sysdeps/mach/hurd/mips/trampoline.c

   1 /* Set thread_state for sighandler, and sigcontext to recover.  MIPS version.
   2 Copyright (C) 1994, 1995 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 Library General Public License as
   7 published by the Free Software Foundation; either version 2 of the
   8 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 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with the GNU C Library; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #include <hurd/signal.h>
  21 #include "thread_state.h"
  22
  23
  24 struct mach_msg_trap_args
  25   {
  26     /* This is the order of arguments to mach_msg_trap.  */
  27     mach_msg_header_t *msg;
  28     mach_msg_option_t option;
  29     mach_msg_size_t send_size;
  30     mach_msg_size_t rcv_size;
  31     mach_port_t rcv_name;
  32     mach_msg_timeout_t timeout;
  33     mach_port_t notify;
  34   };
  35
  36
  37 struct sigcontext *
  38 _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
  39                         int signo, long int sigcode,
  40                         int rpc_wait,
  41                         struct machine_thread_all_state *state)
  42 {
  43
  44   __label__ trampoline, rpc_wait_trampoline;
  45   void *sigsp;
  46   struct sigcontext *scp;
  47
  48   if (ss->context)
  49     {
  50       /* We have a previous sigcontext that sigreturn was about
  51          to restore when another signal arrived.  We will just base
  52          our setup on that.  */
  53       if (! setjmp (_hurd_sigthread_fault_env))
  54         {
  55           memcpy (&state->basic, &ss->context->sc_mips_thread_state,
  56                   sizeof (state->basic));
  57           memcpy (&state->exc, &ss->context->sc_mips_exc_state,
  58                   sizeof (state->exc));
  59           state->set = (1 << MIPS_THREAD_STATE) | (1 << MIPS_EXC_STATE);
  60           if (state->exc.coproc_state & SC_COPROC_USE_FPU)
  61             {
  62               memcpy (&state->fpu, &ss->context->sc_mips_float_state,
  63                       sizeof (state->fpu));
  64               state->set |= (1 << MIPS_FLOAT_STATE);
  65             }
  66           assert (! rpc_wait);
  67           /* The intr_port slot was cleared before sigreturn sent us the
  68              sig_post that made us notice this pending signal, so
  69              _hurd_internal_post_signal wouldn't do interrupt_operation.
  70              After we return, our caller will set SCP->sc_intr_port (in the
  71              new context) from SS->intr_port and clear SS->intr_port.  Now
  72              that we are restoring this old context recorded by sigreturn,
  73              we want to restore its intr_port too; so store it in
  74              SS->intr_port now, so it will end up in SCP->sc_intr_port
  75              later.  */
  76           ss->intr_port = ss->context->sc_intr_port;
  77         }
  78       /* If the sigreturn context was bogus, just ignore it.  */
  79       ss->context = NULL;
  80     }
  81   else if (! machine_get_basic_state (ss->thread, state))
  82     return NULL;
  83
  84   if ((ss->actions[signo].sa_flags & SA_ONSTACK) &&
  85       !(ss->sigaltstack.ss_flags & (SA_DISABLE|SA_ONSTACK)))
  86     {
  87       sigsp = ss->sigaltstack.ss_sp + ss->sigaltstack.ss_size;
  88       ss->sigaltstack.ss_flags |= SA_ONSTACK;
  89       /* XXX need to set up base of new stack for
  90          per-thread variables, cthreads.  */
  91     }
  92   else
  93     sigsp = (char *) state->basic.r29;
  94
  95   /* Set up the sigcontext structure on the stack.  This is all the stack
  96      needs, since the args are passed in registers (below).  */
  97   sigsp -= sizeof (*scp);
  98   scp = sigsp;
  99
 100   if (! setjmp (_hurd_sigthread_fault_env))
 101     {
 102       /* Set up the sigcontext from the current state of the thread.  */
 103
 104       scp->sc_onstack = ss->sigaltstack.ss_flags & SA_ONSTACK ? 1 : 0;
 105
 106       /* struct sigcontext is laid out so that starting at sc_gpr
 107          mimics a struct mips_thread_state.  */
 108       memcpy (&scp->sc_mips_thread_state,
 109               &state->basic, sizeof (state->basic));
 110
 111       /* struct sigcontext is laid out so that starting at sc_cause
 112          mimics a struct mips_exc_state.  */
 113       if (! machine_get_state (ss->thread, state, MIPS_EXC_STATE,
 114                                &state->exc, &scp->sc_cause,
 115                                sizeof (state->exc)))
 116         return NULL;
 117       if ((scp->sc_coproc_used & SC_COPROC_USE_FPU) &&
 118           /* struct sigcontext is laid out so that starting at sc_fpr
 119              mimics a struct mips_float_state.  This state
 120              is only meaningful if the coprocessor was used.  */
 121           ! machine_get_state (ss->thread, state, MIPS_FLOAT_STATE,
 122                                &state->fpu,
 123                                &scp->sc_mips_float_state, sizeof (state->fpu)))
 124         return NULL;
 125     }
 126   else
 127     /* We got a fault trying to write the stack frame.
