1 files changed, 15 insertions, 5 deletions

diff --git a/arch/sparc/kernel/signal_64.c b/arch/sparc/kernel/signal_64.c
index 1ddf0dedb92..f0836cd0e2f 100644
--- a/arch/sparc/kernel/signal_64.c
+++ b/arch/sparc/kernel/signal_64.c
@@ -533,13 +533,23 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
          * register for GDB to save and restore in order to get
          * orig_i0 correct for syscall restarts when debugging.
          *
-         * However, we luckily can use the fact that several registers
-         * are volatile across system calls.  One such register is
-         * %g2, so use that as a place to save away orig_i0.
+         * 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)))
-                regs->u_regs[UREG_G2] = orig_i0;
+                regs->u_regs[UREG_G6] = orig_i0;
 
         if (current_thread_info()->status & TS_RESTORE_SIGMASK)
                 oldset = &current->saved_sigmask;
@@ -560,7 +570,7 @@ static void do_signal(struct pt_regs *regs, unsigned long orig_i0)
         if (pt_regs_is_syscall(regs) &&
             (regs->tstate & (TSTATE_XCARRY | TSTATE_ICARRY))) {
                 restart_syscall = 1;
-                orig_i0 = regs->u_regs[UREG_G2];
+                orig_i0 = regs->u_regs[UREG_G6];
         }
 
         if (signr > 0) {