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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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2
arch/arm64/include/asm/processor.h
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@ -42,7 +42,7 @@
* TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area.
*/
#define DEFAULT_MAP_WINDOW_64 (UL(1) << VA_BITS)
#define DEFAULT_MAP_WINDOW_64 (UL(1) << VA_BITS_MIN)
#define TASK_SIZE_64 (UL(1) << vabits_user)
#ifdef CONFIG_COMPAT