linux-kernel - Re: [PATCH v2] x86, mm: set NX across entire PMD at boot

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Message-ID: <CAE9FiQVQg58Nadooo3U=8BBJ7Qr2ptxan52=LAD_eJMKzNXfMQ@mail.gmail.com>
Date:	Mon, 17 Nov 2014 23:39:43 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Wang Nan <wangnan0@...wei.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [PATCH v2] x86, mm: set NX across entire PMD at boot

On Mon, Nov 17, 2014 at 12:27 PM, Kees Cook <keescook@...omium.org> wrote:
> On Sun, Nov 16, 2014 at 3:44 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>> So the initial patch to get rid of the X mapping is of course to just
>> extend the area to the PMD. A little bit different to your initial
>> patch, but essentially the same.
>>
>> -       unsigned long all_end = PFN_ALIGN(&_end);
>> +       unsigned long all_end = roundup((unsigned long) &_end, PMD_SIZE);
>>
>> I'm going to apply your V1 patch with the above roundup()
>> simplification. If a page of that area gets used later on then we are
>> going to split up the PMD anyway.
>
> That's fine by me. Yinghai Lu seems to have potentially better
> solutions, but my head is spinning after reading more of this thread.
> :) I just want to make sure that at the end of the day, there are no
> RW+x mappings.
>

Please check v3 that cleanup highmap in the middle.


Before patch:
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000          16M                           pmd
0xffffffff81000000-0xffffffff82200000          18M     ro         PSE GLB x  pmd
0xffffffff82200000-0xffffffff82c00000          10M     ro         PSE GLB NX pmd
0xffffffff82c00000-0xffffffff82e00000           2M     RW         PSE GLB NX pmd
0xffffffff82e00000-0xffffffff83000000           2M     RW             GLB NX pte
0xffffffff83000000-0xffffffff83200000           2M     RW         PSE GLB NX pmd
0xffffffff83200000-0xffffffff83400000           2M     RW             GLB NX pte
0xffffffff83400000-0xffffffff84200000          14M     RW         PSE GLB NX pmd
0xffffffff84200000-0xffffffff843a2000        1672K     RW             GLB NX pte
0xffffffff843a2000-0xffffffff84400000         376K     RW             GLB x  pte
0xffffffff84400000-0xffffffffa0000000         444M                           pmd

After patch:
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000          16M                           pmd
0xffffffff81000000-0xffffffff82000000          16M     ro         PSE GLB x  pmd
0xffffffff82000000-0xffffffff82011000          68K     ro             GLB x  pte
0xffffffff82011000-0xffffffff82200000        1980K                           pte
0xffffffff82200000-0xffffffff82a00000           8M     ro         PSE GLB NX pmd
0xffffffff82a00000-0xffffffff82a1d000         116K     ro             GLB NX pte
0xffffffff82a1d000-0xffffffff82c00000        1932K                           pte
0xffffffff82c00000-0xffffffff82e00000           2M     RW         PSE GLB NX pmd
0xffffffff82e00000-0xffffffff82e52000         328K     RW             GLB NX pte
0xffffffff82e52000-0xffffffff83000000        1720K                           pte
0xffffffff83000000-0xffffffff83200000           2M                           pmd
0xffffffff83200000-0xffffffff83213000          76K                           pte
0xffffffff83213000-0xffffffff83400000        1972K     RW             GLB NX pte
0xffffffff83400000-0xffffffff84200000          14M     RW         PSE GLB NX pmd
0xffffffff84200000-0xffffffff84383000        1548K     RW             GLB NX pte
0xffffffff84383000-0xffffffff84400000         500K                           pte
0xffffffff84400000-0xffffffffa0000000         444M                           pmd

Thanks

Yinghai

View attachment "nx_after_end_v3_1.patch" of type "text/x-patch" (3069 bytes)

View attachment "nx_after_end_v3_2.patch" of type "text/x-patch" (6281 bytes)