1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Early cpufeature override framework 4 * 5 * Copyright (C) 2020 Google LLC 6 * Author: Marc Zyngier <maz@kernel.org> 7 */ 8 9 #include <linux/ctype.h> 10 #include <linux/kernel.h> 11 #include <linux/libfdt.h> 12 13 #include <asm/cacheflush.h> 14 #include <asm/cpufeature.h> 15 #include <asm/setup.h> 16 17 #define FTR_DESC_NAME_LEN 20 18 #define FTR_DESC_FIELD_LEN 10 19 #define FTR_ALIAS_NAME_LEN 30 20 #define FTR_ALIAS_OPTION_LEN 116 21 22 struct ftr_set_desc { 23 char name[FTR_DESC_NAME_LEN]; 24 struct arm64_ftr_override *override; 25 struct { 26 char name[FTR_DESC_FIELD_LEN]; 27 u8 shift; 28 bool (*filter)(u64 val); 29 } fields[]; 30 }; 31 32 static bool __init mmfr1_vh_filter(u64 val) 33 { 34 /* 35 * If we ever reach this point while running VHE, we're 36 * guaranteed to be on one of these funky, VHE-stuck CPUs. If 37 * the user was trying to force nVHE on us, proceed with 38 * attitude adjustment. 39 */ 40 return !(is_kernel_in_hyp_mode() && val == 0); 41 } 42 43 static const struct ftr_set_desc mmfr1 __initconst = { 44 .name = "id_aa64mmfr1", 45 .override = &id_aa64mmfr1_override, 46 .fields = { 47 { "vh", ID_AA64MMFR1_VHE_SHIFT, mmfr1_vh_filter }, 48 {} 49 }, 50 }; 51 52 static const struct ftr_set_desc pfr1 __initconst = { 53 .name = "id_aa64pfr1", 54 .override = &id_aa64pfr1_override, 55 .fields = { 56 { "bt", ID_AA64PFR1_BT_SHIFT }, 57 { "mte", ID_AA64PFR1_MTE_SHIFT}, 58 {} 59 }, 60 }; 61 62 static const struct ftr_set_desc isar1 __initconst = { 63 .name = "id_aa64isar1", 64 .override = &id_aa64isar1_override, 65 .fields = { 66 { "gpi", ID_AA64ISAR1_GPI_SHIFT }, 67 { "gpa", ID_AA64ISAR1_GPA_SHIFT }, 68 { "api", ID_AA64ISAR1_API_SHIFT }, 69 { "apa", ID_AA64ISAR1_APA_SHIFT }, 70 {} 71 }, 72 }; 73 74 static const struct ftr_set_desc isar2 __initconst = { 75 .name = "id_aa64isar2", 76 .override = &id_aa64isar2_override, 77 .fields = { 78 { "gpa3", ID_AA64ISAR2_GPA3_SHIFT }, 79 { "apa3", ID_AA64ISAR2_APA3_SHIFT }, 80 {} 81 }, 82 }; 83 84 extern struct arm64_ftr_override kaslr_feature_override; 85 86 static const struct ftr_set_desc kaslr __initconst = { 87 .name = "kaslr", 88 #ifdef CONFIG_RANDOMIZE_BASE 89 .override = &kaslr_feature_override, 90 #endif 91 .fields = { 92 { "disabled", 0 }, 93 {} 94 }, 95 }; 96 97 static const struct ftr_set_desc * const regs[] __initconst = { 98 &mmfr1, 99 &pfr1, 100 &isar1, 101 &isar2, 102 &kaslr, 103 }; 104 105 static const struct { 106 char alias[FTR_ALIAS_NAME_LEN]; 107 char feature[FTR_ALIAS_OPTION_LEN]; 108 } aliases[] __initconst = { 109 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" }, 110 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" }, 111 { "arm64.nobti", "id_aa64pfr1.bt=0" }, 112 { "arm64.nopauth", 113 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 " 114 "id_aa64isar1.api=0 id_aa64isar1.apa=0 " 115 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" }, 116 { "arm64.nomte", "id_aa64pfr1.mte=0" }, 117 { "nokaslr", "kaslr.disabled=1" }, 118 }; 119 120 static int __init find_field(const char *cmdline, 121 const struct