[x86_64] Question about early page tables initialization

From: Alex Kuleshov
Date: Tue Feb 03 2015 - 07:26:05 EST


Hello All,

I have a question about page tables initialization in the
arch/x86/boot/compressed/head_64.S

After we clear memory for page tables, there is code which
build PML4:

leal pgtable + 0(%ebx), %edi
leal 0x1007(%edi), %eax
movl %eax, 0(%edi)

Why there is offset 0x1007 instead just 0x7? 0x1007 is
4k + 7bit (PML4E) flags as i understand correctly. But
why we skip first 4k here?

Thank you.
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