sysdeps/mach/hurd/hppa/trampoline.c

   1 /* Set thread_state for sighandler, and sigcontext to recover.  HPPA version.
   2    Copyright (C) 1995, 1997, 1998 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   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.
   9
  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
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <hurd/signal.h>
  21 #include "thread_state.h"
  22 #include <assert.h>
  23 #include <errno.h>
  24 #include "hurdfault.h"
  25
  26
  27 struct mach_msg_trap_regargs
  28   {
  29     /* These first four arguments are in registers 26..23.  */
  30     mach_msg_size_t rcv_size;   /* arg3 */
  31     mach_msg_size_t send_size;  /* arg2 */
  32     mach_msg_option_t option;   /* arg1 */
  33     mach_msg_header_t *msg;     /* arg0 */
  34   };
  35
  36 struct sigcontext *
  37 _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
  38                         int signo, long int sigcode,
  39                         volatile int rpc_wait,
  40                         struct machine_thread_all_state *state)
  41 {
  42   __label__ trampoline, rpc_wait_trampoline;
  43   void *volatile sigsp;
  44   struct sigcontext *scp;
  45
  46   if (ss->context)
  47     {
  48       /* We have a previous sigcontext that sigreturn was about
  49          to restore when another signal arrived.  We will just base
  50          our setup on that.  */
  51       if (_hurdsig_catch_fault (SIGSEGV))
  52         assert (_hurdsig_fault_sigcode >= (long int) ss->context &&
  53                 _hurdsig_fault_sigcode < (long int) (ss->context + 1));
  54       else
  55         {
  56           memcpy (&state->basic, &ss->context->sc_parisc_thread_state,
  57                   sizeof (state->basic));
  58           state->set = (1 << PARISC_THREAD_STATE);
  59           assert (! rpc_wait);
  60           /* The intr_port slot was cleared before sigreturn sent us the
  61              sig_post that made us notice this pending signal, so
  62              _hurd_internal_post_signal wouldn't do interrupt_operation.
  63              After we return, our caller will set SCP->sc_intr_port (in the
  64              new context) from SS->intr_port and clear SS->intr_port.  Now
  65              that we are restoring this old context recorded by sigreturn,
  66              we want to restore its intr_port too; so store it in
  67              SS->intr_port now, so it will end up in SCP->sc_intr_port
  68              later.  */
  69           ss->intr_port = ss->context->sc_intr_port;
  70         }
  71       /* If the sigreturn context was bogus, just ignore it.  */
  72       ss->context = NULL;
  73     }
  74   else if (! machine_get_basic_state (ss->thread, state))
  75     return NULL;
  76
  77   if ((ss->actions[signo].sa_flags & SA_ONSTACK) &&
  78       !(ss->sigaltstack.ss_flags & (SS_DISABLE|SS_ONSTACK)))
  79     {
  80       sigsp = ss->sigaltstack.ss_sp + ss->sigaltstack.ss_size;
  81       ss->sigaltstack.ss_flags |= SS_ONSTACK;
  82       /* XXX need to set up base of new stack for
  83          per-thread variables, cthreads.  */
  84     }
  85   else
  86     sigsp = (char *) state->basic.uesp;
  87
  88   /* Push the signal context on the stack.  */
  89   sigsp -= sizeof (*scp);
  90   scp = sigsp;
  91
  92   if (_hurdsig_catch_fault (SIGSEGV))
  93     {
  94       assert (_hurdsig_fault_sigcode >= (long int) scp &&
  95               _hurdsig_fault_sigcode <= (long int) (scp + 1));
  96       /* We got a fault trying to write the stack frame.
  97          We cannot set up the signal handler.
  98          Returning NULL tells our caller, who will nuke us with a SIGILL.  */
  99       return NULL;
 100     }
 101   else
 102     {
 103       int ok;
 104
 105       /* Set up the sigcontext from the current state of the thread.  */
 106
 107       scp->sc_onstack = ss->sigaltstack.ss_flags & SS_ONSTACK ? 1 : 0;
 108
 109       /* struct sigcontext is laid out so that starting at sc_regs mimics a
 110          struct parisc_thread_state.  */
 111       memcpy (&scp->sc_parisc_thread_state,
 112               &state->basic, sizeof (state->basic));
 113
 114       _hurdsig_end_catch_fault ();
 115
 116       if (! ok)
 117         return NULL;
 118     }
 119
 120   /* Modify the thread state to call the trampoline code on the new stack.  */
 121   if (rpc_wait)
 122     {
 123       /* The signalee thread was blocked in a mach_msg_trap system call,
 124          still waiting for a reply.  We will have it run the special
 125          trampoline code which retries the message receive before running
 126          the signal handler.
