@@ -1165,6 +1165,20 @@ 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"
+ default n
+ 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
@@ -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__
@@ -64,8 +64,13 @@ 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
@@ -75,12 +80,14 @@ 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)
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> --- Patch added in V3 to allow for testing/preparation for 52-bit support. --- arch/arm64/Kconfig | 14 ++++++++++++++ arch/arm64/include/asm/elf.h | 4 ++++ arch/arm64/include/asm/processor.h | 9 ++++++++- 3 files changed, 26 insertions(+), 1 deletion(-)