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SubjectRe: [PATCH v2 09/18] x86/asm: Move SYSENTER_stack to the beginning of struct tss_struct
On Tue, Nov 21, 2017 at 08:44:04PM -0800, Andy Lutomirski wrote:
> I want SYSENTER_stack to have reliable overflow detection, which
> means that it needs to be at the bottom of a page, not the top.

Passive-impersonal tone pls.

> Move it to the beginning of struct tss_struct and page-align it.
>
> Also add an assertion to make sure that the fixed hardware TSS
> doesn't cross a page boundary.
>
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
> arch/x86/include/asm/processor.h | 21 ++++++++++++---------
> arch/x86/kernel/cpu/common.c | 22 ++++++++++++++++++++++
> 2 files changed, 34 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index d32a3c88a968..8f5dac9dfbdc 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -327,7 +327,16 @@ struct x86_hw_tss {
>
> struct tss_struct {
> /*
> - * The hardware state:
> + * Space for the temporary SYSENTER stack, used for SYSENTER
> + * and the entry trampoline as well.
> + */
> + unsigned long SYSENTER_stack_canary;
> + unsigned long SYSENTER_stack[64];
> +
> + /*
> + * The fixed hardware portion. This must not cross a page boundary
> + * at risk of violating the SDM's advice and potentially triggering
> + * errata.
> */
> struct x86_hw_tss x86_tss;
>
> @@ -338,15 +347,9 @@ struct tss_struct {
> * be within the limit.
> */
> unsigned long io_bitmap[IO_BITMAP_LONGS + 1];
> +} __attribute__((__aligned__(PAGE_SIZE)));

WARNING: __aligned(size) is preferred over __attribute__((aligned(size)))
#58: FILE: arch/x86/include/asm/processor.h:350:
+} __attribute__((__aligned__(PAGE_SIZE)));

--
Regards/Gruss,
Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

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