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 #include "pi.h" 18 19 #define FTR_DESC_NAME_LEN 20 20 #define FTR_DESC_FIELD_LEN 10 21 #define FTR_ALIAS_NAME_LEN 30 22 #define FTR_ALIAS_OPTION_LEN 116 23 24 static u64 __boot_status __initdata; 25 26 typedef bool filter_t(u64 val); 27 28 struct ftr_set_desc { 29 char name[FTR_DESC_NAME_LEN]; 30 PREL64(struct arm64_ftr_override, override); 31 struct { 32 char name[FTR_DESC_FIELD_LEN]; 33 u8 shift; 34 u8 width; 35 PREL64(filter_t, filter); 36 } fields[]; 37 }; 38 39 #define FIELD(n, s, f) { .name = n, .shift = s, .width = 4, .filter = f } 40 41 static bool __init mmfr1_vh_filter(u64 val) 42 { 43 /* 44 * If we ever reach this point while running VHE, we're 45 * guaranteed to be on one of these funky, VHE-stuck CPUs. If 46 * the user was trying to force nVHE on us, proceed with 47 * attitude adjustment. 48 */ 49 return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) && 50 val == 0); 51 } 52 53 static const struct ftr_set_desc mmfr1 __prel64_initconst = { 54 .name = "id_aa64mmfr1", 55 .override = &id_aa64mmfr1_override, 56 .fields = { 57 FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter), 58 {} 59 }, 60 }; 61 62 63 static bool __init mmfr2_varange_filter(u64 val) 64 { 65 int __maybe_unused feat; 66 67 if (val) 68 return false; 69 70 #ifdef CONFIG_ARM64_LPA2 71 feat = cpuid_feature_extract_signed_field(read_sysreg(id_aa64mmfr0_el1), 72 ID_AA64MMFR0_EL1_TGRAN_SHIFT); 73 if (feat >= ID_AA64MMFR0_EL1_TGRAN_LPA2) { 74 id_aa64mmfr0_override.val |= 75 (ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT; 76 id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT; 77 } 78 #endif 79 return true; 80 } 81 82 static const struct ftr_set_desc mmfr2 __prel64_initconst = { 83 .name = "id_aa64mmfr2", 84 .override = &id_aa64mmfr2_override, 85 .fields = { 86 FIELD("varange", ID_AA64MMFR2_EL1_VARange_SHIFT, mmfr2_varange_filter), 87 {} 88 }, 89 }; 90 91 static bool __init pfr0_sve_filter(u64 val) 92 { 93 /* 94 * Disabling SVE also means disabling all the features that 95 * are associated with it. The easiest way to do it is just to 96 * override id_aa64zfr0_el1 to be 0. 97 */ 98 if (!val) { 99 id_aa64zfr0_override.val = 0; 100 id_aa64zfr0_override.mask = GENMASK(63, 0); 101 } 102 103 return true; 104 } 105 106 static const struct ftr_set_desc pfr0 __prel64_initconst = { 107 .name = "id_aa64pfr0", 108 .override = &id_aa64pfr0_override, 109 .fields = { 110 FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter), 111 {} 112 }, 113 }; 114 115 static bool __init pfr1_sme_filter(u64 val) 116 { 117 /* 118 * Similarly to SVE, disabling SME also means disabling all 119 * the features that are associated with it. Just set 120 * id_aa64smfr0_el1 to 0 and don't look back. 121 */ 122 if (!val) { 123 id_aa64smfr0_override.val = 0; 124 id_aa64smfr0_override.mask = GENMASK(63, 0); 125 } 126 127 return true; 128 } 129 130 static const struct ftr_set_desc pfr1 __prel64_initconst = { 131 .name = "id_aa64pfr1", 132 .override = &id_aa64pfr1_override, 133 .fields = { 134 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ), 135 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL), 136 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter), 137 {} 138 }, 139 }; 140 141 static const struct ftr_set_desc isar1 __prel64_initconst = { 142 .name = "id_aa64isar1", 143 .override = &id_aa64isar1_override, 144 .fields = { 145 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL), 146 