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

[pandora-kernel.git] / arch / sparc / kernel / signal_32.c

diff --git a/arch/sparc/kernel/signal_32.c b/arch/sparc/kernel/signal_32.c
index 8ce247a..d54c6e5 100644 (file)
--- a/arch/sparc/kernel/signal_32.c
+++ b/arch/sparc/kernel/signal_32.c
@@ -519,10 +519,26 @@ 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->psr & PSR_C))
-               restart_syscall = 1;
-       else
-               restart_syscall = 0;
+               regs->u_regs[UREG_G6] = orig_i0;
 
        if (test_thread_flag(TIF_RESTORE_SIGMASK))
                oldset = &current->saved_sigmask;
@@ -535,8 +551,12 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
         * 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->psr & PSR_C)) {
+               restart_syscall = 1;
+               orig_i0 = regs->u_regs[UREG_G6];
+       }
+
 
        if (signr > 0) {
                if (restart_syscall)