arch/x86/kernel/i387.c

   1 /*
   2  *  Copyright (C) 1994 Linus Torvalds
   3  *
   4  *  Pentium III FXSR, SSE support
   5  *  General FPU state handling cleanups
   6  *      Gareth Hughes <gareth@valinux.com>, May 2000
   7  */
   8 #include <linux/module.h>
   9 #include <linux/regset.h>
  10 #include <linux/sched.h>
  11 #include <linux/bootmem.h>
  12
  13 #include <asm/sigcontext.h>
  14 #include <asm/processor.h>
  15 #include <asm/math_emu.h>
  16 #include <asm/uaccess.h>
  17 #include <asm/ptrace.h>
  18 #include <asm/i387.h>
  19 #include <asm/user.h>
  20
  21 #ifdef CONFIG_X86_64
  22 # include <asm/sigcontext32.h>
  23 # include <asm/user32.h>
  24 #else
  25 # define save_i387_ia32         save_i387
  26 # define restore_i387_ia32      restore_i387
  27 # define _fpstate_ia32          _fpstate
  28 # define user_i387_ia32_struct  user_i387_struct
  29 # define user32_fxsr_struct     user_fxsr_struct
  30 #endif
  31
  32 #ifdef CONFIG_MATH_EMULATION
  33 # define HAVE_HWFP              (boot_cpu_data.hard_math)
  34 #else
  35 # define HAVE_HWFP              1
  36 #endif
  37
  38 static unsigned int             mxcsr_feature_mask __read_mostly = 0xffffffffu;
  39 unsigned int xstate_size;
  40 static struct i387_fxsave_struct fx_scratch __cpuinitdata;
  41
  42 void __cpuinit mxcsr_feature_mask_init(void)
  43 {
  44         unsigned long mask = 0;
  45
  46         clts();
  47         if (cpu_has_fxsr) {
  48                 memset(&fx_scratch, 0, sizeof(struct i387_fxsave_struct));
  49                 asm volatile("fxsave %0" : : "m" (fx_scratch));
  50                 mask = fx_scratch.mxcsr_mask;
  51                 if (mask == 0)
  52                         mask = 0x0000ffbf;
  53         }
  54         mxcsr_feature_mask &= mask;
  55         stts();
  56 }
  57
  58 void __init init_thread_xstate(void)
  59 {
  60         if (cpu_has_fxsr)
  61                 xstate_size = sizeof(struct i387_fxsave_struct);
  62 #ifdef CONFIG_X86_32
  63         else
  64                 xstate_size = sizeof(struct i387_fsave_struct);
  65 #endif
  66         init_task.thread.xstate = alloc_bootmem(xstate_size);
  67 }
  68
  69 #ifdef CONFIG_X86_64
  70 /*
  71  * Called at bootup to set up the initial FPU state that is later cloned
  72  * into all processes.
  73  */
  74 void __cpuinit fpu_init(void)
  75 {
  76         unsigned long oldcr0 = read_cr0();
  77
  78         set_in_cr4(X86_CR4_OSFXSR);
  79         set_in_cr4(X86_CR4_OSXMMEXCPT);
  80
  81         write_cr0(oldcr0 & ~(X86_CR0_TS|X86_CR0_EM)); /* clear TS and EM */
  82
  83         mxcsr_feature_mask_init();
  84         /* clean state in init */
  85         current_thread_info()->status = 0;
  86         clear_used_math();
  87 }
  88 #endif  /* CONFIG_X86_64 */
  89
  90 /*
  91  * The _current_ task is using the FPU for the first time
  92  * so initialize it and set the mxcsr to its default
  93  * value at reset if we support XMM instructions and then
  94  * remeber the current task has used the FPU.
  95  */
  96 void init_fpu(struct task_struct *tsk)
  97 {
  98         if (tsk_used_math(tsk)) {
  99                 if (tsk == current)
 100                         unlazy_fpu(tsk);
 101                 return;
 102         }
 103
 104         if (cpu_has_fxsr) {
 105                 struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 106
 107                 memset(fx, 0, xstate_size);
 108                 fx->cwd = 0x37f;
 109                 if (cpu_has_xmm)
 110                         fx->mxcsr = MXCSR_DEFAULT;
 111         } else {
 112                 struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 113                 memset(fp, 0, xstate_size);
 114                 fp->cwd = 0xffff037fu;
 115                 fp->swd = 0xffff0000u;
 116                 fp->twd = 0xffffffffu;
 117                 fp->fos = 0xffff0000u;
 118         }
 119         /*
 120          * Only the device not available exception or ptrace can call init_fpu.