 127
 128          To do this we change the OPTION argument on its stack to enable only
 129          message reception, since the request message has already been
 130          sent.  */
 131
 132       struct mach_msg_trap_regargs *args = (void *) &state->basic.r23;
 133
 134       if (_hurdsig_catch_fault (SIGSEGV))
 135         {
 136           assert (_hurdsig_fault_sigcode >= (long int) args &&
 137                   _hurdsig_fault_sigcode < (long int) (args + 1));
 138           /* Faulted accessing ARGS.  Bomb.  */
 139           return NULL;
 140         }
 141
 142       assert (args->option & MACH_RCV_MSG);
 143       /* Disable the message-send, since it has already completed.  The
 144          calls we retry need only wait to receive the reply message.  */
 145       args->option &= ~MACH_SEND_MSG;
 146
 147       /* Limit the time to receive the reply message, in case the server
 148          claimed that `interrupt_operation' succeeded but in fact the RPC
 149          is hung.  */
 150       args->option |= MACH_RCV_TIMEOUT;
 151       args->timeout = _hurd_interrupted_rpc_timeout;
 152
 153       _hurdsig_end_catch_fault ();
 154
 155       MACHINE_THREAD_STATE_SET_PC (&state->basic, &&rpc_wait_trampoline);
 156       /* The reply-receiving trampoline code runs initially on the original
 157          user stack.  We pass it the signal stack pointer in %r5.  */
 158       state->basic.r5 = (int) sigsp;
 159       /* After doing the message receive, the trampoline code will need to
 160          update the %r28 value to be restored by sigreturn.  To simplify
 161          the assembly code, we pass the address of its slot in SCP to the
 162          trampoline code in %r4.  */
 163       state->basic.r4 = (unsigned int) &scp->sc_regs[27];
 164       /* Set up the arguments for the handler function in callee-saved
 165          registers that we will move to the argument registers after
 166          mach_msg_trap returns.  */
 167       state->basic.r6 = signo;
 168       state->basic.r7 = sigcode;
 169       state->basic.r8 = (unsigned int) scp;
 170     }
 171   else
 172     {
 173       MACHINE_THREAD_STATE_SET_PC (&state->basic, &&trampoline);
 174       state->basic.r20 = (unsigned int) sigsp;
 175       /* Set up the arguments for the handler function.  */
 176       state->basic.r26 = signo;
 177       state->basic.r25 = sigcode;
 178       state->basic.r24 = (unsigned int) scp;
 179     }
 180
 181   /* We pass the handler function to the trampoline code in %r9.  */
 182   state->basic.r9 = (unsigned int) handler;
 183   /* For convenience, we pass the address of __sigreturn in %r10.  */
 184   state->basic.r10 = (unsigned int) &__sigreturn;
 185   /* The extra copy of SCP for the __sigreturn arg goes in %r8.  */
 186   state->basic.r10 = (unsigned int) scp;
 187
 188   return scp;
 189
 190   /* The trampoline code follows.  This is not actually executed as part of
 191      this function, it is just convenient to write it that way.  */
 192
 193  rpc_wait_trampoline:
 194   /* This is the entry point when we have an RPC reply message to receive
 195      before running the handler.  The MACH_MSG_SEND bit has already been
 196      cleared in the OPTION argument on our stack.  The interrupted user
 197      stack pointer has not been changed, so the system call can find its
 198      arguments; the signal stack pointer is in %ebx.  For our convenience,
 199      %ecx points to the sc_eax member of the sigcontext.  */
 200   asm volatile
 201     (/* Retry the interrupted mach_msg system call.  */
 202      "ldil L%0xC0000000,%r1\nble 4(%sr7,%r1)\n"
 203      "ldi -25, %r22\n"          /* mach_msg_trap */
 204      /* When the sigcontext was saved, %r28 was MACH_RCV_INTERRUPTED.  But
 205         now the message receive has completed and the original caller of
 206         the RPC (i.e. the code running when the signal arrived) needs to
 207         see the final return value of the message receive in %r28.  So
 208         store the new %r28 value into the sc_regs[27] member of the sigcontext
 209         (whose address is in %r4 to make this code simpler).  */
 210      "stw (%r4), %r28\n"
 211      /* Switch to the signal stack.  */
 212      "copy %r5, %r30\n"
 213      /* Copy the handler arguments to the argument registers.  */
 214      "copy %r6, %r26\n"
 215      "copy %r7, %r25\n"
 216      "copy %r8, %r24\n"
 217      );
 218
 219  trampoline:
 220   /* Entry point for running the handler normally.  The arguments to the
 221      handler function are already in the argument registers.  */
 222   asm volatile
 223     ("bv (%r9); nop"            /* Call the handler function.  */
 224      "bv (%r10)\n"              /* Call __sigreturn (SCP); never returns.  */
 225      "copy %r8, %r26"           /* Set up arg in delay slot.  */
 226      : : "i" (&__sigreturn));
 227
 228   /* NOTREACHED */
 229   return NULL;
 230 }