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arm64: mm: Introduce DEFAULT_MAP_WINDOW

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We wish to introduce a 52-bit virtual address space for userspace but
maintain compatibility with software that assumes the maximum VA space
size is 48 bit.

In order to achieve this, on 52-bit VA systems, we make mmap behave as
if it were running on a 48-bit VA system (unless userspace explicitly
requests a VA where addr[51:48] != 0).

On a system running a 52-bit userspace we need TASK_SIZE to represent
the 52-bit limit as it is used in various places to distinguish between
kernelspace and userspace addresses.

Thus we need a new limit for mmap, stack, ELF loader and EFI (which uses
TTBR0) to represent the non-extended VA space.

This patch introduces DEFAULT_MAP_WINDOW and DEFAULT_MAP_WINDOW_64 and
switches the appropriate logic to use that instead of TASK_SIZE.

Signed-off-by: Steve Capper <[email protected]>
Reviewed-by: Catalin Marinas <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
This commit is contained in:
Steve Capper 2018-12-06 22:50:37 +00:00 • committed by Will Deacon
commit 363524d2b1
5 changed files with 12 additions and 6 deletions
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2
drivers/firmware/efi/arm-runtime.c
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@ -38,7 +38,7 @@ static struct ptdump_info efi_ptdump_info = {
.mm = &efi_mm,
.markers = (struct addr_marker[]){
{ 0, "UEFI runtime start" },
{ TASK_SIZE_64, "UEFI runtime end" }
{ DEFAULT_MAP_WINDOW_64, "UEFI runtime end" }
},
.base_addr = 0,
};

2
drivers/firmware/efi/libstub/arm-stub.c
View file

@ -33,7 +33,7 @@
#define EFI_RT_VIRTUAL_SIZE SZ_512M
#ifdef CONFIG_ARM64
# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE_64
# define EFI_RT_VIRTUAL_LIMIT DEFAULT_MAP_WINDOW_64
#else
# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE
#endif