
3fe9de0d	204	state->basic.uesp = state->basic.esp; /* Restore mach_msg syscall SP. */
28f540f4 RM	205	state->basic.ebx = (int) sigsp;
	206	/* After doing the message receive, the trampoline code will need to
	207	update the %eax value to be restored by sigreturn. To simplify
	208	the assembly code, we pass the address of its slot in SCP to the
	209	trampoline code in %ecx. */
	210	state->basic.ecx = (int) &scp->sc_eax;
	211	}
	212	else
	213	{
83ddec31	214	state->basic.eip = (int) trampoline;
28f540f4 RM	215	state->basic.uesp = (int) sigsp;
	216	}
	217	/* We pass the handler function to the trampoline code in %edx. */
	218	state->basic.edx = (int) handler;
	219
d2ea0b96 RM	220	/* The x86 ABI says the DF bit is clear on entry to any function. */
	221	state->basic.efl &= ~EFL_DF;
	222
28f540f4	223	return scp;
83ddec31	224	}
28f540f4	225
83ddec31 RM	226	/* The trampoline code follows. This used to be located inside
83ddec31 RM	227	_hurd_setup_sighandler, but was optimized away by gcc 2.95. */
28f540f4	228
83ddec31	229	asm ("rpc_wait_trampoline:\n");
28f540f4 RM	230	/* This is the entry point when we have an RPC reply message to receive
	231	before running the handler. The MACH_MSG_SEND bit has already been
	232	cleared in the OPTION argument on our stack. The interrupted user
	233	stack pointer has not been changed, so the system call can find its
	234	arguments; the signal stack pointer is in %ebx. For our convenience,
	235	%ecx points to the sc_eax member of the sigcontext. */
83ddec31	236	asm (/* Retry the interrupted mach_msg system call. */
28f540f4 RM	237	"movl $-25, %eax\n" /* mach_msg_trap */
	238	"lcall $7, $0\n"
	239	/* When the sigcontext was saved, %eax was MACH_RCV_INTERRUPTED. But
	240	now the message receive has completed and the original caller of
	241	the RPC (i.e. the code running when the signal arrived) needs to
	242	see the final return value of the message receive in %eax. So
	243	store the new %eax value into the sc_eax member of the sigcontext
	244	(whose address is in %ecx to make this code simpler). */
	245	"movl %eax, (%ecx)\n"
	246	/* Switch to the signal stack. */
	247	"movl %ebx, %esp\n");
	248
83ddec31	249	asm ("trampoline:\n");
28f540f4 RM	250	/* Entry point for running the handler normally. The arguments to the
	251	handler function are already on the top of the stack:
	252
	253	0(%esp) SIGNO
	254	4(%esp) SIGCODE
	255	8(%esp) SCP
	256	*/
83ddec31	257	asm ("call %edx\n" / Call the handler function. */
f0bf9cb9 RM	258	"addl $12, %esp\n" /* Pop its args. */
	259	/* The word at the top of stack is &__sigreturn; following are a dummy
	260	word to fill the slot for the address for __sigreturn to return to,
	261	and a copy of SCP for __sigreturn's argument. "Return" to calling
	262	__sigreturn (SCP); this call never returns. */
	263	"ret");
28f540f4	264
83ddec31 RM	265	asm ("firewall:\n"
83ddec31 RM	266	"hlt");