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/processor.h>
  17 #include <asm/sigcontext.h>
  18 #include <asm/user.h>
  19 #include <asm/uaccess.h>
  20
  21 extern void fpu_init(void);
  22 extern unsigned int mxcsr_feature_mask;
  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                      "   .section __ex_table,\"a\"\n"
  45                      "  .align 8\n"
  46                      "  .quad 1b,2b\n"
  47                      "  .previous\n");
  48 }
  49
  50 static inline int restore_fpu_checking(struct i387_fxsave_struct *fx)
  51 {
  52         int err;
  53
  54         asm volatile("1:  rex64/fxrstor (%[fx])\n\t"
  55                      "2:\n"
  56                      ".section .fixup,\"ax\"\n"
  57                      "3:  movl $-1,%[err]\n"
  58                      "    jmp  2b\n"
  59                      ".previous\n"
  60                      ".section __ex_table,\"a\"\n"
  61                      "   .align 8\n"
  62                      "   .quad  1b,3b\n"
  63                      ".previous"
  64                      : [err] "=r" (err)
  65 #if 0 /* See comment in __save_init_fpu() below. */
  66                      : [fx] "r" (fx), "m" (*fx), "0" (0));
  67 #else
  68                      : [fx] "cdaSDb" (fx), "m" (*fx), "0" (0));
  69 #endif
  70         if (unlikely(err))
  71                 init_fpu(current);
  72         return err;
  73 }
  74
  75 #define X87_FSW_ES (1 << 7)     /* Exception Summary */
  76
  77 /* AMD CPUs don't save/restore FDP/FIP/FOP unless an exception
  78    is pending. Clear the x87 state here by setting it to fixed
  79    values. The kernel data segment can be sometimes 0 and sometimes
  80    new user value. Both should be ok.
  81    Use the PDA as safe address because it should be already in L1. */
  82 static inline void clear_fpu_state(struct i387_fxsave_struct *fx)
  83 {
  84         if (unlikely(fx->swd & X87_FSW_ES))
  85                  asm volatile("fnclex");
  86         alternative_input(ASM_NOP8 ASM_NOP2,
  87                      "    emms\n"               /* clear stack tags */
  88                      "    fildl %%gs:0",        /* load to clear state */
  89                      X86_FEATURE_FXSAVE_LEAK);
  90 }
  91
  92 static inline int save_i387_checking(struct i387_fxsave_struct __user *fx)
  93 {
  94         int err;
  95
  96         asm volatile("1:  rex64/fxsave (%[fx])\n\t"
  97                      "2:\n"
  98                      ".section .fixup,\"ax\"\n"
  99                      "3:  movl $-1,%[err]\n"
 100                      "    jmp  2b\n"
 101                      ".previous\n"
 102                      ".section __ex_table,\"a\"\n"
 103                      "   .align 8\n"
 104                      "   .quad  1b,3b\n"
 105                      ".previous"
 106                      : [err] "=r" (err), "=m" (*fx)
 107 #if 0 /* See comment in __fxsave_clear() below. */
 108                      : [fx] "r" (fx), "0" (0));
 109 #else
 110                      : [fx] "cdaSDb" (fx), "0" (0));
 111 #endif
 112         if (unlikely(err) && __clear_user(fx, sizeof(struct i387_fxsave_struct)))
 113                 err = -EFAULT;
 114         /* No need to clear here because the caller clears USED_MATH */
 115         return err;
 116 }
 117
 118 static inline void __save_init_fpu(struct task_struct *tsk)
 119 {
 120         /* Using "rex64; fxsave %0" is broken because, if the memory operand
 121            uses any extended registers for addressing, a second REX prefix
 122            will be generated (to the assembler, rex64 followed by semicolon
 123            is a separate instruction), and hence the 64-bitness is lost. */
 124 #if 0
 125         /* Using "fxsaveq %0" would be the ideal choice, but is only supported
 126            starting with gas 2.16. */
 127         __asm__ __volatile__("fxsaveq %0"
 128                              : "=m" (tsk->thread.i387.fxsave));
 129 #elif 0
 130         /* Using, as a workaround, the properly prefixed form below isn't
 131            accepted by any binutils version so far released, complaining that
 132            the same type of prefix is used twice if an extended register is
 133            needed for addressing (fix submitted to mainline 2005-11-21). */
 134         __asm__ __volatile__("rex64/fxsave %0"
 135                              : "=m" (tsk->thread.i387.fxsave));
 136 #else
 137         /* This, however, we can work around by forcing the compiler to select
 138            an addressing mode that doesn't require extended registers. */
 139         __asm__ __volatile__("rex64/fxsave %P2(%1)"
 140                              : "=m" (tsk->thread.i387.fxsave)
 141                              : "cdaSDb" (tsk),
 142                                 "i" (offsetof(__typeof__(*tsk),
 143                                               thread.i387.fxsave)));
 144 #endif
 145         clear_fpu_state(&tsk->thread.i387.fxsave);
 146         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 147 }
 148
 149 /*
 150  * Signal frame handlers.
