arm64: mm: treat memstart_addr as a signed quantity
Commit c031a4213c11 ("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>
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 3b897b9..22c6758 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -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
@@ -181,7 +181,7 @@
* 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);