iwmmxt signal frame handling

[Eric Miao]

On Friday, October 15, 2010, Eric Miao <eric.y.miao at gmail.com> wrote:
> On Thu, Oct 14, 2010 at 10:09 PM, Arnd Bergmann <arnd at arndb.de> wrote:
>> Peter Maydell noticed during code review that the signal frame might
>> be written incorrectly for kernels with CONFIG_IWMMXT set running
>> processes without TIF_USING_IWMMXT, where the magic/size values
>> for the iwmmxt section of the frame are left uninitialized.
>> Instead of skipping this part of the frame, we should instead
>> write a valid header with zero data.
>>
>> This patch is compile-tested only since the problem was only
>> found in review and neither Peter nor myself have access to
>> IWMMXT capable hardware to test this on.
>>
>> Signed-off-by: Arnd Bergmann <arnd at arndb.de>
>> Reported-by: Peter Maydell <peter.maydell at linaro.org>
>
> Looks OK to me as well.
>
> Acked-by: Eric Miao <eric.y.miao at gmail.com>
>

This also passes the internal iwmmxt test, Haojian please add your
Tested-by please.

>>
>> --- a/arch/arm/kernel/signal.c
>> +++ b/arch/arm/kernel/signal.c
>> @@ -154,7 +154,10 @@ static int preserve_iwmmxt_context(struct iwmmxt_sigframe *frame)
>>        kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
>>        kframe->magic = IWMMXT_MAGIC;
>>        kframe->size = IWMMXT_STORAGE_SIZE;
>> -       iwmmxt_task_copy(current_thread_info(), &kframe->storage);
>> +       if (test_thread_flag(TIF_USING_IWMMXT))
>> +               iwmmxt_task_copy(current_thread_info(), &kframe->storage);
>> +       else
>> +               memset(&kframe->storage, 0, sizeof(kframe->storage));
>>        return __copy_to_user(frame, kframe, sizeof(*frame));
>>  }
>>
>> @@ -429,7 +432,7 @@ setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
>>                err |= preserve_crunch_context(&aux->crunch);
>>  #endif
>>  #ifdef CONFIG_IWMMXT
>> -       if (err == 0 && test_thread_flag(TIF_USING_IWMMXT))
>> +       if (err == 0)
>>                err |= preserve_iwmmxt_context(&aux->iwmmxt);
>>  #endif
>>  #ifdef CONFIG_VFP
>>
>