include/asm-x86_64/i387.h

   1 /*
   2  * include/asm-x86_64/i387.h
   3  *
   4  * Copyright (C) 1994 Linus Torvalds
   5  *
   6  * Pentium III FXSR, SSE support
   7  * General FPU state handling cleanups
   8  *      Gareth Hughes <gareth@valinux.com>, May 2000
   9  * x86-64 work by Andi Kleen 2002
  10  */
  11
  12 #ifndef __ASM_X86_64_I387_H
  13 #define __ASM_X86_64_I387_H
  14
  15 #include <linux/sched.h>
  16 #include <asm/processor.h>
  17 #include <asm/sigcontext.h>
  18 #include <asm/user.h>
  19 #include <asm/thread_info.h>
  20 #include <asm/uaccess.h>
  21
  22 extern void fpu_init(void);
  23 extern unsigned int mxcsr_feature_mask;
  24 extern void mxcsr_feature_mask_init(void);
  25 extern void init_fpu(struct task_struct *child);
  26 extern int save_i387(struct _fpstate __user *buf);
  27 extern asmlinkage void math_state_restore(void);
  28
  29 /*
  30  * FPU lazy state save handling...
  31  */
  32
  33 #define unlazy_fpu(tsk) do { \
  34         if (task_thread_info(tsk)->status & TS_USEDFPU) \
  35                 save_init_fpu(tsk);                     \
  36         else                                            \
  37                 tsk->fpu_counter = 0;                   \
  38 } while (0)
  39
  40 /* Ignore delayed exceptions from user space */
  41 static inline void tolerant_fwait(void)
  42 {
  43         asm volatile("1: fwait\n"
  44                      "2:\n"
  45                      "   .section __ex_table,\"a\"\n"
  46                      "  .align 8\n"
  47                      "  .quad 1b,2b\n"
  48                      "  .previous\n");
  49 }
  50
  51 #define clear_fpu(tsk) do { \
  52         if (task_thread_info(tsk)->status & TS_USEDFPU) {       \
  53                 tolerant_fwait();                               \
  54                 task_thread_info(tsk)->status &= ~TS_USEDFPU;   \
  55                 stts();                                         \
  56         }                                                       \
  57 } while (0)
  58
  59 /*
  60  * ptrace request handers...
  61  */
  62 extern int get_fpregs(struct user_i387_struct __user *buf,
  63                       struct task_struct *tsk);
  64 extern int set_fpregs(struct task_struct *tsk,
  65                       struct user_i387_struct __user *buf);
  66
  67 /*
  68  * i387 state interaction
  69  */
  70 #define get_fpu_mxcsr(t) ((t)->thread.i387.fxsave.mxcsr)
  71 #define get_fpu_cwd(t) ((t)->thread.i387.fxsave.cwd)
  72 #define get_fpu_fxsr_twd(t) ((t)->thread.i387.fxsave.twd)
  73 #define get_fpu_swd(t) ((t)->thread.i387.fxsave.swd)
  74 #define set_fpu_cwd(t,val) ((t)->thread.i387.fxsave.cwd = (val))
  75 #define set_fpu_swd(t,val) ((t)->thread.i387.fxsave.swd = (val))
  76 #define set_fpu_fxsr_twd(t,val) ((t)->thread.i387.fxsave.twd = (val))
  77
  78 #define X87_FSW_ES (1 << 7)     /* Exception Summary */
  79
  80 /* AMD CPUs don't save/restore FDP/FIP/FOP unless an exception
  81    is pending. Clear the x87 state here by setting it to fixed
  82    values. The kernel data segment can be sometimes 0 and sometimes
  83    new user value. Both should be ok.
