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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#include <asm/fpu-internal.h>
10#ifdef CONFIG_IA32_EMULATION
11#include <asm/sigcontext32.h>
12#endif
13#include <asm/xcr.h>
14
15/*
16 * Supported feature mask by the CPU and the kernel.
17 */
18u64 pcntxt_mask;
19
20/*
21 * Represents init state for the supported extended state.
22 */
23static struct xsave_struct *init_xstate_buf;
24
25struct _fpx_sw_bytes fx_sw_reserved;
26#ifdef CONFIG_IA32_EMULATION
27struct _fpx_sw_bytes fx_sw_reserved_ia32;
28#endif
29
30static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
31
32/*
33 * If a processor implementation discern that a processor state component is
34 * in its initialized state it may modify the corresponding bit in the
35 * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
36 * layout in the case of xsaveopt. While presenting the xstate information to
37 * the user, we always ensure that the memory layout of a feature will be in
38 * the init state if the corresponding header bit is zero. This is to ensure
39 * that the user doesn't see some stale state in the memory layout during
40 * signal handling, debugging etc.
41 */
42void __sanitize_i387_state(struct task_struct *tsk)
43{
44 u64 xstate_bv;
45 int feature_bit = 0x2;
46 struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
47
48 if (!fx)
49 return;
50
51 xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
52
53 /*
54 * None of the feature bits are in init state. So nothing else
55 * to do for us, as the memory layout is up to date.
56 */
57 if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
58 return;
59
60 /*
61 * FP is in init state
62 */
63 if (!(xstate_bv & XSTATE_FP)) {
64 fx->cwd = 0x37f;
65 fx->swd = 0;
66 fx->twd = 0;
67 fx->fop = 0;
68 fx->rip = 0;
69 fx->rdp = 0;
70 memset(&fx->st_space[0], 0, 128);
71 }
72
73 /*
74 * SSE is in init state
75 */
76 if (!(xstate_bv & XSTATE_SSE))
77 memset(&fx->xmm_space[0], 0, 256);
78
79 xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
80
81 /*
82 * Update all the other memory layouts for which the corresponding
83 * header bit is in the init state.
84 */
85 while (xstate_bv) {
86 if (xstate_bv & 0x1) {
87 int offset = xstate_offsets[feature_bit];
88 int size = xstate_sizes[feature_bit];
89
90 memcpy(((void *) fx) + offset,
91 ((void *) init_xstate_buf) + offset,
92 size);
93 }
94
95 xstate_bv >>= 1;
96 feature_bit++;
97 }
98}
99
100/*
101 * Check for the presence of extended state information in the
102 * user fpstate pointer in the sigcontext.
103 */
104int check_for_xstate(struct i387_fxsave_struct __user *buf,
105 void __user *fpstate,
106 struct _fpx_sw_bytes *fx_sw_user)
107{
108 int min_xstate_size = sizeof(struct i387_fxsave_struct) +
109 sizeof(struct xsave_hdr_struct);
110 unsigned int magic2;
111 int err;
112
113 err = __copy_from_user(fx_sw_user, &buf->sw_reserved[0],
114 sizeof(struct _fpx_sw_bytes));
115 if (err)
116 return -EFAULT;
117
118 /*
119 * First Magic check failed.
120 */
121 if (fx_sw_user->magic1 != FP_XSTATE_MAGIC1)
122 return -EINVAL;
123
124 /*
125 * Check for error scenarios.
126 */
127 if (fx_sw_user->xstate_size < min_xstate_size ||
128 fx_sw_user->xstate_size > xstate_size ||
129 fx_sw_user->xstate_size > fx_sw_user->extended_size)
130 return -EINVAL;
131
132 err = __get_user(magic2, (__u32 *) (((void *)fpstate) +
133 fx_sw_user->extended_size -
134 FP_XSTATE_MAGIC2_SIZE));
135 if (err)
136 return err;
137 /*
138 * Check for the presence of second magic word at the end of memory
139 * layout. This detects the case where the user just copied the legacy
140 * fpstate layout with out copying the extended state information
141 * in the memory layout.
142 */
143 if (magic2 != FP_XSTATE_MAGIC2)
144 return -EFAULT;
145
146 return 0;
147}
148
149#ifdef CONFIG_X86_64
150/*
151 * Signal frame handlers.
