Merge branch 'linus' into core/futexes
[linux-2.6] / 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                 err = __clear_user(buf, sig_xstate_size);
99                 if (err)
100                         return err;
101
102                 if (task_thread_info(tsk)->status & TS_XSAVE)
103                         err = xsave_user(buf);
104                 else
105                         err = fxsave_user(buf);
106
107                 if (err)
108                         return err;
109                 task_thread_info(tsk)->status &= ~TS_USEDFPU;
110                 stts();
111         } else {
112                 if (__copy_to_user(buf, &tsk->thread.xstate->fxsave,
113                                    xstate_size))
114                         return -1;
115         }
116
117         if (task_thread_info(tsk)->status & TS_XSAVE) {
118                 struct _fpstate __user *fx = buf;
119                 struct _xstate __user *x = buf;
120                 u64 xstate_bv;
121
122                 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
123                                      sizeof(struct _fpx_sw_bytes));
124
125                 err |= __put_user(FP_XSTATE_MAGIC2,
126                                   (__u32 __user *) (buf + sig_xstate_size
127                                                     - FP_XSTATE_MAGIC2_SIZE));
128
129                 /*
130                  * Read the xstate_bv which we copied (directly from the cpu or
131                  * from the state in task struct) to the user buffers and
132                  * set the FP/SSE bits.
133                  */
134                 err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
135
136                 /*
137                  * For legacy compatible, we always set FP/SSE bits in the bit
138                  * vector while saving the state to the user context. This will
139                  * enable us capturing any changes(during sigreturn) to
140                  * the FP/SSE bits by the legacy applications which don't touch
141                  * xstate_bv in the xsave header.
142                  *
143                  * xsave aware apps can change the xstate_bv in the xsave
144                  * header as well as change any contents in the memory layout.
145                  * xrestore as part of sigreturn will capture all the changes.
146                  */
147                 xstate_bv |= XSTATE_FPSSE;
148
149                 err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
150
151                 if (err)
152                         return err;
153         }
154
155         return 1;
156 }
157
158 /*
159  * Restore the extended state if present. Otherwise, restore the FP/SSE
160  * state.
161  */
162 int restore_user_xstate(void __user *buf)
163 {
164         struct _fpx_sw_bytes fx_sw_user;
165         u64 mask;
166         int err;
167
168         if (((unsigned long)buf % 64) ||
169              check_for_xstate(buf, buf, &fx_sw_user))
170                 goto fx_only;
171
172         mask = fx_sw_user.xstate_bv;
173
174         /*
175          * restore the state passed by the user.
176          */
177         err = xrestore_user(buf, mask);
178         if (err)
179                 return err;
180
181         /*
182          * init the state skipped by the user.
183          */
184         mask = pcntxt_mask & ~mask;
185
186         xrstor_state(init_xstate_buf, mask);
187
188         return 0;
189
190 fx_only:
191         /*
192          * couldn't find the extended state information in the
193          * memory layout. Restore just the FP/SSE and init all
194          * the other extended state.
195          */
196         xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
197         return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
198 }
199
200 /*
201  * This restores directly out of user space. Exceptions are handled.
202  */
203 int restore_i387_xstate(void __user *buf)
204 {
205         struct task_struct *tsk = current;
206         int err = 0;
207
208         if (!buf) {
209                 if (used_math())
210                         goto clear;
211                 return 0;
212         } else
213                 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
214                         return -EACCES;
215
216         if (!used_math()) {
217                 err = init_fpu(tsk);
218                 if (err)
219                         return err;
220         }
221
222         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
223                 clts();
224                 task_thread_info(current)->status |= TS_USEDFPU;
225         }
226         if (task_thread_info(tsk)->status & TS_XSAVE)
227                 err = restore_user_xstate(buf);
228         else
229                 err = fxrstor_checking((__force struct i387_fxsave_struct *)
230                                        buf);
231         if (unlikely(err)) {
232                 /*
233                  * Encountered an error while doing the restore from the
234                  * user buffer, clear the fpu state.
235                  */
236 clear:
237                 clear_fpu(tsk);
238                 clear_used_math();
239         }
240         return err;
241 }
242 #endif
243
244 /*
245  * Prepare the SW reserved portion of the fxsave memory layout, indicating
246  * the presence of the extended state information in the memory layout
247  * pointed by the fpstate pointer in the sigcontext.
248  * This will be saved when ever the FP and extended state context is
249  * saved on the user stack during the signal handler delivery to the user.
250  */
251 static void prepare_fx_sw_frame(void)
252 {
253         int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
254                              FP_XSTATE_MAGIC2_SIZE;
255
256         sig_xstate_size = sizeof(struct _fpstate) + size_extended;
257
258 #ifdef CONFIG_IA32_EMULATION
259         sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
260 #endif
261
262         memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
263
264         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
265         fx_sw_reserved.extended_size = sig_xstate_size;
266         fx_sw_reserved.xstate_bv = pcntxt_mask;
267         fx_sw_reserved.xstate_size = xstate_size;
268 #ifdef CONFIG_IA32_EMULATION
269         memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
270                sizeof(struct _fpx_sw_bytes));
271         fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
272 #endif
273 }
274
275 /*
276  * Represents init state for the supported extended state.
277  */
278 struct xsave_struct *init_xstate_buf;
279
280 #ifdef CONFIG_X86_64
281 unsigned int sig_xstate_size = sizeof(struct _fpstate);
282 #endif
283
284 /*
285  * Enable the extended processor state save/restore feature
286  */
287 void __cpuinit xsave_init(void)
288 {
289         if (!cpu_has_xsave)
290                 return;
291
292         set_in_cr4(X86_CR4_OSXSAVE);
293
294         /*
295          * Enable all the features that the HW is capable of
296          * and the Linux kernel is aware of.
297          */
298         xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
299 }
300
301 /*
302  * setup the xstate image representing the init state
303  */
304 static void __init setup_xstate_init(void)
305 {
306         init_xstate_buf = alloc_bootmem(xstate_size);
307         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
308 }
309
310 /*
311  * Enable and initialize the xsave feature.
312  */
313 void __init xsave_cntxt_init(void)
314 {
315         unsigned int eax, ebx, ecx, edx;
316
317         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
318         pcntxt_mask = eax + ((u64)edx << 32);
319
320         if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
321                 printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
322                        pcntxt_mask);
323                 BUG();
324         }
325
326         /*
327          * for now OS knows only about FP/SSE
328          */
329         pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
330         xsave_init();
331
332         /*
333          * Recompute the context size for enabled features
334          */
335         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
336         xstate_size = ebx;
337
338         prepare_fx_sw_frame();
339
340         setup_xstate_init();
341
342         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
343                "cntxt size 0x%x\n",
344                pcntxt_mask, xstate_size);
345 }