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Commit 5ebe3a44 authored by James Morse's avatar James Morse Committed by Will Deacon
Browse files

arm64: hibernate: Support DEBUG_PAGEALLOC 



DEBUG_PAGEALLOC removes the valid bit of page table entries to prevent
any access to unallocated memory. Hibernate uses this as a hint that those
pages don't need to be saved/restored. This patch adds the
kernel_page_present() function it uses.

hibernate.c copies the resume kernel's linear map for use during restore.
Add _copy_pte() to fill-in the holes made by DEBUG_PAGEALLOC in the resume
kernel, so we can restore data the original kernel had at these addresses.

Finally, DEBUG_PAGEALLOC means the linear-map alias of KERNEL_START to
KERNEL_END may have holes in it, so we can't lazily clean this whole
area to the PoC. Only clean the new mmuoff region, and the kernel/kvm
idmaps.

This reverts commit da24eb1f.

Reported-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent b6113038

arch/arm64/Kconfig

+0 −1
Original line number Diff line number Diff line
@@ -607,7 +607,6 @@ source kernel/Kconfig.preempt 
source kernel/Kconfig.hz



config ARCH_SUPPORTS_DEBUG_PAGEALLOC

	depends on !HIBERNATION

	def_bool y



config ARCH_HAS_HOLES_MEMORYMODEL

arch/arm64/include/asm/pgtable.h

+10 −0
Original line number Diff line number Diff line
@@ -155,6 +155,16 @@ static inline pte_t pte_mknoncont(pte_t pte) 
	return clear_pte_bit(pte, __pgprot(PTE_CONT));

}



static inline pte_t pte_clear_rdonly(pte_t pte)

{

	return clear_pte_bit(pte, __pgprot(PTE_RDONLY));

}



static inline pte_t pte_mkpresent(pte_t pte)

{

	return set_pte_bit(pte, __pgprot(PTE_VALID));

}



static inline pmd_t pmd_mkcont(pmd_t pmd)

{

	return __pmd(pmd_val(pmd) | PMD_SECT_CONT);

arch/arm64/kernel/hibernate.c

+36 −9
Original line number Diff line number Diff line
@@ -235,6 +235,7 @@ static int create_safe_exec_page(void *src_start, size_t length, 
	return rc;

}



#define dcache_clean_range(start, end)	__flush_dcache_area(start, (end - start))



int swsusp_arch_suspend(void)

{
@@ -252,8 +253,13 @@ int swsusp_arch_suspend(void) 
	if (__cpu_suspend_enter(&state)) {

		ret = swsusp_save();

	} else {

		/* Clean kernel to PoC for secondary core startup */

		__flush_dcache_area(LMADDR(KERNEL_START), KERNEL_END - KERNEL_START);

		/* Clean kernel core startup/idle code to PoC*/

		dcache_clean_range(__mmuoff_data_start, __mmuoff_data_end);

		dcache_clean_range(__idmap_text_start, __idmap_text_end);



		/* Clean kvm setup code to PoC? */

		if (el2_reset_needed())

			dcache_clean_range(__hyp_idmap_text_start, __hyp_idmap_text_end);



		/*

		 * Tell the hibernation core that we've just restored
@@ -269,6 +275,33 @@ int swsusp_arch_suspend(void) 
	return ret;

}



static void _copy_pte(pte_t *dst_pte, pte_t *src_pte, unsigned long addr)

{

	pte_t pte = *src_pte;



	if (pte_valid(pte)) {

		/*

		 * Resume will overwrite areas that may be marked

		 * read only (code, rodata). Clear the RDONLY bit from

		 * the temporary mappings we use during restore.

		 */

		set_pte(dst_pte, pte_clear_rdonly(pte));

	} else if (debug_pagealloc_enabled() && !pte_none(pte)) {

		/*

		 * debug_pagealloc will removed the PTE_VALID bit if

		 * the page isn't in use by the resume kernel. It may have

		 * been in use by the original kernel, in which case we need

		 * to put it back in our copy to do the restore.

		 *

		 * Before marking this entry valid, check the pfn should

		 * be mapped.

		 */

		BUG_ON(!pfn_valid(pte_pfn(pte)));



		set_pte(dst_pte, pte_mkpresent(pte_clear_rdonly(pte)));

	}

}



static int copy_pte(pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long start,

		    unsigned long end)

{
@@ -284,13 +317,7 @@ static int copy_pte(pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long start, 


	src_pte = pte_offset_kernel(src_pmd, start);

	do {

		if (!pte_none(*src_pte))

			/*

			 * Resume will overwrite areas that may be marked

			 * read only (code, rodata). Clear the RDONLY bit from

			 * the temporary mappings we use during restore.

			 */

			set_pte(dst_pte, __pte(pte_val(*src_pte) & ~PTE_RDONLY));

		_copy_pte(dst_pte, src_pte, addr);

	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);



	return 0;

arch/arm64/mm/pageattr.c

+40 −1
Original line number Diff line number Diff line
@@ -139,4 +139,43 @@ void __kernel_map_pages(struct page *page, int numpages, int enable) 
					__pgprot(0),

					__pgprot(PTE_VALID));

}

#endif
 
#ifdef CONFIG_HIBERNATION

/*

 * When built with CONFIG_DEBUG_PAGEALLOC and CONFIG_HIBERNATION, this function

 * is used to determine if a linear map page has been marked as not-valid by

 * CONFIG_DEBUG_PAGEALLOC. Walk the page table and check the PTE_VALID bit.

 * This is based on kern_addr_valid(), which almost does what we need.

 *

 * Because this is only called on the kernel linear map,  p?d_sect() implies

 * p?d_present(). When debug_pagealloc is enabled, sections mappings are

 * disabled.

 */

bool kernel_page_present(struct page *page)

{

	pgd_t *pgd;

	pud_t *pud;

	pmd_t *pmd;

	pte_t *pte;

	unsigned long addr = (unsigned long)page_address(page);



	pgd = pgd_offset_k(addr);

	if (pgd_none(*pgd))

		return false;



	pud = pud_offset(pgd, addr);

	if (pud_none(*pud))

		return false;

	if (pud_sect(*pud))

		return true;



	pmd = pmd_offset(pud, addr);

	if (pmd_none(*pmd))

		return false;

	if (pmd_sect(*pmd))

		return true;



	pte = pte_offset_kernel(pmd, addr);

	return pte_valid(*pte);

}

#endif /* CONFIG_HIBERNATION */

#endif /* CONFIG_DEBUG_PAGEALLOC */