1/*
  2 * xsave/xrstor support.
  3 *
  4 * Author: Suresh Siddha <suresh.b.siddha@intel.com>
  5 */
  6
  7#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  8
  9#include <linux/bootmem.h>
 10#include <linux/compat.h>
 11#include <asm/i387.h>
 12#include <asm/fpu-internal.h>
 13#include <asm/sigframe.h>
 14#include <asm/xcr.h>
 15
 16/*
 17 * Supported feature mask by the CPU and the kernel.
 18 */
 19u64 pcntxt_mask;
 20
 21/*
 22 * Represents init state for the supported extended state.
 23 */
 24struct xsave_struct *init_xstate_buf;
 25
 26static struct _fpx_sw_bytes fx_sw_reserved, fx_sw_reserved_ia32;
 27static unsigned int *xstate_offsets, *xstate_sizes, xstate_features;
 28
 29/*
 30 * If a processor implementation discern that a processor state component is
 31 * in its initialized state it may modify the corresponding bit in the
 32 * xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
 33 * layout in the case of xsaveopt. While presenting the xstate information to
 34 * the user, we always ensure that the memory layout of a feature will be in
 35 * the init state if the corresponding header bit is zero. This is to ensure
 36 * that the user doesn't see some stale state in the memory layout during
 37 * signal handling, debugging etc.
 38 */
 39void __sanitize_i387_state(struct task_struct *tsk)
 40{
 41	struct i387_fxsave_struct *fx = &tsk->thread.fpu.state->fxsave;
 42	int feature_bit = 0x2;
 43	u64 xstate_bv;
 44
 45	if (!fx)
 46		return;
 47
 48	xstate_bv = tsk->thread.fpu.state->xsave.xsave_hdr.xstate_bv;
 49
 50	/*
 51	 * None of the feature bits are in init state. So nothing else
 52	 * to do for us, as the memory layout is up to date.
 53	 */
 54	if ((xstate_bv & pcntxt_mask) == pcntxt_mask)
 55		return;
 56
 57	/*
 58	 * FP is in init state
 59	 */
 60	if (!(xstate_bv & XSTATE_FP)) {
 61		fx->cwd = 0x37f;
 62		fx->swd = 0;
 63		fx->twd = 0;
 64		fx->fop = 0;
 65		fx->rip = 0;
 66		fx->rdp = 0;
 67		memset(&fx->st_space[0], 0, 128);
 68	}
 69
 70	/*
 71	 * SSE is in init state
 72	 */
 73	if (!(xstate_bv & XSTATE_SSE))
 74		memset(&fx->xmm_space[0], 0, 256);
 75
 76	xstate_bv = (pcntxt_mask & ~xstate_bv) >> 2;
 77
 78	/*
 79	 * Update all the other memory layouts for which the corresponding
 80	 * header bit is in the init state.
 81	 */
 82	while (xstate_bv) {
 83		if (xstate_bv & 0x1) {
 84			int offset = xstate_offsets[feature_bit];
 85			int size = xstate_sizes[feature_bit];
 86
 87			memcpy(((void *) fx) + offset,
 88			       ((void *) init_xstate_buf) + offset,
 89			       size);
 90		}
 91
 92		xstate_bv >>= 1;
 93		feature_bit++;
 94	}
 95}
 96
 97/*
 98 * Check for the presence of extended state information in the
 99 * user fpstate pointer in the sigcontext.
