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glibc  2.9
Classes | Functions
trampoline.c File Reference
#include <hurd/signal.h>
#include "thread_state.h"
#include "hurdfault.h"
#include <assert.h>

Go to the source code of this file.


struct  mach_msg_trap_args


struct sigcontext_hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, int signo, struct hurd_signal_detail *detail, int rpc_wait, struct machine_thread_all_state *state)

Class Documentation

struct mach_msg_trap_args

Definition at line 99 of file intr-msg.h.

Class Members
mach_msg_header_t * msg
mach_port_t notify
mach_msg_option_t option
mach_port_t rcv_name
mach_msg_size_t rcv_size
void * retaddr
mach_msg_size_t send_size
mach_msg_timeout_t timeout

Function Documentation

struct sigcontext* _hurd_setup_sighandler ( struct hurd_sigstate ss,
__sighandler_t  handler,
int  signo,
struct hurd_signal_detail detail,
int  rpc_wait,
struct machine_thread_all_state state 
) [read]

Definition at line 39 of file trampoline.c.

  __label__ trampoline, rpc_wait_trampoline;
  void *sigsp;
  struct sigcontext *scp;

  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_alpha_thread_state,
                sizeof (state->basic));
         memcpy (&state->exc, &ss->context->sc_alpha_exc_state,
                sizeof (state->exc));
         state->set = (1 << ALPHA_THREAD_STATE) | (1 << ALPHA_EXC_STATE);
         if (state->exc.used_fpa)
             memcpy (&state->fpu, &ss->context->sc_alpha_float_state,
                    sizeof (state->fpu));
             state->set |= (1 << ALPHA_FLOAT_STATE);
         assert (! rpc_wait);
         /* The intr_port slot was cleared before sigreturn sent us the
            sig_post that made us notice this pending signal, so
            _hurd_internal_post_signal wouldn't do interrupt_operation.
            After we return, our caller will set SCP->sc_intr_port (in the
            new context) from SS->intr_port and clear SS->intr_port.  Now
            that we are restoring this old context recorded by sigreturn,
            we want to restore its intr_port too; so store it in
            SS->intr_port now, so it will end up in SCP->sc_intr_port
            later.  */
         ss->intr_port = ss->context->sc_intr_port;
      _hurdsig_end_catch_fault ();

      /* If the sigreturn context was bogus, just ignore it.  */
      ss->context = NULL;
  else if (! machine_get_basic_state (ss->thread, state))
    return NULL;

  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.  */
    sigsp = (char *) state->basic.SP;

  /* Set up the sigcontext structure on the stack.  This is all the stack
     needs, since the args are passed in registers (below).  */
  sigsp -= sizeof (*scp);
  scp = sigsp;

  if (_hurdsig_catch_memory_fault (scp))
      /* 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;
      /* 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_regs
        mimics a struct alpha_thread_state.  */
      memcpy (&scp->sc_alpha_thread_state,
             &state->basic, sizeof (state->basic));

      /* struct sigcontext is laid out so that starting at sc_badvaddr
        mimics a struct mips_exc_state.  */
      if (! machine_get_state (ss->thread, state, ALPHA_EXC_STATE,
                            &state->exc, &scp->sc_alpha_exc_state,
                            sizeof (state->exc)))
       return NULL;

      if (state->exc.used_fpa &&
         /* struct sigcontext is laid out so that starting at sc_fpregs
            mimics a struct alpha_float_state.  This state
            is only meaningful if the coprocessor was used.  */
         ! machine_get_state (ss->thread, state, ALPHA_FLOAT_STATE,
                            sizeof (state->fpu)))
       return NULL;

      _hurdsig_end_catch_fault ();

  /* 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 in its registers to
        enable only message reception, since the request message has
        already been sent.  */

      /* The system call arguments are stored in consecutive registers
        starting with a0 ($16).  */
      struct mach_msg_trap_args *args = (void *) &state->basic.r16;

      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;

      state->basic.pc = (long int) &&rpc_wait_trampoline;
      /* After doing the message receive, the trampoline code will need to
        update the v0 ($0) 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 at ($28).  */
      state->basic.r28 = (long int) &scp->sc_regs[0];
      /* We must preserve the mach_msg_trap args in a0..a5 and t0
        ($16..$21, $1).  Pass the handler args to the trampoline code in
        t8..t10 ($22.$24).  */
      state->basic.r22 = signo;
      state->basic.r23 = detail->code;
      state->basic.r24 = (long int) scp;
      state->basic.pc = (long int) &&trampoline;
      state->basic.r16 = signo;
      state->basic.r17 = detail->code;
      state->basic.r18 = (long int) scp;

  state->basic.r30 = (long int) sigsp; /* $30 is the stack pointer.  */

  /* We pass the handler function to the trampoline code in ra ($26).  */
  state->basic.r26 = (long int) handler;
  /* In the callee-saved register t12/pv ($27), we store the
     address of __sigreturn itself, for the trampoline code to use.  */
  state->basic.r27 = (long int) &__sigreturn;
  /* In the callee-saved register t11/ai ($25), we save the SCP value to pass
     to __sigreturn after the handler returns.  */
  state->basic.r25 = (long int) scp;

  return scp;

  /* The trampoline code follows.  This is not actually executed as part of
     this function, it is just convenient to write it that way.  */

  /* 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 in our registers.  For our convenience,
     at ($28) points to the sc_regs[0] member of the sigcontext (saved v0
     ($0)).  */
  asm volatile
    (/* Retry the interrupted mach_msg system call.  */
     "lda $0, -25($31)\n"   /* mach_msg_trap */
     "callsys\n"            /* Magic system call instruction.  */
     /* When the sigcontext was saved, v0 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 v0.  So
       store the new v0 value into the sc_regs[0] member of the sigcontext
       (whose address is in at to make this code simpler).  */
     "stq $0, 0($28)\n"
     /* Since the argument registers needed to have the mach_msg_trap
       arguments, we've stored the arguments to the handler function
       in registers t8..t10 ($22..$24).  */
     "mov $22, $16\n"
     "mov $23, $17\n"
     "mov $24, $18\n");

  /* Entry point for running the handler normally.  The arguments to the
     handler function are already in the standard registers:

       a0     SIGNO
       a1     SIGCODE
       a2     SCP

     t12 also contains SCP; this value is callee-saved (and so should not get
     clobbered by running the handler).  We use this saved value to pass to
     __sigreturn, so the handler can clobber the argument registers if it
     likes.  */
  /* Call the handler function, saving return address in ra ($26).  */
  asm volatile ("jsr $26, ($26)");
  /* Reset gp ($29) from the return address (here) in ra ($26).  */
  asm volatile ("ldgp $29, 0($26)");
  asm volatile ("mov $25, $16"); /* Move saved SCP to argument register.  */
  /* Call __sigreturn (SCP); this cannot return.  */
  asm volatile ("jmp $31, ($27)");

  return NULL;

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