From: Will Deacon <will.dea...@arm.com>
commit 179a56f6f9fb upstream.
For non-KASLR kernels where the KPTI behaviour has not been overridden
on the command line we can use ID_AA64PFR0_EL1.CSV3 to determine whether
or not we should unmap the kernel whilst running at EL0.
Reviewed-by: Suzuki K Poulose <suzuki.poul...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
Signed-off-by: Alex Shi <alex....@linaro.org>
Conflicts:
skip cpu features like SVE etc.
and use 5 paramaters function ARM64_FTR_BITS()
replace read_sanitised_ftr_reg with old name read_system_reg
arch/arm64/include/asm/sysreg.h
arch/arm64/kernel/cpufeature.c
---
arch/arm64/include/asm/sysreg.h | 1 +
arch/arm64/kernel/cpufeature.c | 8 +++++++-
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 7393cc7..7cb7f7c 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -117,6 +117,7 @@
#define ID_AA64ISAR0_AES_SHIFT 4
/* id_aa64pfr0 */
+#define ID_AA64PFR0_CSV3_SHIFT 60
#define ID_AA64PFR0_GIC_SHIFT 24
#define ID_AA64PFR0_ASIMD_SHIFT 20
#define ID_AA64PFR0_FP_SHIFT 16
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 74b168c..3ec6517 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -98,6 +98,7 @@ static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT,
4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4,
ID_AA64PFR0_FP_NI),
+ ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT,
4, 0),
/* Linux doesn't care about the EL3 */
ARM64_FTR_BITS(FTR_NONSTRICT, FTR_EXACT, ID_AA64PFR0_EL3_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, ID_AA64PFR0_EL2_SHIFT, 4, 0),
@@ -752,6 +753,8 @@ static int __kpti_forced; /* 0: not forced, >0: forced on,
<0: forced off */
static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
int __unused)
{
+ u64 pfr0 = read_system_reg(SYS_ID_AA64PFR0_EL1);
+
/* Forced on command line? */
if (__kpti_forced) {
pr_info_once("kernel page table isolation forced %s by command
line option\n",
@@ -763,7 +766,9 @@ static bool unmap_kernel_at_el0(const struct
arm64_cpu_capabilities *entry,
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE))
return true;
- return false;
+ /* Defer to CPU feature registers */
+ return !cpuid_feature_extract_unsigned_field(pfr0,
+ ID_AA64PFR0_CSV3_SHIFT);
}
static int __init parse_kpti(char *str)
@@ -865,6 +870,7 @@ static const struct arm64_cpu_capabilities arm64_features[]
= {
},
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
{
+ .desc = "Kernel page table isolation (KPTI)",
.capability = ARM64_UNMAP_KERNEL_AT_EL0,
.def_scope = SCOPE_SYSTEM,
.matches = unmap_kernel_at_el0,
--
2.7.4
