arch/arm64/kernel/pi/idreg-override.c

   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 const struct ftr_set_desc mmfr0 __prel64_initconst = {
  42         .name           = "id_aa64mmfr0",
  43         .override       = &id_aa64mmfr0_override,
  44         .fields         = {
  45                 FIELD("ecv", ID_AA64MMFR0_EL1_ECV_SHIFT, NULL),
  46                 {}
  47         },
  48 };
  49
  50 static bool __init mmfr1_vh_filter(u64 val)
  51 {
  52         /*
  53          * If we ever reach this point while running VHE, we're
  54          * guaranteed to be on one of these funky, VHE-stuck CPUs. If
  55          * the user was trying to force nVHE on us, proceed with
  56          * attitude adjustment.
  57          */
  58         return !(__boot_status == (BOOT_CPU_FLAG_E2H | BOOT_CPU_MODE_EL2) &&
  59                  val == 0);
  60 }
  61
  62 static const struct ftr_set_desc mmfr1 __prel64_initconst = {
  63         .name           = "id_aa64mmfr1",
  64         .override       = &id_aa64mmfr1_override,
  65         .fields         = {
  66                 FIELD("vh", ID_AA64MMFR1_EL1_VH_SHIFT, mmfr1_vh_filter),
  67                 {}
  68         },
  69 };
  70
  71
  72 static bool __init mmfr2_varange_filter(u64 val)
  73 {
  74         int __maybe_unused feat;
  75
  76         if (val)
  77                 return false;
  78
  79 #ifdef CONFIG_ARM64_LPA2
  80         feat = cpuid_feature_extract_signed_field(read_sysreg(id_aa64mmfr0_el1),
  81                                                   ID_AA64MMFR0_EL1_TGRAN_SHIFT);
  82         if (feat >= ID_AA64MMFR0_EL1_TGRAN_LPA2) {
  83                 id_aa64mmfr0_override.val |=
  84                         (ID_AA64MMFR0_EL1_TGRAN_LPA2 - 1) << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
  85                 id_aa64mmfr0_override.mask |= 0xfU << ID_AA64MMFR0_EL1_TGRAN_SHIFT;
  86         }
  87 #endif
  88         return true;
  89 }
  90
  91 static const struct ftr_set_desc mmfr2 __prel64_initconst = {
  92         .name           = "id_aa64mmfr2",
  93         .override       = &id_aa64mmfr2_override,
  94         .fields         = {
  95                 FIELD("varange", ID_AA64MMFR2_EL1_VARange_SHIFT, mmfr2_varange_filter),
  96                 {}
  97         },
  98 };
  99
 100 static bool __init pfr0_sve_filter(u64 val)
 101 {
 102         /*
 103          * Disabling SVE also means disabling all the features that
 104          * are associated with it. The easiest way to do it is just to
 105          * override id_aa64zfr0_el1 to be 0.
 106          */
 107         if (!val) {
 108                 id_aa64zfr0_override.val = 0;
 109                 id_aa64zfr0_override.mask = GENMASK(63, 0);
 110         }
 111
 112         return true;
 113 }
 114
 115 static const struct ftr_set_desc pfr0 __prel64_initconst = {
 116         .name           = "id_aa64pfr0",
 117         .override       = &id_aa64pfr0_override,
 118         .fields         = {
 119                 FIELD("sve", ID_AA64PFR0_EL1_SVE_SHIFT, pfr0_sve_filter),
 120                 FIELD("el0", ID_AA64PFR0_EL1_EL0_SHIFT, NULL),
 121                 {}
 122         },
 123 };
 124
 125 static bool __init pfr1_sme_filter(u64 val)
 126 {
 127         /*
 128          * Similarly to SVE, disabling SME also means disabling all
 129          * the features that are associated with it. Just set
 130          * id_aa64smfr0_el1 to 0 and don't look back.
