Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6
[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
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         clear_used_math(); /* trigger finit */
118
119         if (task_thread_info(tsk)->status & TS_XSAVE) {
120                 struct _fpstate __user *fx = buf;
121                 struct _xstate __user *x = buf;
122                 u64 xstate_bv;
123
124                 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
125                                      sizeof(struct _fpx_sw_bytes));
126
127                 err |= __put_user(FP_XSTATE_MAGIC2,
128                                   (__u32 __user *) (buf + sig_xstate_size
129                                                     - FP_XSTATE_MAGIC2_SIZE));
130
131                 /*
132                  * Read the xstate_bv which we copied (directly from the cpu or
133                  * from the state in task struct) to the user buffers and
134                  * set the FP/SSE bits.
135                  */
136                 err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
137
138                 /*
139                  * For legacy compatible, we always set FP/SSE bits in the bit
140                  * vector while saving the state to the user context. This will
141                  * enable us capturing any changes(during sigreturn) to
142                  * the FP/SSE bits by the legacy applications which don't touch
143                  * xstate_bv in the xsave header.
144                  *
145                  * xsave aware apps can change the xstate_bv in the xsave
146                  * header as well as change any contents in the memory layout.
147                  * xrestore as part of sigreturn will capture all the changes.
148                  */
149                 xstate_bv |= XSTATE_FPSSE;
150
151                 err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
152
153                 if (err)
154                         return err;
155         }
156
157         return 1;
158 }
159
160 /*
161  * Restore the extended state if present. Otherwise, restore the FP/SSE
162  * state.
163  */
164 static int restore_user_xstate(void __user *buf)
165 {
166         struct _fpx_sw_bytes fx_sw_user;
167         u64 mask;
168         int err;
169
170         if (((unsigned long)buf % 64) ||
171              check_for_xstate(buf, buf, &fx_sw_user))
172                 goto fx_only;
173
174         mask = fx_sw_user.xstate_bv;
175
176         /*
177          * restore the state passed by the user.
178          */
179         err = xrestore_user(buf, mask);
180         if (err)
181                 return err;
182
183         /*
184          * init the state skipped by the user.
185          */
186         mask = pcntxt_mask & ~mask;
187
188         xrstor_state(init_xstate_buf, mask);
189
190         return 0;
191
192 fx_only:
193         /*
194          * couldn't find the extended state information in the
195          * memory layout. Restore just the FP/SSE and init all
196          * the other extended state.
197          */
198         xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
199         return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
200 }
201
202 /*
203  * This restores directly out of user space. Exceptions are handled.
204  */
205 int restore_i387_xstate(void __user *buf)
206 {
207         struct task_struct *tsk = current;
208         int err = 0;
209
210         if (!buf) {
211                 if (used_math())
212                         goto clear;
213                 return 0;
214         } else
215                 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
216                         return -EACCES;
217
218         if (!used_math()) {
219                 err = init_fpu(tsk);
220                 if (err)
221                         return err;
222         }
223
224         if (!(task_thread_info(current)->status & TS_USEDFPU)) {
225                 clts();
226                 task_thread_info(current)->status |= TS_USEDFPU;
227         }
228         if (task_thread_info(tsk)->status & TS_XSAVE)
229                 err = restore_user_xstate(buf);
230         else
231                 err = fxrstor_checking((__force struct i387_fxsave_struct *)
232                                        buf);
233         if (unlikely(err)) {
234                 /*
235                  * Encountered an error while doing the restore from the
236                  * user buffer, clear the fpu state.
237                  */
238 clear:
239                 clear_fpu(tsk);
240                 clear_used_math();
241         }
242         return err;
243 }
244 #endif
245
246 /*
247  * Prepare the SW reserved portion of the fxsave memory layout, indicating
248  * the presence of the extended state information in the memory layout
249  * pointed by the fpstate pointer in the sigcontext.
250  * This will be saved when ever the FP and extended state context is
251  * saved on the user stack during the signal handler delivery to the user.
252  */
253 static void prepare_fx_sw_frame(void)
254 {
255         int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
256                              FP_XSTATE_MAGIC2_SIZE;
257
258         sig_xstate_size = sizeof(struct _fpstate) + size_extended;
259
260 #ifdef CONFIG_IA32_EMULATION
261         sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
262 #endif
263
264         memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
265
266         fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
267         fx_sw_reserved.extended_size = sig_xstate_size;
268         fx_sw_reserved.xstate_bv = pcntxt_mask;
269         fx_sw_reserved.xstate_size = xstate_size;
270 #ifdef CONFIG_IA32_EMULATION
271         memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
272                sizeof(struct _fpx_sw_bytes));
273         fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
274 #endif
275 }
276
277 /*
278  * Represents init state for the supported extended state.
279  */
280 struct xsave_struct *init_xstate_buf;
281
282 #ifdef CONFIG_X86_64
283 unsigned int sig_xstate_size = sizeof(struct _fpstate);
284 #endif
285
286 /*
287  * Enable the extended processor state save/restore feature
288  */
289 void __cpuinit xsave_init(void)
290 {
291         if (!cpu_has_xsave)
292                 return;
293
294         set_in_cr4(X86_CR4_OSXSAVE);
295
296         /*
297          * Enable all the features that the HW is capable of
298          * and the Linux kernel is aware of.
299          */
300         xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
301 }
302
303 /*
304  * setup the xstate image representing the init state
305  */
306 static void __init setup_xstate_init(void)
307 {
308         init_xstate_buf = alloc_bootmem(xstate_size);
309         init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
310 }
311
312 /*
313  * Enable and initialize the xsave feature.
314  */
315 void __ref xsave_cntxt_init(void)
316 {
317         unsigned int eax, ebx, ecx, edx;
318
319         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
320         pcntxt_mask = eax + ((u64)edx << 32);
321
322         if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
323                 printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
324                        pcntxt_mask);
325                 BUG();
326         }
327
328         /*
329          * Support only the state known to OS.
330          */
331         pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
332         xsave_init();
333
334         /*
335          * Recompute the context size for enabled features
336          */
337         cpuid_count(0xd, 0, &eax, &ebx, &ecx, &edx);
338         xstate_size = ebx;
339
340         update_regset_xstate_info(xstate_size, pcntxt_mask);
341         prepare_fx_sw_frame();
342
343         setup_xstate_init();
344
345         printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
346                "cntxt size 0x%x\n",
347                pcntxt_mask, xstate_size);
348 }