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arm64: mm: treat memstart_addr as a signed quantity

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Commit c031a4213c ("arm64: kaslr: randomize the linear region")
implements randomization of the linear region, by subtracting a random
multiple of PUD_SIZE from memstart_addr. This causes the virtual mapping
of system RAM to move upwards in the linear region, and at the same time
causes memstart_addr to assume a value which may be negative if the offset
of system RAM in the physical space is smaller than its offset relative to
PAGE_OFFSET in the virtual space.

Since memstart_addr is effectively an offset now, redefine its type as s64
so that expressions involving shifting or division preserve its sign.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 020d044f66)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
This commit is contained in:
Ard Biesheuvel 2016-02-26 17:57:14 +01:00 • committed by Alex Shi
commit b78c702db9
2 changed files with 3 additions and 3 deletions
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2
arch/arm64/include/asm/memory.h
View file

@ -135,7 +135,7 @@
#include <linux/bitops.h>
#include <linux/mmdebug.h>
extern phys_addr_t memstart_addr;
extern s64 memstart_addr;
/* PHYS_OFFSET - the physical address of the start of memory. */
#define PHYS_OFFSET ({ VM_BUG_ON(memstart_addr & 1); memstart_addr; })

4
arch/arm64/mm/init.c
View file

@ -54,7 +54,7 @@
* executes, which assigns it its actual value. So use a default value
* that cannot be mistaken for a real physical address.
*/
phys_addr_t memstart_addr __read_mostly = ~0ULL;
s64 memstart_addr __read_mostly = -1;
phys_addr_t arm64_dma_phys_limit __read_mostly;
#ifdef CONFIG_BLK_DEV_INITRD
@ -188,7 +188,7 @@ void __init arm64_memblock_init(void)
* linear mapping. Take care not to clip the kernel which may be
* high in memory.
*/
memblock_remove(max(memstart_addr + linear_region_size, __pa(_end)),
memblock_remove(max_t(u64, memstart_addr + linear_region_size, __pa(_end)),
ULLONG_MAX);
if (memblock_end_of_DRAM() > linear_region_size)
memblock_remove(0, memblock_end_of_DRAM() - linear_region_size);