 131          */
 132         if (!val) {
 133                 id_aa64smfr0_override.val = 0;
 134                 id_aa64smfr0_override.mask = GENMASK(63, 0);
 135         }
 136
 137         return true;
 138 }
 139
 140 static const struct ftr_set_desc pfr1 __prel64_initconst = {
 141         .name           = "id_aa64pfr1",
 142         .override       = &id_aa64pfr1_override,
 143         .fields         = {
 144                 FIELD("bt", ID_AA64PFR1_EL1_BT_SHIFT, NULL ),
 145                 FIELD("gcs", ID_AA64PFR1_EL1_GCS_SHIFT, NULL),
 146                 FIELD("mte", ID_AA64PFR1_EL1_MTE_SHIFT, NULL),
 147                 FIELD("sme", ID_AA64PFR1_EL1_SME_SHIFT, pfr1_sme_filter),
 148                 {}
 149         },
 150 };
 151
 152 static const struct ftr_set_desc isar1 __prel64_initconst = {
 153         .name           = "id_aa64isar1",
 154         .override       = &id_aa64isar1_override,
 155         .fields         = {
 156                 FIELD("gpi", ID_AA64ISAR1_EL1_GPI_SHIFT, NULL),
 157                 FIELD("gpa", ID_AA64ISAR1_EL1_GPA_SHIFT, NULL),
 158                 FIELD("api", ID_AA64ISAR1_EL1_API_SHIFT, NULL),
 159                 FIELD("apa", ID_AA64ISAR1_EL1_APA_SHIFT, NULL),
 160                 {}
 161         },
 162 };
 163
 164 static const struct ftr_set_desc isar2 __prel64_initconst = {
 165         .name           = "id_aa64isar2",
 166         .override       = &id_aa64isar2_override,
 167         .fields         = {
 168                 FIELD("gpa3", ID_AA64ISAR2_EL1_GPA3_SHIFT, NULL),
 169                 FIELD("apa3", ID_AA64ISAR2_EL1_APA3_SHIFT, NULL),
 170                 FIELD("mops", ID_AA64ISAR2_EL1_MOPS_SHIFT, NULL),
 171                 {}
 172         },
 173 };
 174
 175 static const struct ftr_set_desc smfr0 __prel64_initconst = {
 176         .name           = "id_aa64smfr0",
 177         .override       = &id_aa64smfr0_override,
 178         .fields         = {
 179                 FIELD("smever", ID_AA64SMFR0_EL1_SMEver_SHIFT, NULL),
 180                 /* FA64 is a one bit field... :-/ */
 181                 { "fa64", ID_AA64SMFR0_EL1_FA64_SHIFT, 1, },
 182                 {}
 183         },
 184 };
 185
 186 static bool __init hvhe_filter(u64 val)
 187 {
 188         u64 mmfr1 = read_sysreg(id_aa64mmfr1_el1);
 189
 190         return (val == 1 &&
 191                 lower_32_bits(__boot_status) == BOOT_CPU_MODE_EL2 &&
 192                 cpuid_feature_extract_unsigned_field(mmfr1,
 193                                                      ID_AA64MMFR1_EL1_VH_SHIFT));
 194 }
 195
 196 static const struct ftr_set_desc sw_features __prel64_initconst = {
 197         .name           = "arm64_sw",
 198         .override       = &arm64_sw_feature_override,
 199         .fields         = {
 200                 FIELD("nokaslr", ARM64_SW_FEATURE_OVERRIDE_NOKASLR, NULL),
 201                 FIELD("hvhe", ARM64_SW_FEATURE_OVERRIDE_HVHE, hvhe_filter),
 202                 FIELD("rodataoff", ARM64_SW_FEATURE_OVERRIDE_RODATA_OFF, NULL),
 203                 {}
 204         },
 205 };
 206
 207 static const
 208 PREL64(const struct ftr_set_desc, reg) regs[] __prel64_initconst = {
 209         { &mmfr0        },
 210         { &mmfr1        },
 211         { &mmfr2        },
 212         { &pfr0         },
 213         { &pfr1         },
 214         { &isar1        },
 215         { &isar2        },
 216         { &smfr0        },
 217         { &sw_features  },
 218 };
 219
 220 static const struct {
 221         char    alias[FTR_ALIAS_NAME_LEN];