152 */
153
154int save_i387_xstate(void __user *buf)
155{
156 struct task_struct *tsk = current;
157 int err = 0;
158
159 if (!access_ok(VERIFY_WRITE, buf, sig_xstate_size))
160 return -EACCES;
161
162 BUG_ON(sig_xstate_size < xstate_size);
163
164 if ((unsigned long)buf % 64)
165 printk("save_i387_xstate: bad fpstate %p\n", buf);
166
167 if (!used_math())
168 return 0;
169
170 if (user_has_fpu()) {
171 if (use_xsave())
172 err = xsave_user(buf);
173 else
174 err = fxsave_user(buf);
175
176 if (err)
177 return err;
178 user_fpu_end();
179 } else {
180 sanitize_i387_state(tsk);
181 if (__copy_to_user(buf, &tsk->thread.fpu.state->fxsave,
182 xstate_size))
183 return -1;
184 }
185
186 clear_used_math(); /* trigger finit */
187
188 if (use_xsave()) {
189 struct _fpstate __user *fx = buf;
190 struct _xstate __user *x = buf;
191 u64 xstate_bv;
192
193 err = __copy_to_user(&fx->sw_reserved, &fx_sw_reserved,
194 sizeof(struct _fpx_sw_bytes));
195
196 err |= __put_user(FP_XSTATE_MAGIC2,
197 (__u32 __user *) (buf + sig_xstate_size
198 - FP_XSTATE_MAGIC2_SIZE));
199
200 /*
201 * Read the xstate_bv which we copied (directly from the cpu or
202 * from the state in task struct) to the user buffers and
203 * set the FP/SSE bits.
204 */
205 err |= __get_user(xstate_bv, &x->xstate_hdr.xstate_bv);
206
207 /*
208 * For legacy compatible, we always set FP/SSE bits in the bit
209 * vector while saving the state to the user context. This will
210 * enable us capturing any changes(during sigreturn) to
211 * the FP/SSE bits by the legacy applications which don't touch
212 * xstate_bv in the xsave header.
213 *
214 * xsave aware apps can change the xstate_bv in the xsave
215 * header as well as change any contents in the memory layout.
216 * xrestore as part of sigreturn will capture all the changes.
217 */
218 xstate_bv |= XSTATE_FPSSE;
219
220 err |= __put_user(xstate_bv, &x->xstate_hdr.xstate_bv);
221
222 if (err)
223 return err;
224 }
225
226 return 1;
227}
228
229/*
230 * Restore the extended state if present. Otherwise, restore the FP/SSE
231 * state.
232 */
233static int restore_user_xstate(void __user *buf)
234{
235 struct _fpx_sw_bytes fx_sw_user;
236 u64 mask;
237 int err;
238
239 if (((unsigned long)buf % 64) ||
240 check_for_xstate(buf, buf, &fx_sw_user))
241 goto fx_only;
242
243 mask = fx_sw_user.xstate_bv;
244
245 /*
246 * restore the state passed by the user.
247 */
248 err = xrestore_user(buf, mask);
249 if (err)
250 return err;
251
252 /*
253 * init the state skipped by the user.
254 */
255 mask = pcntxt_mask & ~mask;
256 if (unlikely(mask))
257 xrstor_state(init_xstate_buf, mask);
258
259 return 0;
260
261fx_only:
262 /*
263 * couldn't find the extended state information in the
264 * memory layout. Restore just the FP/SSE and init all
265 * the other extended state.
266 */
267 xrstor_state(init_xstate_buf, pcntxt_mask & ~XSTATE_FPSSE);
268 return fxrstor_checking((__force struct i387_fxsave_struct *)buf);
269}
270
271/*
272 * This restores directly out of user space. Exceptions are handled.
273 */
274int restore_i387_xstate(void __user *buf)
275{
276 struct task_struct *tsk = current;
277 int err = 0;
278
279 if (!buf) {
280 if (used_math())
281 goto clear;
282 return 0;
283 } else
284 if (!access_ok(VERIFY_READ, buf, sig_xstate_size))
285 return -EACCES;
286
287 if (!used_math()) {
288 err = init_fpu(tsk);
289 if (err)
290 return err;
291 }
292
293 user_fpu_begin();
294 if (use_xsave())
295 err = restore_user_xstate(buf);
296 else
297 err = fxrstor_checking((__force struct i387_fxsave_struct *)
298 buf);
299 if (unlikely(err)) {
300 /*
301 * Encountered an error while doing the restore from the
302 * user buffer, clear the fpu state.
303 */
304clear:
305 clear_fpu(tsk);
306 clear_used_math();
307 }
308 return err;
309}
310#endif
311
312/*
313 * Prepare the SW reserved portion of the fxsave memory layout, indicating
314 * the presence of the extended state information in the memory layout
315 * pointed by the fpstate pointer in the sigcontext.
