arch/x86/kernel/fpu/xstate.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * xsave/xrstor support.
   4  *
   5  * Author: Suresh Siddha <suresh.b.siddha@intel.com>
   6  */
   7 #include <linux/compat.h>
   8 #include <linux/cpu.h>
   9 #include <linux/mman.h>
  10 #include <linux/pkeys.h>
  11 #include <linux/seq_file.h>
  12 #include <linux/proc_fs.h>
  13
  14 #include <asm/fpu/api.h>
  15 #include <asm/fpu/internal.h>
  16 #include <asm/fpu/signal.h>
  17 #include <asm/fpu/regset.h>
  18 #include <asm/fpu/xstate.h>
  19
  20 #include <asm/tlbflush.h>
  21 #include <asm/cpufeature.h>
  22
  23 /*
  24  * Although we spell it out in here, the Processor Trace
  25  * xfeature is completely unused.  We use other mechanisms
  26  * to save/restore PT state in Linux.
  27  */
  28 static const char *xfeature_names[] =
  29 {
  30         "x87 floating point registers"  ,
  31         "SSE registers"                 ,
  32         "AVX registers"                 ,
  33         "MPX bounds registers"          ,
  34         "MPX CSR"                       ,
  35         "AVX-512 opmask"                ,
  36         "AVX-512 Hi256"                 ,
  37         "AVX-512 ZMM_Hi256"             ,
  38         "Processor Trace (unused)"      ,
  39         "Protection Keys User registers",
  40         "unknown xstate feature"        ,
  41 };
  42
  43 static short xsave_cpuid_features[] __initdata = {
  44         X86_FEATURE_FPU,
  45         X86_FEATURE_XMM,
  46         X86_FEATURE_AVX,
  47         X86_FEATURE_MPX,
  48         X86_FEATURE_MPX,
  49         X86_FEATURE_AVX512F,
  50         X86_FEATURE_AVX512F,
  51         X86_FEATURE_AVX512F,
  52         X86_FEATURE_INTEL_PT,
  53         X86_FEATURE_PKU,
  54 };
  55
  56 /*
  57  * Mask of xstate features supported by the CPU and the kernel:
  58  */
  59 u64 xfeatures_mask __read_mostly;
  60
  61 static unsigned int xstate_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
  62 static unsigned int xstate_sizes[XFEATURE_MAX]   = { [ 0 ... XFEATURE_MAX - 1] = -1};
  63 static unsigned int xstate_comp_offsets[XFEATURE_MAX] = { [ 0 ... XFEATURE_MAX - 1] = -1};
  64
  65 /*
  66  * The XSAVE area of kernel can be in standard or compacted format;
  67  * it is always in standard format for user mode. This is the user
  68  * mode standard format size used for signal and ptrace frames.
  69  */
  70 unsigned int fpu_user_xstate_size;
  71
  72 /*
  73  * Return whether the system supports a given xfeature.
  74  *
  75  * Also return the name of the (most advanced) feature that the caller requested:
  76  */
  77 int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name)
  78 {
  79         u64 xfeatures_missing = xfeatures_needed & ~xfeatures_mask;
  80
  81         if (unlikely(feature_name)) {
  82                 long xfeature_idx, max_idx;
  83                 u64 xfeatures_print;
  84                 /*
  85                  * So we use FLS here to be able to print the most advanced
  86                  * feature that was requested but is missing. So if a driver
  87                  * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the
  88                  * missing AVX feature - this is the most informative message
  89                  * to users:
  90                  */
  91                 if (xfeatures_missing)
  92                         xfeatures_print = xfeatures_missing;
  93                 else
  94                         xfeatures_print = xfeatures_needed;
  95
  96                 xfeature_idx = fls64(xfeatures_print)-1;
  97                 max_idx = ARRAY_SIZE(xfeature_names)-1;
  98                 xfeature_idx = min(xfeature_idx, max_idx);
  99
 100                 *feature_name = xfeature_names[xfeature_idx];
 101         }
 102
 103         if (xfeatures_missing)
 104                 return 0;
 105
 106         return 1;
 107 }
 108 EXPORT_SYMBOL_GPL(cpu_has_xfeatures);
 109
 110 static bool xfeature_is_supervisor(int xfeature_nr)
 111 {
 112         /*
 113          * Extended State Enumeration Sub-leaves (EAX = 0DH, ECX = n, n > 1)
 114          * returns ECX[0] set to (1) for a supervisor state, and cleared (0)
 115          * for a user state.
 116          */
 117         u32 eax, ebx, ecx, edx;
 118
 119         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 120         return ecx & 1;
 121 }
 122
 123 static bool xfeature_is_user(int xfeature_nr)
 124 {
 125         return !xfeature_is_supervisor(xfeature_nr);
 126 }
 127
 128 /*
 129  * When executing XSAVEOPT (or other optimized XSAVE instructions), if
 130  * a processor implementation detects that an FPU state component is still
 131  * (or is again) in its initialized state, it may clear the corresponding
 132  * bit in the header.xfeatures field, and can skip the writeout of registers
 133  * to the corresponding memory layout.
 134  *
 135  * This means that when the bit is zero, the state component might still contain
 136  * some previous - non-initialized register state.
 137  *
 138  * Before writing xstate information to user-space we sanitize those components,
 139  * to always ensure that the memory layout of a feature will be in the init state
 140  * if the corresponding header bit is zero. This is to ensure that user-space doesn't
 141  * see some stale state in the memory layout during signal handling, debugging etc.