 128        We cannot set up the signal handler.
 129        Returning NULL tells our caller, who will nuke us with a SIGILL.  */
 130     return NULL;
 131
 132   /* Modify the thread state to call the trampoline code on the new stack.  */
 133   if (rpc_wait)
 134     {
 135       /* The signalee thread was blocked in a mach_msg_trap system call,
 136          still waiting for a reply.  We will have it run the special
 137          trampoline code which retries the message receive before running
 138          the signal handler.
 139
 140          To do this we change the OPTION argument in its registers to
 141          enable only message reception, since the request message has
 142          already been sent.  */
 143
 144       /* The system call arguments are stored in consecutive registers
 145          starting with a0 ($4).  */
 146       struct mach_msg_trap_args *args = (void *) &state->basic.r4;
 147
 148       assert (args->option & MACH_RCV_MSG);
 149       /* Disable the message-send, since it has already completed.  The
 150          calls we retry need only wait to receive the reply message.  */
 151       args->option &= ~MACH_SEND_MSG;
 152
 153       /* Limit the time to receive the reply message, in case the server
 154          claimed that `interrupt_operation' succeeded but in fact the RPC
 155          is hung.  */
 156       args->option |= MACH_RCV_TIMEOUT;
 157       args->timeout = _hurd_interrupted_rpc_timeout;
 158
 159       state->basic.pc = (int) &&rpc_wait_trampoline;
 160       state->basic.r29 = (int) sigsp; /* $29 is the stack pointer register.  */
 161       /* After doing the message receive, the trampoline code will need to
 162          update the v0 ($2) value to be restored by sigreturn.  To simplify
 163          the assembly code, we pass the address of its slot in SCP to the
 164          trampoline code in v1 ($3).  */
 165       state->basic.r3 = (int) &scp->sc_gpr[1];
 166       /* We must preserve the mach_msg_trap args in a0..t2 ($4..$10).
 167          Pass the handler args to the trampoline code in s1..s3 ($17..$19).  */
 168       state->basic.r17 = signo;
 169       state->basic.r18 = sigcode;
 170       state->basic.r19 = (int) scp;
 171     }
 172   else
 173     {
 174       state->basic.pc = (int) &&trampoline;
 175       state->basic.r29 = (int) sigsp;
 176       state->basic.r4 = signo;
 177       state->basic.r5 = sigcode;
 178       state->basic.r6 = (int) scp;
 179     }
 180
 181   /* We pass the handler function to the trampoline code in at ($1).  */
 182   state->basic.r1 = (int) handler;
 183   /* In the callee-saved register s0 ($16), we save the SCP value to pass
 184      to __sigreturn after the handler returns.  */
 185   state->basic.r16 = (int) scp;
 186
 187   return scp;
 188
 189   /* The trampoline code follows.  This is not actually executed as part of
 190      this function, it is just convenient to write it that way.  */
 191
 192  rpc_wait_trampoline:
 193   /* This is the entry point when we have an RPC reply message to receive
 194      before running the handler.  The MACH_MSG_SEND bit has already been
 195      cleared in the OPTION argument in our registers.  For our convenience,
 196      $3 points to the sc_gpr[1] member of the sigcontext (saved v0 ($2)).  */
 197   asm volatile
 198     (".set noat; .set noreorder; .set nomacro\n"
 199      /* Retry the interrupted mach_msg system call.  */
 200      "li $2, -25\n"             /* mach_msg_trap */
 201      "syscall\n"
 202      /* When the sigcontext was saved, v0 was MACH_RCV_INTERRUPTED.  But
 203         now the message receive has completed and the original caller of
 204         the RPC (i.e. the code running when the signal arrived) needs to
 205         see the final return value of the message receive in v0.  So
 206         store the new v0 value into the sc_gpr[1] member of the sigcontext
 207         (whose address is in v1 to make this code simpler).  */
 208      "sw $2, ($3)\n"
 209      /* Since the argument registers needed to have the mach_msg_trap
 210         arguments, we've stored the arguments to the handler function
 211         in registers s1..s3 ($17..$19).  */
 212      "move $4, $17\n"
 213      "move $5, $18\n"
 214      "move $6, $19\n");
 215
 216  trampoline:
 217   /* Entry point for running the handler normally.  The arguments to the
 218      handler function are already in the standard registers:
 219
 220        a0       SIGNO
 221        a1       SIGCODE
 222        a2       SCP
 223      */
 224   asm volatile
 225     ("jal $1; nop\n"            /* Call the handler function.  */
 226      /* Call __sigreturn (SCP); this cannot return.  */
 227      "j %0\n"
 228      "move $4, $16"             /* Set up arg from saved SCP in delay slot.  */
 229      : : "i" (&__sigreturn));
 230
 231   /* NOTREACHED */
 232   asm volatile (".set reorder; .set at; .set macro");
 233
 234   return NULL;
 235 }