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authorSteve Capper <steve.capper@arm.com>2018-12-06 22:50:42 +0000
committerWill Deacon <will.deacon@arm.com>2018-12-10 18:42:18 +0000
commitb9567720a1b8e739380e0241413606c056c57859 (patch)
tree760f658f0fbb3ec46f0cbdaa0314245f6f094fb7 /arch/arm64
parentarm64: mm: introduce 52-bit userspace support (diff)
downloadlinux-dev-b9567720a1b8e739380e0241413606c056c57859.tar.xz
linux-dev-b9567720a1b8e739380e0241413606c056c57859.zip
arm64: mm: Allow forcing all userspace addresses to 52-bit
On arm64 52-bit VAs are provided to userspace when a hint is supplied to mmap. This helps maintain compatibility with software that expects at most 48-bit VAs to be returned. In order to help identify software that has 48-bit VA assumptions, this patch allows one to compile a kernel where 52-bit VAs are returned by default on HW that supports it. This feature is intended to be for development systems only. Signed-off-by: Steve Capper <steve.capper@arm.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to '')
-rw-r--r--arch/arm64/Kconfig13
-rw-r--r--arch/arm64/include/asm/elf.h4
-rw-r--r--arch/arm64/include/asm/processor.h9
3 files changed, 25 insertions, 1 deletions
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 858e353b2f40..ca1f93233b22 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1186,6 +1186,19 @@ config ARM64_CNP
at runtime, and does not affect PEs that do not implement
this feature.
+config ARM64_FORCE_52BIT
+ bool "Force 52-bit virtual addresses for userspace"
+ depends on ARM64_52BIT_VA && EXPERT
+ help
+ For systems with 52-bit userspace VAs enabled, the kernel will attempt
+ to maintain compatibility with older software by providing 48-bit VAs
+ unless a hint is supplied to mmap.
+
+ This configuration option disables the 48-bit compatibility logic, and
+ forces all userspace addresses to be 52-bit on HW that supports it. One
+ should only enable this configuration option for stress testing userspace
+ memory management code. If unsure say N here.
+
endmenu
config ARM64_SVE
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index bc9bd9e77d9d..6adc1a90e7e6 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -117,7 +117,11 @@
* 64-bit, this is above 4GB to leave the entire 32-bit address
* space open for things that want to use the area for 32-bit pointers.
*/
+#ifdef CONFIG_ARM64_FORCE_52BIT
+#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
+#else
#define ELF_ET_DYN_BASE (2 * DEFAULT_MAP_WINDOW_64 / 3)
+#endif /* CONFIG_ARM64_FORCE_52BIT */
#ifndef __ASSEMBLY__
diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 7ff75e52b762..efa0210cf927 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -74,8 +74,13 @@ extern u64 vabits_user;
#define DEFAULT_MAP_WINDOW DEFAULT_MAP_WINDOW_64
#endif /* CONFIG_COMPAT */
-#define TASK_UNMAPPED_BASE (PAGE_ALIGN(DEFAULT_MAP_WINDOW / 4))
+#ifdef CONFIG_ARM64_FORCE_52BIT
+#define STACK_TOP_MAX TASK_SIZE_64
+#define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 4))
+#else
#define STACK_TOP_MAX DEFAULT_MAP_WINDOW_64
+#define TASK_UNMAPPED_BASE (PAGE_ALIGN(DEFAULT_MAP_WINDOW / 4))
+#endif /* CONFIG_ARM64_FORCE_52BIT */
#ifdef CONFIG_COMPAT
#define AARCH32_VECTORS_BASE 0xffff0000
@@ -85,12 +90,14 @@ extern u64 vabits_user;
#define STACK_TOP STACK_TOP_MAX
#endif /* CONFIG_COMPAT */
+#ifndef CONFIG_ARM64_FORCE_52BIT
#define arch_get_mmap_end(addr) ((addr > DEFAULT_MAP_WINDOW) ? TASK_SIZE :\
DEFAULT_MAP_WINDOW)
#define arch_get_mmap_base(addr, base) ((addr > DEFAULT_MAP_WINDOW) ? \
base + TASK_SIZE - DEFAULT_MAP_WINDOW :\
base)
+#endif /* CONFIG_ARM64_FORCE_52BIT */
extern phys_addr_t arm64_dma_phys_limit;
#define ARCH_LOW_ADDRESS_LIMIT (arm64_dma_phys_limit - 1)