 142  */
 143 void fpstate_sanitize_xstate(struct fpu *fpu)
 144 {
 145         struct fxregs_state *fx = &fpu->state.fxsave;
 146         int feature_bit;
 147         u64 xfeatures;
 148
 149         if (!use_xsaveopt())
 150                 return;
 151
 152         xfeatures = fpu->state.xsave.header.xfeatures;
 153
 154         /*
 155          * None of the feature bits are in init state. So nothing else
 156          * to do for us, as the memory layout is up to date.
 157          */
 158         if ((xfeatures & xfeatures_mask) == xfeatures_mask)
 159                 return;
 160
 161         /*
 162          * FP is in init state
 163          */
 164         if (!(xfeatures & XFEATURE_MASK_FP)) {
 165                 fx->cwd = 0x37f;
 166                 fx->swd = 0;
 167                 fx->twd = 0;
 168                 fx->fop = 0;
 169                 fx->rip = 0;
 170                 fx->rdp = 0;
 171                 memset(&fx->st_space[0], 0, 128);
 172         }
 173
 174         /*
 175          * SSE is in init state
 176          */
 177         if (!(xfeatures & XFEATURE_MASK_SSE))
 178                 memset(&fx->xmm_space[0], 0, 256);
 179
 180         /*
 181          * First two features are FPU and SSE, which above we handled
 182          * in a special way already:
 183          */
 184         feature_bit = 0x2;
 185         xfeatures = (xfeatures_mask & ~xfeatures) >> 2;
 186
 187         /*
 188          * Update all the remaining memory layouts according to their
 189          * standard xstate layout, if their header bit is in the init
 190          * state:
 191          */
 192         while (xfeatures) {
 193                 if (xfeatures & 0x1) {
 194                         int offset = xstate_comp_offsets[feature_bit];
 195                         int size = xstate_sizes[feature_bit];
 196
 197                         memcpy((void *)fx + offset,
 198                                (void *)&init_fpstate.xsave + offset,
 199                                size);
 200                 }
 201
 202                 xfeatures >>= 1;
 203                 feature_bit++;
 204         }
 205 }
 206
 207 /*
 208  * Enable the extended processor state save/restore feature.
 209  * Called once per CPU onlining.
 210  */
 211 void fpu__init_cpu_xstate(void)
 212 {
 213         if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
 214                 return;
 215         /*
 216          * Make it clear that XSAVES supervisor states are not yet
 217          * implemented should anyone expect it to work by changing
 218          * bits in XFEATURE_MASK_* macros and XCR0.
 219          */
 220         WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
 221                 "x86/fpu: XSAVES supervisor states are not yet implemented.\n");
 222
 223         xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;
 224
 225         cr4_set_bits(X86_CR4_OSXSAVE);
 226         xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 227 }
 228
 229 /*
 230  * Note that in the future we will likely need a pair of
 231  * functions here: one for user xstates and the other for
 232  * system xstates.  For now, they are the same.
 233  */
 234 static int xfeature_enabled(enum xfeature xfeature)
 235 {
 236         return !!(xfeatures_mask & (1UL << xfeature));
 237 }
 238
 239 /*
 240  * Record the offsets and sizes of various xstates contained
 241  * in the XSAVE state memory layout.
 242  */
 243 static void __init setup_xstate_features(void)
 244 {
 245         u32 eax, ebx, ecx, edx, i;
 246         /* start at the beginnning of the "extended state" */
 247         unsigned int last_good_offset = offsetof(struct xregs_state,
 248                                                  extended_state_area);
 249         /*
 250          * The FP xstates and SSE xstates are legacy states. They are always
 251          * in the fixed offsets in the xsave area in either compacted form
 252          * or standard form.
 253          */
 254         xstate_offsets[XFEATURE_FP]     = 0;
 255         xstate_sizes[XFEATURE_FP]       = offsetof(struct fxregs_state,
 256                                                    xmm_space);
 257
 258         xstate_offsets[XFEATURE_SSE]    = xstate_sizes[XFEATURE_FP];
 259         xstate_sizes[XFEATURE_SSE]      = sizeof_field(struct fxregs_state,
 260                                                        xmm_space);
 261
 262         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 263                 if (!xfeature_enabled(i))
 264                         continue;
 265
 266                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 267
 268                 /*
 269                  * If an xfeature is supervisor state, the offset
 270                  * in EBX is invalid. We leave it to -1.
 271                  */
 272                 if (xfeature_is_user(i))
 273                         xstate_offsets[i] = ebx;
 274
 275                 xstate_sizes[i] = eax;
 276                 /*
 277                  * In our xstate size checks, we assume that the
 278                  * highest-numbered xstate feature has the
 279                  * highest offset in the buffer.  Ensure it does.
 280                  */
 281                 WARN_ONCE(last_good_offset > xstate_offsets[i],
 282                         "x86/fpu: misordered xstate at %d\n", last_good_offset);
 283                 last_good_offset = xstate_offsets[i];
 284         }
 285 }
 286
 287 static void __init print_xstate_feature(u64 xstate_mask)
 288 {
 289         const char *feature_name;
 290
 291         if (cpu_has_xfeatures(xstate_mask, &feature_name))
 292                 pr_info("x86/fpu: Supporting XSAVE feature 0x%03Lx: '%s'\n", xstate_mask, feature_name);
 293 }
 294
 295 /*
 296  * Print out all the supported xstate features:
 297  */
 298 static void __init print_xstate_features(void)
 299 {
 300         print_xstate_feature(XFEATURE_MASK_FP);
 301         print_xstate_feature(XFEATURE_MASK_SSE);
 302         print_xstate_feature(XFEATURE_MASK_YMM);
 303         print_xstate_feature(XFEATURE_MASK_BNDREGS);
 304         print_xstate_feature(XFEATURE_MASK_BNDCSR);
 305         print_xstate_feature(XFEATURE_MASK_OPMASK);
 306         print_xstate_feature(XFEATURE_MASK_ZMM_Hi256);
 307         print_xstate_feature(XFEATURE_MASK_Hi16_ZMM);
 308         print_xstate_feature(XFEATURE_MASK_PKRU);
 309 }
 310
 311 /*
 312  * This check is important because it is easy to get XSTATE_*
 313  * confused with XSTATE_BIT_*.
