From: Sam Bobroff <sam.bobroff@au1.ibm.com>
Date: Tue, 7 Feb 2017 03:21:39 +0000 (+1100)
Subject: target-ppc, tcg: fix usermode segfault with pthread_create()
X-Git-Tag: qemu-xen-4.10.0-rc1~495^2~25
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=2635531f2006bfb0f943ad25b41e176709b79b37;p=qemu-xen.git

target-ppc, tcg: fix usermode segfault with pthread_create()

Programs run under qemu-ppc64 on an x86_64 host currently segfault
if they use pthread_create() due to the adjustment made to the NIP in
commit bd6fefe71cec5a0c7d2be4ac96307f25db56abf9.

This patch changes cpu_loop() to set the NIP back to the
pre-incremented value before calling do_syscall(), which causes the
correct address to be used for the new thread and corrects the fault.

Signed-off-by: Sam Bobroff <sam.bobroff@au1.ibm.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---

diff --git a/linux-user/main.c b/linux-user/main.c
index 4fd49ce6b6..9645122aa6 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -1712,10 +1712,12 @@ void cpu_loop(CPUPPCState *env)
              * in syscalls.
              */
             env->crf[0] &= ~0x1;
+            env->nip += 4;
             ret = do_syscall(env, env->gpr[0], env->gpr[3], env->gpr[4],
                              env->gpr[5], env->gpr[6], env->gpr[7],
                              env->gpr[8], 0, 0);
             if (ret == -TARGET_ERESTARTSYS) {
+                env->nip -= 4;
                 break;
             }
             if (ret == (target_ulong)(-TARGET_QEMU_ESIGRETURN)) {
@@ -1723,7 +1725,6 @@ void cpu_loop(CPUPPCState *env)
                    Avoid corrupting register state.  */
                 break;
             }
-            env->nip += 4;
             if (ret > (target_ulong)(-515)) {
                 env->crf[0] |= 0x1;
                 ret = -ret;