Commit 9b31cf49 authored by Will Deacon's avatar Will Deacon
Browse files

arm64: mm: Introduce MAX_USER_VA_BITS definition 



With the introduction of 52-bit virtual addressing for userspace, we are
now in a position where the virtual addressing capability of userspace
may exceed that of the kernel. Consequently, the VA_BITS definition
cannot be used blindly, since it reflects only the size of kernel
virtual addresses.

This patch introduces MAX_USER_VA_BITS which is either VA_BITS or 52
depending on whether 52-bit virtual addressing has been configured at
build time, removing a few places where the 52 is open-coded based on
explicit CONFIG_ guards.

Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 4d08d20f

arch/arm64/include/asm/memory.h

+6 −0
Original line number Diff line number Diff line
@@ -73,6 +73,12 @@ 
#define KERNEL_START      _text

#define KERNEL_END        _end



#ifdef CONFIG_ARM64_USER_VA_BITS_52

#define MAX_USER_VA_BITS	52

#else

#define MAX_USER_VA_BITS	VA_BITS

#endif



/*

 * KASAN requires 1/8th of the kernel virtual address space for the shadow

 * region. KASAN can bloat the stack significantly, so double the (minimum)

arch/arm64/include/asm/pgtable-hwdef.h

+1 −5
Original line number Diff line number Diff line
@@ -80,11 +80,7 @@ 
#define PGDIR_SHIFT		ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - CONFIG_PGTABLE_LEVELS)

#define PGDIR_SIZE		(_AC(1, UL) << PGDIR_SHIFT)

#define PGDIR_MASK		(~(PGDIR_SIZE-1))

#ifdef CONFIG_ARM64_USER_VA_BITS_52

#define PTRS_PER_PGD		(1 << (52 - PGDIR_SHIFT))

#else

#define PTRS_PER_PGD		(1 << (VA_BITS - PGDIR_SHIFT))

#endif

#define PTRS_PER_PGD		(1 << (MAX_USER_VA_BITS - PGDIR_SHIFT))



/*

 * Section address mask and size definitions.

arch/arm64/include/asm/processor.h

+1 −5
Original line number Diff line number Diff line
@@ -20,11 +20,7 @@ 
#define __ASM_PROCESSOR_H



#define KERNEL_DS		UL(-1)

#ifdef CONFIG_ARM64_USER_VA_BITS_52

#define USER_DS			((UL(1) << 52) - 1)

#else

#define USER_DS			((UL(1) << VA_BITS) - 1)

#endif /* CONFIG_ARM64_USER_VA_BITS_52 */

#define USER_DS			((UL(1) << MAX_USER_VA_BITS) - 1)



/*

 * On arm64 systems, unaligned accesses by the CPU are cheap, and so there is

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