include/asm-x86/i387.h

   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  * x86-64 work by Andi Kleen 2002
   8  */
   9
  10 #ifndef _ASM_X86_I387_H
  11 #define _ASM_X86_I387_H
  12
  13 #include <linux/sched.h>
  14 #include <linux/kernel_stat.h>
  15 #include <linux/regset.h>
  16 #include <asm/asm.h>
  17 #include <asm/processor.h>
  18 #include <asm/sigcontext.h>
  19 #include <asm/user.h>
  20 #include <asm/uaccess.h>
  21
  22 extern void fpu_init(void);
  23 extern void mxcsr_feature_mask_init(void);
  24 extern void init_fpu(struct task_struct *child);
  25 extern asmlinkage void math_state_restore(void);
  26
  27 extern user_regset_active_fn fpregs_active, xfpregs_active;
  28 extern user_regset_get_fn fpregs_get, xfpregs_get, fpregs_soft_get;
  29 extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set;
  30
  31 #ifdef CONFIG_IA32_EMULATION
  32 struct _fpstate_ia32;
  33 extern int save_i387_ia32(struct _fpstate_ia32 __user *buf);
  34 extern int restore_i387_ia32(struct _fpstate_ia32 __user *buf);
  35 #endif
  36
  37 #ifdef CONFIG_X86_64
  38
  39 /* Ignore delayed exceptions from user space */
  40 static inline void tolerant_fwait(void)
  41 {
  42         asm volatile("1: fwait\n"
  43                      "2:\n"
  44                      _ASM_EXTABLE(1b, 2b));
  45 }
  46
  47 static inline int restore_fpu_checking(struct i387_fxsave_struct *fx)
  48 {
  49         int err;
  50
  51         asm volatile("1:  rex64/fxrstor (%[fx])\n\t"
  52                      "2:\n"
  53                      ".section .fixup,\"ax\"\n"
  54                      "3:  movl $-1,%[err]\n"
  55                      "    jmp  2b\n"
  56                      ".previous\n"
  57                      _ASM_EXTABLE(1b, 3b)
  58                      : [err] "=r" (err)
  59 #if 0 /* See comment in __save_init_fpu() below. */
  60                      : [fx] "r" (fx), "m" (*fx), "0" (0));
  61 #else
  62                      : [fx] "cdaSDb" (fx), "m" (*fx), "0" (0));
  63 #endif
  64         if (unlikely(err))
  65                 init_fpu(current);
  66         return err;
  67 }
  68
  69 #define X87_FSW_ES (1 << 7)     /* Exception Summary */
  70
  71 /* AMD CPUs don't save/restore FDP/FIP/FOP unless an exception
  72    is pending. Clear the x87 state here by setting it to fixed
  73    values. The kernel data segment can be sometimes 0 and sometimes
  74    new user value. Both should be ok.
  75    Use the PDA as safe address because it should be already in L1. */
  76 static inline void clear_fpu_state(struct i387_fxsave_struct *fx)
  77 {
  78         if (unlikely(fx->swd & X87_FSW_ES))
  79                 asm volatile("fnclex");
  80         alternative_input(ASM_NOP8 ASM_NOP2,
  81                           "    emms\n"          /* clear stack tags */
  82                           "    fildl %%gs:0",   /* load to clear state */
  83                           X86_FEATURE_FXSAVE_LEAK);
  84 }
  85
  86 static inline int save_i387_checking(struct i387_fxsave_struct __user *fx)
  87 {
  88         int err;
  89
  90         asm volatile("1:  rex64/fxsave (%[fx])\n\t"
  91                      "2:\n"
  92                      ".section .fixup,\"ax\"\n"
  93                      "3:  movl $-1,%[err]\n"
  94                      "    jmp  2b\n"
  95                      ".previous\n"
  96                      _ASM_EXTABLE(1b, 3b)
  97                      : [err] "=r" (err), "=m" (*fx)
  98 #if 0 /* See comment in __fxsave_clear() below. */
  99                      : [fx] "r" (fx), "0" (0));
 100 #else
 101                      : [fx] "cdaSDb" (fx), "0" (0));
 102 #endif
 103         if (unlikely(err) &&
 104             __clear_user(fx, sizeof(struct i387_fxsave_struct)))
 105                 err = -EFAULT;
