1 files changed, 118 insertions, 0 deletions
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
new file mode 100644
index 000000000000..c9d0d3c53223
--- /dev/null
+++ b/arch/riscv/kernel/alternative.c
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * alternative runtime patching
+ * inspired by the ARM64 and x86 version
+ *
+ * Copyright (C) 2021 Sifive.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cpu.h>
+#include <linux/uaccess.h>
+#include <asm/alternative.h>
+#include <asm/sections.h>
+#include <asm/vendorid_list.h>
+#include <asm/sbi.h>
+#include <asm/csr.h>
+
+struct cpu_manufacturer_info_t {
+	unsigned long vendor_id;
+	unsigned long arch_id;
+	unsigned long imp_id;
+	void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
+				  unsigned long archid, unsigned long impid,
+				  unsigned int stage);
+};
+
+static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_info_t *cpu_mfr_info)
+{
+#ifdef CONFIG_RISCV_M_MODE
+	cpu_mfr_info->vendor_id = csr_read(CSR_MVENDORID);
+	cpu_mfr_info->arch_id = csr_read(CSR_MARCHID);
+	cpu_mfr_info->imp_id = csr_read(CSR_MIMPID);
+#else
+	cpu_mfr_info->vendor_id = sbi_get_mvendorid();
+	cpu_mfr_info->arch_id = sbi_get_marchid();
+	cpu_mfr_info->imp_id = sbi_get_mimpid();
+#endif
+
+	switch (cpu_mfr_info->vendor_id) {
+#ifdef CONFIG_ERRATA_SIFIVE
+	case SIFIVE_VENDOR_ID:
+		cpu_mfr_info->vendor_patch_func = sifive_errata_patch_func;
+		break;
+#endif
+#ifdef CONFIG_ERRATA_THEAD
+	case THEAD_VENDOR_ID:
+		cpu_mfr_info->vendor_patch_func = thead_errata_patch_func;
+		break;
+#endif
+	default:
+		cpu_mfr_info->vendor_patch_func = NULL;
+	}
+}
+
+/*
+ * This is called very early in the boot process (directly after we run
+ * a feature detect on the boot CPU). No need to worry about other CPUs
+ * here.
+ */
+static void __init_or_module _apply_alternatives(struct alt_entry *begin,
+						 struct alt_entry *end,
+						 unsigned int stage)
+{
+	struct cpu_manufacturer_info_t cpu_mfr_info;
+
+	riscv_fill_cpu_mfr_info(&cpu_mfr_info);
+
+	riscv_cpufeature_patch_func(begin, end, stage);
+
+	if (!cpu_mfr_info.vendor_patch_func)
+		return;
+
+	cpu_mfr_info.vendor_patch_func(begin, end,
+				   cpu_mfr_info.arch_id,
+				   cpu_mfr_info.imp_id,
+				   stage);
+}
+
+void __init apply_boot_alternatives(void)
+{
+	/* If called on non-boot cpu things could go wrong */
+	WARN_ON(smp_processor_id() != 0);
+
+	_apply_alternatives((struct alt_entry *)__alt_start,
+			    (struct alt_entry *)__alt_end,
+			    RISCV_ALTERNATIVES_BOOT);
+}
+
+/*
+ * apply_early_boot_alternatives() is called from setup_vm() with MMU-off.
+ *
+ * Following requirements should be honoured for it to work correctly:
+ * 1) It should use PC-relative addressing for accessing kernel symbols.
+ *    To achieve this we always use GCC cmodel=medany.
+ * 2) The compiler instrumentation for FTRACE will not work for setup_vm()
+ *    so disable compiler instrumentation when FTRACE is enabled.
+ *
+ * Currently, the above requirements are honoured by using custom CFLAGS
+ * for alternative.o in kernel/Makefile.
+ */
+void __init apply_early_boot_alternatives(void)
+{
+#ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+	_apply_alternatives((struct alt_entry *)__alt_start,
+			    (struct alt_entry *)__alt_end,
+			    RISCV_ALTERNATIVES_EARLY_BOOT);
+#endif
+}
+
+#ifdef CONFIG_MODULES
+void apply_module_alternatives(void *start, size_t length)
+{
+	_apply_alternatives((struct alt_entry *)start,
+			    (struct alt_entry *)(start + length),
+			    RISCV_ALTERNATIVES_MODULE);
+}
+#endif