 314  */
 315 #define CHECK_XFEATURE(nr) do {         \
 316         WARN_ON(nr < FIRST_EXTENDED_XFEATURE);  \
 317         WARN_ON(nr >= XFEATURE_MAX);    \
 318 } while (0)
 319
 320 /*
 321  * We could cache this like xstate_size[], but we only use
 322  * it here, so it would be a waste of space.
 323  */
 324 static int xfeature_is_aligned(int xfeature_nr)
 325 {
 326         u32 eax, ebx, ecx, edx;
 327
 328         CHECK_XFEATURE(xfeature_nr);
 329         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 330         /*
 331          * The value returned by ECX[1] indicates the alignment
 332          * of state component 'i' when the compacted format
 333          * of the extended region of an XSAVE area is used:
 334          */
 335         return !!(ecx & 2);
 336 }
 337
 338 /*
 339  * This function sets up offsets and sizes of all extended states in
 340  * xsave area. This supports both standard format and compacted format
 341  * of the xsave aread.
 342  */
 343 static void __init setup_xstate_comp(void)
 344 {
 345         unsigned int xstate_comp_sizes[XFEATURE_MAX];
 346         int i;
 347
 348         /*
 349          * The FP xstates and SSE xstates are legacy states. They are always
 350          * in the fixed offsets in the xsave area in either compacted form
 351          * or standard form.
 352          */
 353         xstate_comp_offsets[XFEATURE_FP] = 0;
 354         xstate_comp_offsets[XFEATURE_SSE] = offsetof(struct fxregs_state,
 355                                                      xmm_space);
 356
 357         if (!boot_cpu_has(X86_FEATURE_XSAVES)) {
 358                 for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 359                         if (xfeature_enabled(i)) {
 360                                 xstate_comp_offsets[i] = xstate_offsets[i];
 361                                 xstate_comp_sizes[i] = xstate_sizes[i];
 362                         }
 363                 }
 364                 return;
 365         }
 366
 367         xstate_comp_offsets[FIRST_EXTENDED_XFEATURE] =
 368                 FXSAVE_SIZE + XSAVE_HDR_SIZE;
 369
 370         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 371                 if (xfeature_enabled(i))
 372                         xstate_comp_sizes[i] = xstate_sizes[i];
 373                 else
 374                         xstate_comp_sizes[i] = 0;
 375
 376                 if (i > FIRST_EXTENDED_XFEATURE) {
 377                         xstate_comp_offsets[i] = xstate_comp_offsets[i-1]
 378                                         + xstate_comp_sizes[i-1];
 379
 380                         if (xfeature_is_aligned(i))
 381                                 xstate_comp_offsets[i] =
 382                                         ALIGN(xstate_comp_offsets[i], 64);
 383                 }
 384         }
 385 }
 386
 387 /*
 388  * Print out xstate component offsets and sizes
 389  */
 390 static void __init print_xstate_offset_size(void)
 391 {
 392         int i;
 393
 394         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 395                 if (!xfeature_enabled(i))
 396                         continue;
 397                 pr_info("x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n",
 398                          i, xstate_comp_offsets[i], i, xstate_sizes[i]);
 399         }
 400 }
 401
 402 /*
 403  * setup the xstate image representing the init state
 404  */
 405 static void __init setup_init_fpu_buf(void)
 406 {
 407         static int on_boot_cpu __initdata = 1;
 408
 409         WARN_ON_FPU(!on_boot_cpu);
 410         on_boot_cpu = 0;
 411
 412         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 413                 return;
 414
 415         setup_xstate_features();
 416         print_xstate_features();
 417
 418         if (boot_cpu_has(X86_FEATURE_XSAVES))
 419                 init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT |
 420                                                      xfeatures_mask;
 421
 422         /*
 423          * Init all the features state with header.xfeatures being 0x0
 424          */
 425         copy_kernel_to_xregs_booting(&init_fpstate.xsave);
 426
 427         /*
 428          * Dump the init state again. This is to identify the init state
 429          * of any feature which is not represented by all zero's.
 430          */
 431         copy_xregs_to_kernel_booting(&init_fpstate.xsave);
 432 }
 433
 434 static int xfeature_uncompacted_offset(int xfeature_nr)
 435 {
 436         u32 eax, ebx, ecx, edx;
 437
 438         /*
 439          * Only XSAVES supports supervisor states and it uses compacted
 440          * format. Checking a supervisor state's uncompacted offset is
 441          * an error.
 442          */
 443         if (XFEATURE_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
 444                 WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
 445                 return -1;
 446         }
 447
 448         CHECK_XFEATURE(xfeature_nr);
 449         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 450         return ebx;
 451 }
 452
 453 static int xfeature_size(int xfeature_nr)
 454 {
 455         u32 eax, ebx, ecx, edx;
 456
 457         CHECK_XFEATURE(xfeature_nr);
 458         cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx);
 459         return eax;
 460 }
 461
 462 /*
 463  * 'XSAVES' implies two different things:
 464  * 1. saving of supervisor/system state
 465  * 2. using the compacted format
 466  *
 467  * Use this function when dealing with the compacted format so
 468  * that it is obvious which aspect of 'XSAVES' is being handled
 469  * by the calling code.
