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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 22 Mar 2018 11:07:40 +0000
Message-ID: <CAFEAcA9ZAxkvc-Rn=oP5Bgksk6zo8PYNkhP8SC1+aaWN_vQduw@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [Qemu-devel] [PULL 12/13] page_unprotect(): handle calls to
 pages that are PAGE_WRITE
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To: Laurent Vivier <laurent@vivier.eu>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 22 March 2018 at 11:05, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 22 March 2018 at 10:36, Laurent Vivier <laurent@vivier.eu> 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