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arm64: mm: Introduce DEFAULT_MAP_WINDOW 

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 <steve.capper@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Steve Capper 2018-12-06 22:50:37 +00:00 committed by Will Deacon
parent f6795053da
commit 363524d2b1
5 changed files with 12 additions and 6 deletions
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2
arch/arm64/include/asm/elf.h
View File

@ -117,7 +117,7 @@
* 64-bit, this is above 4GB to leave the entire 32-bit address
* space open for things that want to use the area for 32-bit pointers.
*/
#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3)
#define ELF_ET_DYN_BASE (2 * DEFAULT_MAP_WINDOW_64 / 3)
#ifndef __ASSEMBLY__

10
arch/arm64/include/asm/processor.h
View File

@ -53,19 +53,25 @@
* TASK_SIZE - the maximum size of a user space task.
* TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area.
*/
#define DEFAULT_MAP_WINDOW_64 (UL(1) << VA_BITS)
#ifdef CONFIG_COMPAT
#define TASK_SIZE_32 UL(0x100000000)
#define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \
TASK_SIZE_32 : TASK_SIZE_64)
#define TASK_SIZE_OF(tsk) (test_tsk_thread_flag(tsk, TIF_32BIT) ? \
TASK_SIZE_32 : TASK_SIZE_64)
#define DEFAULT_MAP_WINDOW (test_thread_flag(TIF_32BIT) ? \
TASK_SIZE_32 : DEFAULT_MAP_WINDOW_64)
#else
#define TASK_SIZE TASK_SIZE_64
#define DEFAULT_MAP_WINDOW DEFAULT_MAP_WINDOW_64
#endif /* CONFIG_COMPAT */
#define TASK_UNMAPPED_BASE (PAGE_ALIGN(TASK_SIZE / 4))
#define TASK_UNMAPPED_BASE (PAGE_ALIGN(DEFAULT_MAP_WINDOW / 4))
#define STACK_TOP_MAX DEFAULT_MAP_WINDOW_64
#define STACK_TOP_MAX TASK_SIZE_64
#ifdef CONFIG_COMPAT
#define AARCH32_VECTORS_BASE 0xffff0000
#define STACK_TOP (test_thread_flag(TIF_32BIT) ? \

2
arch/arm64/mm/init.c
View File

@ -609,7 +609,7 @@ void __init mem_init(void)
* detected at build time already.
*/
#ifdef CONFIG_COMPAT
BUILD_BUG_ON(TASK_SIZE_32 > TASK_SIZE_64);
BUILD_BUG_ON(TASK_SIZE_32 > DEFAULT_MAP_WINDOW_64);
#endif
#ifdef CONFIG_SPARSEMEM_VMEMMAP

2
drivers/firmware/efi/arm-runtime.c
View File

@ -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