 470  */
 471 int using_compacted_format(void)
 472 {
 473         return boot_cpu_has(X86_FEATURE_XSAVES);
 474 }
 475
 476 /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */
 477 int validate_xstate_header(const struct xstate_header *hdr)
 478 {
 479         /* No unknown or supervisor features may be set */
 480         if (hdr->xfeatures & (~xfeatures_mask | XFEATURE_MASK_SUPERVISOR))
 481                 return -EINVAL;
 482
 483         /* Userspace must use the uncompacted format */
 484         if (hdr->xcomp_bv)
 485                 return -EINVAL;
 486
 487         /*
 488          * If 'reserved' is shrunken to add a new field, make sure to validate
 489          * that new field here!
 490          */
 491         BUILD_BUG_ON(sizeof(hdr->reserved) != 48);
 492
 493         /* No reserved bits may be set */
 494         if (memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved)))
 495                 return -EINVAL;
 496
 497         return 0;
 498 }
 499
 500 static void __xstate_dump_leaves(void)
 501 {
 502         int i;
 503         u32 eax, ebx, ecx, edx;
 504         static int should_dump = 1;
 505
 506         if (!should_dump)
 507                 return;
 508         should_dump = 0;
 509         /*
 510          * Dump out a few leaves past the ones that we support
 511          * just in case there are some goodies up there
 512          */
 513         for (i = 0; i < XFEATURE_MAX + 10; i++) {
 514                 cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx);
 515                 pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n",
 516                         XSTATE_CPUID, i, eax, ebx, ecx, edx);
 517         }
 518 }
 519
 520 #define XSTATE_WARN_ON(x) do {                                                  \
 521         if (WARN_ONCE(x, "XSAVE consistency problem, dumping leaves")) {        \
 522                 __xstate_dump_leaves();                                         \
 523         }                                                                       \
 524 } while (0)
 525
 526 #define XCHECK_SZ(sz, nr, nr_macro, __struct) do {                      \
 527         if ((nr == nr_macro) &&                                         \
 528             WARN_ONCE(sz != sizeof(__struct),                           \
 529                 "%s: struct is %zu bytes, cpu state %d bytes\n",        \
 530                 __stringify(nr_macro), sizeof(__struct), sz)) {         \
 531                 __xstate_dump_leaves();                                 \
 532         }                                                               \
 533 } while (0)
 534
 535 /*
 536  * We have a C struct for each 'xstate'.  We need to ensure
 537  * that our software representation matches what the CPU
 538  * tells us about the state's size.
 539  */
 540 static void check_xstate_against_struct(int nr)
 541 {
 542         /*
 543          * Ask the CPU for the size of the state.
 544          */
 545         int sz = xfeature_size(nr);
 546         /*
 547          * Match each CPU state with the corresponding software
 548          * structure.
 549          */
 550         XCHECK_SZ(sz, nr, XFEATURE_YMM,       struct ymmh_struct);
 551         XCHECK_SZ(sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
 552         XCHECK_SZ(sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
 553         XCHECK_SZ(sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
 554         XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
 555         XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
 556         XCHECK_SZ(sz, nr, XFEATURE_PKRU,      struct pkru_state);
 557
 558         /*
 559          * Make *SURE* to add any feature numbers in below if
 560          * there are "holes" in the xsave state component
 561          * numbers.
 562          */
 563         if ((nr < XFEATURE_YMM) ||
 564             (nr >= XFEATURE_MAX) ||
 565             (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR)) {
 566                 WARN_ONCE(1, "no structure for xstate: %d\n", nr);
 567                 XSTATE_WARN_ON(1);
 568         }
 569 }
 570
 571 /*
 572  * This essentially double-checks what the cpu told us about
 573  * how large the XSAVE buffer needs to be.  We are recalculating
 574  * it to be safe.
 575  */
 576 static void do_extra_xstate_size_checks(void)
 577 {
 578         int paranoid_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE;
 579         int i;
 580
 581         for (i = FIRST_EXTENDED_XFEATURE; i < XFEATURE_MAX; i++) {
 582                 if (!xfeature_enabled(i))
 583                         continue;
 584
 585                 check_xstate_against_struct(i);
 586                 /*
 587                  * Supervisor state components can be managed only by
 588                  * XSAVES, which is compacted-format only.
 589                  */
 590                 if (!using_compacted_format())
 591                         XSTATE_WARN_ON(xfeature_is_supervisor(i));
 592
 593                 /* Align from the end of the previous feature */
 594                 if (xfeature_is_aligned(i))
 595                         paranoid_xstate_size = ALIGN(paranoid_xstate_size, 64);
 596                 /*
 597                  * The offset of a given state in the non-compacted
 598                  * format is given to us in a CPUID leaf.  We check
 599                  * them for being ordered (increasing offsets) in
 600                  * setup_xstate_features().
 601                  */
 602                 if (!using_compacted_format())
 603                         paranoid_xstate_size = xfeature_uncompacted_offset(i);
 604                 /*
 605                  * The compacted-format offset always depends on where
 606                  * the previous state ended.
 607                  */
 608                 paranoid_xstate_size += xfeature_size(i);
 609         }
 610         XSTATE_WARN_ON(paranoid_xstate_size != fpu_kernel_xstate_size);
 611 }
 612
 613
 614 /*
 615  * Get total size of enabled xstates in XCR0/xfeatures_mask.
 616  *
 617  * Note the SDM's wording here.  "sub-function 0" only enumerates
 618  * the size of the *user* states.  If we use it to size a buffer
 619  * that we use 'XSAVES' on, we could potentially overflow the
 620  * buffer because 'XSAVES' saves system states too.
 621  *
 622  * Note that we do not currently set any bits on IA32_XSS so
 623  * 'XCR0 | IA32_XSS == XCR0' for now.
