arch/x86_64/kernel/i387.c

   1 /*
   2  *  linux/arch/x86_64/kernel/i387.c
   3  *
   4  *  Copyright (C) 1994 Linus Torvalds
   5  *  Copyright (C) 2002 Andi Kleen, SuSE Labs
   6  *
   7  *  Pentium III FXSR, SSE support
   8  *  General FPU state handling cleanups
   9  *      Gareth Hughes <gareth@valinux.com>, May 2000
  10  *
  11  *  x86-64 rework 2002 Andi Kleen.
  12  *  Does direct fxsave in and out of user space now for signal handlers.
  13  *  All the FSAVE<->FXSAVE conversion code has been moved to the 32bit emulation,
  14  *  the 64bit user space sees a FXSAVE frame directly.
  15  */
  16
  17 #include <linux/sched.h>
  18 #include <linux/init.h>
  19 #include <asm/processor.h>
  20 #include <asm/i387.h>
  21 #include <asm/sigcontext.h>
  22 #include <asm/user.h>
  23 #include <asm/ptrace.h>
  24 #include <asm/uaccess.h>
  25
  26 unsigned int mxcsr_feature_mask __read_mostly = 0xffffffff;
  27
  28 void mxcsr_feature_mask_init(void)
  29 {
  30         unsigned int mask;
  31         clts();
  32         memset(&current->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
  33         asm volatile("fxsave %0" : : "m" (current->thread.i387.fxsave));
  34         mask = current->thread.i387.fxsave.mxcsr_mask;
  35         if (mask == 0) mask = 0x0000ffbf;
  36         mxcsr_feature_mask &= mask;
  37         stts();
  38 }
  39
  40 /*
  41  * Called at bootup to set up the initial FPU state that is later cloned
  42  * into all processes.
  43  */
  44 void __cpuinit fpu_init(void)
  45 {
  46         unsigned long oldcr0 = read_cr0();
  47         extern void __bad_fxsave_alignment(void);
  48
  49         if (offsetof(struct task_struct, thread.i387.fxsave) & 15)
  50                 __bad_fxsave_alignment();
  51         set_in_cr4(X86_CR4_OSFXSR);
  52         set_in_cr4(X86_CR4_OSXMMEXCPT);
  53
  54         write_cr0(oldcr0 & ~((1UL<<3)|(1UL<<2))); /* clear TS and EM */
  55
  56         mxcsr_feature_mask_init();
  57         /* clean state in init */
  58         current_thread_info()->status = 0;
  59         clear_used_math();
  60 }
  61
  62 void init_fpu(struct task_struct *child)
  63 {
  64         if (tsk_used_math(child)) {
  65                 if (child == current)
  66                         unlazy_fpu(child);
  67                 return;
  68         }
  69         memset(&child->thread.i387.fxsave, 0, sizeof(struct i387_fxsave_struct));
  70         child->thread.i387.fxsave.cwd = 0x37f;
  71         child->thread.i387.fxsave.mxcsr = 0x1f80;
  72         /* only the device not available exception or ptrace can call init_fpu */
  73         set_stopped_child_used_math(child);
  74 }
  75
  76 /*
  77  * Signal frame handlers.
  78  */
  79
  80 int save_i387(struct _fpstate __user *buf)
  81 {
  82         struct task_struct *tsk = current;
  83         int err = 0;
  84
  85         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
  86                         sizeof(tsk->thread.i387.fxsave));
  87
  88         if ((unsigned long)buf % 16)
  89                 printk("save_i387: bad fpstate %p\n",buf);
  90
  91         if (!used_math())
  92                 return 0;
  93         clear_used_math(); /* trigger finit */
  94         if (task_thread_info(tsk)->status & TS_USEDFPU) {
  95                 err = save_i387_checking((struct i387_fxsave_struct __user *)buf);
  96                 if (err) return err;
  97                 stts();
  98                 } else {
  99                 if (__copy_to_user(buf, &tsk->thread.i387.fxsave,
 100                                    sizeof(struct i387_fxsave_struct)))
 101                         return -1;
 102         }
 103                 return 1;
 104 }
 105
 106 /*
 107  * ptrace request handlers.
 108  */
 109
 110 int get_fpregs(struct user_i387_struct __user *buf, struct task_struct *tsk)
 111 {
 112         init_fpu(tsk);
 113         return __copy_to_user(buf, &tsk->thread.i387.fxsave,
 114                                sizeof(struct user_i387_struct)) ? -EFAULT : 0;
 115 }
 116
 117 int set_fpregs(struct task_struct *tsk, struct user_i387_struct __user *buf)
 118 {
 119         if (__copy_from_user(&tsk->thread.i387.fxsave, buf,
 120                              sizeof(struct user_i387_struct)))
 121                 return -EFAULT;
 122                 return 0;
 123 }
 124
 125 /*
 126  * FPU state for core dumps.
 127  */
 128
 129 int dump_fpu( struct pt_regs *regs, struct user_i387_struct *fpu )
 130 {
 131         struct task_struct *tsk = current;
 132
 133         if (!used_math())
 134                 return 0;
 135
 136         unlazy_fpu(tsk);
 137         memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(struct user_i387_struct));
 138         return 1;
 139 }
 140
 141 int dump_task_fpu(struct task_struct *tsk, struct user_i387_struct *fpu)
 142 {
 143         int fpvalid = !!tsk_used_math(tsk);
 144
 145         if (fpvalid) {
 146                 if (tsk == current)
 147                         unlazy_fpu(tsk);
 148                 memcpy(fpu, &tsk->thread.i387.fxsave, sizeof(struct user_i387_struct));
 149 }
 150         return fpvalid;
 151 }