From 93ad55b7852b324a3fd7d46910b88c81deb62357 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 8 Feb 2021 09:57:29 +0000 Subject: [PATCH] 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 Reviewed-by: Catalin Marinas Acked-by: David Brazdil Tested-by: Srinivas Ramana Link: https://lore.kernel.org/r/20210208095732.3267263-21-maz@kernel.org Signed-off-by: Will Deacon --- Documentation/admin-guide/kernel-parameters.txt | 3 +++ arch/arm64/include/asm/cpufeature.h | 1 + arch/arm64/kernel/cpufeature.c | 4 +++- arch/arm64/kernel/idreg-override.c | 11 +++++++++++ arch/arm64/mm/mmu.c | 2 +- 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: ,, + 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); } -- 2.11.0