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL), 147 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL), 148 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL), 149 {} 150 }, 151 }; 152 153 static const struct ftr_set_desc isar2 __prel64_initconst = { 154 .name = "id_aa64isar2", 155 .override = &id_aa64isar2_override, 156 .fields = { 157 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL), 158 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL), 159 FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL), 160 {} 161 }, 162 }; 163 164 static const struct ftr_set_desc smfr0 __prel64_initconst = { 165 .name = "id_aa64smfr0", 166 .override = &id_aa64smfr0_override, 167 .fields = { 168 FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL), 169 /* FA64 is a one bit field... :-/ */ 170 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, }, 171 {} 172 }, 173 }; 174 175 static bool __init hvhe_filter(u64 val) 176 { 177 u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1); 178 179 return (val == 1 && 180 lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 && 181 cpuid_feature_extract_unsigned_field(mmfr1, 182 ID_AA64MMFR1_EL1_VH_SHIFT)); 183 } 184 185 static const struct ftr_set_desc sw_features __prel64_initconst = { 186 .name = "arm64_sw", 187 .override = &arm64_sw_feature_override, 188 .fields = { 189 FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL), 190 FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter), 191 FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL), 192 {} 193 }, 194 }; 195 196 static const 197 PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = { 198 { &mmfr1 }, 199 { &mmfr2 }, 200 { &pfr0 }, 201 { &pfr1 }, 202 { &isar1 }, 203 { &isar2 }, 204 { &smfr0 }, 205 { &sw_features }, 206 }; 207 208 static const struct { 209 char alias[FTR_ALIAS_NAME_LEN]; 210 char feature[FTR_ALIAS_OPTION_LEN]; 211 } aliases[] __initconst = { 212 { "kvm_arm.mode=nvhe", "id_aa64mmfr1.vh=0" }, 213 { "kvm_arm.mode=protected", "id_aa64mmfr1.vh=0" }, 214 { "arm64.nosve", "id_aa64pfr0.sve=0" }, 215 { "arm64.nosme", "id_aa64pfr1.sme=0" }, 216 { "arm64.nobti", "id_aa64pfr1.bt=0" }, 217 { "arm64.nopauth", 218 "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 " 219 "id_aa64isar1.api=0 id_aa64isar1.apa=0 " 220 "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0" }, 221 { "arm64.nomops", "id_aa64isar2.mops=0" }, 222 { "arm64.nomte", "id_aa64pfr1.mte=0" }, 223 { "nokaslr", "arm64_sw.nokaslr=1" }, 224 { "rodata=off", "arm64_sw.rodataoff=1" }, 225 { "arm64.nolva", "id_aa64mmfr2.varange=0" }, 226 }; 227 228 static int __init parse_hexdigit(const char *p, u64 *v) 229 { 230 // skip "0x" if it comes next 231 if (p[0] == '0' && tolower(p[1]) == 'x') 232 p += 2; 233 234 // check whether the RHS is a single hex digit 235 if (!isxdigit(p[0]) || (p[1] && !isspace(p[1]))) 236 return -EINVAL; 237 238 *v = tolower(*p) - (isdigit(*p) ? '0' : 'a' - 10); 239 return 0; 240 } 241 242 static int __init find_field(const char *cmdline, char *opt, int len, 243 const struct ftr_set_desc *reg, int f, u64 *v) 244 { 245 int flen = strlen(reg->fields[f].name); 246 247 // append '<fieldname>=' to obtain '<name>.<fieldname>=' 248 memcpy(opt + len, reg->fields[f].name, flen); 249 len += flen; 250 opt[len++] = '='; 251 252 if (memcmp(cmdline, opt, len)) 253 return -1; 254 255 return parse_hexdigit(cmdline + len, v); 256 } 257 258 static void __init match_options(const char *cmdline) 259 { 260 char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2]; 261 int i; 262 263 for (i = 0; i < ARRAY_SIZE(regs); i++) { 264 const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg); 265 struct arm64_ftr_override *override; 266 int len = strlen(reg->name); 267 int f; 268 269 override = prel64_pointer(reg->override); 270 271 // set opt[] to '<name>.' 