sysdeps/mach/hurd/alpha/trampoline.c

   1 /* Set thread_state for sighandler, and sigcontext to recover.  Alpha version.
   2    Copyright (C) 1994,95,97,98,2002 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 "hurdfault.h"
  23 #include <assert.h>
  24
  25 struct mach_msg_trap_args
  26   {
  27     /* This is the order of arguments to mach_msg_trap.  */
  28     mach_msg_header_t *msg;
  29     mach_msg_option_t option;
  30     mach_msg_size_t send_size;
  31     mach_msg_size_t rcv_size;
  32     mach_port_t rcv_name;
  33     mach_msg_timeout_t timeout;
  34     mach_port_t notify;
  35   };
  36
  37
  38 struct sigcontext *
  39 _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler,
  40                         int signo, struct hurd_signal_detail *detail,
  41                         int rpc_wait, struct machine_thread_all_state *state)
  42 {
  43   __label__ trampoline, rpc_wait_trampoline;
  44   void *sigsp;
  45   struct sigcontext *scp;
  46
  47   if (ss->context)
  48     {
  49       /* We have a previous sigcontext that sigreturn was about
  50          to restore when another signal arrived.  We will just base
  51          our setup on that.  */
  52       if (! _hurdsig_catch_memory_fault (ss->context))
  53         {
  54           memcpy (&state->basic, &ss->context->sc_alpha_thread_state,
  55                   sizeof (state->basic));
  56           memcpy (&state->exc, &ss->context->sc_alpha_exc_state,
  57                   sizeof (state->exc));
  58           state->set = (1 << ALPHA_THREAD_STATE) | (1 << ALPHA_EXC_STATE);
  59           if (state->exc.used_fpa)
  60             {
  61               memcpy (&state->fpu, &ss->context->sc_alpha_float_state,
  62                       sizeof (state->fpu));
  63               state->set |= (1 << ALPHA_FLOAT_STATE);
  64             }
  65           assert (! rpc_wait);
  66           /* The intr_port slot was cleared before sigreturn sent us the
  67              sig_post that made us notice this pending signal, so
  68              _hurd_internal_post_signal wouldn't do interrupt_operation.
  69              After we return, our caller will set SCP->sc_intr_port (in the
  70              new context) from SS->intr_port and clear SS->intr_port.  Now
  71              that we are restoring this old context recorded by sigreturn,
  72              we want to restore its intr_port too; so store it in
  73              SS->intr_port now, so it will end up in SCP->sc_intr_port
  74              later.  */
  75           ss->intr_port = ss->context->sc_intr_port;
  76         }
  77       _hurdsig_end_catch_fault ();
  78
  79       /* If the sigreturn context was bogus, just ignore it.  */
  80       ss->context = NULL;
  81     }
  82   else if (! machine_get_basic_state (ss->thread, state))
  83     return NULL;
  84
  85   if ((ss->actions[signo].sa_flags & SA_ONSTACK) &&
  86       !(ss->sigaltstack.ss_flags & (SS_DISABLE|SS_ONSTACK)))
  87     {
  88       sigsp = ss->sigaltstack.ss_sp + ss->sigaltstack.ss_size;
  89       ss->sigaltstack.ss_flags |= SS_ONSTACK;
  90       /* XXX need to set up base of new stack for
  91          per-thread variables, cthreads.  */
  92     }
  93   else
  94     sigsp = (char *) state->basic.SP;
  95
  96   /* Set up the sigcontext structure on the stack.  This is all the stack
  97      needs, since the args are passed in registers (below).  */
  98   sigsp -= sizeof (*scp);
  99   scp = sigsp;
 100
 101   if (_hurdsig_catch_memory_fault (scp))
 102     {
 103       /* We got a fault trying to write the stack frame.
 104          We cannot set up the signal handler.
 105          Returning NULL tells our caller, who will nuke us with a SIGILL.  */
 106       return NULL;
 107     }
 108   else
 109     {
 110       /* Set up the sigcontext from the current state of the thread.  */
 111
 112       scp->sc_onstack = ss->sigaltstack.ss_flags & SS_ONSTACK ? 1 : 0;
 113
 114       /* struct sigcontext is laid out so that starting at sc_regs
 115          mimics a struct alpha_thread_state.  */
 116       memcpy (&scp->sc_alpha_thread_state,
 117               &state->basic, sizeof (state->basic));
 118
 119       /* struct sigcontext is laid out so that starting at sc_badvaddr
 120          mimics a struct mips_exc_state.  */
 121       if (! machine_get_state (ss->thread, state, ALPHA_EXC_STATE,
 122                                &state->exc, &scp->sc_alpha_exc_state,
 123                                sizeof (state->exc)))
 124         return NULL;
 125
 126       if (state->exc.used_fpa &&
 127           /* struct sigcontext is laid out so that starting at sc_fpregs
 128              mimics a struct alpha_float_state.  This state
 129              is only meaningful if the coprocessor was used.  */
 130           ! machine_get_state (ss->thread, state, ALPHA_FLOAT_STATE,
 131                                &state->fpu,
 132                                &scp->sc_alpha_float_state,
 133                                sizeof (state->fpu)))
 134         return NULL;
 135
 136       _hurdsig_end_catch_fault ();
 137     }
 138
 139   /* Modify the thread state to call the trampoline code on the new stack.  */
 140   if (rpc_wait)
 141     {
 142       /* The signalee thread was blocked in a mach_msg_trap system call,
 143          still waiting for a reply.  We will have it run the special
 144          trampoline code which retries the message receive before running
 145          the signal handler.
