arch/x86/kernel/xsave.c

   1 /*
   2  * xsave/xrstor support.
   3  *
   4  * Author: Suresh Siddha <suresh.b.siddha@intel.com>
   5  */
   6 #include <linux/bootmem.h>
   7 #include <linux/compat.h>
   8 #include <asm/i387.h>
   9
  10 /*
  11  * Supported feature mask by the CPU and the kernel.
  12  */
  13 unsigned int pcntxt_hmask, pcntxt_lmask;
  14
  15 #ifdef CONFIG_X86_64
  16 /*
  17  * Signal frame handlers.
  18  */
  19
  20 int save_i387_xstate(void __user *buf)
  21 {
  22         struct task_struct *tsk = current;
  23         int err = 0;
  24
  25         if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
  26                 return -EACCES;
  27
  28         BUILD_BUG_ON(sizeof(struct user_i387_struct) !=
  29                         sizeof(tsk->thread.xstate->fxsave));
  30
  31         if ((unsigned long)buf % 16)
  32                 printk("save_i387_xstate: bad fpstate %p\n", buf);
  33
  34         if (!used_math())
  35                 return 0;
  36         clear_used_math(); /* trigger finit */
  37         if (task_thread_info(tsk)->status & TS_USEDFPU) {
  38                 err = save_i387_checking((struct i387_fxsave_struct __user *)
  39                                          buf);
  40                 if (err)
  41                         return err;
  42                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
  43                 stts();
  44         } else {
  45                 if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
  46                                    xstate_size))
  47                         return -1;
  48         }
  49         return 1;
  50 }
  51
  52 /*
  53  * This restores directly out of user space. Exceptions are handled.
  54  */
  55 int restore_i387_xstate(void __user *buf)
  56 {
  57         struct task_struct *tsk = current;
  58         int err;
  59
  60         if (!buf) {
  61                 if (used_math()) {
  62                         clear_fpu(tsk);
  63                         clear_used_math();
  64                 }
  65
  66                 return 0;
  67         } else
  68                 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
  69                         return -EACCES;
  70
  71         if (!used_math()) {
  72                 err = init_fpu(tsk);
  73                 if (err)
  74                         return err;
  75         }
  76
  77         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
  78                 clts();
  79                 task_thread_info(current)->status |= TS_USEDFPU;
  80         }
  81         err = fxrstor_checking((__force struct i387_fxsave_struct *)buf);
  82         if (unlikely(err)) {
  83                 /*
  84                  * Encountered an error while doing the restore from the
  85                  * user buffer, clear the fpu state.
  86                  */
  87                 clear_fpu(tsk);
  88                 clear_used_math();
  89         }
  90         return err;
  91 }
  92 #endif
  93
  94 /*
  95  * Represents init state for the supported extended state.
  96  */
  97 struct xsave_struct *init_xstate_buf;
  98
  99 #ifdef CONFIG_X86_64
 100 unsigned int sig_xstate_size = sizeof(struct _fpstate);
 101 #endif
 102
 103 /*
 104  * Enable the extended processor state save/restore feature
 105  */
 106 void __cpuinit xsave_init(void)
 107 {
 108         if (!cpu_has_xsave)
 109                 return;
 110
 111         set_in_cr4(X86_CR4_OSXSAVE);
 112
 113         /*
 114          * Enable all the features that the HW is capable of
 115          * and the Linux kernel is aware of.
 116          *
 117          * xsetbv();
 118          */
 119         asm volatile(".byte 0x0f,0x01,0xd1" : : "c" (0),
 120                      "a" (pcntxt_lmask), "d" (pcntxt_hmask));
 121 }
 122
 123 /*
 124  * setup the xstate image representing the init state
 125  */
 126 void setup_xstate_init(void)
 127 {
 128         init_xstate_buf = alloc_bootmem(xstate_size);
 129         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
 130 }
 131
 132 /*
 133  * Enable and initialize the xsave feature.
 134  */
 135 void __init xsave_cntxt_init(void)
 136 {
 137         unsigned int eax, ebx, ecx, edx;
 138
 139         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
 140
 141         pcntxt_lmask = eax;
 142         pcntxt_hmask = edx;
 143
 144         if ((pcntxt_lmask & XSTATE_FPSSE) != XSTATE_FPSSE) {
 145                 printk(KERN_ERR "FP/SSE not shown under xsave features %x\n",
 146                        pcntxt_lmask);
 147                 BUG();
 148         }
 149
 150         /*
 151          * for now OS knows only about FP/SSE
 152          */
 153         pcntxt_lmask = pcntxt_lmask & XCNTXT_LMASK;
 154         pcntxt_hmask = pcntxt_hmask & XCNTXT_HMASK;
 155
 156         xsave_init();
 157
 158         /*
 159          * Recompute the context size for enabled features
 160          */
 161         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
 162
 163         xstate_size = ebx;
 164
 165         setup_xstate_init();
 166
 167         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%Lx, "
 168                "cntxt size 0x%x\n",
 169                (pcntxt_lmask | ((u64) pcntxt_hmask << 32)), xstate_size);
 170 }