Re: [PATCH v2] linux-user/s390x: Use the guest pointer for the sigreturn stub

[Andreas Krebbel <krebbel@linux.ibm.com>]

On 3/24/21 6:53 PM, Laurent Vivier wrote:
> Le 24/03/2021 à 16:55, Andreas Krebbel a écrit :
>> When setting up the pointer for the sigreturn stub in the return
>> address register (r14) we have to use the guest frame pointer instead
>> of the host frame pointer.
>>
>> Note: This only caused problems if Qemu has been built with
>> --disable-pie (as it is in distros nowadays). Otherwise guest_base
>> defaults to 0 hiding the actual problem.
>>
>> Signed-off-by: Andreas Krebbel <krebbel@linux.ibm.com>
>> ---
>>  linux-user/s390x/signal.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
>> index ecfa2a14a9..e9bf865074 100644
>> --- a/linux-user/s390x/signal.c
>> +++ b/linux-user/s390x/signal.c
>> @@ -213,7 +213,8 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
>>      if (ka->sa_flags & TARGET_SA_RESTORER) {
>>          env->regs[14] = (unsigned long) ka->sa_restorer | PSW_ADDR_AMODE;
>>      } else {
>> -        env->regs[14] = (unsigned long) frame->retcode | PSW_ADDR_AMODE;
>> +        env->regs[14] = (target_ulong) (frame_addr + offsetof(rt_sigframe, retcode))
>> +                        | PSW_ADDR_AMODE;
>>          __put_user(S390_SYSCALL_OPCODE | TARGET_NR_rt_sigreturn,
>>                     (uint16_t *)(frame->retcode));
>>      }
>>
> 
> Reviewed-by: Laurent Vivier <laurent@vivier.eu>
> 
> but if you want to send a v3:

Sure, will do.

> - to be consistent with lines below, use "offsetof(typeof(*frame), ..."
> - in the line above, you can remove the (unsigned long) of the sa_restorer as it is an abi_ulong,

The (target_ulong) cast could probably go away as well since frame_addr is also abi_ulong.

> - don't send the "v2" as a reply to the v1 as it can be hidden in the mail thread and missed by the
> maintainer :)

Ok.

Andreas

> 
> Thanks,
> Laurent
>