arm64: Remove Spectre-related CONFIG_* options

The spectre mitigations are too configurable for their own good, leading
to confusing logic trying to figure out when we should mitigate and when
we shouldn't. Although the plethora of command-line options need to stick
around for backwards compatibility, the default-on CONFIG options that
depend on EXPERT can be dropped, as the mitigations only do anything if
the system is vulnerable, a mitigation is available and the command-line
hasn't disabled it.

Remove CONFIG_HARDEN_BRANCH_PREDICTOR and CONFIG_ARM64_SSBD in favour of
enabling this code unconditionally.

Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 2 insertions, 17 deletions

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index abfef5f3b5fd..dd9103915f1e 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -254,9 +254,7 @@ static int detect_harden_bp_fw(void)
 	    ((midr & MIDR_CPU_MODEL_MASK) == MIDR_QCOM_FALKOR_V1))
 		cb = qcom_link_stack_sanitization;
 
-	if (IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR))
-		install_bp_hardening_cb(cb, smccc_start, smccc_end);
-
+	install_bp_hardening_cb(cb, smccc_start, smccc_end);
 	return 1;
 }
 
@@ -335,11 +333,6 @@ void arm64_set_ssbd_mitigation(bool state)
 {
 	int conduit;
 
-	if (!IS_ENABLED(CONFIG_ARM64_SSBD)) {
-		pr_info_once("SSBD disabled by kernel configuration\n");
-		return;
-	}
-
 	if (this_cpu_has_cap(ARM64_SSBS)) {
 		if (state)
 			asm volatile(SET_PSTATE_SSBS(0));
@@ -584,12 +577,6 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope)
 
 	__spectrev2_safe = false;
 
-	if (!IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR)) {
-		pr_warn_once("spectrev2 mitigation disabled by kernel configuration\n");
-		__hardenbp_enab = false;
-		return false;
-	}
-
 	/* forced off */
 	if (__nospectre_v2 || cpu_mitigations_off()) {
 		pr_info_once("spectrev2 mitigation disabled by command line option\n");
@@ -1004,9 +991,7 @@ ssize_t cpu_show_spec_store_bypass(struct device *dev,
 	switch (ssbd_state) {
 	case ARM64_SSBD_KERNEL:
 	case ARM64_SSBD_FORCE_ENABLE:
-		if (IS_ENABLED(CONFIG_ARM64_SSBD))
-			return sprintf(buf,
-			    "Mitigation: Speculative Store Bypass disabled via prctl\n");
+		return sprintf(buf, "Mitigation: Speculative Store Bypass disabled via prctl\n");
 	}
 
 	return sprintf(buf, "Vulnerable\n");