 151  */
 152
 153 static inline int save_i387(struct _fpstate __user *buf)
 154 {
 155         struct task_struct *tsk = current;
 156         int err = 0;
 157
 158         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
 159                         sizeof(tsk->thread.i387.fxsave));
 160
 161         if ((unsigned long)buf % 16)
 162                 printk("save_i387: bad fpstate %p\n", buf);
 163
 164         if (!used_math())
 165                 return 0;
 166         clear_used_math(); /* trigger finit */
 167         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 168                 err = save_i387_checking((struct i387_fxsave_struct __user *)buf);
 169                 if (err) return err;
 170                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 171                 stts();
 172         } else {
 173                 if (__copy_to_user(buf, &tsk->thread.i387.fxsave,
 174                                    sizeof(struct i387_fxsave_struct)))
 175                         return -1;
 176         }
 177         return 1;
 178 }
 179
 180 /*
 181  * This restores directly out of user space. Exceptions are handled.
 182  */
 183 static inline int restore_i387(struct _fpstate __user *buf)
 184 {
 185         set_used_math();
 186         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
 187                 clts();
 188                 task_thread_info(current)->status |= TS_USEDFPU;
 189         }
 190         return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 191 }
 192
 193 #else  /* CONFIG_X86_32 */
 194
 195 static inline void tolerant_fwait(void)
 196 {
 197         asm volatile("fnclex ; fwait");
 198 }
 199
 200 static inline void restore_fpu(struct task_struct *tsk)
 201 {
 202         /*
 203          * The "nop" is needed to make the instructions the same
 204          * length.
 205          */
 206         alternative_input(
 207                 "nop ; frstor %1",
 208                 "fxrstor %1",
 209                 X86_FEATURE_FXSR,
 210                 "m" ((tsk)->thread.i387.fxsave));
 211 }
 212
 213 /* We need a safe address that is cheap to find and that is already
 214    in L1 during context switch. The best choices are unfortunately
 215    different for UP and SMP */
 216 #ifdef CONFIG_SMP
 217 #define safe_address (__per_cpu_offset[0])
 218 #else
 219 #define safe_address (kstat_cpu(0).cpustat.user)
 220 #endif
 221
 222 /*
 223  * These must be called with preempt disabled
 224  */
 225 static inline void __save_init_fpu(struct task_struct *tsk)
 226 {
 227         /* Use more nops than strictly needed in case the compiler
 228            varies code */
 229         alternative_input(
 230                 "fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4,
 231                 "fxsave %[fx]\n"
 232                 "bt $7,%[fsw] ; jnc 1f ; fnclex\n1:",
 233                 X86_FEATURE_FXSR,
 234                 [fx] "m" (tsk->thread.i387.fxsave),
 235                 [fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory");
 236         /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception
 237            is pending.  Clear the x87 state here by setting it to fixed
 238            values. safe_address is a random variable that should be in L1 */
 239         alternative_input(
 240                 GENERIC_NOP8 GENERIC_NOP2,
 241                 "emms\n\t"              /* clear stack tags */
 242                 "fildl %[addr]",        /* set F?P to defined value */
 243                 X86_FEATURE_FXSAVE_LEAK,
 244                 [addr] "m" (safe_address));
 245         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 246 }
 247
 248 /*
 249  * Signal frame handlers...
