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Commit 53594547 authored by Huang Ying's avatar Huang Ying Committed by H. Peter Anvin
Browse files

x86, kexec: x86_64: add identity map for pages at image->start 



Impact: Fix corner case that cannot yet occur

image->start may be outside of 0 ~ max_pfn, for example when jumping
back to original kernel from kexeced kenrel. This patch add identity
map for pages at image->start.

Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent fef3a7a1

arch/x86/kernel/machine_kexec_64.c

+42 −0
Original line number Diff line number Diff line
@@ -18,6 +18,41 @@ 
#include <asm/tlbflush.h>

#include <asm/mmu_context.h>



static int init_one_level2_page(struct kimage *image, pgd_t *pgd,

				unsigned long addr)

{

	pud_t *pud;

	pmd_t *pmd;

	struct page *page;

	int result = -ENOMEM;



	addr &= PMD_MASK;

	pgd += pgd_index(addr);

	if (!pgd_present(*pgd)) {

		page = kimage_alloc_control_pages(image, 0);

		if (!page)

			goto out;

		pud = (pud_t *)page_address(page);

		memset(pud, 0, PAGE_SIZE);

		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));

	}

	pud = pud_offset(pgd, addr);

	if (!pud_present(*pud)) {

		page = kimage_alloc_control_pages(image, 0);

		if (!page)

			goto out;

		pmd = (pmd_t *)page_address(page);

		memset(pmd, 0, PAGE_SIZE);

		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));

	}

	pmd = pmd_offset(pud, addr);

	if (!pmd_present(*pmd))

		set_pmd(pmd, __pmd(addr | __PAGE_KERNEL_LARGE_EXEC));

	result = 0;

out:

	return result;

}



static void init_level2_page(pmd_t *level2p, unsigned long addr)

{

	unsigned long end_addr;
@@ -153,6 +188,13 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable) 
	int result;

	level4p = (pgd_t *)__va(start_pgtable);

	result = init_level4_page(image, level4p, 0, max_pfn << PAGE_SHIFT);

	if (result)

		return result;

	/*

	 * image->start may be outside 0 ~ max_pfn, for example when

	 * jump back to original kernel from kexeced kernel

	 */

	result = init_one_level2_page(image, level4p, image->start);

	if (result)

		return result;

	return init_transition_pgtable(image, level4p);