Re: [Qemu-devel] [PATCH] linux-user/signal.c: Generate opcode data for restorer in setup_rt_frame

[Chen Gang]

On 3/29/16 06:17, Laurent Vivier wrote:
>> On 3/15/16 05:51, address@hidden wrote:
>>>
>>> Original implementation uses do_rt_sigreturn directly in host space,
>>> when a guest program is in unwind procedure in guest space, it will get
>>> an incorrect restore address, then causes unwind failure.
>>>
>>> Also cleanup the original incorrect indentation.
>>>
>>> Signed-off-by: Chen Gang <address@hidden>
>>> ---
>>>  linux-user/signal.c | 12 ++++++++++--
>>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/linux-user/signal.c b/linux-user/signal.c
>>> index 919aa83..0e3b1c6 100644
>>> --- a/linux-user/signal.c
>>> +++ b/linux-user/signal.c
>>> @@ -5566,8 +5566,13 @@ struct target_rt_sigframe {
>>>      unsigned char save_area[16]; /* caller save area */
>>>      struct target_siginfo info;
>>>      struct target_ucontext uc;
>>> +    abi_ulong retcode[2];
>>>  };
>>>  
>>> +#define INSN_MOVELI_R10_139  0x00045fe551483000ULL /* { moveli r10, 139 } 
>>> */
>>> +#define INSN_SWINT1          0x286b180051485000ULL /* { swint1 } */
>>> +
>>> +
>>>  static void setup_sigcontext(struct target_sigcontext *sc,
>>>                               CPUArchState *env, int signo)
>>>  {
>>> @@ -5643,9 +5648,12 @@ static void setup_rt_frame(int sig, struct 
>>> target_sigaction *ka,
>>>      __put_user(target_sigaltstack_used.ss_size, 
>>> &frame->uc.tuc_stack.ss_size);
>>>      setup_sigcontext(&frame->uc.tuc_mcontext, env, info->si_signo);
>>>  
>>> -    restorer = (unsigned long) do_rt_sigreturn;
>>>      if (ka->sa_flags & TARGET_SA_RESTORER) {
>>> -            restorer = (unsigned long) ka->sa_restorer;
>>> +        restorer = (unsigned long) ka->sa_restorer;
>>> +    } else {
>>> +        __put_user(INSN_MOVELI_R10_139, &frame->retcode[0]);
>>> +        __put_user(INSN_SWINT1, &frame->retcode[1]);
>>> +        restorer = (unsigned long)frame->retcode;
> 
> The address of retcode in host and guest can differ.
> You need something like:
> 
>       restorer = (unsigned long)(frame_addr + offsetof(struct
> target_rt_sigframe, retcode));
> 
> I've experienced this on sh4 (see commit 2a0fa68)
> 

OK, thanks. What you said above sounds reasonable to me. :-)

I shall send patch v2 for it (although tilegx is a pure 64-bit target,
with this patch, I guess, tilegx target should still run correctly under
32-bit host).

By the way, it looks that s390x and microblaze targets also have the
same issue.


Thanks.
-- 
Chen Gang (陈刚)

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