 121          */
 122         set_stopped_child_used_math(tsk);
 123 }
 124
 125 int fpregs_active(struct task_struct *target, const struct user_regset *regset)
 126 {
 127         return tsk_used_math(target) ? regset->n : 0;
 128 }
 129
 130 int xfpregs_active(struct task_struct *target, const struct user_regset *regset)
 131 {
 132         return (cpu_has_fxsr && tsk_used_math(target)) ? regset->n : 0;
 133 }
 134
 135 int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 136                 unsigned int pos, unsigned int count,
 137                 void *kbuf, void __user *ubuf)
 138 {
 139         if (!cpu_has_fxsr)
 140                 return -ENODEV;
 141
 142         init_fpu(target);
 143
 144         return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 145                                    &target->thread.xstate->fxsave, 0, -1);
 146 }
 147
 148 int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 149                 unsigned int pos, unsigned int count,
 150                 const void *kbuf, const void __user *ubuf)
 151 {
 152         int ret;
 153
 154         if (!cpu_has_fxsr)
 155                 return -ENODEV;
 156
 157         init_fpu(target);
 158         set_stopped_child_used_math(target);
 159
 160         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 161                                  &target->thread.xstate->fxsave, 0, -1);
 162
 163         /*
 164          * mxcsr reserved bits must be masked to zero for security reasons.
 165          */
 166         target->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 167
 168         return ret;
 169 }
 170
 171 #if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
 172
 173 /*
 174  * FPU tag word conversions.
 175  */
 176
 177 static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
 178 {
 179         unsigned int tmp; /* to avoid 16 bit prefixes in the code */
 180
 181         /* Transform each pair of bits into 01 (valid) or 00 (empty) */
 182         tmp = ~twd;
 183         tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
 184         /* and move the valid bits to the lower byte. */
 185         tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
 186         tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
 187         tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
 188
 189         return tmp;
 190 }
 191
 192 #define FPREG_ADDR(f, n)        ((void *)&(f)->st_space + (n) * 16);
 193 #define FP_EXP_TAG_VALID        0
 194 #define FP_EXP_TAG_ZERO         1
 195 #define FP_EXP_TAG_SPECIAL      2
 196 #define FP_EXP_TAG_EMPTY        3
 197
 198 static inline u32 twd_fxsr_to_i387(struct i387_fxsave_struct *fxsave)
 199 {
 200         struct _fpxreg *st;
 201         u32 tos = (fxsave->swd >> 11) & 7;
 202         u32 twd = (unsigned long) fxsave->twd;
 203         u32 tag;
 204         u32 ret = 0xffff0000u;
 205         int i;
 206
 207         for (i = 0; i < 8; i++, twd >>= 1) {
 208                 if (twd & 0x1) {
 209                         st = FPREG_ADDR(fxsave, (i - tos) & 7);
 210
 211                         switch (st->exponent & 0x7fff) {
 212                         case 0x7fff:
 213                                 tag = FP_EXP_TAG_SPECIAL;
 214                                 break;
 215                         case 0x0000:
 216                                 if (!st->significand[0] &&
 217                                     !st->significand[1] &&
 218                                     !st->significand[2] &&
 219                                     !st->significand[3])
 220                                         tag = FP_EXP_TAG_ZERO;
 221                                 else
 222                                         tag = FP_EXP_TAG_SPECIAL;
 223                                 break;
 224                         default:
 225                                 if (st->significand[3] & 0x8000)
 226                                         tag = FP_EXP_TAG_VALID;
 227                                 else
 228                                         tag = FP_EXP_TAG_SPECIAL;
 229                                 break;
 230                         }
 231                 } else {
 232                         tag = FP_EXP_TAG_EMPTY;
 233                 }
 234                 ret |= tag << (2 * i);
 235         }
 236         return ret;
 237 }
 238
 239 /*
 240  * FXSR floating point environment conversions.
