Commit 179a56f6 authored by Will Deacon's avatar Will Deacon Committed by Catalin Marinas
Browse files

arm64: Take into account ID_AA64PFR0_EL1.CSV3 



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: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 0617052d

arch/arm64/include/asm/sysreg.h

+1 −0
Original line number Diff line number Diff line
@@ -438,6 +438,7 @@ 
#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

arch/arm64/kernel/cpufeature.c

+7 −1
Original line number Diff line number Diff line
@@ -146,6 +146,7 @@ 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),
@@ -852,6 +853,8 @@ 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",
@@ -863,7 +866,9 @@ 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)
@@ -968,6 +973,7 @@ 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,

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