 222         char    feature[FTR_ALIAS_OPTION_LEN];
 223 } aliases[] __initconst = {
 224         { "kvm_arm.mode=nvhe",          "arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" },
 225         { "kvm_arm.mode=protected",     "arm64_sw.hvhe=1" },
 226         { "arm64.nosve",                "id_aa64pfr0.sve=0" },
 227         { "arm64.nosme",                "id_aa64pfr1.sme=0" },
 228         { "arm64.nobti",                "id_aa64pfr1.bt=0" },
 229         { "arm64.nogcs",                "id_aa64pfr1.gcs=0" },
 230         { "arm64.nopauth",
 231           "id_aa64isar1.gpi=0 id_aa64isar1.gpa=0 "
 232           "id_aa64isar1.api=0 id_aa64isar1.apa=0 "
 233           "id_aa64isar2.gpa3=0 id_aa64isar2.apa3=0"        },
 234         { "arm64.nomops",               "id_aa64isar2.mops=0" },
 235         { "arm64.nomte",                "id_aa64pfr1.mte=0" },
 236         { "nokaslr",                    "arm64_sw.nokaslr=1" },
 237         { "rodata=off",                 "arm64_sw.rodataoff=1" },
 238         { "arm64.nolva",                "id_aa64mmfr2.varange=0" },
 239         { "arm64.no32bit_el0",          "id_aa64pfr0.el0=1" },
 240 };
 241
 242 static int __init parse_hexdigit(const char *p, u64 *v)
 243 {
 244         // skip "0x" if it comes next
 245         if (p[0] == '0' && tolower(p[1]) == 'x')
 246                 p += 2;
 247
 248         // check whether the RHS is a single hex digit
 249         if (!isxdigit(p[0]) || (p[1] && !isspace(p[1])))
 250                 return -EINVAL;
 251
 252         *v = tolower(*p) - (isdigit(*p) ? '0' : 'a' - 10);
 253         return 0;
 254 }
 255
 256 static int __init find_field(const char *cmdline, char *opt, int len,
 257                              const struct ftr_set_desc *reg, int f, u64 *v)
 258 {
 259         int flen = strlen(reg->fields[f].name);
 260
 261         // append '<fieldname>=' to obtain '<name>.<fieldname>='
 262         memcpy(opt + len, reg->fields[f].name, flen);
 263         len += flen;
 264         opt[len++] = '=';
 265
 266         if (memcmp(cmdline, opt, len))
 267                 return -1;
 268
 269         return parse_hexdigit(cmdline + len, v);
 270 }
 271
 272 static void __init match_options(const char *cmdline)
 273 {
 274         char opt[FTR_DESC_NAME_LEN + FTR_DESC_FIELD_LEN + 2];
 275         int i;
 276
 277         for (i = 0; i < ARRAY_SIZE(regs); i++) {
 278                 const struct ftr_set_desc *reg = prel64_pointer(regs[i].reg);
 279                 struct arm64_ftr_override *override;
 280                 int len = strlen(reg->name);
 281                 int f;
 282
 283                 override = prel64_pointer(reg->override);
 284
 285                 // set opt[] to '<name>.'
 286                 memcpy(opt, reg->name, len);
 287                 opt[len++] = '.';
 288
 289                 for (f = 0; reg->fields[f].name[0] != '\0'; f++) {
 290                         u64 shift = reg->fields[f].shift;
 291                         u64 width = reg->fields[f].width ?: 4;
 292                         u64 mask = GENMASK_ULL(shift + width - 1, shift);
 293                         bool (*filter)(u64 val);
 294                         u64 v;
 295
 296                         if (find_field(cmdline, opt, len, reg, f, &v))
 297                                 continue;
 298
 299                         /*
 300                          * If an override gets filtered out, advertise
 301                          * it by setting the value to the all-ones while
 302                          * clearing the mask... Yes, this is fragile.
