Re: [CFT][PATCH] 2.6.4-rc1 remove x86 boot page tables

[H. Peter Anvin]

Followup to:  <m1vflp81kq.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx>
By author:    ebiederm@xxxxxxxxxxxx (Eric W. Biederman)
In newsgroup: linux.dev.kernel
> 
> -	.quad 0x0000000000000000	/* 0x20 unused */
> -	.quad 0x0000000000000000	/* 0x28 unused */
> +	.quad 0x40cf9a000000ffff	/* 0x20 kernel 4G code at 0-__PAGE_OFFSET */
> +	.quad 0x40cf92000000ffff	/* 0x28 kernel 4G data at 0-__PAGE_OFFSET */
> 

This needs to actually be derived from __PAGE_OFFSET (it may or may
not be 0xc0000000.)

I'd suggest:

/* Create a descriptor from (base,limit,flags) */
/* Limit is in 20-bit form! */
#define DESC(b,l,f)     .long (((l) & 0x0ffff)) |\
                              (((b) & 0x0000ffff) << 16), \
			      (((b) & 0x00ff0000) >> 16) | \
                              (((l) & 0xf0000)) | \
                              (((f) & 0xf0ff) << 8) | \
			      (((b) & 0xff000000))

        DESC(-__PAGE_OFFSET,0xfffff,0xc09a)       /* 0x20 kernel 4G code at -__PAGE_OFFSET */
        DESC(-__PAGE_OFFSET,0xfffff,0xc092)       /* 0x28 kernel 4G code at -__PAGE_OFFSET */

[It broken up into .longs like that, because gas doesn't seem to
handle 64-bit arithmetric.]

Writing all the descriptors in that form may be a good thing :)

	-hpa
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