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Subject: Re: [PATCH 03/39] x86/entry/32: Load task stack from x86_tss.sp1 in SYSENTER handler
From:   Andy Lutomirski <luto@amacapital.net>
In-Reply-To: <1531308586-29340-4-git-send-email-joro@8bytes.org>
Date:   Thu, 12 Jul 2018 13:49:13 -0700
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To:     Joerg Roedel <joro@8bytes.org>
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> On Jul 11, 2018, at 4:29 AM, Joerg Roedel <joro@8bytes.org> wrote:
>=20
> From: Joerg Roedel <jroedel@suse.de>
> We want x86_tss.sp0 point to the entry stack later to use
> it as a trampoline stack for other kernel entry points
> besides SYSENTER.

Makes sense: sp0 will be the entry stack. But:

>=20
>=20
>    /* Offset from the sysenter stack to tss.sp0 */
> -    DEFINE(TSS_entry_stack, offsetof(struct cpu_entry_area, tss.x86_tss.s=
p0) -
> +    DEFINE(TSS_entry_stack, offsetof(struct cpu_entry_area, tss.x86_tss.s=
p1) -
>           offsetofend(struct cpu_entry_area, entry_stack_page.stack));
>=20

The code reads differently. Did you perhaps mean TSS_task_stack?

Also, the =E2=80=9Ctop of task stack=E2=80=9D is a bit weird on 32-bit due t=
o vm86. Can you document *exactly* what goes in sp1?