diff options
| author | Will Deacon <will.deacon@arm.com> | 2019-01-08 16:19:01 +0000 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2019-01-10 17:49:35 +0000 |
| commit | b89d82ef01b33bc50cbaa8ff05607879b40d0704 (patch) | |
| tree | ae9df3844e5cb08338a8945d4a4fb9547ba27e26 /arch/arm64/include/asm/pgtable-prot.h | |
| parent | d9ed41962ee202f653a5fa8d2ea0f52924abe629 (diff) | |
| download | linux-b89d82ef01b33bc50cbaa8ff05607879b40d0704.tar.gz | |
arm64: kpti: Avoid rewriting early page tables when KASLR is enabled
A side effect of commit c55191e96caa ("arm64: mm: apply r/o permissions
of VM areas to its linear alias as well") is that the linear map is
created with page granularity, which means that transitioning the early
page table from global to non-global mappings when enabling kpti can
take a significant amount of time during boot.
Given that most CPU implementations do not require kpti, this mainly
impacts KASLR builds where kpti is forcefully enabled. However, in these
situations we know early on that non-global mappings are required and
can avoid the use of global mappings from the beginning. The only gotcha
is Cavium erratum #27456, which we must detect based on the MIDR value
of the boot CPU.
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reported-by: John Garry <john.garry@huawei.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/pgtable-prot.h')
| -rw-r--r-- | arch/arm64/include/asm/pgtable-prot.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index 78b942c1bea4..986e41c4c32b 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -37,8 +37,8 @@ #define _PROT_DEFAULT (PTE_TYPE_PAGE | PTE_AF | PTE_SHARED) #define _PROT_SECT_DEFAULT (PMD_TYPE_SECT | PMD_SECT_AF | PMD_SECT_S) -#define PTE_MAYBE_NG (arm64_kernel_unmapped_at_el0() ? PTE_NG : 0) -#define PMD_MAYBE_NG (arm64_kernel_unmapped_at_el0() ? PMD_SECT_NG : 0) +#define PTE_MAYBE_NG (arm64_kernel_use_ng_mappings() ? PTE_NG : 0) +#define PMD_MAYBE_NG (arm64_kernel_use_ng_mappings() ? PMD_SECT_NG : 0) #define PROT_DEFAULT (_PROT_DEFAULT | PTE_MAYBE_NG) #define PROT_SECT_DEFAULT (_PROT_SECT_DEFAULT | PMD_MAYBE_NG) |