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