summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/xsave.c
blob: ada87a329edcde71763601e19b1fc4a8c9062f3d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
/*
 * xsave/xrstor support.
 *
 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bootmem.h>
#include <linux/compat.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/sigframe.h>
#include <asm/xcr.h>

/*
 * Supported feature mask by the CPU and the kernel.
 */
u64 pcntxt_mask;

/*
 * Represents init state for the supported extended state.
 */
struct xsave_struct *init_xstate_buf;

static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;

/*
 * If a processor implementation discern that a processor state component is
 * in its initialized state it may modify the corresponding bit in the
 * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
 * layout in the case of xsaveopt. While presenting the xstate information to
 * the user, we always ensure that the memory layout of a feature will be in
 * the init state if the corresponding header bit is zero. This is to ensure
 * that the user doesn't see some stale state in the memory layout during
 * signal handling, debugging etc.
 */
void __sanitize_i387_state(struct task_struct *tsk)
{
	struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
	int feature_bit = 0x2;
	u64 xstate_bv;

	if (!fx)
		return;

	xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;

	/*
	 * None of the feature bits are in init state. So nothing else
	 * to do for us, as the memory layout is up to date.
	 */
	if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
		return;

	/*
	 * FP is in init state
	 */
	if (!(xstate_bv & XSTATE_FP)) {
		fx->cwd = 0x37f;
		fx->swd = 0;
		fx->twd = 0;
		fx->fop = 0;
		fx->rip = 0;
		fx->rdp = 0;
		memset(&fx->st_space[0], 0, 128);
	}

	/*
	 * SSE is in init state
	 */
	if (!(xstate_bv & XSTATE_SSE))
		memset(&fx->xmm_space[0], 0, 256);

	xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;

	/*
	 * Update all the other memory layouts for which the corresponding
	 * header bit is in the init state.
	 */
	while (xstate_bv) {
		if (xstate_bv & 0x1) {
			int offset = xstate_offsets[feature_bit];
			int size = xstate_sizes[feature_bit];

			memcpy(((void *) fx) + offset,
			       ((void *) init_xstate_buf) + offset,
			       size);
		}

		xstate_bv >>= 1;
		feature_bit++;
	}
}

/*
 * Check for the presence of extended state information in the
 * user fpstate pointer in the sigcontext.
 */
static inline int check_for_xstate(struct i387_fxsave_struct __user *buf,
				   void __user *fpstate,
				   struct _fpx_sw_bytes *fx_sw)
{
	int min_xstate_size = sizeof(struct i387_fxsave_struct) +
			      sizeof(struct xsave_hdr_struct);
	unsigned int magic2;

	if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
		return -1;

	/* Check for the first magic field and other error scenarios. */
	if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
	    fx_sw->xstate_size < min_xstate_size ||
	    fx_sw->xstate_size > xstate_size ||
	    fx_sw->xstate_size > fx_sw->extended_size)
		return -1;

	/*
	 * Check for the presence of second magic word at the end of memory
	 * layout. This detects the case where the user just copied the legacy
	 * fpstate layout with out copying the extended state information
	 * in the memory layout.
	 */
	if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
	    || magic2 != FP_XSTATE_MAGIC2)
		return -1;

	return 0;
}

/*
 * Signal frame handlers.
 */
static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
{
	if (use_fxsr()) {
		struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
		struct user_i387_ia32_struct env;
		struct _fpstate_ia32 __user *fp = buf;

		convert_from_fxsr(&env, tsk);

		if (__copy_to_user(buf, &env, sizeof(env)) ||
		    __put_user(xsave->i387.swd, &fp->status) ||
		    __put_user(X86_FXSR_MAGIC, &fp->magic))
			return -1;
	} else {
		struct i387_fsave_struct __user *fp = buf;
		u32 swd;
		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
			return -1;
	}

	return 0;
}

static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
{
	struct xsave_struct __user *x = buf;
	struct _fpx_sw_bytes *sw_bytes;
	u32 xstate_bv;
	int err;

