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SubjectRe: [PATCH 3/5] x86-64, docs, mm: Add vsyscall range to virtual address space layout
On Mon, Mar 04, 2013 at 01:45:20PM -0800, Andy Lutomirski wrote:
> vsyscalls are only 4k. Am I missing something obvious her?

Right, but we're reserving 5 level2 pages for this, i.e. 5*512*4K = 10M.
I.e., each level2 page contains 512 ptes, each pointing to a 4K page.

arch/x86/kernel/head_64.S:

...
NEXT_PAGE(level2_fixmap_pgt)
.fill 506,8,0
.quad level1_fixmap_pgt - __START_KERNEL_map + _PAGE_TABLE
/* 8MB reserved for vsyscalls + a 2MB hole = 4 + 1 entries */
.fill 5,8,0

NEXT_PAGE(level1_fixmap_pgt)
.fill 512,8,0

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
--


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