arch/riscv/kernel/alternative.c

   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
  19 struct cpu_manufacturer_info_t {
  20         unsigned long vendor_id;
  21         unsigned long arch_id;
  22         unsigned long imp_id;
  23         void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
  24                                   unsigned long archid, unsigned long impid,
  25                                   unsigned int stage);
  26 };
  27
  28 static 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->vendor_patch_func = sifive_errata_patch_func;
  44                 break;
  45 #endif
  46 #ifdef CONFIG_ERRATA_THEAD
  47         case THEAD_VENDOR_ID:
  48                 cpu_mfr_info->vendor_patch_func = thead_errata_patch_func;
  49                 break;
  50 #endif
  51         default:
  52                 cpu_mfr_info->vendor_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  */
  61 static 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.vendor_patch_func)
  72                 return;
  73
  74         cpu_mfr_info.vendor_patch_func(begin, end,
  75                                    cpu_mfr_info.arch_id,
  76                                    cpu_mfr_info.imp_id,
  77                                    stage);
  78 }
  79
  80 void __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  */
 102 void __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
 112 void 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