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arm64: mm: Introduce MAX_USER_VA_BITS definition

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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: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2018-12-12 11:51:40 +00:00
parent 4d08d20f1c
commit 9b31cf493f
3 changed files with 8 additions and 10 deletions
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6
arch/arm64/include/asm/memory.h
View File

@ -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)

6
arch/arm64/include/asm/pgtable-hwdef.h
View File

@ -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.

6
arch/arm64/include/asm/processor.h
View File

@ -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