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Commit 7354772a authored by Will Deacon's avatar Will Deacon Committed by Greg Kroah-Hartman
Browse files

arm64: Take into account ID_AA64PFR0_EL1.CSV3 



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: 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>
[Alex: s/read_sanitised_ftr_reg/read_system_reg/ to match v4.9 naming]
Signed-off-by: Alex Shi <alex.shi@linaro.org> [v4.9 backport]
[Mark: correct zero bits in ftr_id_aa64pfr0 to account for CSV3]
Signed-off-by: Mark Rutland <mark.rutland@arm.com> [v4.9 backport]
Tested-by: default avatarWill Deacon <will.deacon@arm.com>
Tested-by: default avatarGreg Hackmann <ghackmann@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ded98c66

arch/arm64/include/asm/sysreg.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/arm64/kernel/cpufeature.c

+8 −2
Original line number Diff line number Diff line
@@ -93,7 +93,8 @@ static const struct arm64_ftr_bits ftr_id_aa64isar0[] = { 
};



static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {

	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 32, 32, 0),

	ARM64_FTR_BITS(FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_CSV3_SHIFT, 4, 0),

	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 32, 28, 0),

	ARM64_FTR_BITS(FTR_STRICT, FTR_EXACT, 28, 4, 0),

	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),
@@ -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,