Re: [Qemu-devel] [PATCH 3/3] linux-user:Signal handling for MIPS64

["Andreas Färber" <andreas.faerber@web.de>]

Am 29.12.2011 11:58, schrieb Khansa Butt:
> On Wed, Dec 14, 2011 at 9:20 PM, Richard Henderson <rth@twiddle.net> wrote:
>> On 12/07/2011 09:25 PM, khansa@kics.edu.pk wrote:
>>> +#if defined(TARGET_MIPS64)
>>> +        /* tswapal() do 64 bit swap in case of MIPS64 but
>>> +           we need 32 bit swap as sa_flags is 32 bit */
>>> +        k->sa_flags = bswap32(act->sa_flags);
>>> +#else
>>>          k->sa_flags = tswapal(act->sa_flags);
>>> +#endif
>>
>> The condition in syscall_defs.h is TARGET_MIPS, not TARGET_MIPS64.
>> They should match, despite the fact that it doesn't actually matter
>> for the 32-bit abis.
>>
>>>  #elif defined(TARGET_ABI_MIPSN64)
>>>
>>> -# warning signal handling not implemented
>>> +struct target_sigcontext {
>>> +    uint32_t   sc_regmask;     /* Unused */
>>> +    uint32_t   sc_status;
>>
>> There's no reason to duplicate all this code.  Yes, when someone wrote
>> this in the first place, they wrote separate sectons for each mips abi.
>> However, as you can see that huge portions of this block are identical,
>> this was obviously a mistake.
>>
>> Start by changing the original section to #elif defined(TARGET_MIPS)
>> and see what needs changing specifically for the ABIs.  I'm not even
>> sure there are any differences at all.
> 
> The difference lies in setup_frame(). the trampoline function needs
> syscall number
>     install_sigtramp(frame->sf_code, TARGET_NR_sigreturn);
> sigreturn is not defined for MIPS64 instead it has only rt_sigreturn.
> I tried with #elif defined(TARGET_MIPS). cross compile the following
> small program and run it on
> qemu-mips64
> #include <stdio.h>
> #include <signal.h>
> #include <string.h>
> #include <unistd.h>
> 
> struct sigaction act;
> 
> void sighandler(int signum, siginfo_t *info, void *ptr)
> {
>     printf("Received signal %d\n", signum);
>     printf("Signal originates from process %lu\n",(unsigned long)info->si_pid);
> }
> 
> int main()
> {
>     printf("I am %lu\n", (unsigned long)getpid());
> 
>     memset(&act, 0, sizeof(act));
> 
>     act.sa_sigaction = sighandler;
>     act.sa_flags = SA_SIGINFO;
> 
>     sigaction(SIGILL, &act, NULL);
> 
>     // Waiting
>     sleep(100);
> 
>     return 0;
> }
> 
> and again I found that only install_sigtramp line is needed to be changed.
> keeping  #elif defined(TARGET_MIPS) above signal handling portion, can i use
>  #if defined(TARGET_MIPS64)
>  ....
> #else
> for install_sigtramp() difference

That's not the only difference - the sigcontext is different, too, for
instance. I hope to get something finished for n32 later today.

Andreas