From 2ccb89d411f0382059a5ec4c382b4ce633906335 Mon Sep 17 00:00:00 2001
From: Will Deacon <will.deacon@arm.com>
Date: Mon, 27 Nov 2017 18:29:30 +0000
Subject: [PATCH 08/24] arm64: Take into account ID_AA64PFR0_EL1.CSV3
Git-commit: 179a56f6f9fbda28f6ca07db1fc3dfad6bc7343c
Patch-mainline: v4.16-rc1
References: bsc#1068032
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@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
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
@@ -436,6 +436,7 @@
#define ID_AA64ISAR1_JSCVT_SHIFT 12
/* 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
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -145,6 +145,7 @@ 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_VISIBLE_IF_IS_ENABLED(CONFIG_ARM64_SVE),
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),
@@ -852,6 +853,8 @@ 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",
@@ -863,7 +866,9 @@ 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)
@@ -968,6 +973,7 @@ 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,