 624  */
 625 static unsigned int __init get_xsaves_size(void)
 626 {
 627         unsigned int eax, ebx, ecx, edx;
 628         /*
 629          * - CPUID function 0DH, sub-function 1:
 630          *    EBX enumerates the size (in bytes) required by
 631          *    the XSAVES instruction for an XSAVE area
 632          *    containing all the state components
 633          *    corresponding to bits currently set in
 634          *    XCR0 | IA32_XSS.
 635          */
 636         cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx);
 637         return ebx;
 638 }
 639
 640 static unsigned int __init get_xsave_size(void)
 641 {
 642         unsigned int eax, ebx, ecx, edx;
 643         /*
 644          * - CPUID function 0DH, sub-function 0:
 645          *    EBX enumerates the size (in bytes) required by
 646          *    the XSAVE instruction for an XSAVE area
 647          *    containing all the *user* state components
 648          *    corresponding to bits currently set in XCR0.
 649          */
 650         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 651         return ebx;
 652 }
 653
 654 /*
 655  * Will the runtime-enumerated 'xstate_size' fit in the init
 656  * task's statically-allocated buffer?
 657  */
 658 static bool is_supported_xstate_size(unsigned int test_xstate_size)
 659 {
 660         if (test_xstate_size <= sizeof(union fpregs_state))
 661                 return true;
 662
 663         pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n",
 664                         sizeof(union fpregs_state), test_xstate_size);
 665         return false;
 666 }
 667
 668 static int __init init_xstate_size(void)
 669 {
 670         /* Recompute the context size for enabled features: */
 671         unsigned int possible_xstate_size;
 672         unsigned int xsave_size;
 673
 674         xsave_size = get_xsave_size();
 675
 676         if (boot_cpu_has(X86_FEATURE_XSAVES))
 677                 possible_xstate_size = get_xsaves_size();
 678         else
 679                 possible_xstate_size = xsave_size;
 680
 681         /* Ensure we have the space to store all enabled: */
 682         if (!is_supported_xstate_size(possible_xstate_size))
 683                 return -EINVAL;
 684
 685         /*
 686          * The size is OK, we are definitely going to use xsave,
 687          * make it known to the world that we need more space.
 688          */
 689         fpu_kernel_xstate_size = possible_xstate_size;
 690         do_extra_xstate_size_checks();
 691
 692         /*
 693          * User space is always in standard format.
 694          */
 695         fpu_user_xstate_size = xsave_size;
 696         return 0;
 697 }
 698
 699 /*
 700  * We enabled the XSAVE hardware, but something went wrong and
 701  * we can not use it.  Disable it.
 702  */
 703 static void fpu__init_disable_system_xstate(void)
 704 {
 705         xfeatures_mask = 0;
 706         cr4_clear_bits(X86_CR4_OSXSAVE);
 707         setup_clear_cpu_cap(X86_FEATURE_XSAVE);
 708 }
 709
 710 /*
 711  * Enable and initialize the xsave feature.
 712  * Called once per system bootup.
 713  */
 714 void __init fpu__init_system_xstate(void)
 715 {
 716         unsigned int eax, ebx, ecx, edx;
 717         static int on_boot_cpu __initdata = 1;
 718         int err;
 719         int i;
 720
 721         WARN_ON_FPU(!on_boot_cpu);
 722         on_boot_cpu = 0;
 723
 724         if (!boot_cpu_has(X86_FEATURE_FPU)) {
 725                 pr_info("x86/fpu: No FPU detected\n");
 726                 return;
 727         }
 728
 729         if (!boot_cpu_has(X86_FEATURE_XSAVE)) {
 730                 pr_info("x86/fpu: x87 FPU will use %s\n",
 731                         boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE");
 732                 return;
 733         }
 734
 735         if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
 736                 WARN_ON_FPU(1);
 737                 return;
 738         }
 739
 740         cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
 741         xfeatures_mask = eax + ((u64)edx << 32);
 742
 743         if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) {
 744                 /*
 745                  * This indicates that something really unexpected happened
 746                  * with the enumeration.  Disable XSAVE and try to continue
 747                  * booting without it.  This is too early to BUG().
 748                  */
 749                 pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask);
 750                 goto out_disable;
 751         }
 752
 753         /*
 754          * Clear XSAVE features that are disabled in the normal CPUID.
 755          */
 756         for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) {
 757                 if (!boot_cpu_has(xsave_cpuid_features[i]))
 758                         xfeatures_mask &= ~BIT(i);
 759         }
 760
 761         xfeatures_mask &= fpu__get_supported_xfeatures_mask();
 762
 763         /* Enable xstate instructions to be able to continue with initialization: */
 764         fpu__init_cpu_xstate();
 765         err = init_xstate_size();
 766         if (err)
 767                 goto out_disable;
 768
 769         /*
 770          * Update info used for ptrace frames; use standard-format size and no
 771          * supervisor xstates:
 772          */
 773         update_regset_xstate_info(fpu_user_xstate_size, xfeatures_mask & ~XFEATURE_MASK_SUPERVISOR);
 774
 775         fpu__init_prepare_fx_sw_frame();
 776         setup_init_fpu_buf();
 777         setup_xstate_comp();
 778         print_xstate_offset_size();
 779
 780         pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n",
 781                 xfeatures_mask,
 782                 fpu_kernel_xstate_size,
 783                 boot_cpu_has(X86_FEATURE_XSAVES) ? "compacted" : "standard");
 784         return;
 785
 786 out_disable:
 787         /* something went wrong, try to boot without any XSAVE support */
 788         fpu__init_disable_system_xstate();
 789 }
 790
 791 /*
 792  * Restore minimal FPU state after suspend:
 793  */
 794 void fpu__resume_cpu(void)
 795 {
 796         /*
 797          * Restore XCR0 on xsave capable CPUs:
 798          */
 799         if (boot_cpu_has(X86_FEATURE_XSAVE))
 800                 xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
 801 }
 802
 803 /*
 804  * Given an xstate feature nr, calculate where in the xsave
 805  * buffer the state is.  Callers should ensure that the buffer
 806  * is valid.
