arm64: mm: treat memstart_addr as a signed quantity (020d044f) · Commits · 戴 / test

Commit ("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>

arch/arm64/include/asm/memory.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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; })

arch/arm64/mm/init.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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 @@ 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);

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