	/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
	sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
	err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));

	if (!use_xsave())
		return err;

	err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));

	/*
	 * Read the xstate_bv which we copied (directly from the cpu or
	 * from the state in task struct) to the user buffers.
	 */
	err |= __get_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);

	/*
	 * For legacy compatible, we always set FP/SSE bits in the bit
	 * vector while saving the state to the user context. This will
	 * enable us capturing any changes(during sigreturn) to
	 * the FP/SSE bits by the legacy applications which don't touch
	 * xstate_bv in the xsave header.
	 *
	 * xsave aware apps can change the xstate_bv in the xsave
	 * header as well as change any contents in the memory layout.
	 * xrestore as part of sigreturn will capture all the changes.
	 */
	xstate_bv |= XSTATE_FPSSE;

	err |= __put_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);

	return err;
}

static inline int save_user_xstate(struct xsave_struct __user *buf)
{
	int err;

	if (use_xsave())
		err = xsave_user(buf);
	else if (use_fxsr())
		err = fxsave_user((struct i387_fxsave_struct __user *) buf);
	else
		err = fsave_user((struct i387_fsave_struct __user *) buf);

	if (unlikely(err) && __clear_user(buf, xstate_size))
		err = -EFAULT;
	return err;
}

/*
 * Save the fpu, extended register state to the user signal frame.
 *
 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
 *  state is copied.
 *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
 *
 *	buf == buf_fx for 64-bit frames and 32-bit fsave frame.
 *	buf != buf_fx for 32-bit frames with fxstate.
 *
 * If the fpu, extended register state is live, save the state directly
 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
 * copy the thread's fpu state to the user frame starting at 'buf_fx'.
 *
 * If this is a 32-bit frame with fxstate, put a fsave header before
 * the aligned state at 'buf_fx'.
 *
 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
 * indicating the absence/presence of the extended state to the user.
 */
int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
{
	struct xsave_struct *xsave = &current->thread.fpu.state->xsave;
	struct task_struct *tsk = current;
	int ia32_fxstate = (buf != buf_fx);

	ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
			 config_enabled(CONFIG_IA32_EMULATION));

	if (!access_ok(VERIFY_WRITE, buf, size))
		return -EACCES;

	if (!HAVE_HWFP)
		return fpregs_soft_get(current, NULL, 0,
			sizeof(struct user_i387_ia32_struct), NULL,
			(struct _fpstate_ia32 __user *) buf) ? -1 : 1;

	if (user_has_fpu()) {
		/* Save the live register state to the user directly. */
		if (save_user_xstate(buf_fx))
			return -1;
		/* Update the thread's fxstate to save the fsave header. */
		if (ia32_fxstate)
			fpu_fxsave(&tsk->thread.fpu);
	} else {
		sanitize_i387_state(tsk);
		if (__copy_to_user(buf_fx, xsave, xstate_size))
			return -1;
	}

	/* Save the fsave header for the 32-bit frames. */
	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
		return -1;

	if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
		return -1;

	drop_init_fpu(tsk);	/* trigger finit */

	return 0;
}

static inline void
sanitize_restored_xstate(struct task_struct *tsk,
			 struct user_i387_ia32_struct *ia32_env,
			 u64 xstate_bv, int fx_only)
{
	struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
	struct xsave_hdr_struct *xsave_hdr = &xsave->xsave_hdr;

	if (use_xsave()) {
		/* These bits must be zero. */
		xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;

		/*
		 * Init the state that is not present in the memory
		 * layout and not enabled by the OS.
		 */
		if (fx_only)
			xsave_hdr->xstate_bv = XSTATE_FPSSE;
		else
			xsave_hdr->xstate_bv &= (pcntxt_mask & xstate_bv);
	}

	if (use_fxsr()) {
		/*
		 * mscsr reserved bits must be masked to zero for security
		 * reasons.
		 */
		xsave->i387.mxcsr &= mxcsr_feature_mask;