 241  */
 242
 243 static void
 244 convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 245 {
 246         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 247         struct _fpreg *to = (struct _fpreg *) &env->st_space[0];
 248         struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0];
 249         int i;
 250
 251         env->cwd = fxsave->cwd | 0xffff0000u;
 252         env->swd = fxsave->swd | 0xffff0000u;
 253         env->twd = twd_fxsr_to_i387(fxsave);
 254
 255 #ifdef CONFIG_X86_64
 256         env->fip = fxsave->rip;
 257         env->foo = fxsave->rdp;
 258         if (tsk == current) {
 259                 /*
 260                  * should be actually ds/cs at fpu exception time, but
 261                  * that information is not available in 64bit mode.
 262                  */
 263                 asm("mov %%ds, %[fos]" : [fos] "=r" (env->fos));
 264                 asm("mov %%cs, %[fcs]" : [fcs] "=r" (env->fcs));
 265         } else {
 266                 struct pt_regs *regs = task_pt_regs(tsk);
 267
 268                 env->fos = 0xffff0000 | tsk->thread.ds;
 269                 env->fcs = regs->cs;
 270         }
 271 #else
 272         env->fip = fxsave->fip;
 273         env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16);
 274         env->foo = fxsave->foo;
 275         env->fos = fxsave->fos;
 276 #endif
 277
 278         for (i = 0; i < 8; ++i)
 279                 memcpy(&to[i], &from[i], sizeof(to[0]));
 280 }
 281
 282 static void convert_to_fxsr(struct task_struct *tsk,
 283                             const struct user_i387_ia32_struct *env)
 284
 285 {
 286         struct i387_fxsave_struct *fxsave = &tsk->thread.xstate->fxsave;
 287         struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 288         struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 289         int i;
 290
 291         fxsave->cwd = env->cwd;
 292         fxsave->swd = env->swd;
 293         fxsave->twd = twd_i387_to_fxsr(env->twd);
 294         fxsave->fop = (u16) ((u32) env->fcs >> 16);
 295 #ifdef CONFIG_X86_64
 296         fxsave->rip = env->fip;
 297         fxsave->rdp = env->foo;
 298         /* cs and ds ignored */
 299 #else
 300         fxsave->fip = env->fip;
 301         fxsave->fcs = (env->fcs & 0xffff);
 302         fxsave->foo = env->foo;
 303         fxsave->fos = env->fos;
 304 #endif
 305
 306         for (i = 0; i < 8; ++i)
 307                 memcpy(&to[i], &from[i], sizeof(from[0]));
 308 }
 309
 310 int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 311                unsigned int pos, unsigned int count,
 312                void *kbuf, void __user *ubuf)
 313 {
 314         struct user_i387_ia32_struct env;
 315
 316         if (!HAVE_HWFP)
 317                 return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 318
 319         init_fpu(target);
 320
 321         if (!cpu_has_fxsr) {
 322                 return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 323                                            &target->thread.xstate->fsave, 0,
 324                                            -1);
 325         }
 326
 327         if (kbuf && pos == 0 && count == sizeof(env)) {
 328                 convert_from_fxsr(kbuf, target);
 329                 return 0;
 330         }
 331
 332         convert_from_fxsr(&env, target);
 333
 334         return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 335 }
 336
 337 int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 338                unsigned int pos, unsigned int count,
 339                const void *kbuf, const void __user *ubuf)
 340 {
 341         struct user_i387_ia32_struct env;
 342         int ret;
 343
 344         if (!HAVE_HWFP)
 345                 return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 346
 347         init_fpu(target);
 348         set_stopped_child_used_math(target);
 349
 350         if (!cpu_has_fxsr) {
 351                 return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 352                                           &target->thread.xstate->fsave, 0, -1);
 353         }
 354
 355         if (pos > 0 || count < sizeof(env))
 356                 convert_from_fxsr(&env, target);
 357
 358         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 359         if (!ret)
 360                 convert_to_fxsr(target, &env);
 361
 362         return ret;
 363 }
 364
 365 /*
 366  * Signal frame handlers.
