powerpc: fix double syscall restarts

Make sigreturn zero regs->trap, make do_signal() do the same on all
paths.  As it is, signal interrupting e.g. read() from fd 512 (==
ERESTARTSYS) with another signal getting unblocked when the first
handler finishes will lead to restart one insn earlier than it ought
to.  Same for multiple signals with in-kernel handlers interrupting
that sucker at the same time.  Same for multiple signals of any kind
interrupting that sucker on 64bit...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 266610119f6..b96a3a010c2 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -511,6 +511,7 @@ static long restore_user_regs(struct pt_regs *regs,
         if (!sig)
                 save_r2 = (unsigned int)regs->gpr[2];
         err = restore_general_regs(regs, sr);
+        regs->trap = 0;
         err |= __get_user(msr, &sr->mc_gregs[PT_MSR]);
         if (!sig)
                 regs->gpr[2] = (unsigned long) save_r2;
@@ -884,7 +885,6 @@ int handle_rt_signal32(unsigned long sig, struct k_sigaction *ka,
         regs->nip = (unsigned long) ka->sa.sa_handler;
         /* enter the signal handler in big-endian mode */
         regs->msr &= ~MSR_LE;
-        regs->trap = 0;
         return 1;
 
 badframe:
@@ -1228,7 +1228,6 @@ int handle_signal32(unsigned long sig, struct k_sigaction *ka,
         regs->nip = (unsigned long) ka->sa.sa_handler;
         /* enter the signal handler in big-endian mode */
         regs->msr &= ~MSR_LE;
-        regs->trap = 0;
 
         return 1;