 303                          */
 304                         filter = prel64_pointer(reg->fields[f].filter);
 305                         if (filter && !filter(v)) {
 306                                 override->val  |= mask;
 307                                 override->mask &= ~mask;
 308                                 continue;
 309                         }
 310
 311                         override->val  &= ~mask;
 312                         override->val  |= (v << shift) & mask;
 313                         override->mask |= mask;
 314
 315                         return;
 316                 }
 317         }
 318 }
 319
 320 static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 321 {
 322         do {
 323                 char buf[256];
 324                 size_t len;
 325                 int i;
 326
 327                 cmdline = skip_spaces(cmdline);
 328
 329                 /* terminate on "--" appearing on the command line by itself */
 330                 if (cmdline[0] == '-' && cmdline[1] == '-' && isspace(cmdline[2]))
 331                         return;
 332
 333                 for (len = 0; cmdline[len] && !isspace(cmdline[len]); len++) {
 334                         if (len >= sizeof(buf) - 1)
 335                                 break;
 336                         if (cmdline[len] == '-')
 337                                 buf[len] = '_';
 338                         else
 339                                 buf[len] = cmdline[len];
 340                 }
 341                 if (!len)
 342                         return;
 343
 344                 buf[len] = 0;
 345
 346                 cmdline += len;
 347
 348                 match_options(buf);
 349
 350                 for (i = 0; parse_aliases && i < ARRAY_SIZE(aliases); i++)
 351                         if (!memcmp(buf, aliases[i].alias, len + 1))
 352                                 __parse_cmdline(aliases[i].feature, false);
 353         } while (1);
 354 }
 355
 356 static __init const u8 *get_bootargs_cmdline(const void *fdt, int node)
 357 {
 358         static char const bootargs[] __initconst = "bootargs";
 359         const u8 *prop;
 360
 361         if (node < 0)
 362                 return NULL;
 363
 364         prop = fdt_getprop(fdt, node, bootargs, NULL);
 365         if (!prop)
 366                 return NULL;
 367
 368         return strlen(prop) ? prop : NULL;
 369 }
 370
 371 static __init void parse_cmdline(const void *fdt, int chosen)
 372 {
 373         static char const cmdline[] __initconst = CONFIG_CMDLINE;
 374         const u8 *prop = get_bootargs_cmdline(fdt, chosen);
 375
 376         if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
 377                 __parse_cmdline(cmdline, true);
 378
 379         if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
 380                 __parse_cmdline(prop, true);
 381 }
 382
 383 void __init init_feature_override(u64 boot_status, const void *fdt,
 384                                   int chosen)
 385 {
 386         struct arm64_ftr_override *override;
 387         const struct ftr_set_desc *reg;
 388         int i;
 389
 390         for (i = 0; i < ARRAY_SIZE(regs); i++) {
 391                 reg = prel64_pointer(regs[i].reg);
 392                 override = prel64_pointer(reg->override);
 393
 394                 override->val  = 0;
 395                 override->mask = 0;
 396         }
 397
 398         __boot_status = boot_status;
 399
 400         parse_cmdline(fdt, chosen);
 401
 402         for (i = 0; i < ARRAY_SIZE(regs); i++) {
 403                 reg = prel64_pointer(regs[i].reg);
 404                 override = prel64_pointer(reg->override);
 405                 dcache_clean_inval_poc((unsigned long)override,
 406                                        (unsigned long)(override + 1));
 407         }
 408 }
 409
 410 char * __init skip_spaces(const char *str)
 411 {
 412         while (isspace(*str))
 413                 ++str;
 414         return (char *)str;
 415 }