 807  */
 808 static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 809 {
 810         if (!xfeature_enabled(xfeature_nr)) {
 811                 WARN_ON_FPU(1);
 812                 return NULL;
 813         }
 814
 815         return (void *)xsave + xstate_comp_offsets[xfeature_nr];
 816 }
 817 /*
 818  * Given the xsave area and a state inside, this function returns the
 819  * address of the state.
 820  *
 821  * This is the API that is called to get xstate address in either
 822  * standard format or compacted format of xsave area.
 823  *
 824  * Note that if there is no data for the field in the xsave buffer
 825  * this will return NULL.
 826  *
 827  * Inputs:
 828  *      xstate: the thread's storage area for all FPU data
 829  *      xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
 830  *      XFEATURE_SSE, etc...)
 831  * Output:
 832  *      address of the state in the xsave area, or NULL if the
 833  *      field is not present in the xsave buffer.
 834  */
 835 void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 836 {
 837         /*
 838          * Do we even *have* xsave state?
 839          */
 840         if (!boot_cpu_has(X86_FEATURE_XSAVE))
 841                 return NULL;
 842
 843         /*
 844          * We should not ever be requesting features that we
 845          * have not enabled.  Remember that xfeatures_mask is
 846          * what we write to the XCR0 register.
 847          */
 848         WARN_ONCE(!(xfeatures_mask & BIT_ULL(xfeature_nr)),
 849                   "get of unsupported state");
 850         /*
 851          * This assumes the last 'xsave*' instruction to
 852          * have requested that 'xfeature_nr' be saved.
 853          * If it did not, we might be seeing and old value
 854          * of the field in the buffer.
 855          *
 856          * This can happen because the last 'xsave' did not
 857          * request that this feature be saved (unlikely)
 858          * or because the "init optimization" caused it
 859          * to not be saved.
 860          */
 861         if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr)))
 862                 return NULL;
 863
 864         return __raw_xsave_addr(xsave, xfeature_nr);
 865 }
 866 EXPORT_SYMBOL_GPL(get_xsave_addr);
 867
 868 /*
 869  * This wraps up the common operations that need to occur when retrieving
 870  * data from xsave state.  It first ensures that the current task was
 871  * using the FPU and retrieves the data in to a buffer.  It then calculates
 872  * the offset of the requested field in the buffer.
 873  *
 874  * This function is safe to call whether the FPU is in use or not.
 875  *
 876  * Note that this only works on the current task.
 877  *
 878  * Inputs:
 879  *      @xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
 880  *      XFEATURE_SSE, etc...)
 881  * Output:
 882  *      address of the state in the xsave area or NULL if the state
 883  *      is not present or is in its 'init state'.
 884  */
 885 const void *get_xsave_field_ptr(int xfeature_nr)
 886 {
 887         struct fpu *fpu = &current->thread.fpu;
 888
 889         /*
 890          * fpu__save() takes the CPU's xstate registers
 891          * and saves them off to the 'fpu memory buffer.
 892          */
 893         fpu__save(fpu);
 894
 895         return get_xsave_addr(&fpu->state.xsave, xfeature_nr);
 896 }
 897
 898 #ifdef CONFIG_ARCH_HAS_PKEYS
 899
 900 #define NR_VALID_PKRU_BITS (CONFIG_NR_PROTECTION_KEYS * 2)
 901 #define PKRU_VALID_MASK (NR_VALID_PKRU_BITS - 1)
 902 /*
 903  * This will go out and modify PKRU register to set the access
 904  * rights for @pkey to @init_val.
 905  */
 906 int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 907                 unsigned long init_val)
 908 {
 909         u32 old_pkru;
 910         int pkey_shift = (pkey * PKRU_BITS_PER_PKEY);
 911         u32 new_pkru_bits = 0;
 912
 913         /*
 914          * This check implies XSAVE support.  OSPKE only gets
 915          * set if we enable XSAVE and we enable PKU in XCR0.
 916          */
 917         if (!boot_cpu_has(X86_FEATURE_OSPKE))
 918                 return -EINVAL;
 919
 920         /* Set the bits we need in PKRU:  */
 921         if (init_val & PKEY_DISABLE_ACCESS)
 922                 new_pkru_bits |= PKRU_AD_BIT;
 923         if (init_val & PKEY_DISABLE_WRITE)
 924                 new_pkru_bits |= PKRU_WD_BIT;
 925
 926         /* Shift the bits in to the correct place in PKRU for pkey: */
 927         new_pkru_bits <<= pkey_shift;
 928
 929         /* Get old PKRU and mask off any old bits in place: */
 930         old_pkru = read_pkru();
 931         old_pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift);
 932
 933         /* Write old part along with new part: */
 934         write_pkru(old_pkru | new_pkru_bits);
 935
 936         return 0;
 937 }
 938 #endif /* ! CONFIG_ARCH_HAS_PKEYS */
 939
 940 /*
 941  * Weird legacy quirk: SSE and YMM states store information in the
 942  * MXCSR and MXCSR_FLAGS fields of the FP area. That means if the FP
 943  * area is marked as unused in the xfeatures header, we need to copy
 944  * MXCSR and MXCSR_FLAGS if either SSE or YMM are in use.
