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.

diff --git a/sysdeps/mach/hurd/mips/sigreturn.c b/sysdeps/mach/hurd/mips/sigreturn.c
index 147243f5b9bc5b35fcaa89655392e89e6c02fae2..8082acaf9b9eff0666db5c01f0f01f0ff34f829c 100644 (file)
--- 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;");
   }