 106         /* No need to clear here because the caller clears USED_MATH */
 107         return err;
 108 }
 109
 110 static inline void __save_init_fpu(struct task_struct *tsk)
 111 {
 112         /* Using "rex64; fxsave %0" is broken because, if the memory operand
 113            uses any extended registers for addressing, a second REX prefix
 114            will be generated (to the assembler, rex64 followed by semicolon
 115            is a separate instruction), and hence the 64-bitness is lost. */
 116 #if 0
 117         /* Using "fxsaveq %0" would be the ideal choice, but is only supported
 118            starting with gas 2.16. */
 119         __asm__ __volatile__("fxsaveq %0"
 120                              : "=m" (tsk->thread.i387.fxsave));
 121 #elif 0
 122         /* Using, as a workaround, the properly prefixed form below isn't
 123            accepted by any binutils version so far released, complaining that
 124            the same type of prefix is used twice if an extended register is
 125            needed for addressing (fix submitted to mainline 2005-11-21). */
 126         __asm__ __volatile__("rex64/fxsave %0"
 127                              : "=m" (tsk->thread.i387.fxsave));
 128 #else
 129         /* This, however, we can work around by forcing the compiler to select
 130            an addressing mode that doesn't require extended registers. */
 131         __asm__ __volatile__("rex64/fxsave %P2(%1)"
 132                              : "=m" (tsk->thread.i387.fxsave)
 133                              : "cdaSDb" (tsk),
 134                                 "i" (offsetof(__typeof__(*tsk),
 135                                               thread.i387.fxsave)));
 136 #endif
 137         clear_fpu_state(&tsk->thread.i387.fxsave);
 138         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 139 }
 140
 141 /*
 142  * Signal frame handlers.
 143  */
 144
 145 static inline int save_i387(struct _fpstate __user *buf)
 146 {
 147         struct task_struct *tsk = current;
 148         int err = 0;
 149
 150         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
 151                         sizeof(tsk->thread.i387.fxsave));
 152
 153         if ((unsigned long)buf % 16)
 154                 printk("save_i387: bad fpstate %p\n", buf);
 155
 156         if (!used_math())
 157                 return 0;
 158         clear_used_math(); /* trigger finit */
 159         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 160                 err = save_i387_checking((struct i387_fxsave_struct __user *)
 161                                          buf);
 162                 if (err)
 163                         return err;
 164                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 165                 stts();
 166         } else {
 167                 if (__copy_to_user(buf, &tsk->thread.i387.fxsave,
 168                                    sizeof(struct i387_fxsave_struct)))
 169                         return -1;
 170         }
 171         return 1;
 172 }
 173
 174 /*
 175  * This restores directly out of user space. Exceptions are handled.
 176  */
 177 static inline int restore_i387(struct _fpstate __user *buf)
 178 {
 179         set_used_math();
 180         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
 181                 clts();
 182                 task_thread_info(current)->status |= TS_USEDFPU;
 183         }
 184         return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 185 }
 186
 187 #else  /* CONFIG_X86_32 */
 188
 189 static inline void tolerant_fwait(void)
 190 {
 191         asm volatile("fnclex ; fwait");
 192 }
 193
 194 static inline void restore_fpu(struct task_struct *tsk)
 195 {
 196         /*
 197          * The "nop" is needed to make the instructions the same
 198          * length.
