| Message ID | 1515078515-13723-4-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 01/04/2018 07:08 AM, Will Deacon wrote: > 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. > > Signed-off-by: Will Deacon <will.deacon@arm.com> > --- > arch/arm64/include/asm/sysreg.h | 1 + > arch/arm64/kernel/cpufeature.c | 7 ++++++- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 08cc88574659..ae519bbd3f9e 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -437,6 +437,7 @@ > #define ID_AA64ISAR1_DPB_SHIFT 0 > > /* id_aa64pfr0 */ > +#define ID_AA64PFR0_CSV3_SHIFT 60 > #define ID_AA64PFR0_SVE_SHIFT 32 > #define ID_AA64PFR0_GIC_SHIFT 24 > #define ID_AA64PFR0_ASIMD_SHIFT 20 > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 9f0545dfe497..e11c11bb5b02 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = { > }; > > 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_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0), > ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 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), > @@ -851,6 +852,8 @@ 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_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", > @@ -862,7 +865,9 @@ 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) > Nit: we only print a message if it's forced on the command line, can we get a message similar to x86 regardless of state to clearly indicate if KPTI is enabled? Thanks, Laura
On 04/01/18 15:08, Will Deacon wrote: > 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. > > Signed-off-by: Will Deacon <will.deacon@arm.com> > --- > arch/arm64/include/asm/sysreg.h | 1 + > arch/arm64/kernel/cpufeature.c | 7 ++++++- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 08cc88574659..ae519bbd3f9e 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -437,6 +437,7 @@ > #define ID_AA64ISAR1_DPB_SHIFT 0 > > /* id_aa64pfr0 */ > +#define ID_AA64PFR0_CSV3_SHIFT 60 > #define ID_AA64PFR0_SVE_SHIFT 32 > #define ID_AA64PFR0_GIC_SHIFT 24 > #define ID_AA64PFR0_ASIMD_SHIFT 20 > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 9f0545dfe497..e11c11bb5b02 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = { > }; > > 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_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0), > ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 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), > @@ -851,6 +852,8 @@ 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_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", > @@ -862,7 +865,9 @@ 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); > } > The cpufeature bit changes look good to me. FWIW, Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index 08cc88574659..ae519bbd3f9e 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -437,6 +437,7 @@ #define ID_AA64ISAR1_DPB_SHIFT 0 /* id_aa64pfr0 */ +#define ID_AA64PFR0_CSV3_SHIFT 60 #define ID_AA64PFR0_SVE_SHIFT 32 #define ID_AA64PFR0_GIC_SHIFT 24 #define ID_AA64PFR0_ASIMD_SHIFT 20 diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 9f0545dfe497..e11c11bb5b02 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -145,6 +145,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar1[] = { }; 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_VISIBLE, FTR_STRICT, FTR_LOWER_SAFE, ID_AA64PFR0_SVE_SHIFT, 4, 0), ARM64_FTR_BITS(FTR_HIDDEN, FTR_STRICT, FTR_LOWER_SAFE, 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), @@ -851,6 +852,8 @@ 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_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", @@ -862,7 +865,9 @@ 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)
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. Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/kernel/cpufeature.c | 7 ++++++- 2 files changed, 7 insertions(+), 1 deletion(-)