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Re: [Xen-devel] [PATCH v2 3/3] x86: Make the GDT remapping read-only on 64 bit
- To: Ingo Molnar <mingo@xxxxxxxxxx>
- From: Andy Lutomirski <luto@xxxxxxxxxx>
- Date: Wed, 1 Feb 2017 21:13:55 -0800
- Cc: X86 ML <x86@xxxxxxxxxx>, Stanislaw Gruszka <sgruszka@xxxxxxxxxx>, kvm list <kvm@xxxxxxxxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>, Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>, Radim Krčmář <rkrcmar@xxxxxxxxxx>, "linux-efi@xxxxxxxxxxxxxxx" <linux-efi@xxxxxxxxxxxxxxx>, Alexander Potapenko <glider@xxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, "H . Peter Anvin" <hpa@xxxxxxxxx>, "kernel-hardening@xxxxxxxxxxxxxxxxxx" <kernel-hardening@xxxxxxxxxxxxxxxxxx>, Jiri Olsa <jolsa@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxx>, Andi Kleen <ak@xxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, Prarit Bhargava <prarit@xxxxxxxxxx>, kasan-dev <kasan-dev@xxxxxxxxxxxxxxxx>, Christian Borntraeger <borntraeger@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Len Brown <len.brown@xxxxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Jiri Kosina <jikos@xxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, He Chen <he.chen@xxxxxxxxxxxxxxx>, Brian Gerst <brgerst@xxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, lguest@xxxxxxxxxxxxxxxx, Andy Lutomirski <luto@xxxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Chen Yucong <slaoub@xxxxxxxxx>, Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>, Adam Buchbinder <adam.buchbinder@xxxxxxxxx>, Dmitry Vyukov <dvyukov@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>, "linux-pm@xxxxxxxxxxxxxxx" <linux-pm@xxxxxxxxxxxxxxx>, "Rafael J . Wysocki" <rjw@xxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, "Luis R . Rodriguez" <mcgrof@xxxxxxxxxx>, David Vrabel <david.vrabel@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, Thomas Garnier <thgarnie@xxxxxxxxxx>
- Delivery-date: Thu, 02 Feb 2017 05:14:50 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Wed, Feb 1, 2017 at 1:15 AM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>
> * Thomas Garnier <thgarnie@xxxxxxxxxx> wrote:
>
>> This patch makes the GDT remapped pages read-only to prevent corruption.
>> This change is done only on 64 bit.
>
>>
>> - table_base = gdt->address;
>> + table_base = (unsigned long)get_current_direct_gdt();
>
> Instead of spreading these type casts far and wide please introduce another
> accessor the returns 'unsigned long':
>
> get_cpu_gdt_rw_vaddr()
>
That whole function is an abomination. How about replacing 'unsigned
long table_base' with 'struct desc_struct *table'? If you're feeling
really adventurous, *delete* that function and replace all of its
users with something sane.
--Andy
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