Commit 36b8db01 authored by Andy Ross's avatar Andy Ross Committed by Carles Cufi
Browse files

arch/x86: Map 512G by default when booting x86_64 



The default page table (the architecturally required one used for
entrance to long mode, before the OS page tables get assembled) was
mapping the first 4G of memory.

Extend this to 512G by fully populating the second level page table.
We have devices now (up_squared) which have real RAM mapped above 4G.
There's really no good reason not to do this, the page is present
always anyway.

Signed-off-by: default avatarAndy Ross <andrew.j.ross@intel.com>
parent af063ccd

arch/x86/core/intel64/locore.S

+29 −14
Original line number Diff line number Diff line
@@ -948,28 +948,43 @@ idt80: /* LIDT descriptor for 64 bit mode */ 
	.word (idt_end - idt - 1)

	.quad idt



/*

 * Page tables. Long mode requires them, but we don't implement any memory

 * protection yet, so these simply identity-map the first 4GB w/ 1GB pages.

/* Initial page tables for long mode entry.  This generates a second

 * level page full of 512 1G PTE entries of the form:

 *

 * 0x000000nnn0000083

 *

 * Where nnn is an identity-mapped 1G page index in the range

 * 0x000-0x1ff, and 0x83 marks a present, 1G, read/write page

 * entry. It's split up somewhat awkwardly to get around gas's

 * recursion limits in macro expansion.

 *

 * This maps the first 512GB of memory space by default, which will

 * hopefully be enough to reach everything we need before we can

 * bootstrap the real page tables later.

 */

.macro populate_ptable base, count=64

	.long 0x00000083

	.long 64 - \count + \base

	.long 0x40000083

	.long 64 - \count + \base

	.long 0x80000083

	.long 64 - \count + \base

	.long 0xC0000083

	.long 64 - \count + \base

.if \count > 1

	populate_ptable \base, (\count - 1)

.endif

.endm



.align 4096



.globl z_x86_flat_ptables

z_x86_flat_ptables:

	.long pdp + 0x03		/* 0x03 = R/W, P */

	.long 0

	.fill 4088, 1, 0



pdp:	.long 0x00000083		/* 0x83 = 1GB, R/W, P */

	.long 0

	.long 0x40000083

	.long 0

	.long 0x80000083

	.long 0

	.long 0xC0000083

	.long 0

	.fill 4064, 1, 0

pdp:

	populate_ptable 0

	populate_ptable 64



.section .gdt,"ad"

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