linux-kernel - Re: [PATCH v3 31/75] x86/head/64: Install boot GDT

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Message-ID: <20200518082313.GA25034@zn.tnic>
Date:   Mon, 18 May 2020 10:23:13 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Joerg Roedel <jroedel@...e.de>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v3 31/75] x86/head/64: Install boot GDT

On Tue, Apr 28, 2020 at 05:16:41PM +0200, Joerg Roedel wrote:
> @@ -480,6 +500,22 @@ SYM_DATA_LOCAL(early_gdt_descr_base,	.quad INIT_PER_CPU_VAR(gdt_page))
>  SYM_DATA(phys_base, .quad 0x0)
>  EXPORT_SYMBOL(phys_base)
>
> +/* Boot GDT used when kernel addresses are not mapped yet */
> +SYM_DATA_LOCAL(boot_gdt_descr,		.word boot_gdt_end - boot_gdt)
> +SYM_DATA_LOCAL(boot_gdt_base,		.quad 0)
> +SYM_DATA_START(boot_gdt)
> +	.quad	0
> +	.quad   0x00cf9a000000ffff	/* __KERNEL32_CS */
> +	.quad   0x00af9a000000ffff	/* __KERNEL_CS */
> +	.quad   0x00cf92000000ffff	/* __KERNEL_DS */
> +	.quad	0			/* __USER32_CS - unused */
> +	.quad	0			/* __USER_DS   - unused */
> +	.quad	0			/* __USER_CS   - unused */
> +	.quad	0			/* unused */
> +	.quad   0x0080890000000000	/* TSS descriptor */
> +	.quad   0x0000000000000000	/* TSS continued */

Any chance you could use macros ala GDT_ENTRY_INIT() for those instead
of the naked values?

-- 
Regards/Gruss,
    Boris.

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