Re: [Qemu-devel] [PULL 12/13] page_unprotect(): handle calls to pages that are PAGE_WRITE

[Peter Maydell]

On 22 March 2018 at 11:05, Peter Maydell <address@hidden> wrote:
> On 22 March 2018 at 10:36, Laurent Vivier <address@hidden> wrote:
>> It goes wrong in this part:
>>
>> +     */
>> +    if (is_write && info->si_signo == SIGSEGV && info->si_code ==
>> SEGV_ACCERR &&
>> +        h2g_valid(address)) {
>>
>> Because, on ppc, si_code is SEGV_MAPERR and not SEGV_ACCERR
>> (on x86_64, si_code is SEGV_ACCERR as expected)
>
> So on PPC if you have a page mapped, and you access it with
> the wrong permissions, you get SEGV_MAPERR? This seems like
> a host kernel bug to me.

...in particular, kernel commit ecb101aed86156e (dated Dec 2017)
fixes a regression introduced in commit c3350602e876 that broke
the ppc kernels so they started returning SEGV_MAPERR here
instead of SEGV_ACCERR. Presumably your host kernel is missing
this fix.

thanks
-- PMM