arm64: Add BTAC/LinkStack sanitizations for Kryo cores

Kryo cores are exposed to two vulnerabilities due to subroutine return
(called LINK-STACK) and branch target predictors.
These two issues can be mitigated through software workarounds.

Kernel:
 - Apply LINK-STACK mitigation which is to issue 16 nested BL instructions
   on process context switch 'cpu_do_switch_mm()' where ASID changes.
 - Apply psci based branch predictor invalidation.

use the kryo core detection routine (based on MIDR) from the
commit bb48711800e6d ("arm64: cpu_errata: Add Kryo to Falkor 1003 errata")
by Stephen Boyd <sboyd@codeaurora.org>.

Change-Id: I81e8e72e7fa219f12dfe8ec39836eb8eb3c4c7b0
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>

arch/arm64/include/asm/cputype.h

@@ -86,6 +86,7 @@
 #define ARM_CPU_PART_CORTEX_A75		0xD0A
 #define ARM_CPU_PART_KRYO2XX_GOLD	0x800
 #define ARM_CPU_PART_KRYO2XX_SILVER	0x801
+#define	QCOM_CPU_PART_KRYO		0x200
 
 #define APM_CPU_PART_POTENZA		0x000
 
@@ -101,6 +102,7 @@
 	MIDR_CPU_MODEL(ARM_CPU_IMP_QCOM, ARM_CPU_PART_KRYO2XX_SILVER)
 #define MIDR_KRYO2XX_GOLD \
 	MIDR_CPU_MODEL(ARM_CPU_IMP_QCOM, ARM_CPU_PART_KRYO2XX_GOLD)
+#define MIDR_QCOM_KRYO MIDR_CPU_MODEL(ARM_CPU_IMP_QCOM, QCOM_CPU_PART_KRYO)
 
 #ifndef __ASSEMBLY__
 

arch/arm64/kernel/cpu_errata.c

@@ -29,6 +29,18 @@ is_affected_midr_range(const struct arm64_cpu_capabilities *entry)
 				       entry->midr_range_max);
 }
 
+static bool __maybe_unused
+is_kryo_midr(const struct arm64_cpu_capabilities *entry)
+{
+	u32 model;
+
+	model = read_cpuid_id();
+	model &= MIDR_IMPLEMENTOR_MASK | (0xf00 << MIDR_PARTNUM_SHIFT) |
+		MIDR_ARCHITECTURE_MASK;
+
+	return model == entry->midr_model;
+}
+
 #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
@@ -139,16 +151,24 @@ static void __maybe_unused qcom_link_stack_sanitization(void)
 		     : "=&r" (tmp));
 }
 
-static int __maybe_unused qcom_enable_link_stack_sanitization(void *data)
+static void __maybe_unused qcom_bp_hardening(void)
+{
+	qcom_link_stack_sanitization();
+	if (psci_ops.get_version)
+		psci_ops.get_version();
+}
+
+static int __maybe_unused enable_qcom_bp_hardening(void *data)
 {
 	const struct arm64_cpu_capabilities *entry = data;
 
-	install_bp_hardening_cb(entry, qcom_link_stack_sanitization,
-				__qcom_hyp_sanitize_link_stack_start,
-				__qcom_hyp_sanitize_link_stack_end);
-
+	install_bp_hardening_cb(entry,
+				(bp_hardening_cb_t)qcom_bp_hardening,
+				__psci_hyp_bp_inval_start,
+				__psci_hyp_bp_inval_end);
 	return 0;
 }
+
 #endif	/* CONFIG_HARDEN_BRANCH_PREDICTOR */
 
 #define MIDR_RANGE(model, min, max) \
@@ -257,6 +277,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		MIDR_ALL_VERSIONS(MIDR_KRYO2XX_GOLD),
 		.enable = enable_psci_bp_hardening,
 	},
+	{
+		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
+		.midr_model = MIDR_QCOM_KRYO,
+		.matches = is_kryo_midr,
+		.enable = enable_qcom_bp_hardening,
+	},
 #endif
 	{
 	}