 945  */
 946 static inline bool xfeatures_mxcsr_quirk(u64 xfeatures)
 947 {
 948         if (!(xfeatures & (XFEATURE_MASK_SSE|XFEATURE_MASK_YMM)))
 949                 return false;
 950
 951         if (xfeatures & XFEATURE_MASK_FP)
 952                 return false;
 953
 954         return true;
 955 }
 956
 957 /*
 958  * This is similar to user_regset_copyout(), but will not add offset to
 959  * the source data pointer or increment pos, count, kbuf, and ubuf.
 960  */
 961 static inline void
 962 __copy_xstate_to_kernel(void *kbuf, const void *data,
 963                         unsigned int offset, unsigned int size, unsigned int size_total)
 964 {
 965         if (offset < size_total) {
 966                 unsigned int copy = min(size, size_total - offset);
 967
 968                 memcpy(kbuf + offset, data, copy);
 969         }
 970 }
 971
 972 /*
 973  * Convert from kernel XSAVES compacted format to standard format and copy
 974  * to a kernel-space ptrace buffer.
 975  *
 976  * It supports partial copy but pos always starts from zero. This is called
 977  * from xstateregs_get() and there we check the CPU has XSAVES.
 978  */
 979 int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
 980 {
 981         unsigned int offset, size;
 982         struct xstate_header header;
 983         int i;
 984
 985         /*
 986          * Currently copy_regset_to_user() starts from pos 0:
 987          */
 988         if (unlikely(offset_start != 0))
 989                 return -EFAULT;
 990
 991         /*
 992          * The destination is a ptrace buffer; we put in only user xstates:
 993          */
 994         memset(&header, 0, sizeof(header));
 995         header.xfeatures = xsave->header.xfeatures;
 996         header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
 997
 998         /*
 999          * Copy xregs_state->header:
1000          */
1001         offset = offsetof(struct xregs_state, header);
1002         size = sizeof(header);
1003
1004         __copy_xstate_to_kernel(kbuf, &header, offset, size, size_total);
1005
1006         for (i = 0; i < XFEATURE_MAX; i++) {
1007                 /*
1008                  * Copy only in-use xstates:
1009                  */
1010                 if ((header.xfeatures >> i) & 1) {
1011                         void *src = __raw_xsave_addr(xsave, i);
1012
1013                         offset = xstate_offsets[i];
1014                         size = xstate_sizes[i];
1015
1016                         /* The next component has to fit fully into the output buffer: */
1017                         if (offset + size > size_total)
1018                                 break;
1019
1020                         __copy_xstate_to_kernel(kbuf, src, offset, size, size_total);
1021                 }
1022
1023         }
1024
1025         if (xfeatures_mxcsr_quirk(header.xfeatures)) {
1026                 offset = offsetof(struct fxregs_state, mxcsr);
1027                 size = MXCSR_AND_FLAGS_SIZE;
1028                 __copy_xstate_to_kernel(kbuf, &xsave->i387.mxcsr, offset, size, size_total);
1029         }
1030
1031         /*
1032          * Fill xsave->i387.sw_reserved value for ptrace frame:
1033          */
1034         offset = offsetof(struct fxregs_state, sw_reserved);
1035         size = sizeof(xstate_fx_sw_bytes);
1036
1037         __copy_xstate_to_kernel(kbuf, xstate_fx_sw_bytes, offset, size, size_total);
1038
1039         return 0;
1040 }
1041
1042 static inline int
1043 __copy_xstate_to_user(void __user *ubuf, const void *data, unsigned int offset, unsigned int size, unsigned int size_total)
1044 {
1045         if (!size)
1046                 return 0;
1047
1048         if (offset < size_total) {
1049                 unsigned int copy = min(size, size_total - offset);
1050
1051                 if (__copy_to_user(ubuf + offset, data, copy))
1052                         return -EFAULT;
1053         }
1054         return 0;
1055 }
1056
1057 /*
1058  * Convert from kernel XSAVES compacted format to standard format and copy
1059  * to a user-space buffer. It supports partial copy but pos always starts from
1060  * zero. This is called from xstateregs_get() and there we check the CPU
1061  * has XSAVES.
1062  */
1063 int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset_start, unsigned int size_total)
1064 {
1065         unsigned int offset, size;
1066         int ret, i;
1067         struct xstate_header header;
1068
1069         /*
1070          * Currently copy_regset_to_user() starts from pos 0:
1071          */
1072         if (unlikely(offset_start != 0))
1073                 return -EFAULT;
1074
1075         /*
1076          * The destination is a ptrace buffer; we put in only user xstates:
1077          */
1078         memset(&header, 0, sizeof(header));
1079         header.xfeatures = xsave->header.xfeatures;
1080         header.xfeatures &= ~XFEATURE_MASK_SUPERVISOR;
1081
1082         /*
1083          * Copy xregs_state->header:
1084          */
1085         offset = offsetof(struct xregs_state, header);
1086         size = sizeof(header);
1087
1088         ret = __copy_xstate_to_user(ubuf, &header, offset, size, size_total);
1089         if (ret)
1090                 return ret;
1091
1092         for (i = 0; i < XFEATURE_MAX; i++) {
1093                 /*
1094                  * Copy only in-use xstates:
1095                  */
1096                 if ((header.xfeatures >> i) & 1) {
1097                         void *src = __raw_xsave_addr(xsave, i);
1098
1099                         offset = xstate_offsets[i];
1100                         size = xstate_sizes[i];
1101
1102                         /* The next component has to fit fully into the output buffer: */
1103                         if (offset + size > size_total)
1104                                 break;
1105
1106                         ret = __copy_xstate_to_user(ubuf, src, offset, size, size_total);
1107                         if (ret)
1108                                 return ret;
1109                 }
1110
1111         }
1112
1113         if (xfeatures_mxcsr_quirk(header.xfeatures)) {
1114                 offset = offsetof(struct fxregs_state, mxcsr);
1115                 size = MXCSR_AND_FLAGS_SIZE;
1116                 __copy_xstate_to_user(ubuf, &xsave->i387.mxcsr, offset, size, size_total);
1117         }
1118
1119         /*
1120          * Fill xsave->i387.sw_reserved value for ptrace frame:
1121          */
1122         offset = offsetof(struct fxregs_state, sw_reserved);
1123         size = sizeof(xstate_fx_sw_bytes);
1124
1125         ret = __copy_xstate_to_user(ubuf, xstate_fx_sw_bytes, offset, size, size_total);
1126         if (ret)
1127                 return ret;
1128
1129         return 0;
1130 }
1131
1132 /*
1133  * Convert from a ptrace standard-format kernel buffer to kernel XSAVES format
1134  * and copy to the target thread. This is called from xstateregs_set().