ftr_set_desc *reg, int f, u64 *v) 122 { 123 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2]; 124 int len; 125 126 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=", 127 reg->name, reg->fields[f].name); 128 129 if (!parameqn(cmdline, opt, len)) 130 return -1; 131 132 return kstrtou64(cmdline + len, 0, v); 133 } 134 135 static void __init match_options(const char *cmdline) 136 { 137 int i; 138 139 for (i = 0; i < ARRAY_SIZE(regs); i++) { 140 int f; 141 142 if (!regs[i]->override) 143 continue; 144 145 for (f = 0; strlen(regs[i]->fields[f].name); f++) { 146 u64 shift = regs[i]->fields[f].shift; 147 u64 mask = 0xfUL << shift; 148 u64 v; 149 150 if (find_field(cmdline, regs[i], f, &v)) 151 continue; 152 153 /* 154 * If an override gets filtered out, advertise 155 * it by setting the value to 0xf, but 156 * clearing the mask... Yes, this is fragile. 157 */ 158 if (regs[i]->fields[f].filter && 159 !regs[i]->fields[f].filter(v)) { 160 regs[i]->override->val |= mask; 161 regs[i]->override->mask &= ~mask; 162 continue; 163 } 164 165 regs[i]->override->val &= ~mask; 166 regs[i]->override->val |= (v << shift) & mask; 167 regs[i]->override->mask |= mask; 168 169 return; 170 } 171 } 172 } 173 174 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) 175 { 176 do { 177 char buf[256]; 178 size_t len; 179 int i; 180 181 cmdline = skip_spaces(cmdline); 182 183 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++); 184 if (!len) 185 return; 186 187 len = min(len, ARRAY_SIZE(buf) - 1); 188 strncpy(buf, cmdline, len); 189 buf[len] = 0; 190 191 if (strcmp(buf, "--") == 0) 192 return; 193 194 cmdline += len; 195 196 match_options(buf); 197 198 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++) 199 if (parameq(buf, aliases[i].alias)) 200 __parse_cmdline(aliases[i].feature, false); 201 } while (1); 202 } 203 204 static __init const u8 *get_bootargs_cmdline(void) 205 { 206 const u8 *prop; 207 void *fdt; 208 int node; 209 210 fdt = get_early_fdt_ptr(); 211 if (!fdt) 212 return NULL; 213 214 node = fdt_path_offset(fdt, "/chosen"); 215 if (node < 0) 216 return NULL; 217 218 prop = fdt_getprop(fdt, node, "bootargs", NULL); 219 if (!prop) 220 return NULL; 221 222 return strlen(prop) ? prop : NULL; 223 } 224 225 static __init void parse_cmdline(void) 226 { 227 const u8 *prop = get_bootargs_cmdline(); 228 229 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop) 230 __parse_cmdline(CONFIG_CMDLINE, true); 231 232 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop) 233 __parse_cmdline(prop, true); 234 } 235 236 /* Keep checkers quiet */ 237 void init_feature_override(void); 238 239 asmlinkage void __init init_feature_override(void) 240 { 241 int i; 242 243 for (i = 0; i < ARRAY_SIZE(regs); i++) { 244 if (regs[i]->override) { 245 regs[i]->override->val = 0; 246 regs[i]->override->mask = 0; 247 } 248 } 249 250 parse_cmdline(); 251 252 for (i = 0; i < ARRAY_SIZE(regs); i++) { 253 if (regs[i]->override) 254 dcache_clean_inval_poc((unsigned long)regs[i]->override, 255 (unsigned long)regs[i]->override + 256 sizeof(*regs[i]->override)); 257 } 258 } 259