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arm64: mm: Allow forcing all userspace addresses to 52-bit

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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>
This commit is contained in:
Steve Capper 2018-12-06 22:50:42 +00:00 committed by Will Deacon
parent 67e7fdfcc6
commit b9567720a1
3 changed files with 25 additions and 1 deletions
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13
arch/arm64/Kconfig
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@ -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

4
arch/arm64/include/asm/elf.h
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@ -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__

9
arch/arm64/include/asm/processor.h
View File

@ -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)