From: Dave Hansen <dave.hansen@intel.com>
To: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC 5/7] x86/asm: Rearrange struct cpu_tss to enlarge SYSENTER_stack and fix alignment
Date: Mon, 13 Nov 2017 11:19:25 -0800 [thread overview]
Message-ID: <cfcd0693-e5ea-ddbe-622a-bde24e58f84a@intel.com> (raw)
In-Reply-To: <2a675c72e35f737156c98ccad5cc3c73c3aa9d72.1510371795.git.luto@kernel.org>
On 11/10/2017 08:05 PM, Andy Lutomirski wrote:
> struct tss_struct {
> /*
> + * Space for the temporary SYSENTER stack. Used for the entry
> + * trampoline as well. Size it such that tss_struct ends up
> + * as a multiple of PAGE_SIZE. This calculation assumes that
> + * io_bitmap is a multiple of PAGE_SIZE (8192 bytes) plus one
> + * long.
> + */
> + unsigned long SYSENTER_stack_canary;
> + unsigned long SYSENTER_stack[(PAGE_SIZE - sizeof(struct x86_hw_tss)) / sizeof(unsigned long) - 2];
> +
> + /*
> * The hardware state:
> */
> struct x86_hw_tss x86_tss;
> @@ -337,15 +347,9 @@ struct tss_struct {
> * be within the limit.
> */
> unsigned long io_bitmap[IO_BITMAP_LONGS + 1];
> -
> - /*
> - * Space for the temporary SYSENTER stack.
> - */
> - unsigned long SYSENTER_stack_canary;
> - unsigned long SYSENTER_stack[64];
> } ____cacheline_aligned;
If io_bitmap[] is already page-size-aligned, how does it help us to move
SYSENTER_stack[]?
It seems like it would be easier to just leave SYSENTER_stack[] where it
is, make it SYSENTER_stack[0], and just find somewhere else to choose
how much to bloat the tss_struct *allocation* instead of trying to make
sure that sizeof(tss_struct) matches the allocation.
That SYSENTER_stack[] size calculation is pretty hideous. :)
next prev parent reply other threads:[~2017-11-13 19:19 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-11 4:05 [RFC 0/7] Prep code for better stack switching Andy Lutomirski
2017-11-11 4:05 ` [RFC 1/7] x86/asm/64: Allocate and enable the SYSENTER stack Andy Lutomirski
2017-11-13 19:07 ` Dave Hansen
2017-11-14 2:17 ` Andy Lutomirski
2017-11-14 7:15 ` Ingo Molnar
2017-11-11 4:05 ` [RFC 2/7] x86/gdt: Put per-cpu GDT remaps in ascending order Andy Lutomirski
2017-11-11 4:05 ` [RFC 3/7] x86/fixmap: Generalize the GDT fixmap mechanism Andy Lutomirski
2017-11-11 4:05 ` [RFC 4/7] x86/asm: Fix assumptions that the HW TSS is at the beginning of cpu_tss Andy Lutomirski
2017-11-13 17:01 ` Dave Hansen
2017-11-26 13:48 ` [PATCH v2] x86/entry: " Ingo Molnar
2017-11-26 15:41 ` Andy Lutomirski
2017-11-26 15:58 ` Ingo Molnar
2017-11-26 16:00 ` Ingo Molnar
2017-11-26 16:05 ` Andy Lutomirski
2017-11-26 16:43 ` Ingo Molnar
2017-11-11 4:05 ` [RFC 5/7] x86/asm: Rearrange struct cpu_tss to enlarge SYSENTER_stack and fix alignment Andy Lutomirski
2017-11-11 4:11 ` Andy Lutomirski
2017-11-13 19:19 ` Dave Hansen [this message]
2017-11-11 4:05 ` [RFC 6/7] x86/asm: Remap the TSS into the cpu entry area Andy Lutomirski
2017-11-13 19:22 ` Dave Hansen
2017-11-13 19:36 ` Linus Torvalds
2017-11-14 2:25 ` Andy Lutomirski
2017-11-14 2:28 ` Linus Torvalds
2017-11-14 2:30 ` Andy Lutomirski
2017-11-14 2:27 ` Andy Lutomirski
2017-11-11 4:05 ` [RFC 7/7] x86/unwind/64: Add support for the SYSENTER stack Andy Lutomirski
2017-11-13 22:46 ` Josh Poimboeuf
2017-11-14 2:13 ` Andy Lutomirski
2017-11-11 10:58 ` [RFC 0/7] Prep code for better stack switching Borislav Petkov
2017-11-12 2:59 ` Andy Lutomirski
2017-11-12 4:25 ` Andy Lutomirski
2017-11-13 4:37 ` Andy Lutomirski
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