		convert_to_fxsr(tsk, ia32_env);
	}
}

/*
 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
 */
static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only)
{
	if (use_xsave()) {
		if ((unsigned long)buf % 64 || fx_only) {
			u64 init_bv = pcntxt_mask & ~XSTATE_FPSSE;
			xrstor_state(init_xstate_buf, init_bv);
			return fxrstor_user(buf);
		} else {
			u64 init_bv = pcntxt_mask & ~xbv;
			if (unlikely(init_bv))
				xrstor_state(init_xstate_buf, init_bv);
			return xrestore_user(buf, xbv);
		}
	} else if (use_fxsr()) {
		return fxrstor_user(buf);
	} else
		return frstor_user(buf);
}

int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
{
	int ia32_fxstate = (buf != buf_fx);
	struct task_struct *tsk = current;
	int state_size = xstate_size;
	u64 xstate_bv = 0;
	int fx_only = 0;

	ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
			 config_enabled(CONFIG_IA32_EMULATION));

	if (!buf) {
		drop_init_fpu(tsk);
		return 0;
	}

	if (!access_ok(VERIFY_READ, buf, size))
		return -EACCES;

	if (!used_math() && init_fpu(tsk))
		return -1;

	if (!HAVE_HWFP) {
		return fpregs_soft_set(current, NULL,
				       0, sizeof(struct user_i387_ia32_struct),
				       NULL, buf) != 0;
	}

	if (use_xsave()) {
		struct _fpx_sw_bytes fx_sw_user;
		if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
			/*
			 * Couldn't find the extended state information in the
			 * memory layout. Restore just the FP/SSE and init all
			 * the other extended state.
			 */
			state_size = sizeof(struct i387_fxsave_struct);
			fx_only = 1;
		} else {
			state_size = fx_sw_user.xstate_size;
			xstate_bv = fx_sw_user.xstate_bv;
		}
	}

	if (ia32_fxstate) {
		/*
		 * For 32-bit frames with fxstate, copy the user state to the
		 * thread's fpu state, reconstruct fxstate from the fsave
		 * header. Sanitize the copied state etc.
		 */
		struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
		struct user_i387_ia32_struct env;
		int err = 0;

		/*
		 * Drop the current fpu which clears used_math(). This ensures
		 * that any context-switch during the copy of the new state,
		 * avoids the intermediate state from getting restored/saved.
		 * Thus avoiding the new restored state from getting corrupted.
		 * We will be ready to restore/save the state only after
		 * set_used_math() is again set.
		 */
		drop_fpu(tsk);

		if (__copy_from_user(xsave, buf_fx, state_size) ||
		    __copy_from_user(&env, buf, sizeof(env))) {
			err = -1;
		} else {
			sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
			set_used_math();
		}

		if (use_eager_fpu())
			math_state_restore();

		return err;
	} else {
		/*
		 * For 64-bit frames and 32-bit fsave frames, restore the user
		 * state to the registers directly (with exceptions handled).
		 */
		user_fpu_begin();
		if (restore_user_xstate(buf_fx, xstate_bv, fx_only)) {
			drop_init_fpu(tsk);
			return -1;
		}
	}

	return 0;
}

/*
 * Prepare the SW reserved portion of the fxsave memory layout, indicating
 * the presence of the extended state information in the memory layout
 * pointed by the fpstate pointer in the sigcontext.
 * This will be saved when ever the FP and extended state context is
 * saved on the user stack during the signal handler delivery to the user.
 */
static void prepare_fx_sw_frame(void)
{
	int fsave_header_size = sizeof(struct i387_fsave_struct);
	int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;

	if (config_enabled(CONFIG_X86_32))
		size += fsave_header_size;

	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
	fx_sw_reserved.extended_size = size;
	fx_sw_reserved.xstate_bv = pcntxt_mask;
	fx_sw_reserved.xstate_size = xstate_size;

	if (config_enabled(CONFIG_IA32_EMULATION)) {
		fx_sw_reserved_ia32 = fx_sw_reserved;
		fx_sw_reserved_ia32.extended_size += fsave_header_size;
	}
}

/*
 * Enable the extended processor state save/restore feature
 */
static inline void xstate_enable(void)
{
	set_in_cr4(X86_CR4_OSXSAVE);
	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
}

