Merge branch 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
[linux-2.6.git] / 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 #ifdef CONFIG_IA32_EMULATION
10 #include <asm/sigcontext32.h>
11 #endif
12 #include <asm/xcr.h>
13
14 /*
15  * Supported feature mask by the CPU and the kernel.
16  */
17 u64 pcntxt_mask;
18
19 struct _fpx_sw_bytes fx_sw_reserved;
20 #ifdef CONFIG_IA32_EMULATION
21 struct _fpx_sw_bytes fx_sw_reserved_ia32;
22 #endif
23
24 /*
25  * Check for the presence of extended state information in the
26  * user fpstate pointer in the sigcontext.
27  */
28 int check_for_xstate(struct i387_fxsave_struct __user *buf,
29                      void __user *fpstate,
30                      struct _fpx_sw_bytes *fx_sw_user)
31 {
32         int min_xstate_size = sizeof(struct i387_fxsave_struct) +
33                               sizeof(struct xsave_hdr_struct);
34         unsigned int magic2;
35         int err;
36
37         err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
38                                sizeof(struct _fpx_sw_bytes));
39
40         if (err)
41                 return err;
42
43         /*
44          * First Magic check failed.
45          */
46         if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
47                 return -1;
48
49         /*
50          * Check for error scenarios.
51          */
52         if (fx_sw_user->xstate_size < min_xstate_size ||
53             fx_sw_user->xstate_size > xstate_size ||
54             fx_sw_user->xstate_size > fx_sw_user->extended_size)
55                 return -1;
56
57         err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
58                                             fx_sw_user->extended_size -
59                                             FP_XSTATE_MAGIC2_SIZE));
60         /*
61          * Check for the presence of second magic word at the end of memory
62          * layout. This detects the case where the user just copied the legacy
63          * fpstate layout with out copying the extended state information
64          * in the memory layout.
65          */
66         if (err || magic2 != FP_XSTATE_MAGIC2)
67                 return -1;
68
69         return 0;
70 }
71
72 #ifdef CONFIG_X86_64
73 /*
74  * Signal frame handlers.
75  */
76
77 int save_i387_xstate(void __user *buf)
78 {
79         struct task_struct *tsk = current;
80         int err = 0;
81
82         if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
83                 return -EACCES;
84
85         BUG_ON(sig_xstate_size < xstate_size);
86
87         if ((unsigned long)buf % 64)
88                 printk("save_i387_xstate: bad fpstate %p\n", buf);
89
90         if (!used_math())
91                 return 0;
92         clear_used_math(); /* trigger finit */
93         if (task_thread_info(tsk)->status & TS_USEDFPU) {
94                 /*
95                  * Start with clearing the user buffer. This will present a
96                  * clean context for the bytes not touched by the fxsave/xsave.
97                  */
98                 __clear_user(buf, sig_xstate_size);
99
100                 if (task_thread_info(tsk)->status & TS_XSAVE)
101                         err = xsave_user(buf);
102                 else
103                         err = fxsave_user(buf);
104
105                 if (err)
106                         return err;
107                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
108                 stts();
109         } else {
110                 if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
111                                    xstate_size))
112                         return -1;
113         }
114
115         if (task_thread_info(tsk)->status & TS_XSAVE) {
116                 struct _fpstate __user *fx = buf;
117
118                 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
119                                      sizeof(struct _fpx_sw_bytes));
120
121                 err |= __put_user(FP_XSTATE_MAGIC2,
122                                   (__u32 __user *) (buf + sig_xstate_size
123                                                     - FP_XSTATE_MAGIC2_SIZE));
124         }
125
126         return 1;
127 }
128
129 /*
130  * Restore the extended state if present. Otherwise, restore the FP/SSE
131  * state.
132  */
133 int restore_user_xstate(void __user *buf)
134 {
135         struct _fpx_sw_bytes fx_sw_user;
136         u64 mask;
137         int err;
138
139         if (((unsigned long)buf % 64) ||
140              check_for_xstate(buf, buf, &fx_sw_user))
141                 goto fx_only;
142
143         mask = fx_sw_user.xstate_bv;
144
145         /*
146          * restore the state passed by the user.
