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glibc  2.9
trampoline.c File Reference
#include <hurd/signal.h>
#include <hurd/userlink.h>
#include <thread_state.h>
#include <mach/machine/eflags.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)
 asm ("rpc_wait_trampoline:\n")
 asm ("movl $-25, %eax\n""lcall $7, $0\n""movl %eax, (%ecx)\n""movl %ebx, %esp\n")
 asm ("trampoline:\n")
 asm ("call *%edx\n""addl $12, %esp\n""ret")
 asm ("firewall:\n""hlt")

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 32 of file trampoline.c.

  void trampoline (void);
  void rpc_wait_trampoline (void);
  void firewall (void);
  extern const void _hurd_intr_rpc_msg_in_trap;
  extern const void _hurd_intr_rpc_msg_cx_sp;
  extern const void _hurd_intr_rpc_msg_sp_restored;
  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_i386_thread_state,
                sizeof (state->basic));
         memcpy (&state->fpu, &ss->context->sc_i386_float_state,
                sizeof (state->fpu));
         state->set |= (1 << i386_THREAD_STATE) | (1 << i386_FLOAT_STATE);

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

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

  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.  */
  /* This code has intimate knowledge of the special mach_msg system call
     done in intr-msg.c; that code does (see intr-msg.h):
                                   movl %esp, %ecx
                                   leal ARGS, %esp
       _hurd_intr_rpc_msg_cx_sp:   movl $-25, %eax
       _hurd_intr_rpc_msg_do_trap: lcall $7, $0
       _hurd_intr_rpc_msg_in_trap: movl %ecx, %esp
     We must check for the window during which %esp points at the
     mach_msg arguments.  The space below until %ecx is used by
     the _hurd_intr_rpc_mach_msg frame, and must not be clobbered.  */
  else if (state->basic.eip >= (int) &_hurd_intr_rpc_msg_cx_sp &&
          state->basic.eip < (int) &_hurd_intr_rpc_msg_sp_restored)
    /* The SP now points at the mach_msg args, but there is more stack
       space used below it.  The real SP is saved in %ecx; we must push the
       new frame below there, and restore that value as the SP on
       sigreturn.  */
    sigsp = (char *) (state->basic.uesp = state->basic.ecx);
    sigsp = (char *) state->basic.uesp;

  /* 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_gs mimics a
        struct i386_thread_state.  */
      memcpy (&scp->sc_i386_thread_state,
             &state->basic, sizeof (state->basic));

      /* struct sigcontext is laid out so that starting at sc_fpkind mimics
        a struct i386_float_state.  */
      ok = machine_get_state (ss->thread, state, i386_FLOAT_STATE,
                           &state->fpu, &scp->sc_i386_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 on its stack to enable only
        message reception, since the request message has already been
        sent.  */

      struct mach_msg_trap_args *args = (void *) state->basic.esp;

      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.eip = (int) rpc_wait_trampoline;
      /* The reply-receiving trampoline code runs initially on the original
        user stack.  We pass it the signal stack pointer in %ebx.  */
      state->basic.uesp = state->basic.esp; /* Restore mach_msg syscall SP.  */
      state->basic.ebx = (int) sigsp;
      /* After doing the message receive, the trampoline code will need to
        update the %eax 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 %ecx.  */
      state->basic.ecx = (int) &scp->sc_eax;
      state->basic.eip = (int) trampoline;
      state->basic.uesp = (int) sigsp;
  /* We pass the handler function to the trampoline code in %edx.  */
  state->basic.edx = (int) handler;

  /* The x86 ABI says the DF bit is clear on entry to any function.  */
  state->basic.efl &= ~EFL_DF;

  return scp;

Here is the call graph for this function:

asm ( "rpc_wait_trampoline:\n"  )
asm ( "movl $-  25,
%eax\n""lcall $  7,
$0\n""movl%  eax,
(%ecx)\n""movl%  ebx,
asm ( "trampoline:\n"  )
asm ( "call *%edx\n""addl $  12,
asm ( "firewall:\n""hlt"  )