100 */
101static inline int check_for_xstate(struct i387_fxsave_struct __user *buf,
102				   void __user *fpstate,
103				   struct _fpx_sw_bytes *fx_sw)
104{
105	int min_xstate_size = sizeof(struct i387_fxsave_struct) +
106			      sizeof(struct xsave_hdr_struct);
107	unsigned int magic2;
108
109	if (__copy_from_user(fx_sw, &buf->sw_reserved[0], sizeof(*fx_sw)))
110		return -1;
111
112	/* Check for the first magic field and other error scenarios. */
113	if (fx_sw->magic1 != FP_XSTATE_MAGIC1 ||
114	    fx_sw->xstate_size < min_xstate_size ||
115	    fx_sw->xstate_size > xstate_size ||
116	    fx_sw->xstate_size > fx_sw->extended_size)
117		return -1;
118
119	/*
120	 * Check for the presence of second magic word at the end of memory
121	 * layout. This detects the case where the user just copied the legacy
122	 * fpstate layout with out copying the extended state information
123	 * in the memory layout.
124	 */
125	if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))
126	    || magic2 != FP_XSTATE_MAGIC2)
127		return -1;
128
129	return 0;
130}
131
132/*
133 * Signal frame handlers.
134 */
135static inline int save_fsave_header(struct task_struct *tsk, void __user *buf)
136{
137	if (use_fxsr()) {
138		struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
139		struct user_i387_ia32_struct env;
140		struct _fpstate_ia32 __user *fp = buf;
141
142		convert_from_fxsr(&env, tsk);
143
144		if (__copy_to_user(buf, &env, sizeof(env)) ||
145		    __put_user(xsave->i387.swd, &fp->status) ||
146		    __put_user(X86_FXSR_MAGIC, &fp->magic))
147			return -1;
148	} else {
149		struct i387_fsave_struct __user *fp = buf;
150		u32 swd;
151		if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status))
152			return -1;
153	}
154
155	return 0;
156}
157
158static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
159{
160	struct xsave_struct __user *x = buf;
161	struct _fpx_sw_bytes *sw_bytes;
162	u32 xstate_bv;
163	int err;
164
165	/* Setup the bytes not touched by the [f]xsave and reserved for SW. */
166	sw_bytes = ia32_frame ? &fx_sw_reserved_ia32 : &fx_sw_reserved;
167	err = __copy_to_user(&x->i387.sw_reserved, sw_bytes, sizeof(*sw_bytes));
168
169	if (!use_xsave())
170		return err;
171
172	err |= __put_user(FP_XSTATE_MAGIC2, (__u32 *)(buf + xstate_size));
173
174	/*
175	 * Read the xstate_bv which we copied (directly from the cpu or
176	 * from the state in task struct) to the user buffers.
177	 */
178	err |= __get_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);
179
180	/*
181	 * For legacy compatible, we always set FP/SSE bits in the bit
182	 * vector while saving the state to the user context. This will
183	 * enable us capturing any changes(during sigreturn) to
184	 * the FP/SSE bits by the legacy applications which don't touch
185	 * xstate_bv in the xsave header.
186	 *
187	 * xsave aware apps can change the xstate_bv in the xsave
188	 * header as well as change any contents in the memory layout.
189	 * xrestore as part of sigreturn will capture all the changes.
190	 */
191	xstate_bv |= XSTATE_FPSSE;
192
193	err |= __put_user(xstate_bv, (__u32 *)&x->xsave_hdr.xstate_bv);
194
195	return err;
196}
197
198static inline int save_user_xstate(struct xsave_struct __user *buf)
199{
200	int err;
201
202	if (use_xsave())
203		err = xsave_user(buf);
204	else if (use_fxsr())
205		err = fxsave_user((struct i387_fxsave_struct __user *) buf);
206	else
207		err = fsave_user((struct i387_fsave_struct __user *) buf);
208
209	if (unlikely(err) && __clear_user(buf, xstate_size))
210		err = -EFAULT;
211	return err;
212}
213
214/*
215 * Save the fpu, extended register state to the user signal frame.
216 *
217 * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save
218 *  state is copied.
219 *  'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'.
220 *
221 *	buf == buf_fx for 64-bit frames and 32-bit fsave frame.
222 *	buf != buf_fx for 32-bit frames with fxstate.
223 *
224 * If the fpu, extended register state is live, save the state directly
225 * to the user frame pointed by the aligned pointer 'buf_fx'. Otherwise,
226 * copy the thread's fpu state to the user frame starting at 'buf_fx'.