316 * This will be saved when ever the FP and extended state context is
317 * saved on the user stack during the signal handler delivery to the user.
318 */
319static void prepare_fx_sw_frame(void)
320{
321 int size_extended = (xstate_size - sizeof(struct i387_fxsave_struct)) +
322 FP_XSTATE_MAGIC2_SIZE;
323
324 sig_xstate_size = sizeof(struct _fpstate) + size_extended;
325
326#ifdef CONFIG_IA32_EMULATION
327 sig_xstate_ia32_size = sizeof(struct _fpstate_ia32) + size_extended;
328#endif
329
330 memset(&fx_sw_reserved, 0, sizeof(fx_sw_reserved));
331
332 fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
333 fx_sw_reserved.extended_size = sig_xstate_size;
334 fx_sw_reserved.xstate_bv = pcntxt_mask;
335 fx_sw_reserved.xstate_size = xstate_size;
336#ifdef CONFIG_IA32_EMULATION
337 memcpy(&fx_sw_reserved_ia32, &fx_sw_reserved,
338 sizeof(struct _fpx_sw_bytes));
339 fx_sw_reserved_ia32.extended_size = sig_xstate_ia32_size;
340#endif
341}
342
343#ifdef CONFIG_X86_64
344unsigned int sig_xstate_size = sizeof(struct _fpstate);
345#endif
346
347/*
348 * Enable the extended processor state save/restore feature
349 */
350static inline void xstate_enable(void)
351{
352 set_in_cr4(X86_CR4_OSXSAVE);
353 xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
354}
355
356/*
357 * Record the offsets and sizes of different state managed by the xsave
358 * memory layout.
359 */
360static void __init setup_xstate_features(void)
361{
362 int eax, ebx, ecx, edx, leaf = 0x2;
363
364 xstate_features = fls64(pcntxt_mask);
365 xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
366 xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
367
368 do {
369 cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
370
371 if (eax == 0)
372 break;
373
374 xstate_offsets[leaf] = ebx;
375 xstate_sizes[leaf] = eax;
376
377 leaf++;
378 } while (1);
379}
380
381/*
382 * setup the xstate image representing the init state
383 */
384static void __init setup_xstate_init(void)
385{
386 setup_xstate_features();
387
388 /*
389 * Setup init_xstate_buf to represent the init state of
390 * all the features managed by the xsave
391 */
392 init_xstate_buf = alloc_bootmem_align(xstate_size,
393 __alignof__(struct xsave_struct));
394 init_xstate_buf->i387.mxcsr = MXCSR_DEFAULT;
395
396 clts();
397 /*
398 * Init all the features state with header_bv being 0x0
399 */
400 xrstor_state(init_xstate_buf, -1);
401 /*
402 * Dump the init state again. This is to identify the init state
403 * of any feature which is not represented by all zero's.
404 */
405 xsave_state(init_xstate_buf, -1);
406 stts();
407}
408
409/*
410 * Enable and initialize the xsave feature.
411 */
412static void __init xstate_enable_boot_cpu(void)
413{
414 unsigned int eax, ebx, ecx, edx;
415
416 if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
417 WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
418 return;
419 }
420
421 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
422 pcntxt_mask = eax + ((u64)edx << 32);
423
424 if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
425 printk(KERN_ERR "FP/SSE not shown under xsave features 0x%llx\n",
426 pcntxt_mask);
427 BUG();
428 }
429
430 /*
431 * Support only the state known to OS.
432 */
433 pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
434
435 xstate_enable();
436
437 /*
438 * Recompute the context size for enabled features
439 */
440 cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
441 xstate_size = ebx;
442
443 update_regset_xstate_info(xstate_size, pcntxt_mask);
444 prepare_fx_sw_frame();
445
446 setup_xstate_init();
447
448 printk(KERN_INFO "xsave/xrstor: enabled xstate_bv 0x%llx, "
449 "cntxt size 0x%x\n",
450 pcntxt_mask, xstate_size);
451}
452
453/*
454 * For the very first instance, this calls xstate_enable_boot_cpu();
455 * for all subsequent instances, this calls xstate_enable().
456 *
457 * This is somewhat obfuscated due to the lack of powerful enough
458 * overrides for the section checks.
459 */
460void __cpuinit xsave_init(void)
461{
462 static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
463 void (*this_func)(void);
464
465 if (!cpu_has_xsave)
466 return;
467
468 this_func = next_func;
469 next_func = xstate_enable;
470 this_func();
471}