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) && __clear_user(fx, sizeof(struct i387_fxsave_struct)))
 104                 err = -EFAULT;
 105         /* No need to clear here because the caller clears USED_MATH */
 106         return err;
 107 }
 108
 109 static inline void __save_init_fpu(struct task_struct *tsk)
 110 {
 111         /* Using "rex64; fxsave %0" is broken because, if the memory operand
 112            uses any extended registers for addressing, a second REX prefix
 113            will be generated (to the assembler, rex64 followed by semicolon
 114            is a separate instruction), and hence the 64-bitness is lost. */
 115 #if 0
 116         /* Using "fxsaveq %0" would be the ideal choice, but is only supported
 117            starting with gas 2.16. */
 118         __asm__ __volatile__("fxsaveq %0"
 119                              : "=m" (tsk->thread.i387.fxsave));
 120 #elif 0
 121         /* Using, as a workaround, the properly prefixed form below isn't
 122            accepted by any binutils version so far released, complaining that
 123            the same type of prefix is used twice if an extended register is
 124            needed for addressing (fix submitted to mainline 2005-11-21). */
 125         __asm__ __volatile__("rex64/fxsave %0"
 126                              : "=m" (tsk->thread.i387.fxsave));
 127 #else
 128         /* This, however, we can work around by forcing the compiler to select
 129            an addressing mode that doesn't require extended registers. */
 130         __asm__ __volatile__("rex64/fxsave %P2(%1)"
 131                              : "=m" (tsk->thread.i387.fxsave)
 132                              : "cdaSDb" (tsk),
 133                                 "i" (offsetof(__typeof__(*tsk),
 134                                               thread.i387.fxsave)));
 135 #endif
 136         clear_fpu_state(&tsk->thread.i387.fxsave);
 137         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 138 }
 139
 140 /*
 141  * Signal frame handlers.
 142  */
 143
 144 static inline int save_i387(struct _fpstate __user *buf)
 145 {
 146         struct task_struct *tsk = current;
 147         int err = 0;
 148
 149         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
 150                         sizeof(tsk->thread.i387.fxsave));
 151
 152         if ((unsigned long)buf % 16)
 153                 printk("save_i387: bad fpstate %p\n", buf);
 154
 155         if (!used_math())
 156                 return 0;
 157         clear_used_math(); /* trigger finit */
 158         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 159                 err = save_i387_checking((struct i387_fxsave_struct __user *)buf);
 160                 if (err) return err;
 161                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 162                 stts();
 163         } else {
 164                 if (__copy_to_user(buf, &tsk->thread.i387.fxsave,
 165                                    sizeof(struct i387_fxsave_struct)))
 166                         return -1;
 167         }
 168         return 1;
 169 }
 170
 171 /*
 172  * This restores directly out of user space. Exceptions are handled.
 173  */
 174 static inline int restore_i387(struct _fpstate __user *buf)
 175 {
 176         set_used_math();
 177         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
 178                 clts();
 179                 task_thread_info(current)->status |= TS_USEDFPU;
 180         }
 181         return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 182 }
 183
 184 #else  /* CONFIG_X86_32 */
 185
 186 static inline void tolerant_fwait(void)
 187 {
 188         asm volatile("fnclex ; fwait");
 189 }
 190
 191 static inline void restore_fpu(struct task_struct *tsk)
 192 {
 193         /*
 194          * The "nop" is needed to make the instructions the same
 195          * length.
