Commit dfd55ad8 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Will Deacon
Browse files

arm64: vmemmap: use virtual projection of linear region 



Commit dd006da2 ("arm64: mm: increase VA range of identity map") made
some changes to the memory mapping code to allow physical memory to reside
at an offset that exceeds the size of the virtual mapping.

However, since the size of the vmemmap area is proportional to the size of
the VA area, but it is populated relative to the physical space, we may
end up with the struct page array being mapped outside of the vmemmap
region. For instance, on my Seattle A0 box, I can see the following output
in the dmesg log.

   vmemmap : 0xffffffbdc0000000 - 0xffffffbfc0000000   (     8 GB maximum)
             0xffffffbfc0000000 - 0xffffffbfd0000000   (   256 MB actual)

We can fix this by deciding that the vmemmap region is not a projection of
the physical space, but of the virtual space above PAGE_OFFSET, i.e., the
linear region. This way, we are guaranteed that the vmemmap region is of
sufficient size, and we can even reduce the size by half.

Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 81f70ba2

arch/arm64/include/asm/pgtable.h

+4 −3
Original line number Original line Diff line number Diff line
@@ -34,13 +34,13 @@ 
/*

/*

 * VMALLOC and SPARSEMEM_VMEMMAP ranges.

 * VMALLOC and SPARSEMEM_VMEMMAP ranges.

 *

 *

 * VMEMAP_SIZE: allows the whole VA space to be covered by a struct page array

 * VMEMAP_SIZE: allows the whole linear region to be covered by a struct page array

 *	(rounded up to PUD_SIZE).

 *	(rounded up to PUD_SIZE).

 * VMALLOC_START: beginning of the kernel VA space

 * VMALLOC_START: beginning of the kernel VA space

 * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space,

 * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space,

 *	fixed mappings and modules

 *	fixed mappings and modules

 */

 */

#define VMEMMAP_SIZE		ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)

#define VMEMMAP_SIZE		ALIGN((1UL << (VA_BITS - PAGE_SHIFT - 1)) * sizeof(struct page), PUD_SIZE)





#ifndef CONFIG_KASAN

#ifndef CONFIG_KASAN

#define VMALLOC_START		(VA_START)

#define VMALLOC_START		(VA_START)
@@ -51,7 +51,8 @@ 




#define VMALLOC_END		(PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)

#define VMALLOC_END		(PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)





#define vmemmap			((struct page *)(VMALLOC_END + SZ_64K))

#define VMEMMAP_START		(VMALLOC_END + SZ_64K)

#define vmemmap			((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))





#define FIRST_USER_ADDRESS	0UL

#define FIRST_USER_ADDRESS	0UL

arch/arm64/mm/init.c

+2 −2
Original line number Original line Diff line number Diff line
@@ -319,8 +319,8 @@ void __init mem_init(void) 
#endif

#endif

		  MLG(VMALLOC_START, VMALLOC_END),

		  MLG(VMALLOC_START, VMALLOC_END),

#ifdef CONFIG_SPARSEMEM_VMEMMAP

#ifdef CONFIG_SPARSEMEM_VMEMMAP

		  MLG((unsigned long)vmemmap,

		  MLG(VMEMMAP_START,

		      (unsigned long)vmemmap + VMEMMAP_SIZE),

		      VMEMMAP_START + VMEMMAP_SIZE),

		  MLM((unsigned long)virt_to_page(PAGE_OFFSET),

		  MLM((unsigned long)virt_to_page(PAGE_OFFSET),

		      (unsigned long)virt_to_page(high_memory)),

		      (unsigned long)virt_to_page(high_memory)),

#endif

#endif

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