 146
 147          To do this we change the OPTION argument in its registers to
 148          enable only message reception, since the request message has
 149          already been sent.  */
 150
 151       /* The system call arguments are stored in consecutive registers
 152          starting with a0 ($16).  */
 153       struct mach_msg_trap_args *args = (void *) &state->basic.r16;
 154
 155       assert (args->option & MACH_RCV_MSG);
 156       /* Disable the message-send, since it has already completed.  The
 157          calls we retry need only wait to receive the reply message.  */
 158       args->option &= ~MACH_SEND_MSG;
 159
 160       /* Limit the time to receive the reply message, in case the server
 161          claimed that `interrupt_operation' succeeded but in fact the RPC
 162          is hung.  */
 163       args->option |= MACH_RCV_TIMEOUT;
 164       args->timeout = _hurd_interrupted_rpc_timeout;
 165
 166       state->basic.pc = (long int) &&rpc_wait_trampoline;
 167       /* After doing the message receive, the trampoline code will need to
 168          update the v0 ($0) value to be restored by sigreturn.  To simplify
 169          the assembly code, we pass the address of its slot in SCP to the
 170          trampoline code in at ($28).  */
 171       state->basic.r28 = (long int) &scp->sc_regs[0];
 172       /* We must preserve the mach_msg_trap args in a0..a5 and t0
 173          ($16..$21, $1).  Pass the handler args to the trampoline code in
 174          t8..t10 ($22.$24).  */
 175       state->basic.r22 = signo;
 176       state->basic.r23 = detail->code;
 177       state->basic.r24 = (long int) scp;
 178     }
 179   else
 180     {
 181       state->basic.pc = (long int) &&trampoline;
 182       state->basic.r16 = signo;
 183       state->basic.r17 = detail->code;
 184       state->basic.r18 = (long int) scp;
 185     }
 186
 187   state->basic.r30 = (long int) sigsp; /* $30 is the stack pointer.  */
 188
 189   /* We pass the handler function to the trampoline code in ra ($26).  */
 190   state->basic.r26 = (long int) handler;
 191   /* In the callee-saved register t12/pv ($27), we store the
 192      address of __sigreturn itself, for the trampoline code to use.  */
 193   state->basic.r27 = (long int) &__sigreturn;
 194   /* In the callee-saved register t11/ai ($25), we save the SCP value to pass
 195      to __sigreturn after the handler returns.  */
 196   state->basic.r25 = (long int) scp;
 197
 198   return scp;
 199
 200   /* The trampoline code follows.  This is not actually executed as part of
 201      this function, it is just convenient to write it that way.  */
 202
 203  rpc_wait_trampoline:
 204   /* This is the entry point when we have an RPC reply message to receive
 205      before running the handler.  The MACH_MSG_SEND bit has already been
 206      cleared in the OPTION argument in our registers.  For our convenience,
 207      at ($28) points to the sc_regs[0] member of the sigcontext (saved v0
 208      ($0)).  */
 209   asm volatile
 210     (/* Retry the interrupted mach_msg system call.  */
 211      "lda $0, -25($31)\n"       /* mach_msg_trap */
 212      "callsys\n"                /* Magic system call instruction.  */
 213      /* When the sigcontext was saved, v0 was MACH_RCV_INTERRUPTED.  But
 214         now the message receive has completed and the original caller of
 215         the RPC (i.e. the code running when the signal arrived) needs to
 216         see the final return value of the message receive in v0.  So
 217         store the new v0 value into the sc_regs[0] member of the sigcontext
 218         (whose address is in at to make this code simpler).  */
 219      "stq $0, 0($28)\n"
 220      /* Since the argument registers needed to have the mach_msg_trap
 221         arguments, we've stored the arguments to the handler function
 222         in registers t8..t10 ($22..$24).  */
 223      "mov $22, $16\n"
 224      "mov $23, $17\n"
 225      "mov $24, $18\n");
 226
 227  trampoline:
 228   /* Entry point for running the handler normally.  The arguments to the
 229      handler function are already in the standard registers:
 230
 231        a0       SIGNO
 232        a1       SIGCODE
 233        a2       SCP
 234
 235      t12 also contains SCP; this value is callee-saved (and so should not get
 236      clobbered by running the handler).  We use this saved value to pass to
 237      __sigreturn, so the handler can clobber the argument registers if it
 238      likes.  */
 239   /* Call the handler function, saving return address in ra ($26).  */
 240   asm volatile ("jsr $26, ($26)");
 241   /* Reset gp ($29) from the return address (here) in ra ($26).  */
 242   asm volatile ("ldgp $29, 0($26)");
 243   asm volatile ("mov $25, $16"); /* Move saved SCP to argument register.  */
 244   /* Call __sigreturn (SCP); this cannot return.  */
 245   asm volatile ("jmp $31, ($27)");
 246
 247   /* NOTREACHED */
 248   return NULL;
 249 }