Re: [Qemu-stable] [Qemu-devel] [PATCH v2 1/1] target-ppc, tcg: fix usermode segfault with pthread_create()

[Michael Roth]

Quoting Sam Bobroff (2017-02-06 21:21:39)
> 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 <address@hidden>

Cc'ing address@hidden

> ---
> 
> v2:
> 
> * Remove the NIP adjustment from the -TARGET_QEMU_ESIGRETURN case, it must
> break out with the same NIP as do_syscall().
> 
>  linux-user/main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 30049581ef..4ea49f68be 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;
> -- 
> 2.11.0
> 
>