147          */
148         err = xrestore_user(buf, mask);
149         if (err)
150                 return err;
151
152         /*
153          * init the state skipped by the user.
154          */
155         mask = pcntxt_mask & ~mask;
156
157         xrstor_state(init_xstate_buf, mask);
158
159         return 0;
160
161 fx_only:
162         /*
163          * couldn't find the extended state information in the
164          * memory layout. Restore just the FP/SSE and init all
165          * the other extended state.
166          */
167         xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
168         return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
169 }
170
171 /*
172  * This restores directly out of user space. Exceptions are handled.
173  */
174 int restore_i387_xstate(void __user *buf)
175 {
176         struct task_struct *tsk = current;
177         int err = 0;
178
179         if (!buf) {
180                 if (used_math())
181                         goto clear;
182                 return 0;
183         } else
184                 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
185                         return -EACCES;
186
187         if (!used_math()) {
188                 err = init_fpu(tsk);
189                 if (err)
190                         return err;
191         }
192
193         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
194                 clts();
195                 task_thread_info(current)->status |= TS_USEDFPU;
196         }
197         if (task_thread_info(tsk)->status & TS_XSAVE)
198                 err = restore_user_xstate(buf);
199         else
200                 err = fxrstor_checking((__force struct i387_fxsave_struct *)
201                                        buf);
202         if (unlikely(err)) {
203                 /*
204                  * Encountered an error while doing the restore from the
205                  * user buffer, clear the fpu state.
206                  */
207 clear:
208                 clear_fpu(tsk);
209                 clear_used_math();
210         }
211         return err;
212 }
213 #endif
214
215 /*
216  * Prepare the SW reserved portion of the fxsave memory layout, indicating
217  * the presence of the extended state information in the memory layout
218  * pointed by the fpstate pointer in the sigcontext.
219  * This will be saved when ever the FP and extended state context is
220  * saved on the user stack during the signal handler delivery to the user.
221  */
222 void prepare_fx_sw_frame(void)
223 {
224         int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
225                              FP_XSTATE_MAGIC2_SIZE;
226
227         sig_xstate_size = sizeof(struct _fpstate) + size_extended;
228
229 #ifdef CONFIG_IA32_EMULATION
230         sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
231 #endif
232
233         memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
234
235         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
236         fx_sw_reserved.extended_size = sig_xstate_size;
237         fx_sw_reserved.xstate_bv = pcntxt_mask;
238         fx_sw_reserved.xstate_size = xstate_size;
239 #ifdef CONFIG_IA32_EMULATION
240         memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
241                sizeof(struct _fpx_sw_bytes));
242         fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
243 #endif
244 }
245
246 /*
247  * Represents init state for the supported extended state.
248  */
249 struct xsave_struct *init_xstate_buf;
250
251 #ifdef CONFIG_X86_64
252 unsigned int sig_xstate_size = sizeof(struct _fpstate);
253 #endif
254
255 /*
256  * Enable the extended processor state save/restore feature
257  */
258 void __cpuinit xsave_init(void)
259 {
260         if (!cpu_has_xsave)
261                 return;
262
263         set_in_cr4(X86_CR4_OSXSAVE);
264
265         /*
266          * Enable all the features that the HW is capable of
267          * and the Linux kernel is aware of.
268          */
269         xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
270 }
271
272 /*
273  * setup the xstate image representing the init state
274  */
275 void setup_xstate_init(void)
276 {
277         init_xstate_buf = alloc_bootmem(xstate_size);
278         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
279 }
280
281 /*
282  * Enable and initialize the xsave feature.
283  */
284 void __init xsave_cntxt_init(void)
285 {
286         unsigned int eax, ebx, ecx, edx;
287
288         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
289         pcntxt_mask = eax + ((u64)edx << 32);
290
291         if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
292                 printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
293                        pcntxt_mask);
294                 BUG();
295         }
296
297         /*
298          * for now OS knows only about FP/SSE
299          */
300         pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
301         xsave_init();
302
303         /*
304          * Recompute the context size for enabled features
305          */
306         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
307         xstate_size = ebx;
308
309         prepare_fx_sw_frame();
310
311         setup_xstate_init();
312
313         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
314                "cntxt size 0x%x\n",
315                pcntxt_mask, xstate_size);
316 }