 196          */
 197         alternative_input(
 198                 "nop ; frstor %1",
 199                 "fxrstor %1",
 200                 X86_FEATURE_FXSR,
 201                 "m" ((tsk)->thread.i387.fxsave));
 202 }
 203
 204 /* We need a safe address that is cheap to find and that is already
 205    in L1 during context switch. The best choices are unfortunately
 206    different for UP and SMP */
 207 #ifdef CONFIG_SMP
 208 #define safe_address (__per_cpu_offset[0])
 209 #else
 210 #define safe_address (kstat_cpu(0).cpustat.user)
 211 #endif
 212
 213 /*
 214  * These must be called with preempt disabled
 215  */
 216 static inline void __save_init_fpu(struct task_struct *tsk)
 217 {
 218         /* Use more nops than strictly needed in case the compiler
 219            varies code */
 220         alternative_input(
 221                 "fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4,
 222                 "fxsave %[fx]\n"
 223                 "bt $7,%[fsw] ; jnc 1f ; fnclex\n1:",
 224                 X86_FEATURE_FXSR,
 225                 [fx] "m" (tsk->thread.i387.fxsave),
 226                 [fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory");
 227         /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
 228            is pending.  Clear the x87 state here by setting it to fixed
 229            values. safe_address is a random variable that should be in L1 */
 230         alternative_input(
 231                 GENERIC_NOP8 GENERIC_NOP2,
 232                 "emms\n\t"              /* clear stack tags */
 233                 "fildl %[addr]",        /* set F?P to defined value */
 234                 X86_FEATURE_FXSAVE_LEAK,
 235                 [addr] "m" (safe_address));
 236         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 237 }
 238
 239 /*
 240  * Signal frame handlers...
 241  */
 242 extern int save_i387(struct _fpstate __user *buf);
 243 extern int restore_i387(struct _fpstate __user *buf);
 244
 245 #endif  /* CONFIG_X86_64 */
 246
 247 static inline void __unlazy_fpu(struct task_struct *tsk)
 248 {
 249         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 250                 __save_init_fpu(tsk);
 251                 stts();
 252         } else
 253                 tsk->fpu_counter = 0;
 254 }
 255
 256 static inline void __clear_fpu(struct task_struct *tsk)
 257 {
 258         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 259                 tolerant_fwait();
 260                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 261                 stts();
 262         }
 263 }
 264
 265 static inline void kernel_fpu_begin(void)
 266 {
 267         struct thread_info *me = current_thread_info();
 268         preempt_disable();
 269         if (me->status & TS_USEDFPU)
 270                 __save_init_fpu(me->task);
 271         else
 272                 clts();
 273 }
 274
 275 static inline void kernel_fpu_end(void)
 276 {
 277         stts();
 278         preempt_enable();
 279 }
 280
 281 #ifdef CONFIG_X86_64
 282
 283 static inline void save_init_fpu(struct task_struct *tsk)
 284 {
 285         __save_init_fpu(tsk);
 286         stts();
 287 }
 288
 289 #define unlazy_fpu      __unlazy_fpu
 290 #define clear_fpu       __clear_fpu
 291
 292 #else  /* CONFIG_X86_32 */
 293
 294 /*
 295  * These disable preemption on their own and are safe
 296  */
 297 static inline void save_init_fpu(struct task_struct *tsk)
 298 {
 299         preempt_disable();
 300         __save_init_fpu(tsk);
 301         stts();
 302         preempt_enable();
 303 }
 304
 305 static inline void unlazy_fpu(struct task_struct *tsk)
 306 {
 307         preempt_disable();
 308         __unlazy_fpu(tsk);
 309         preempt_enable();
 310 }
 311
 312 static inline void clear_fpu(struct task_struct *tsk)
 313 {
 314         preempt_disable();
 315         __clear_fpu(tsk);
 316         preempt_enable();
 317 }
 318
 319 #endif  /* CONFIG_X86_64 */
 320
 321 /*
 322  * i387 state interaction
 323  */
 324 static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
 325 {
 326         if (cpu_has_fxsr) {
 327                 return tsk->thread.i387.fxsave.cwd;
 328         } else {
 329                 return (unsigned short)tsk->thread.i387.fsave.cwd;
 330         }
 331 }
 332
 333 static inline unsigned short get_fpu_swd(struct task_struct *tsk)
 334 {
 335         if (cpu_has_fxsr) {
 336                 return tsk->thread.i387.fxsave.swd;
 337         } else {
 338                 return (unsigned short)tsk->thread.i387.fsave.swd;
 339         }
 340 }
 341
 342 static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
 343 {
 344         if (cpu_has_xmm) {
 345                 return tsk->thread.i387.fxsave.mxcsr;
 346         } else {
 347                 return MXCSR_DEFAULT;
 348         }
 349 }
 350
 351 #endif  /* _ASM_X86_I387_H */