1135  */
1136 int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
1137 {
1138         unsigned int offset, size;
1139         int i;
1140         struct xstate_header hdr;
1141
1142         offset = offsetof(struct xregs_state, header);
1143         size = sizeof(hdr);
1144
1145         memcpy(&hdr, kbuf + offset, size);
1146
1147         if (validate_xstate_header(&hdr))
1148                 return -EINVAL;
1149
1150         for (i = 0; i < XFEATURE_MAX; i++) {
1151                 u64 mask = ((u64)1 << i);
1152
1153                 if (hdr.xfeatures & mask) {
1154                         void *dst = __raw_xsave_addr(xsave, i);
1155
1156                         offset = xstate_offsets[i];
1157                         size = xstate_sizes[i];
1158
1159                         memcpy(dst, kbuf + offset, size);
1160                 }
1161         }
1162
1163         if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
1164                 offset = offsetof(struct fxregs_state, mxcsr);
1165                 size = MXCSR_AND_FLAGS_SIZE;
1166                 memcpy(&xsave->i387.mxcsr, kbuf + offset, size);
1167         }
1168
1169         /*
1170          * The state that came in from userspace was user-state only.
1171          * Mask all the user states out of 'xfeatures':
1172          */
1173         xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
1174
1175         /*
1176          * Add back in the features that came in from userspace:
1177          */
1178         xsave->header.xfeatures |= hdr.xfeatures;
1179
1180         return 0;
1181 }
1182
1183 /*
1184  * Convert from a ptrace or sigreturn standard-format user-space buffer to
1185  * kernel XSAVES format and copy to the target thread. This is called from
1186  * xstateregs_set(), as well as potentially from the sigreturn() and
1187  * rt_sigreturn() system calls.
1188  */
1189 int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
1190 {
1191         unsigned int offset, size;
1192         int i;
1193         struct xstate_header hdr;
1194
1195         offset = offsetof(struct xregs_state, header);
1196         size = sizeof(hdr);
1197
1198         if (__copy_from_user(&hdr, ubuf + offset, size))
1199                 return -EFAULT;
1200
1201         if (validate_xstate_header(&hdr))
1202                 return -EINVAL;
1203
1204         for (i = 0; i < XFEATURE_MAX; i++) {
1205                 u64 mask = ((u64)1 << i);
1206
1207                 if (hdr.xfeatures & mask) {
1208                         void *dst = __raw_xsave_addr(xsave, i);
1209
1210                         offset = xstate_offsets[i];
1211                         size = xstate_sizes[i];
1212
1213                         if (__copy_from_user(dst, ubuf + offset, size))
1214                                 return -EFAULT;
1215                 }
1216         }
1217
1218         if (xfeatures_mxcsr_quirk(hdr.xfeatures)) {
1219                 offset = offsetof(struct fxregs_state, mxcsr);
1220                 size = MXCSR_AND_FLAGS_SIZE;
1221                 if (__copy_from_user(&xsave->i387.mxcsr, ubuf + offset, size))
1222                         return -EFAULT;
1223         }
1224
1225         /*
1226          * The state that came in from userspace was user-state only.
1227          * Mask all the user states out of 'xfeatures':
1228          */
1229         xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR;
1230
1231         /*
1232          * Add back in the features that came in from userspace:
1233          */
1234         xsave->header.xfeatures |= hdr.xfeatures;
1235
1236         return 0;
1237 }
1238
1239 #ifdef CONFIG_PROC_PID_ARCH_STATUS
1240 /*
1241  * Report the amount of time elapsed in millisecond since last AVX512
1242  * use in the task.
1243  */
1244 static void avx512_status(struct seq_file *m, struct task_struct *task)
1245 {
1246         unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp);
1247         long delta;
1248
1249         if (!timestamp) {
1250                 /*
1251                  * Report -1 if no AVX512 usage
1252                  */
1253                 delta = -1;
1254         } else {
1255                 delta = (long)(jiffies - timestamp);
1256                 /*
1257                  * Cap to LONG_MAX if time difference > LONG_MAX
1258                  */
1259                 if (delta < 0)
1260                         delta = LONG_MAX;
1261                 delta = jiffies_to_msecs(delta);
1262         }
1263
1264         seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta);
1265         seq_putc(m, '\n');
1266 }
1267
1268 /*
1269  * Report architecture specific information
1270  */
1271 int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns,
1272                         struct pid *pid, struct task_struct *task)
1273 {
1274         /*
1275          * Report AVX512 state if the processor and build option supported.
1276          */
1277         if (cpu_feature_enabled(X86_FEATURE_AVX512F))
1278                 avx512_status(m, task);
1279
1280         return 0;
1281 }
1282 #endif /* CONFIG_PROC_PID_ARCH_STATUS */