 199          */
 200         alternative_input(
 201                 "nop ; frstor %1",
 202                 "fxrstor %1",
 203                 X86_FEATURE_FXSR,
 204                 "m" ((tsk)->thread.i387.fxsave));
 205 }
 206
 207 /* We need a safe address that is cheap to find and that is already
 208    in L1 during context switch. The best choices are unfortunately
 209    different for UP and SMP */
 210 #ifdef CONFIG_SMP
 211 #define safe_address (__per_cpu_offset[0])
 212 #else
 213 #define safe_address (kstat_cpu(0).cpustat.user)
 214 #endif
 215
 216 /*
 217  * These must be called with preempt disabled
 218  */
 219 static inline void __save_init_fpu(struct task_struct *tsk)
 220 {
 221         /* Use more nops than strictly needed in case the compiler
 222            varies code */
 223         alternative_input(
 224                 "fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4,
 225                 "fxsave %[fx]\n"
 226                 "bt $7,%[fsw] ; jnc 1f ; fnclex\n1:",
 227                 X86_FEATURE_FXSR,
 228                 [fx] "m" (tsk->thread.i387.fxsave),
 229                 [fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory");
 230         /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
 231            is pending.  Clear the x87 state here by setting it to fixed
 232            values. safe_address is a random variable that should be in L1 */
 233         alternative_input(
 234                 GENERIC_NOP8 GENERIC_NOP2,
 235                 "emms\n\t"              /* clear stack tags */
 236                 "fildl %[addr]",        /* set F?P to defined value */
 237                 X86_FEATURE_FXSAVE_LEAK,
 238                 [addr] "m" (safe_address));
 239         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 240 }
 241
 242 /*
 243  * Signal frame handlers...
 244  */
 245 extern int save_i387(struct _fpstate __user *buf);
 246 extern int restore_i387(struct _fpstate __user *buf);
 247
 248 #endif  /* CONFIG_X86_64 */
 249
 250 static inline void __unlazy_fpu(struct task_struct *tsk)
 251 {
 252         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 253                 __save_init_fpu(tsk);
 254                 stts();
 255         } else
 256                 tsk->fpu_counter = 0;
 257 }
 258
 259 static inline void __clear_fpu(struct task_struct *tsk)
 260 {
 261         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 262                 tolerant_fwait();
 263                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 264                 stts();
 265         }
 266 }
 267
 268 static inline void kernel_fpu_begin(void)
 269 {
 270         struct thread_info *me = current_thread_info();
 271         preempt_disable();
 272         if (me->status & TS_USEDFPU)
 273                 __save_init_fpu(me->task);
 274         else
 275                 clts();
 276 }
 277
 278 static inline void kernel_fpu_end(void)
 279 {
 280         stts();
 281         preempt_enable();
 282 }
 283
 284 #ifdef CONFIG_X86_64
 285
 286 static inline void save_init_fpu(struct task_struct *tsk)
 287 {
 288         __save_init_fpu(tsk);
 289         stts();
 290 }
 291
 292 #define unlazy_fpu      __unlazy_fpu
 293 #define clear_fpu       __clear_fpu
 294
 295 #else  /* CONFIG_X86_32 */
 296
 297 /*
 298  * These disable preemption on their own and are safe
 299  */
 300 static inline void save_init_fpu(struct task_struct *tsk)
 301 {
 302         preempt_disable();
 303         __save_init_fpu(tsk);
 304         stts();
 305         preempt_enable();
 306 }
 307
 308 static inline void unlazy_fpu(struct task_struct *tsk)
 309 {
 310         preempt_disable();
 311         __unlazy_fpu(tsk);
 312         preempt_enable();
 313 }
 314
 315 static inline void clear_fpu(struct task_struct *tsk)
 316 {
 317         preempt_disable();
 318         __clear_fpu(tsk);
 319         preempt_enable();
 320 }
 321
 322 #endif  /* CONFIG_X86_64 */
 323
 324 /*
 325  * i387 state interaction
 326  */
 327 static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
 328 {
 329         if (cpu_has_fxsr) {
 330                 return tsk->thread.i387.fxsave.cwd;
 331         } else {
 332                 return (unsigned short)tsk->thread.i387.fsave.cwd;
 333         }
 334 }
 335
 336 static inline unsigned short get_fpu_swd(struct task_struct *tsk)
 337 {
 338         if (cpu_has_fxsr) {
 339                 return tsk->thread.i387.fxsave.swd;
 340         } else {
 341                 return (unsigned short)tsk->thread.i387.fsave.swd;
 342         }
 343 }
 344
 345 static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
 346 {
 347         if (cpu_has_xmm) {
 348                 return tsk->thread.i387.fxsave.mxcsr;
 349         } else {
 350                 return MXCSR_DEFAULT;
 351         }
 352 }
 353
 354 #endif  /* _ASM_X86_I387_H */