diff options
| author | Will Deacon <will@kernel.org> | 2020-03-18 20:38:29 +0000 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2020-03-19 08:28:43 +0000 |
| commit | c83557859eaa1286330a4d3d2e1ea0c0988c4604 (patch) | |
| tree | 71ae1a4d4b85e5f6d6494a62ce2b8e94dcb932dc | |
| parent | f50b7dacccbab2b9e3ef18f52a6dcc18ed2050b9 (diff) | |
arm64: kpti: Fix "kpti=off" when KASLR is enabled
Enabling KASLR forces the use of non-global page-table entries for kernel
mappings, as this is a decision that we have to make very early on before
mapping the kernel proper. When used in conjunction with the "kpti=off"
command-line option, it is possible to use non-global kernel mappings but
with the kpti trampoline disabled.
Since commit 09e3c22a86f6 ("arm64: Use a variable to store non-global
mappings decision"), arm64_kernel_unmapped_at_el0() reflects only the use of
non-global mappings and does not take into account whether the kpti
trampoline is enabled. This breaks context switching of the TPIDRRO_EL0
register for 64-bit tasks, where the clearing of the register is deferred to
the ret-to-user code, but it also breaks the ARM SPE PMU driver which
helpfully recommends passing "kpti=off" on the command line!
Report whether or not KPTI is actually enabled in
arm64_kernel_unmapped_at_el0() and check the 'arm64_use_ng_mappings' global
variable directly when determining the protection flags for kernel mappings.
Cc: Mark Brown <broonie@kernel.org>
Reported-by: Hongbo Yao <yaohongbo@huawei.com>
Tested-by: Hongbo Yao <yaohongbo@huawei.com>
Fixes: 09e3c22a86f6 ("arm64: Use a variable to store non-global mappings decision")
Signed-off-by: Will Deacon <will@kernel.org>
| -rw-r--r-- | arch/arm64/include/asm/mmu.h | 4 | ||||
| -rw-r--r-- | arch/arm64/include/asm/pgtable-prot.h | 6 |
2 files changed, 5 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h index e4d862420bb4..d79ce6df9e12 100644 --- a/arch/arm64/include/asm/mmu.h +++ b/arch/arm64/include/asm/mmu.h @@ -29,11 +29,9 @@ typedef struct { */ #define ASID(mm) ((mm)->context.id.counter & 0xffff) -extern bool arm64_use_ng_mappings; - static inline bool arm64_kernel_unmapped_at_el0(void) { - return arm64_use_ng_mappings; + return cpus_have_const_cap(ARM64_UNMAP_KERNEL_AT_EL0); } typedef void (*bp_hardening_cb_t)(void); diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h index 6f87839f0249..1305e28225fc 100644 --- a/arch/arm64/include/asm/pgtable-prot.h +++ b/arch/arm64/include/asm/pgtable-prot.h @@ -23,11 +23,13 @@ #include <asm/pgtable-types.h> +extern bool arm64_use_ng_mappings; + #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_use_ng_mappings ? PTE_NG : 0) +#define PMD_MAYBE_NG (arm64_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) |