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arm64: mm: Introduce VA_BITS_MIN

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In order to support 52-bit kernel addresses detectable at boot time, the
kernel needs to know the most conservative VA_BITS possible should it
need to fall back to this quantity due to lack of hardware support.

A new compile time constant VA_BITS_MIN is introduced in this patch and
it is employed in the KASAN end address, KASLR, and EFI stub.

For Arm, if 52-bit VA support is unavailable the fallback is to 48-bits.

In other words: VA_BITS_MIN = min (48, VA_BITS)

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Steve Capper
2019-08-07 16:55:17 +01:00
committed by Will Deacon
parent 99426e5e8c
commit 90ec95cda9
6 changed files with 17 additions and 9 deletions
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9
arch/arm64/include/asm/memory.h
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@@ -52,6 +52,13 @@
#define PCI_IO_END (VMEMMAP_START - SZ_2M)
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
#define FIXADDR_TOP (PCI_IO_START - SZ_2M)
#if VA_BITS > 48
#define VA_BITS_MIN (48)
#else
#define VA_BITS_MIN (VA_BITS)
#endif
#define _VA_START(va) (UL(0xffffffffffffffff) - \
(UL(1) << ((va) - 1)) + 1)
#define KERNEL_START _text
#define KERNEL_END _end
@@ -74,7 +81,7 @@
#define KASAN_THREAD_SHIFT 1
#else
#define KASAN_THREAD_SHIFT 0
#define KASAN_SHADOW_END (VA_START)
#define KASAN_SHADOW_END (_VA_START(VA_BITS_MIN))
#endif
#define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT)