4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.deacon@xxxxxxx>
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.poulose@xxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/arm64/include/asm/sysreg.h | 1 +
arch/arm64/kernel/cpufeature.c | 8 +++++++-
2 files changed, 8 insertions(+), 1 deletion(-)
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -332,6 +332,7 @@
#define ID_AA64ISAR1_DPB_SHIFT 0
/* 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
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -125,6 +125,7 @@ static const struct arm64_ftr_bits ftr_i
};
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_EXACT, ID_AA64PFR0_GIC_SHIFT, 4, 0),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_ASIMD_SHIFT, 4, ID_AA64PFR0_ASIMD_NI),
S_ARM64_FTR_BITS(FTR_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_FP_SHIFT, 4, ID_AA64PFR0_FP_NI),
@@ -802,6 +803,8 @@ static int __kpti_forced; /* 0: not forc
static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
int __unused)
{
+ u64 pfr0 = read_sanitised_ftr_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",
@@ -813,7 +816,9 @@ static bool unmap_kernel_at_el0(const st
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)
@@ -918,6 +923,7 @@ static const struct arm64_cpu_capabiliti
},
#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,