[hurd,commited] hurd: Fix intr-msg parameter/stack kludge

[Samuel Thibault]

INTR_MSG_TRAP was tinkering with esp to make it point to
_hurd_intr_rpc_mach_msg's parameters, and notably use (&msg)[-1] which is
meaningless in C.

Instead, just push the parameters on the stack, which also avoids leaving
local variables of _hurd_intr_rpc_mach_msg below esp. We now also
properly express that OPTION and TIMEOUT may be updated during the trap
call.
---
 sysdeps/mach/hurd/i386/intr-msg.h | 49 ++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 10 deletions(-)

diff --git a/sysdeps/mach/hurd/i386/intr-msg.h 
b/sysdeps/mach/hurd/i386/intr-msg.h
index bd94aaf65f..ac3e5c07ed 100644
--- a/sysdeps/mach/hurd/i386/intr-msg.h
+++ b/sysdeps/mach/hurd/i386/intr-msg.h
@@ -21,8 +21,6 @@
    to indicate that the signal thread might mutate them as part
    of sending us to a signal handler.  */
 
-/* After _hurd_intr_rpc_msg_about_to we need to make a last check of cancel, in
-   case we got interrupted right before _hurd_intr_rpc_msg_about_to.  */
 #define INTR_MSG_TRAP(msg, option, send_size, rcv_size, rcv_name, timeout, 
notify, cancel_p, intr_port_p) \
 ({                                                                           \
   error_t err;                                                               \
@@ -31,21 +29,52 @@
        ".globl _hurd_intr_rpc_msg_do_trap\n"                                 \
        ".globl _hurd_intr_rpc_msg_in_trap\n"                                 \
        ".globl _hurd_intr_rpc_msg_sp_restored\n"                             \
-       "_hurd_intr_rpc_msg_about_to:   cmpl $0, %5\n"                        \
+       "_hurd_intr_rpc_msg_about_to:"                                        \
+       /* We need to make a last check of cancel, in case we got interrupted
+          right before _hurd_intr_rpc_msg_about_to.  */                        
      \
+       "                               cmpl $0, %5\n"                        \
        "                               jz _hurd_intr_rpc_msg_do\n"           \
+       /* We got interrupted, note so and return EINTR.  */                  \
        "                               movl $0, %3\n"                        \
        "                               movl %6, %%eax\n"                     \
        "                               jmp _hurd_intr_rpc_msg_sp_restored\n" \
-       "_hurd_intr_rpc_msg_do:         movl %%esp, %%ecx\n"                  \
-       "                               .cfi_def_cfa_register %%ecx\n"        \
-       "                               leal %4, %%esp\n"                     \
+       "_hurd_intr_rpc_msg_do:"                                                
      \
+       /* Ok, push the mach_msg_trap arguments.  */                          \
+       "                               pushl 24(%4)\n"                       \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl %2\n"                           \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl 16(%4)\n"                       \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl 12(%4)\n"                       \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl 8(%4)\n"                        \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl %1\n"                           \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl (%4)\n"                         \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       "                               pushl $0\n"                           \
+       "                               .cfi_adjust_cfa_offset 4\n"           \
+       /* TODO: remove this ecx kludge, we don't need it any more */         \
+       "                               movl %%esp, %%ecx\n"                  \
        "_hurd_intr_rpc_msg_cx_sp:      movl $-25, %%eax\n"                   \
        "_hurd_intr_rpc_msg_do_trap:    lcall $7, $0 # status in %0\n"        \
-       "_hurd_intr_rpc_msg_in_trap:    movl %%ecx, %%esp\n"                  \
-       "                               .cfi_def_cfa_register %%esp\n"        \
+       "_hurd_intr_rpc_msg_in_trap:"                                         \
+       /* Ok, clean the arguments and update OPTION and TIMEOUT.  */         \
+       "                               addl $8, %%esp\n"                     \
+       "                               .cfi_adjust_cfa_offset -8\n"          \
+       "                               popl %1\n"                            \
+       "                               .cfi_adjust_cfa_offset -4\n"          \
+       "                               addl $12, %%esp\n"                    \
+       "                               .cfi_adjust_cfa_offset -12\n"         \
+       "                               popl %2\n"                            \
+       "                               .cfi_adjust_cfa_offset -4\n"          \
+       "                               addl $4, %%esp\n"                     \
+       "                               .cfi_adjust_cfa_offset -4\n"          \
        "_hurd_intr_rpc_msg_sp_restored:"                                     \
-       : "=a" (err), "+m" (option), "+m" (timeout), "=m" (*intr_port_p)        
      \
-       : "m" ((&msg)[-1]), "m" (*cancel_p), "i" (EINTR)                        
      \
+       : "=a" (err), "+r" (option), "+r" (timeout), "=m" (*intr_port_p)        
      \
+       : "r" (&msg), "m" (*cancel_p), "i" (EINTR)                            \
        : "ecx");                                                             \
   err;                                                                       \
 })
-- 
2.33.0