1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * alternative runtime patching
  4 * inspired by the ARM64 and x86 version
  5 *
  6 * Copyright (C) 2021 Sifive.
  7 */
  8
  9#include <linux/init.h>
 10#include <linux/module.h>
 11#include <linux/cpu.h>
 12#include <linux/uaccess.h>
 13#include <asm/alternative.h>
 14#include <asm/sections.h>
 15#include <asm/vendorid_list.h>
 16#include <asm/sbi.h>
 17#include <asm/csr.h>
 18
 19struct cpu_manufacturer_info_t {
 20	unsigned long vendor_id;
 21	unsigned long arch_id;
 22	unsigned long imp_id;
 23	void (*patch_func)(struct alt_entry *begin, struct alt_entry *end,
 24				  unsigned long archid, unsigned long impid,
 25				  unsigned int stage);
 26};
 27
 28static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_info_t *cpu_mfr_info)
 29{
 30#ifdef CONFIG_RISCV_M_MODE
 31	cpu_mfr_info->vendor_id = csr_read(CSR_MVENDORID);
 32	cpu_mfr_info->arch_id = csr_read(CSR_MARCHID);
 33	cpu_mfr_info->imp_id = csr_read(CSR_MIMPID);
 34#else
 35	cpu_mfr_info->vendor_id = sbi_get_mvendorid();
 36	cpu_mfr_info->arch_id = sbi_get_marchid();
 37	cpu_mfr_info->imp_id = sbi_get_mimpid();
 38#endif
 39
 40	switch (cpu_mfr_info->vendor_id) {
 41#ifdef CONFIG_ERRATA_SIFIVE
 42	case SIFIVE_VENDOR_ID:
 43		cpu_mfr_info->patch_func = sifive_errata_patch_func;
 44		break;
 45#endif
 46#ifdef CONFIG_ERRATA_THEAD
 47	case THEAD_VENDOR_ID:
 48		cpu_mfr_info->patch_func = thead_errata_patch_func;
 49		break;
 50#endif
 51	default:
 52		cpu_mfr_info->patch_func = NULL;
 53	}
 54}
 55
 56/*
 57 * This is called very early in the boot process (directly after we run
 58 * a feature detect on the boot CPU). No need to worry about other CPUs
 59 * here.
 60 */
 61static void __init_or_module _apply_alternatives(struct alt_entry *begin,
 62						 struct alt_entry *end,
 63						 unsigned int stage)
 64{
 65	struct cpu_manufacturer_info_t cpu_mfr_info;
 66
 67	riscv_fill_cpu_mfr_info(&cpu_mfr_info);
 68
 69	riscv_cpufeature_patch_func(begin, end, stage);
 70
 71	if (!cpu_mfr_info.patch_func)
 72		return;
 73
 74	cpu_mfr_info.patch_func(begin, end,
 75				cpu_mfr_info.arch_id,
 76				cpu_mfr_info.imp_id,
 77				stage);
 78}
 79
 80void __init apply_boot_alternatives(void)
 81{
 82	/* If called on non-boot cpu things could go wrong */
 83	WARN_ON(smp_processor_id() != 0);
 84
 85	_apply_alternatives((struct alt_entry *)__alt_start,
 86			    (struct alt_entry *)__alt_end,
 87			    RISCV_ALTERNATIVES_BOOT);
 88}
 89
 90/*
 91 * apply_early_boot_alternatives() is called from setup_vm() with MMU-off.
 92 *
 93 * Following requirements should be honoured for it to work correctly:
 94 * 1) It should use PC-relative addressing for accessing kernel symbols.
 95 *    To achieve this we always use GCC cmodel=medany.
 96 * 2) The compiler instrumentation for FTRACE will not work for setup_vm()
 97 *    so disable compiler instrumentation when FTRACE is enabled.
 98 *
 99 * Currently, the above requirements are honoured by using custom CFLAGS
100 * for alternative.o in kernel/Makefile.
101 */
102void __init apply_early_boot_alternatives(void)
103{
104#ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
105	_apply_alternatives((struct alt_entry *)__alt_start,
106			    (struct alt_entry *)__alt_end,
107			    RISCV_ALTERNATIVES_EARLY_BOOT);
108#endif
109}
110
111#ifdef CONFIG_MODULES
112void apply_module_alternatives(void *start, size_t length)
113{
114	_apply_alternatives((struct alt_entry *)start,
115			    (struct alt_entry *)(start + length),
116			    RISCV_ALTERNATIVES_MODULE);
117}
118#endif