Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[pandora-kernel.git] / arch / sparc / kernel / signal_64.c

diff --git a/arch/sparc/kernel/signal_64.c b/arch/sparc/kernel/signal_64.c
index a2b8159..f0836cd 100644 (file)
--- a/arch/sparc/kernel/signal_64.c
+++ b/arch/sparc/kernel/signal_64.c
@@ -529,11 +529,27 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
        siginfo_t info;
        int signr;
        
+       /* It's a lot of work and synchronization to add a new ptrace
+        * register for GDB to save and restore in order to get
+        * orig_i0 correct for syscall restarts when debugging.
+        *
+        * Although it should be the case that most of the global
+        * registers are volatile across a system call, glibc already
+        * depends upon that fact that we preserve them.  So we can't
+        * just use any global register to save away the orig_i0 value.
+        *
+        * In particular %g2, %g3, %g4, and %g5 are all assumed to be
+        * preserved across a system call trap by various pieces of
+        * code in glibc.
+        *
+        * %g7 is used as the "thread register".   %g6 is not used in
+        * any fixed manner.  %g6 is used as a scratch register and
+        * a compiler temporary, but it's value is never used across
+        * a system call.  Therefore %g6 is usable for orig_i0 storage.
+        */
        if (pt_regs_is_syscall(regs) &&
-           (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) {
-               restart_syscall = 1;
-       } else
-               restart_syscall = 0;
+           (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY)))
+               regs->u_regs[UREG_G6] = orig_i0;
 
        if (current_thread_info()->status & TS_RESTORE_SIGMASK)
                oldset = &current->saved_sigmask;
@@ -542,22 +558,20 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
 
 #ifdef CONFIG_COMPAT
        if (test_thread_flag(TIF_32BIT)) {
-               extern void do_signal32(sigset_t *, struct pt_regs *,
-                                       int restart_syscall,
-                                       unsigned long orig_i0);
-               do_signal32(oldset, regs, restart_syscall, orig_i0);
+               extern void do_signal32(sigset_t *, struct pt_regs *);
+               do_signal32(oldset, regs);
                return;
        }
 #endif 
 
        signr = get_signal_to_deliver(&info, &ka, regs, NULL);
 
-       /* If the debugger messes with the program counter, it clears
-        * the software "in syscall" bit, directing us to not perform
-        * a syscall restart.
-        */
-       if (restart_syscall && !pt_regs_is_syscall(regs))
-               restart_syscall = 0;
+       restart_syscall = 0;
+       if (pt_regs_is_syscall(regs) &&
+           (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) {
+               restart_syscall = 1;
+               orig_i0 = regs->u_regs[UREG_G6];
+       }
 
        if (signr > 0) {
                if (restart_syscall)