From b8f04323dc64d1221e5fb3f1162bd6a5aea81912 Mon Sep 17 00:00:00 2001
From: Roland McGrath <roland@gnu.org>
Date: Wed, 3 Aug 1994 06:45:59 +0000
Subject: [PATCH] Compare *reply_port to MACH_PORT_NULL, not implicit zero.
 (restore_gpr): Use N-1 as subscript into sc_gpr (sc_gpr[0] => $1). Before
 general regs, restore from sc_mdlo and sc_mdhi. Don't treat sp, fp specially;
 use restore_gpr for them too. For final return, store user $1 value beyond
 top of user stack ahead of time; Then use $1 to hold the user PC, and restore
 it from the stack in the delay slot.

---
 sysdeps/mach/hurd/mips/sigreturn.c | 42 +++++++++++++++++-------------
 1 file changed, 24 insertions(+), 18 deletions(-)

diff --git a/sysdeps/mach/hurd/mips/sigreturn.c b/sysdeps/mach/hurd/mips/sigreturn.c
index 147243f5b9..8082acaf9b 100644
--- a/sysdeps/mach/hurd/mips/sigreturn.c
+++ b/sysdeps/mach/hurd/mips/sigreturn.c
@@ -16,8 +16,6 @@ License along with the GNU C Library; see the file COPYING.LIB.  If
 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
 Cambridge, MA 02139, USA.  */
 
-register int sp asm ("$29"), fp asm ("$30");
-
 #include <hurd.h>
 #include <hurd/signal.h>
 #include <hurd/threadvar.h>
@@ -45,19 +43,31 @@ __sigreturn (const struct sigcontext *scp)
      reply port in use by the thread when interrupted.  */
   reply_port =
     (mach_port_t *) __hurd_threadvar_location (_HURD_THREADVAR_MIG_REPLY);
-  if (*reply_port)
+  if (*reply_port != MACH_PORT_NULL)
     __mach_port_destroy (__mach_task_self (), *reply_port);
   *reply_port = scp->sc_reply_port;
 
-  /* Restore registers.  */
+  /* Load all the registers from the sigcontext.  */
 #define restore_gpr(n) \
-  asm volatile ("lw $" #n ",%0" : : "m" (scpreg->sc_gpr[n]))
+  asm volatile ("lw $" #n ",%0" : : "m" (scpreg->sc_gpr[n - 1]))
 
-  asm volatile (".set noreorder; .set noat;");
   {
     register const struct sigcontext *const scpreg asm ("$1") = scp;
 
-    /* Load the general-purpose registers from the sigcontext.  */
+    /* Just beyond the top of the user stack, store the user's value for $1
+       (which we are using for SCPREG).  We restore this register as the
+       very last thing, below.  */
+    ((int *) scpreg->sc_gpr[29 - 1])[-1] = scpreg->sc_gpr[0];
+
+    /* First restore the multiplication result registers.  The compiler
+       will use some temporary registers, so we do this before restoring
+       the general registers.  */
+    asm volatile ("mtlo %0" : : "r" (scpreg->sc_mdlo));
+    asm volatile ("mthi %0" : : "r" (scpreg->sc_mdhi));
+
+    asm volatile (".set noreorder; .set noat;");
+
+    /* Restore the normal registers.  */
     restore_gpr (2);
     restore_gpr (3);
     restore_gpr (4);
@@ -84,20 +94,16 @@ __sigreturn (const struct sigcontext *scp)
     restore_gpr (25);
     /* Registers 26-27 are kernel-only.  */
     restore_gpr (28);
-
-    /* Now the special-purpose registers.  */
-    sp = scpreg->sc_sp;		/* Stack pointer.  */
-    fp = scpreg->sc_fp;		/* Frame pointer.  */
+    restore_gpr (29);		/* Stack pointer.  */
+    restore_gpr (30);		/* Frame pointer.  */
     restore_gpr (31);		/* Return address.  */
 
     /* Now jump to the saved PC.  */
-    asm volatile ("lw $24, %0\n" /* Load saved PC into temporary $t8.  */
-		  "j $24\n"	/* Jump to the saved PC value.  */
-		  "lw $1, %1\n" /* Restore $at in delay slot.  */
-		  : :
-		  "m" (scpreg->sc_pc),
-		  "m" (scpreg->sc_r1) /* $at */
-		  : "$24");	/* XXX clobbers $24 (aka $t8)!! */
+    asm volatile ("lw $1, %0\n"	/* Load saved PC into $1.  */
+		  "j $1\n"	/* Jump to the saved PC value.  */
+		  "lw $1, -4(sp)\n" /* Restore $1 from stack in delay slot.  */
+		  : : "m" (scpreg->sc_pc));
+
     asm volatile (".set reorder; .set at;");
   }
 
-- 
2.43.5