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 static u64 __boot_status __initdata; 23 24 struct ftr_set_desc { 25 char name[FTR_DESC_NAME_LEN]; 26 struct arm64_ftr_override *override; 27 struct { 28 char name[FTR_DESC_FIELD_LEN]; 29 u8 shift; 30 u8 width; 31 bool (*filter)(u64 val); 32 } fields[]; 33 }; 34 35 #define FIELD(n, s, f) { .name = n, .shift = s, .width = 4, .filter = f } 36 37 static bool __init mmfr1_vh_filter(u64 val) 38 { 39 /* 40 * If we ever reach this point while running VHE, we're 41 * guaranteed to be on one of these funky, VHE-stuck CPUs. If 42 * the user was trying to force nVHE on us, proceed with 43 * attitude adjustment. 44 */ 45 return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) && 46 val == 0); 47 } 48 49 static const struct ftr_set_desc mmfr1 __initconst = { 50 .name = "id_aa64mmfr1", 51 .override = &id_aa64mmfr1_override, 52 .fields = { 53 FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter), 54 {} 55 }, 56 }; 57 58 static bool __init pfr0_sve_filter(u64 val) 59 { 60 /* 61 * Disabling SVE also means disabling all the features that 62 * are associated with it. The easiest way to do it is just to 63 * override id_aa64zfr0_el1 to be 0. 64 */ 65 if (!val) { 66 id_aa64zfr0_override.val = 0; 67 id_aa64zfr0_override.mask = GENMASK(63, 0); 68 } 69 70 return true; 71 } 72 73 static const struct ftr_set_desc pfr0 __initconst = { 74 .name = "id_aa64pfr0", 75 .override = &id_aa64pfr0_override, 76 .fields = { 77 FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter), 78 {} 79 }, 80 }; 81 82 static bool __init pfr1_sme_filter(u64 val) 83 { 84 /* 85 * Similarly to SVE, disabling SME also means disabling all 86 * the features that are associated with it. Just set 87 * id_aa64smfr0_el1 to 0 and don't look back. 88 */ 89 if (!val) { 90 id_aa64smfr0_override.val = 0; 91 id_aa64smfr0_override.mask = GENMASK(63, 0); 92 } 93 94 return true; 95 } 96 97 static const struct ftr_set_desc pfr1 __initconst = { 98 .name = "id_aa64pfr1", 99 .override = &id_aa64pfr1_override, 100 .fields = { 101 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ), 102 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL), 103 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter), 104 {} 105 }, 106 }; 107 108 static const struct ftr_set_desc isar1 __initconst = { 109 .name = "id_aa64isar1", 110 .override = &id_aa64isar1_override, 111 .fields = { 112 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL), 113 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL), 114 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL), 115 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL), 116 {} 117 }, 118 }; 119 120 static const struct ftr_set_desc isar2 __initconst = { 121 .name = "id_aa64isar2", 122 .override = &id_aa64isar2_override, 123 .fields = { 124 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL), 125 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL), 126 {} 127 }, 128 }; 129 130 static const struct ftr_set_desc smfr0 __initconst = { 131 .name = "id_aa64smfr0", 132 .override = &id_aa64smfr0_override, 133 .fields = { 134 FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL), 135 /* FA64 is a one bit field... :-/ */ 136 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, }, 137 {} 138 }, 139 }; 140 141 extern struct arm64_ftr_override kaslr_feature_override; 142 143 static const struct ftr_set_desc kaslr __initconst = { 144 .name = "kaslr", 145 #ifdef CONFIG_RANDOMIZE_BASE 146 .override = &kaslr_feature_override, 147 #endif 148 .fields = { 149 FIELD("disabled", 0, NULL), 150 {} 151 }, 152 }; 153 154 static const struct ftr_set_desc * const regs[] __initconst = { 155 &mmfr1, 156 &pfr0, 157 &pfr1, 158 &isar1, 159 &isar2, 160 &smfr0, 161 &kaslr, 162 }; 163 164 static const struct { 165 char alias[FTR_ALIAS_NAME_LEN]; 166 char feature[FTR_ALIAS_OPTION_LEN]; 167 } aliases[] __initconst = { 168 { "kvm-arm.mode=nvhe", "id_aa64mmfr1.vh=0" }, 169 { "kvm-arm.mode=protected", "id_aa64mmfr1.vh=0" }, 170 { "arm64.nosve", "id_aa64pfr0.sve=0 id_aa64pfr1.sme=0" }, 171 { "arm64.nosme", "id_aa64pfr1.sme=0" }, 172 { "arm64.nobti", "id_aa64pfr1.bt=0" }, 173 { "arm64.nopauth", 174 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 " 175 "id_aa64isar1.api=0 id_aa64isar1.apa=0 " 176 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" }, 177 { "arm64.nomte", "id_aa64pfr1.mte=0" }, 178 { "nokaslr", "kaslr.disabled=1" }, 179 }; 180 181 static int __init find_field(const char *cmdline, 182 const struct ftr_set_desc *reg, int f, u64 *v) 183 { 184 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2]; 185 int len; 186 187 len = snprintf(opt, ARRAY_SIZE(opt), "%s.%s=", 188 reg->name, reg->fields[f].name); 189 190 if (!parameqn(cmdline, opt, len)) 191 return -1; 192 193 return kstrtou64(cmdline + len, 0, v); 194 } 195 196 static void __init match_options(const char *cmdline) 197 { 198 int i; 199 200 for (i = 0; i < ARRAY_SIZE(regs); i++) { 201 int f; 202 203 if (!regs[i]->override) 204 continue; 205 206 for (f = 0; strlen(regs[i]->fields[f].name); f++) { 207 u64 shift = regs[i]->fields[f].shift; 208 u64 width = regs[i]->fields[f].width ?: 4; 209 u64 mask = GENMASK_ULL(shift + width - 1, shift); 210 u64 v; 211 212 if (find_field(cmdline, regs[i], f, &v)) 213 continue; 214 215 /* 216 * If an override gets filtered out, advertise 217 * it by setting the value to the all-ones while 218 * clearing the mask... Yes, this is fragile. 219 */ 220 if (regs[i]->fields[f].filter && 221 !regs[i]->fields[f].filter(v)) { 222 regs[i]->override->val |= mask; 223 regs[i]->override->mask &= ~mask; 224 continue; 225 } 226 227 regs[i]->override->val &= ~mask; 228 regs[i]->override->val |= (v << shift) & mask; 229 regs[i]->override->mask |= mask; 230 231 return; 232 } 233 } 234 } 235 236 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) 237 { 238 do { 239 char buf[256]; 240 size_t len; 241 int i; 242 243 cmdline = skip_spaces(cmdline); 244 245 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++); 246 if (!len) 247 return; 248 249 len = min(len, ARRAY_SIZE(buf) - 1); 250 strncpy(buf, cmdline, len); 251 buf[len] = 0; 252 253 if (strcmp(buf, "--") == 0) 254 return; 255 256 cmdline += len; 257 258 match_options(buf); 259 260 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++) 261 if (parameq(buf, aliases[i].alias)) 262 __parse_cmdline(aliases[i].feature, false); 263 } while (1); 264 } 265 266 static __init const u8 *get_bootargs_cmdline(void) 267 { 268 const u8 *prop; 269 void *fdt; 270 int node; 271 272 fdt = get_early_fdt_ptr(); 273 if (!fdt) 274 return NULL; 275 276 node = fdt_path_offset(fdt, "/chosen"); 277 if (node < 0) 278 return NULL; 279 280 prop = fdt_getprop(fdt, node, "bootargs", NULL); 281 if (!prop) 282 return NULL; 283 284 return strlen(prop) ? prop : NULL; 285 } 286 287 static __init void parse_cmdline(void) 288 { 289 const u8 *prop = get_bootargs_cmdline(); 290 291 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop) 292 __parse_cmdline(CONFIG_CMDLINE, true); 293 294 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop) 295 __parse_cmdline(prop, true); 296 } 297 298 /* Keep checkers quiet */ 299 void init_feature_override(u64 boot_status); 300 301 asmlinkage void __init init_feature_override(u64 boot_status) 302 { 303 int i; 304 305 for (i = 0; i < ARRAY_SIZE(regs); i++) { 306 if (regs[i]->override) { 307 regs[i]->override->val = 0; 308 regs[i]->override->mask = 0; 309 } 310 } 311 312 __boot_status = boot_status; 313 314 parse_cmdline(); 315 316 for (i = 0; i < ARRAY_SIZE(regs); i++) { 317 if (regs[i]->override) 318 dcache_clean_inval_poc((unsigned long)regs[i]->override, 319 (unsigned long)regs[i]->override + 320 sizeof(*regs[i]->override)); 321 } 322 } 323