linux-kernel - RE: [PATCH 1/4] xen/PVH: Replace GDT

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Date:   Tue, 1 May 2018 11:31:16 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Boris Ostrovsky' <boris.ostrovsky@...cle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
CC:     "jgross@...e.com" <jgross@...e.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH 1/4] xen/PVH: Replace GDT_ENTRY with explicit constant

From: Boris Ostrovsky
> Sent: 30 April 2018 17:24
> To: linux-kernel@...r.kernel.org; xen-devel@...ts.xenproject.org
> Cc: jgross@...e.com; Boris Ostrovsky; stable@...r.kernel.org
> Subject: [PATCH 1/4] xen/PVH: Replace GDT_ENTRY with explicit constant
> 
> Latest binutils release (2.29.1) will no longer allow proper computation
> of GDT entries on 32-bits, with warning:
> 
> arch/x86/xen/xen-pvh.S: Assembler messages:
> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31)
> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (40 is not between 0 and 31)
> arch/x86/xen/xen-pvh.S:150: Warning: shift count out of range (32 is not between 0 and 31)
> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31)
> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (40 is not between 0 and 31)
> arch/x86/xen/xen-pvh.S:152: Warning: shift count out of range (32 is not between 0 and 31)
> 
> Use explicit value of the entry instead of using GDT_ENTRY() macro.
...
>  #ifdef CONFIG_X86_64
> -	.quad GDT_ENTRY(0xa09a, 0, 0xfffff) /* __KERNEL_CS */
> +	.quad 0x00af9a000000ffff            /* __BOOT_CS */
>  #else
> -	.quad GDT_ENTRY(0xc09a, 0, 0xfffff) /* __KERNEL_CS */
> +	.quad 0x00cf9a000000ffff            /* __BOOT_CS */
>  #endif
> -	.quad GDT_ENTRY(0xc092, 0, 0xfffff) /* __KERNEL_DS */
> +	.quad 0x00cf92000000ffff            /* __BOOT_DS */
>  gdt_end:

It has to be possible to fix the GDT_ENTRY() macro.
Even if you end up with one that generates two 32bit values.

You've also changed the name in the comments.

	David