[PATCH v2 2/2] arm64: mm: treat memstart_addr as a signed quantity
From: Ard Biesheuvel <hidden>
Date: 2016-02-29 12:39:48
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
On 26 February 2016 at 17:57, Ard Biesheuvel [off-list ref] wrote:
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 <redacted>FYI this results in a warning, please fold
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 67ce440cb702..9cfe94b41b54 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c@@ -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);
quoted hunk ↗ jump to hunk
--- arch/arm64/include/asm/memory.h | 2 +- arch/arm64/mm/init.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 5f8667a99e41..12f8a00fb3f1 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h@@ -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; })diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 4ea7efc28e65..a2977d33e0dc 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 --2.5.0