 250  */
 251 extern int save_i387(struct _fpstate __user *buf);
 252 extern int restore_i387(struct _fpstate __user *buf);
 253
 254 #endif  /* CONFIG_X86_64 */
 255
 256 static inline void __unlazy_fpu(struct task_struct *tsk)
 257 {
 258         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 259                 __save_init_fpu(tsk);
 260                 stts();
 261         } else
 262                 tsk->fpu_counter = 0;
 263 }
 264
 265 static inline void __clear_fpu(struct task_struct *tsk)
 266 {
 267         if (task_thread_info(tsk)->status & TS_USEDFPU) {
 268                 tolerant_fwait();
 269                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
 270                 stts();
 271         }
 272 }
 273
 274 static inline void kernel_fpu_begin(void)
 275 {
 276         struct thread_info *me = current_thread_info();
 277         preempt_disable();
 278         if (me->status & TS_USEDFPU)
 279                 __save_init_fpu(me->task);
 280         else
 281                 clts();
 282 }
 283
 284 static inline void kernel_fpu_end(void)
 285 {
 286         stts();
 287         preempt_enable();
 288 }
 289
 290 #ifdef CONFIG_X86_64
 291
 292 static inline void save_init_fpu(struct task_struct *tsk)
 293 {
 294         __save_init_fpu(tsk);
 295         stts();
 296 }
 297
 298 #define unlazy_fpu      __unlazy_fpu
 299 #define clear_fpu       __clear_fpu
 300
 301 #else  /* CONFIG_X86_32 */
 302
 303 /*
 304  * These disable preemption on their own and are safe
 305  */
 306 static inline void save_init_fpu(struct task_struct *tsk)
 307 {
 308         preempt_disable();
 309         __save_init_fpu(tsk);
 310         stts();
 311         preempt_enable();
 312 }
 313
 314 static inline void unlazy_fpu(struct task_struct *tsk)
 315 {
 316         preempt_disable();
 317         __unlazy_fpu(tsk);
 318         preempt_enable();
 319 }
 320
 321 static inline void clear_fpu(struct task_struct *tsk)
 322 {
 323         preempt_disable();
 324         __clear_fpu(tsk);
 325         preempt_enable();
 326 }
 327
 328 #endif  /* CONFIG_X86_64 */
 329
 330 /*
 331  * i387 state interaction
 332  */
 333 static inline unsigned short get_fpu_cwd(struct task_struct *tsk)
 334 {
 335         if (cpu_has_fxsr) {
 336                 return tsk->thread.i387.fxsave.cwd;
 337         } else {
 338                 return (unsigned short)tsk->thread.i387.fsave.cwd;
 339         }
 340 }
 341
 342 static inline unsigned short get_fpu_swd(struct task_struct *tsk)
 343 {
 344         if (cpu_has_fxsr) {
 345                 return tsk->thread.i387.fxsave.swd;
 346         } else {
 347                 return (unsigned short)tsk->thread.i387.fsave.swd;
 348         }
 349 }
 350
 351 static inline unsigned short get_fpu_mxcsr(struct task_struct *tsk)
 352 {
 353         if (cpu_has_xmm) {
 354                 return tsk->thread.i387.fxsave.mxcsr;
 355         } else {
 356                 return MXCSR_DEFAULT;
 357         }
 358 }
 359
 360 #endif  /* _ASM_X86_I387_H */