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glibc  2.9
trampoline.c File Reference
#include <hurd/signal.h>
#include <hurd/userlink.h>
#include <thread_state.h>
#include <assert.h>
#include <errno.h>
#include "hurdfault.h"
#include <intr-msg.h>

Go to the source code of this file.


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)

Function Documentation

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 
) [read]

Definition at line 30 of file trampoline.c.

  __label__ trampoline, rpc_wait_trampoline, firewall;
  void *volatile sigsp;
  struct sigcontext *scp;
      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_mips_thread_state,
                sizeof (state->basic));
         memcpy (&state->exc, &ss->context->sc_mips_exc_state,
                sizeof (state->exc));
         state->set = (1 << MIPS_THREAD_STATE) | (1 << MIPS_EXC_STATE);
         if (state->exc.coproc_state & SC_COPROC_USE_FPU)
             memcpy (&state->fpu, &ss->context->sc_mips_float_state,
                    sizeof (state->fpu));
             state->set |= (1 << MIPS_FLOAT_STATE);

  if (! machine_get_basic_state (ss->thread, state))
    return NULL;

  /* Save the original SP in the gratuitous s0 ($16) slot.
     We may need to reset the SP (the `r29' slot) to avoid clobbering an
     interrupted RPC frame.  */
  state->basic.r16 = state->basic.r29;

  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.r29;

  /* 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;
      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-> = NULL;
      stackframe->link.resource.prevp = NULL;
      stackframe-> = ss->active_resources;
      stackframe->link.thread.prevp = &ss->active_resources;
      if (stackframe->
         = &stackframe->;
      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_gpr
        mimics a struct mips_thread_state.  */
      memcpy (&scp->sc_mips_thread_state,
             &state->basic, sizeof (state->basic));

      /* struct sigcontext is laid out so that starting at sc_cause
        mimics a struct mips_exc_state.  */
      ok = machine_get_state (ss->thread, state, MIPS_EXC_STATE,
                           &state->exc, &scp->sc_cause,
                           sizeof (state->exc));

      if (ok && (scp->sc_coproc_used & SC_COPROC_USE_FPU))
       /* struct sigcontext is laid out so that starting at sc_fpr
          mimics a struct mips_float_state.  This state
          is only meaningful if the coprocessor was used.  */
         ok = machine_get_state (ss->thread, state, MIPS_FLOAT_STATE,
                              &state->fpu, &scp->sc_mips_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 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 ($4).  */
      struct mach_msg_trap_args *args = (void *) &state->basic.r4;

      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.pc = (int) &&rpc_wait_trampoline;
      /* The reply-receiving trampoline code runs initially on the original
        user stack.  We pass it the signal stack pointer in s4 ($20).  */
      state->basic.r29 = state->basic.r16; /* Restore mach_msg syscall SP.  */
      state->basic.r20 = (int) sigsp;
      /* After doing the message receive, the trampoline code will need to
        update the v0 ($2) 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 s5 ($21).  */
      state->basic.r21 = (int) &scp->sc_gpr[1];
      /* We must preserve the mach_msg_trap args in a0..t2 ($4..$10).
        Pass the handler args to the trampoline code in s1..s3 ($17..$19).  */
      state->basic.r17 = signo;
      state->basic.r18 = detail->code;
      state->basic.r19 = (int) scp;
      state->basic.pc = (int) &&trampoline;
      state->basic.r29 = (int) sigsp;
      state->basic.r4 = signo;
      state->basic.r5 = detail->code;
      state->basic.r6 = (int) scp;

  /* We pass the handler function to the trampoline code in s6 ($22).  */
  state->basic.r22 = (int) handler;
  /* In the callee-saved register s0 ($16), we save the SCP value to pass
     to __sigreturn after the handler returns.  */
  state->basic.r16 = (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,
     $3 points to the sc_gpr[1] member of the sigcontext (saved v0 ($2)).  */
  asm volatile
    (".set noat; .set noreorder; .set nomacro\n"
     /* Retry the interrupted mach_msg system call.  */
#ifdef __mips64
     "dli $2, -25\n"        /* mach_msg_trap */
     "li $2, -25\n"         /* mach_msg_trap */
     /* 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_gpr[1] member of the sigcontext
       (whose address is in s5 to make this code simpler).  */
#ifdef __mips64
     "sd $2, ($21)\n"
     "sw $2, ($21)\n"
     /* Since the argument registers needed to have the mach_msg_trap
       arguments, we've stored the arguments to the handler function
       in registers s1..s3 ($17..$19).  */
     "move $4, $17\n"
     "move $5, $18\n"
     "move $6, $19\n"
     /* Switch to the signal stack.  */
     "move $29, $20\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
  asm volatile
    ("move $25, $22\n"             /* Copy s6 to t9 for MIPS ABI.  */
     "jal $25; nop\n"              /* Call the handler function.  */
     /* Call __sigreturn (SCP); this cannot return.  */
#ifdef __mips64
     "dla $1,%0\n"
     "la $1,%0\n"
     "j $1\n"
     "move $4, $16"         /* Set up arg from saved SCP in delay slot.  */
     : : "i" (&__sigreturn));

  asm volatile (".set reorder; .set at; .set macro");

  asm volatile ("hlt: j hlt");

  return NULL;

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