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authorMarc Zyngier <maz@kernel.org>2021-02-08 09:57:29 +0000
committerWill Deacon <will@kernel.org>2021-02-09 13:50:57 +0000
commit93ad55b7852b324a3fd7d46910b88c81deb62357 (patch)
treee1066fe48afa3e16df6b0f9cd1f66fc5bf239831
parenta762f4ffc3c8a434da1b712e57a80d8d10404198 (diff)
arm64: cpufeatures: Allow disabling of BTI from the command-line
In order to be able to disable BTI at runtime, whether it is for testing purposes, or to work around HW issues, let's add support for overriding the ID_AA64PFR1_EL1.BTI field. This is further mapped on the arm64.nobti command-line alias. Signed-off-by: Marc Zyngier <maz@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: David Brazdil <dbrazdil@google.com> Tested-by: Srinivas Ramana <sramana@codeaurora.org> Link: https://lore.kernel.org/r/20210208095732.3267263-21-maz@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt3
-rw-r--r--arch/arm64/include/asm/cpufeature.h1
-rw-r--r--arch/arm64/kernel/cpufeature.c4
-rw-r--r--arch/arm64/kernel/idreg-override.c11
-rw-r--r--arch/arm64/mm/mmu.c2
5 files changed, 19 insertions, 2 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 41786d205e0d..c00236b22c6e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -373,6 +373,9 @@
arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
Format: <io>,<irq>,<nodeID>
+ arm64.nobti [ARM64] Unconditionally disable Branch Target
+ Identification support
+
ataflop= [HW,M68k]
atarimouse= [HW,MOUSE] Atari Mouse
diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 570f1b4ba3cc..30917b9a760b 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -819,6 +819,7 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
}
extern struct arm64_ftr_override id_aa64mmfr1_override;
+extern struct arm64_ftr_override id_aa64pfr1_override;
u32 get_kvm_ipa_limit(void);
void dump_cpu_features(void);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index faada5d8bea6..7fbeab497adb 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -558,6 +558,7 @@ static const struct arm64_ftr_bits ftr_raz[] = {
#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, &no_override)
struct arm64_ftr_override __ro_after_init id_aa64mmfr1_override;
+struct arm64_ftr_override __ro_after_init id_aa64pfr1_override;
static const struct __ftr_reg_entry {
u32 sys_id;
@@ -593,7 +594,8 @@ static const struct __ftr_reg_entry {
/* Op1 = 0, CRn = 0, CRm = 4 */
ARM64_FTR_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0),
- ARM64_FTR_REG(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1),
+ ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1,
+ &id_aa64pfr1_override),
ARM64_FTR_REG(SYS_ID_AA64ZFR0_EL1, ftr_id_aa64zfr0),
/* Op1 = 0, CRn = 0, CRm = 5 */
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 70dd70eee7a2..d691e9015c62 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -37,6 +37,15 @@ static const struct ftr_set_desc mmfr1 __initconst = {
},
};
+static const struct ftr_set_desc pfr1 __initconst = {
+ .name = "id_aa64pfr1",
+ .override = &id_aa64pfr1_override,
+ .fields = {
+ { "bt", ID_AA64PFR1_BT_SHIFT },
+ {}
+ },
+};
+
extern struct arm64_ftr_override kaslr_feature_override;
static const struct ftr_set_desc kaslr __initconst = {
@@ -52,6 +61,7 @@ static const struct ftr_set_desc kaslr __initconst = {
static const struct ftr_set_desc * const regs[] __initconst = {
&mmfr1,
+ &pfr1,
&kaslr,
};
@@ -61,6 +71,7 @@ static const struct {
} aliases[] __initconst = {
{ "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
{ "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
+ { "arm64.nobti", "id_aa64pfr1.bt=0" },
{ "nokaslr", "kaslr.disabled=1" },
};
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index ae0c3d023824..617e704c980b 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -628,7 +628,7 @@ static bool arm64_early_this_cpu_has_bti(void)
if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
return false;
- pfr1 = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
+ pfr1 = __read_sysreg_by_encoding(SYS_ID_AA64PFR1_EL1);
return cpuid_feature_extract_unsigned_field(pfr1,
ID_AA64PFR1_BT_SHIFT);
}