/*
 * Record the offsets and sizes of different state managed by the xsave
 * memory layout.
 */
static void __init setup_xstate_features(void)
{
	int eax, ebx, ecx, edx, leaf = 0x2;

	xstate_features = fls64(pcntxt_mask);
	xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
	xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));

	do {
		cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);

		if (eax == 0)
			break;

		xstate_offsets[leaf] = ebx;
		xstate_sizes[leaf] = eax;

		leaf++;
	} while (1);
}

/*
 * setup the xstate image representing the init state
 */
static void __init setup_init_fpu_buf(void)
{
	/*
	 * Setup init_xstate_buf to represent the init state of
	 * all the features managed by the xsave
	 */
	init_xstate_buf = alloc_bootmem_align(xstate_size,
					      __alignof__(struct xsave_struct));
	fx_finit(&init_xstate_buf->i387);

	if (!cpu_has_xsave)
		return;

	setup_xstate_features();

	/*
	 * Init all the features state with header_bv being 0x0
	 */
	xrstor_state(init_xstate_buf, -1);
	/*
	 * Dump the init state again. This is to identify the init state
	 * of any feature which is not represented by all zero's.
	 */
	xsave_state(init_xstate_buf, -1);
}

static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
static int __init eager_fpu_setup(char *s)
{
	if (!strcmp(s, "on"))
		eagerfpu = ENABLE;
	else if (!strcmp(s, "off"))
		eagerfpu = DISABLE;
	else if (!strcmp(s, "auto"))
		eagerfpu = AUTO;
	return 1;
}
__setup("eagerfpu=", eager_fpu_setup);

/*
 * Enable and initialize the xsave feature.
 */
static void __init xstate_enable_boot_cpu(void)
{
	unsigned int eax, ebx, ecx, edx;

	if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
		WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
		return;
	}

	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
	pcntxt_mask = eax + ((u64)edx << 32);

	if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
		pr_err("FP/SSE not shown under xsave features 0x%llx\n",
		       pcntxt_mask);
		BUG();
	}

	/*
	 * Support only the state known to OS.
	 */
	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;

	xstate_enable();

	/*
	 * Recompute the context size for enabled features
	 */
	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
	xstate_size = ebx;

	update_regset_xstate_info(xstate_size, pcntxt_mask);
	prepare_fx_sw_frame();
	setup_init_fpu_buf();

	/* Auto enable eagerfpu for xsaveopt */
	if (cpu_has_xsaveopt && eagerfpu != DISABLE)
		eagerfpu = ENABLE;

	pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
		pcntxt_mask, xstate_size);
}

/*
 * For the very first instance, this calls xstate_enable_boot_cpu();
 * for all subsequent instances, this calls xstate_enable().
 *
 * This is somewhat obfuscated due to the lack of powerful enough
 * overrides for the section checks.
 */
void __cpuinit xsave_init(void)
{
	static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
	void (*this_func)(void);

	if (!cpu_has_xsave)
		return;

	this_func = next_func;
	next_func = xstate_enable;
	this_func();
}

static inline void __init eager_fpu_init_bp(void)
{
	current->thread.fpu.state =
	    alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
	if (!init_xstate_buf)
		setup_init_fpu_buf();
}

void __cpuinit eager_fpu_init(void)
{
	static __refdata void (*boot_func)(void) = eager_fpu_init_bp;

	clear_used_math();
	current_thread_info()->status = 0;

	if (eagerfpu == ENABLE)
		setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);

	if (!cpu_has_eager_fpu) {
		stts();
		return;
	}

	if (boot_func) {
		boot_func();
		boot_func = NULL;
	}

	/*
	 * This is same as math_state_restore(). But use_xsave() is
	 * not yet patched to use math_state_restore().
	 */
	init_fpu(current);
	__thread_fpu_begin(current);
	if (cpu_has_xsave)
		xrstor_state(init_xstate_buf, -1);
	else
		fxrstor_checking(&init_xstate_buf->i387);
}