 367  */
 368
 369 static inline int save_i387_fsave(struct _fpstate_ia32 __user *buf)
 370 {
 371         struct task_struct *tsk = current;
 372         struct i387_fsave_struct *fp = &tsk->thread.xstate->fsave;
 373
 374         unlazy_fpu(tsk);
 375         fp->status = fp->swd;
 376         if (__copy_to_user(buf, fp, sizeof(struct i387_fsave_struct)))
 377                 return -1;
 378         return 1;
 379 }
 380
 381 static int save_i387_fxsave(struct _fpstate_ia32 __user *buf)
 382 {
 383         struct task_struct *tsk = current;
 384         struct i387_fxsave_struct *fx = &tsk->thread.xstate->fxsave;
 385         struct user_i387_ia32_struct env;
 386         int err = 0;
 387
 388         unlazy_fpu(tsk);
 389
 390         convert_from_fxsr(&env, tsk);
 391         if (__copy_to_user(buf, &env, sizeof(env)))
 392                 return -1;
 393
 394         err |= __put_user(fx->swd, &buf->status);
 395         err |= __put_user(X86_FXSR_MAGIC, &buf->magic);
 396         if (err)
 397                 return -1;
 398
 399         if (__copy_to_user(&buf->_fxsr_env[0], fx,
 400                            sizeof(struct i387_fxsave_struct)))
 401                 return -1;
 402         return 1;
 403 }
 404
 405 int save_i387_ia32(struct _fpstate_ia32 __user *buf)
 406 {
 407         if (!used_math())
 408                 return 0;
 409         /*
 410          * This will cause a "finit" to be triggered by the next
 411          * attempted FPU operation by the 'current' process.
 412          */
 413         clear_used_math();
 414
 415         if (!HAVE_HWFP) {
 416                 return fpregs_soft_get(current, NULL,
 417                                        0, sizeof(struct user_i387_ia32_struct),
 418                                        NULL, buf) ? -1 : 1;
 419         }
 420
 421         if (cpu_has_fxsr)
 422                 return save_i387_fxsave(buf);
 423         else
 424                 return save_i387_fsave(buf);
 425 }
 426
 427 static inline int restore_i387_fsave(struct _fpstate_ia32 __user *buf)
 428 {
 429         struct task_struct *tsk = current;
 430
 431         clear_fpu(tsk);
 432         return __copy_from_user(&tsk->thread.xstate->fsave, buf,
 433                                 sizeof(struct i387_fsave_struct));
 434 }
 435
 436 static int restore_i387_fxsave(struct _fpstate_ia32 __user *buf)
 437 {
 438         struct task_struct *tsk = current;
 439         struct user_i387_ia32_struct env;
 440         int err;
 441
 442         clear_fpu(tsk);
 443         err = __copy_from_user(&tsk->thread.xstate->fxsave, &buf->_fxsr_env[0],
 444                                sizeof(struct i387_fxsave_struct));
 445         /* mxcsr reserved bits must be masked to zero for security reasons */
 446         tsk->thread.xstate->fxsave.mxcsr &= mxcsr_feature_mask;
 447         if (err || __copy_from_user(&env, buf, sizeof(env)))
 448                 return 1;
 449         convert_to_fxsr(tsk, &env);
 450
 451         return 0;
 452 }
 453
 454 int restore_i387_ia32(struct _fpstate_ia32 __user *buf)
 455 {
 456         int err;
 457
 458         if (HAVE_HWFP) {
 459                 if (cpu_has_fxsr)
 460                         err = restore_i387_fxsave(buf);
 461                 else
 462                         err = restore_i387_fsave(buf);
 463         } else {
 464                 err = fpregs_soft_set(current, NULL,
 465                                       0, sizeof(struct user_i387_ia32_struct),
 466                                       NULL, buf) != 0;
 467         }
 468         set_used_math();
 469
 470         return err;
 471 }
 472
 473 /*
 474  * FPU state for core dumps.
 475  * This is only used for a.out dumps now.
 476  * It is declared generically using elf_fpregset_t (which is
 477  * struct user_i387_struct) but is in fact only used for 32-bit
 478  * dumps, so on 64-bit it is really struct user_i387_ia32_struct.
 479  */
 480 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu)
 481 {
 482         struct task_struct *tsk = current;
 483         int fpvalid;
 484
 485         fpvalid = !!used_math();
 486         if (fpvalid)
 487                 fpvalid = !fpregs_get(tsk, NULL,
 488                                       0, sizeof(struct user_i387_ia32_struct),
 489                                       fpu, NULL);
 490
 491         return fpvalid;
 492 }
 493 EXPORT_SYMBOL(dump_fpu);
 494
 495 #endif  /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */