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Commit b9567720 authored by Steve Capper's avatar Steve Capper Committed by Will Deacon
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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: default avatarSteve Capper <steve.capper@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 67e7fdfc

arch/arm64/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/include/asm/elf.h

+4 −0
Original line number Diff line number Diff line
@@ -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__

arch/arm64/include/asm/processor.h

+8 −1
Original line number Diff line number Diff line
@@ -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)