  84    Use the PDA as safe address because it should be already in L1. */
  85 static inline void clear_fpu_state(struct i387_fxsave_struct *fx)
  86 {
  87         if (unlikely(fx->swd & X87_FSW_ES))
  88                  asm volatile("fnclex");
  89         alternative_input(ASM_NOP8 ASM_NOP2,
  90                      "    emms\n"               /* clear stack tags */
  91                      "    fildl %%gs:0",        /* load to clear state */
  92                      X86_FEATURE_FXSAVE_LEAK);
  93 }
  94
  95 static inline int restore_fpu_checking(struct i387_fxsave_struct *fx)
  96 {
  97         int err;
  98
  99         asm volatile("1:  rex64/fxrstor (%[fx])\n\t"
 100                      "2:\n"
 101                      ".section .fixup,\"ax\"\n"
 102                      "3:  movl $-1,%[err]\n"
 103                      "    jmp  2b\n"
 104                      ".previous\n"
 105                      ".section __ex_table,\"a\"\n"
 106                      "   .align 8\n"
 107                      "   .quad  1b,3b\n"
 108                      ".previous"
 109                      : [err] "=r" (err)
 110 #if 0 /* See comment in __fxsave_clear() below. */
 111                      : [fx] "r" (fx), "m" (*fx), "0" (0));
 112 #else
 113                      : [fx] "cdaSDb" (fx), "m" (*fx), "0" (0));
 114 #endif
 115         if (unlikely(err))
 116                 init_fpu(current);
 117         return err;
 118 }
 119
 120 static inline int save_i387_checking(struct i387_fxsave_struct __user *fx)
 121 {
 122         int err;
 123
 124         asm volatile("1:  rex64/fxsave (%[fx])\n\t"
 125                      "2:\n"
 126                      ".section .fixup,\"ax\"\n"
 127                      "3:  movl $-1,%[err]\n"
 128                      "    jmp  2b\n"
 129                      ".previous\n"
 130                      ".section __ex_table,\"a\"\n"
 131                      "   .align 8\n"
 132                      "   .quad  1b,3b\n"
 133                      ".previous"
 134                      : [err] "=r" (err), "=m" (*fx)
 135 #if 0 /* See comment in __fxsave_clear() below. */
 136                      : [fx] "r" (fx), "0" (0));
 137 #else
 138                      : [fx] "cdaSDb" (fx), "0" (0));
 139 #endif
 140         if (unlikely(err) && __clear_user(fx, sizeof(struct i387_fxsave_struct)))
 141                 err = -EFAULT;
 142         /* No need to clear here because the caller clears USED_MATH */
 143         return err;
 144 }
 145
 146 static inline void __fxsave_clear(struct task_struct *tsk)
 147 {
 148         /* Using "rex64; fxsave %0" is broken because, if the memory operand
 149            uses any extended registers for addressing, a second REX prefix
 150            will be generated (to the assembler, rex64 followed by semicolon
 151            is a separate instruction), and hence the 64-bitness is lost. */
 152 #if 0
 153         /* Using "fxsaveq %0" would be the ideal choice, but is only supported
 154            starting with gas 2.16. */
 155         __asm__ __volatile__("fxsaveq %0"
 156                              : "=m" (tsk->thread.i387.fxsave));
 157 #elif 0
 158         /* Using, as a workaround, the properly prefixed form below isn't
 159            accepted by any binutils version so far released, complaining that
 160            the same type of prefix is used twice if an extended register is
 161            needed for addressing (fix submitted to mainline 2005-11-21). */
 162         __asm__ __volatile__("rex64/fxsave %0"
 163                              : "=m" (tsk->thread.i387.fxsave));
 164 #else
 165         /* This, however, we can work around by forcing the compiler to select
 166            an addressing mode that doesn't require extended registers. */
 167         __asm__ __volatile__("rex64/fxsave %P2(%1)"
 168                              : "=m" (tsk->thread.i387.fxsave)
 169                              : "cdaSDb" (tsk),
 170                                 "i" (offsetof(__typeof__(*tsk),
 171                                               thread.i387.fxsave)));
 172 #endif
 173         clear_fpu_state(&tsk->thread.i387.fxsave);
 174 }
 175
 176 static inline void kernel_fpu_begin(void)
 177 {
 178         struct thread_info *me = current_thread_info();
 179         preempt_disable();
 180         if (me->status & TS_USEDFPU) {
 181                 __fxsave_clear(me->task);
 182                 me->status &= ~TS_USEDFPU;
 183                 return;
 184         }
 185         clts();
 186 }
 187
 188 static inline void kernel_fpu_end(void)
 189 {
 190         stts();
 191         preempt_enable();
 192 }
 193
 194 static inline void save_init_fpu(struct task_struct *tsk)
 195 {
 196         __fxsave_clear(tsk);
 197         task_thread_info(tsk)->status &= ~TS_USEDFPU;
 198         stts();
 199 }
 200
 201 /*
 202  * This restores directly out of user space. Exceptions are handled.
 203  */
 204 static inline int restore_i387(struct _fpstate __user *buf)
 205 {
 206         return restore_fpu_checking((__force struct i387_fxsave_struct *)buf);
 207 }
 208
 209 #endif /* __ASM_X86_64_I387_H */