1 files changed, 69 insertions, 0 deletions
diff --git a/arch/riscv/errata/alternative.c b/arch/riscv/errata/alternative.c
new file mode 100644
index 000000000000..8efa60ad69b7
--- /dev/null
+++ b/arch/riscv/errata/alternative.c
@@ -0,0 +1,69 @@
+// 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/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>
+
+static struct cpu_manufacturer_info_t {
+	unsigned long vendor_id;
+	unsigned long arch_id;
+	unsigned long imp_id;
+} cpu_mfr_info;
+
+static void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
+				 unsigned long archid, unsigned long impid);
+
+static inline void __init riscv_fill_cpu_mfr_info(void)
+{
+#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
+}
+
+static void __init init_alternative(void)
+{
+	riscv_fill_cpu_mfr_info();
+
+	switch (cpu_mfr_info.vendor_id) {
+	default:
+		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.
+ */
+void __init apply_boot_alternatives(void)
+{
+	/* If called on non-boot cpu things could go wrong */
+	WARN_ON(smp_processor_id() != 0);
+
+	init_alternative();
+
+	if (!vendor_patch_func)
+		return;
+
+	vendor_patch_func((struct alt_entry *)__alt_start,
+			  (struct alt_entry *)__alt_end,
+			  cpu_mfr_info.arch_id, cpu_mfr_info.imp_id);
+}
+