forked from Minki/linux
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>
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@ -373,6 +373,9 @@
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arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
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Format: <io>,<irq>,<nodeID>
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arm64.nobti [ARM64] Unconditionally disable Branch Target
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Identification support
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ataflop= [HW,M68k]
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atarimouse= [HW,MOUSE] Atari Mouse
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@ -819,6 +819,7 @@ static inline unsigned int get_vmid_bits(u64 mmfr1)
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}
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extern struct arm64_ftr_override id_aa64mmfr1_override;
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extern struct arm64_ftr_override id_aa64pfr1_override;
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u32 get_kvm_ipa_limit(void);
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void dump_cpu_features(void);
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@ -558,6 +558,7 @@ static const struct arm64_ftr_bits ftr_raz[] = {
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#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, &no_override)
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struct arm64_ftr_override __ro_after_init id_aa64mmfr1_override;
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struct arm64_ftr_override __ro_after_init id_aa64pfr1_override;
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static const struct __ftr_reg_entry {
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u32 sys_id;
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@ -593,7 +594,8 @@ static const struct __ftr_reg_entry {
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/* Op1 = 0, CRn = 0, CRm = 4 */
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ARM64_FTR_REG(SYS_ID_AA64PFR0_EL1, ftr_id_aa64pfr0),
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ARM64_FTR_REG(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1),
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ARM64_FTR_REG_OVERRIDE(SYS_ID_AA64PFR1_EL1, ftr_id_aa64pfr1,
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&id_aa64pfr1_override),
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ARM64_FTR_REG(SYS_ID_AA64ZFR0_EL1, ftr_id_aa64zfr0),
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/* Op1 = 0, CRn = 0, CRm = 5 */
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@ -37,6 +37,15 @@ static const struct ftr_set_desc mmfr1 __initconst = {
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},
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};
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static const struct ftr_set_desc pfr1 __initconst = {
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.name = "id_aa64pfr1",
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.override = &id_aa64pfr1_override,
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.fields = {
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{ "bt", ID_AA64PFR1_BT_SHIFT },
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{}
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},
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};
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extern struct arm64_ftr_override kaslr_feature_override;
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static const struct ftr_set_desc kaslr __initconst = {
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@ -52,6 +61,7 @@ static const struct ftr_set_desc kaslr __initconst = {
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static const struct ftr_set_desc * const regs[] __initconst = {
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&mmfr1,
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&pfr1,
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&kaslr,
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};
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@ -61,6 +71,7 @@ static const struct {
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} aliases[] __initconst = {
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{ "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" },
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{ "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" },
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{ "arm64.nobti", "id_aa64pfr1.bt=0" },
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{ "nokaslr", "kaslr.disabled=1" },
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};
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@ -628,7 +628,7 @@ static bool arm64_early_this_cpu_has_bti(void)
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if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
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return false;
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pfr1 = read_sysreg_s(SYS_ID_AA64PFR1_EL1);
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pfr1 = __read_sysreg_by_encoding(SYS_ID_AA64PFR1_EL1);
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return cpuid_feature_extract_unsigned_field(pfr1,
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ID_AA64PFR1_BT_SHIFT);
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}
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