[RFC/RFT PATCH 11/16] arm64: Always enable spectre-v2 vulnerability detection

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Mark Rutland <mark.rutland@arm.com>,
	Stefan Wahren <stefan.wahren@i2se.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	Jeremy Linton <jeremy.linton@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>
Subject: [RFC/RFT PATCH 11/16] arm64: Always enable spectre-v2 vulnerability detection
Date: Fri,  4 Oct 2019 14:04:25 +0200	[thread overview]
Message-ID: <20191004120430.11929-12-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <20191004120430.11929-1-ard.biesheuvel@linaro.org>

From: Jeremy Linton <jeremy.linton@arm.com>

Ensure we are always able to detect whether or not the CPU is affected
by Spectre-v2, so that we can later advertise this to userspace.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit 8c1e3d2bb44cbb998cb28ff9a18f105fee7f1eb3)
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 arch/arm64/kernel/cpu_errata.c | 47 ++++----------------
 1 file changed, 8 insertions(+), 39 deletions(-)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index def847873d21..ae7d6761262f 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -87,7 +87,6 @@ cpu_enable_trap_ctr_access(const struct arm64_cpu_capabilities *__unused)
 
 atomic_t arm64_el2_vector_last_slot = ATOMIC_INIT(-1);
 
-#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 
@@ -225,11 +224,11 @@ static int detect_harden_bp_fw(void)
 	    ((midr & MIDR_CPU_MODEL_MASK) == MIDR_QCOM_FALKOR_V1))
 		cb = qcom_link_stack_sanitization;
 
-	install_bp_hardening_cb(cb, smccc_start, smccc_end);
+	if (IS_ENABLED(CONFIG_HARDEN_BRANCH_PREDICTOR))
+		install_bp_hardening_cb(cb, smccc_start, smccc_end);
 
 	return 1;
 }
-#endif	/* CONFIG_HARDEN_BRANCH_PREDICTOR */
 
 #ifdef CONFIG_ARM64_SSBD
 DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
@@ -478,39 +477,6 @@ has_cortex_a76_erratum_1463225(const struct arm64_cpu_capabilities *entry,
 	.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,			\
 	CAP_MIDR_RANGE_LIST(midr_list)
 
-/*
- * Generic helper for handling capabilties with multiple (match,enable) pairs
- * of call backs, sharing the same capability bit.
- * Iterate over each entry to see if at least one matches.
- */
-static bool __maybe_unused
-multi_entry_cap_matches(const struct arm64_cpu_capabilities *entry, int scope)
-{
-	const struct arm64_cpu_capabilities *caps;
-
-	for (caps = entry->match_list; caps->matches; caps++)
-		if (caps->matches(caps, scope))
-			return true;
-
-	return false;
-}
-
-/*
- * Take appropriate action for all matching entries in the shared capability
- * entry.
- */
-static void __maybe_unused
-multi_entry_cap_cpu_enable(const struct arm64_cpu_capabilities *entry)
-{
-	const struct arm64_cpu_capabilities *caps;
-
-	for (caps = entry->match_list; caps->matches; caps++)
-		if (caps->matches(caps, SCOPE_LOCAL_CPU) &&
-		    caps->cpu_enable)
-			caps->cpu_enable(caps);
-}
-
-#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 /*
  * List of CPUs that do not need any Spectre-v2 mitigation at all.
  */
@@ -542,6 +508,12 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope)
 	if (!need_wa)
 		return 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) {
 		pr_info_once("spectrev2 mitigation disabled by command line option\n");
@@ -553,7 +525,6 @@ check_branch_predictor(const struct arm64_cpu_capabilities *entry, int scope)
 
 	return (need_wa > 0);
 }
-#endif
 
 #ifdef CONFIG_HARDEN_EL2_VECTORS
 
@@ -712,13 +683,11 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		ERRATA_MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
 	},
 #endif
-#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 	{
 		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = check_branch_predictor,
 	},
-#endif
 #ifdef CONFIG_HARDEN_EL2_VECTORS
 	{
 		.desc = "EL2 vector hardening",
-- 
2.20.1


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