Re: [Qemu-devel] [PATCH 09/12] linux-user: Minimum Sig Handler Stack Size for PPC64 ELF V2

[Alexander Graf <agraf@suse.de>]

On 04.08.14 19:39, Peter Maydell wrote:
> On 4 August 2014 17:45, Tom Musta <tommusta@gmail.com> wrote:
>> The ELF V2 ABI for PPC64 defines MINSIGSTKSZ as 4096 bytes whereas it was
>> 2048 previously.
> Alpha and SPARC also have a 4096 byte MINSIGSTKSZ...
>
>> Signed-off-by: Tom Musta <tommusta@gmail.com>
>>
>> diff --git a/linux-user/signal.c b/linux-user/signal.c
>> index cdfcc52..b2a6e53 100644
>> --- a/linux-user/signal.c
>> +++ b/linux-user/signal.c
>> @@ -617,6 +617,15 @@ abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp)
>>       {
>>           struct target_sigaltstack *uss;
>>           struct target_sigaltstack ss;
>> +        size_t minstacksize = MINSIGSTKSZ;
>> +
>> +#if defined(TARGET_PPC64)
>> +        /* ELF V2 for PPC64 has a 4K minimum stack size for signal handlers */
>> +        struct image_info *image = ((TaskState *)thread_cpu->opaque)->info;
>> +        if (get_ppc64_abi(image) > 1) {
>> +            minstacksize = 4096;
>> +        }
>> +#endif
> Shouldn't we just define and use a TARGET_MINSIGSTKSZ ?
> Checking against the host's MINSIGSTKSZ is wrong, I think.
>
> Again, define the TARGET_MINSIGSTKSZ in a file in
> linux-user/$ARCH/, for all targets:
>   alpha, sparc, ppc64: 4096
>   everything else: 2048
> (itanium is weird here but we don't support that for linux-user guests)

and supporting ia64 is really hard, because it uses the full 64bit 
virtual address space which we can't provide on x86_64.


Alex