diff options
Diffstat (limited to 'sysdeps/mach/hurd/i386/trampoline.c')
| -rw-r--r-- | sysdeps/mach/hurd/i386/trampoline.c | 29 |
1 files changed, 28 insertions, 1 deletions
diff --git a/sysdeps/mach/hurd/i386/trampoline.c b/sysdeps/mach/hurd/i386/trampoline.c index 7adffc40be..9e947a46e7 100644 --- a/sysdeps/mach/hurd/i386/trampoline.c +++ b/sysdeps/mach/hurd/i386/trampoline.c @@ -45,6 +45,9 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, struct machine_thread_all_state *state) { __label__ trampoline, rpc_wait_trampoline, firewall; + 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; struct @@ -80,6 +83,11 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, 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 & (SA_DISABLE|SA_ONSTACK))) { @@ -88,6 +96,24 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, /* 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: + 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 + _hurd_intr_rpc_msg_sp_restored: + 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); else sigsp = (char *) state->basic.uesp; @@ -166,7 +192,7 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, message reception, since the request message has already been sent. */ - struct mach_msg_trap_args *args = (void *) state->basic.uesp; + struct mach_msg_trap_args *args = (void *) state->basic.esp; if (_hurdsig_catch_fault (SIGSEGV)) { @@ -192,6 +218,7 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, __sighandler_t handler, 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 |