272 memcpy(opt, reg->name, len); 273 opt[len++] = '.'; 274 275 for (f = 0; reg->fields[f].name[0] != '\0'; f++) { 276 u64 shift = reg->fields[f].shift; 277 u64 width = reg->fields[f].width ?: 4; 278 u64 mask = GENMASK_ULL(shift + width - 1, shift); 279 bool (*filter)(u64 val); 280 u64 v; 281 282 if (find_field(cmdline, opt, len, reg, f, &v)) 283 continue; 284 285 /* 286 * If an override gets filtered out, advertise 287 * it by setting the value to the all-ones while 288 * clearing the mask... Yes, this is fragile. 289 */ 290 filter = prel64_pointer(reg->fields[f].filter); 291 if (filter && !filter(v)) { 292 override->val |= mask; 293 override->mask &= ~mask; 294 continue; 295 } 296 297 override->val &= ~mask; 298 override->val |= (v << shift) & mask; 299 override->mask |= mask; 300 301 return; 302 } 303 } 304 } 305 306 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases) 307 { 308 do { 309 char buf[256]; 310 size_t len; 311 int i; 312 313 cmdline = skip_spaces(cmdline); 314 315 /* terminate on "--" appearing on the command line by itself */ 316 if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2])) 317 return; 318 319 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) { 320 if (len >= sizeof(buf) - 1) 321 break; 322 if (cmdline[len] == '-') 323 buf[len] = '_'; 324 else 325 buf[len] = cmdline[len]; 326 } 327 if (!len) 328 return; 329 330 buf[len] = 0; 331 332 cmdline += len; 333 334 match_options(buf); 335 336 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++) 337 if (!memcmp(buf, aliases[i].alias, len + 1)) 338 __parse_cmdline(aliases[i].feature, false); 339 } while (1); 340 } 341 342 static __init const u8 *get_bootargs_cmdline(const void *fdt, int node) 343 { 344 static char const bootargs[] __initconst = "bootargs"; 345 const u8 *prop; 346 347 if (node < 0) 348 return NULL; 349 350 prop = fdt_getprop(fdt, node, bootargs, NULL); 351 if (!prop) 352 return NULL; 353 354 return strlen(prop) ? prop : NULL; 355 } 356 357 static __init void parse_cmdline(const void *fdt, int chosen) 358 { 359 static char const cmdline[] __initconst = CONFIG_CMDLINE; 360 const u8 *prop = get_bootargs_cmdline(fdt, chosen); 361 362 if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop) 363 __parse_cmdline(cmdline, true); 364 365 if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop) 366 __parse_cmdline(prop, true); 367 } 368 369 void __init init_feature_override(u64 boot_status, const void *fdt, 370 int chosen) 371 { 372 struct arm64_ftr_override *override; 373 const struct ftr_set_desc *reg; 374 int i; 375 376 for (i = 0; i < ARRAY_SIZE(regs); i++) { 377 reg = prel64_pointer(regs[i].reg); 378 override = prel64_pointer(reg->override); 379 380 override->val = 0; 381 override->mask = 0; 382 } 383 384 __boot_status = boot_status; 385 386 parse_cmdline(fdt, chosen); 387 388 for (i = 0; i < ARRAY_SIZE(regs); i++) { 389 reg = prel64_pointer(regs[i].reg); 390 override = prel64_pointer(reg->override); 391 dcache_clean_inval_poc((unsigned long)override, 392 (unsigned long)(override + 1)); 393 } 394 } 395 396 char * __init skip_spaces(const char *str) 397 { 398 while (isspace(*str)) 399 ++str; 400 return (char *)str; 401 } 402