227 *
228 * If this is a 32-bit frame with fxstate, put a fsave header before
229 * the aligned state at 'buf_fx'.
230 *
231 * For [f]xsave state, update the SW reserved fields in the [f]xsave frame
232 * indicating the absence/presence of the extended state to the user.
233 */
234int save_xstate_sig(void __user *buf, void __user *buf_fx, int size)
235{
236	struct xsave_struct *xsave = &current->thread.fpu.state->xsave;
237	struct task_struct *tsk = current;
238	int ia32_fxstate = (buf != buf_fx);
239
240	ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
241			 config_enabled(CONFIG_IA32_EMULATION));
242
243	if (!access_ok(VERIFY_WRITE, buf, size))
244		return -EACCES;
245
246	if (!static_cpu_has(X86_FEATURE_FPU))
247		return fpregs_soft_get(current, NULL, 0,
248			sizeof(struct user_i387_ia32_struct), NULL,
249			(struct _fpstate_ia32 __user *) buf) ? -1 : 1;
250
251	if (user_has_fpu()) {
252		/* Save the live register state to the user directly. */
253		if (save_user_xstate(buf_fx))
254			return -1;
255		/* Update the thread's fxstate to save the fsave header. */
256		if (ia32_fxstate)
257			fpu_fxsave(&tsk->thread.fpu);
258	} else {
259		sanitize_i387_state(tsk);
260		if (__copy_to_user(buf_fx, xsave, xstate_size))
261			return -1;
262	}
263
264	/* Save the fsave header for the 32-bit frames. */
265	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
266		return -1;
267
268	if (use_fxsr() && save_xstate_epilog(buf_fx, ia32_fxstate))
269		return -1;
270
271	drop_init_fpu(tsk);	/* trigger finit */
272
273	return 0;
274}
275
276static inline void
277sanitize_restored_xstate(struct task_struct *tsk,
278			 struct user_i387_ia32_struct *ia32_env,
279			 u64 xstate_bv, int fx_only)
280{
281	struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
282	struct xsave_hdr_struct *xsave_hdr = &xsave->xsave_hdr;
283
284	if (use_xsave()) {
285		/* These bits must be zero. */
286		xsave_hdr->reserved1[0] = xsave_hdr->reserved1[1] = 0;
287
288		/*
289		 * Init the state that is not present in the memory
290		 * layout and not enabled by the OS.
291		 */
292		if (fx_only)
293			xsave_hdr->xstate_bv = XSTATE_FPSSE;
294		else
295			xsave_hdr->xstate_bv &= (pcntxt_mask & xstate_bv);
296	}
297
298	if (use_fxsr()) {
299		/*
300		 * mscsr reserved bits must be masked to zero for security
301		 * reasons.
302		 */
303		xsave->i387.mxcsr &= mxcsr_feature_mask;
304
305		convert_to_fxsr(tsk, ia32_env);
306	}
307}
308
309/*
310 * Restore the extended state if present. Otherwise, restore the FP/SSE state.
311 */
312static inline int restore_user_xstate(void __user *buf, u64 xbv, int fx_only)
313{
314	if (use_xsave()) {
315		if ((unsigned long)buf % 64 || fx_only) {
316			u64 init_bv = pcntxt_mask & ~XSTATE_FPSSE;
317			xrstor_state(init_xstate_buf, init_bv);
318			return fxrstor_user(buf);
319		} else {
320			u64 init_bv = pcntxt_mask & ~xbv;
321			if (unlikely(init_bv))
322				xrstor_state(init_xstate_buf, init_bv);
323			return xrestore_user(buf, xbv);
324		}
325	} else if (use_fxsr()) {
326		return fxrstor_user(buf);
327	} else
328		return frstor_user(buf);
329}
330
331int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
332{
333	int ia32_fxstate = (buf != buf_fx);
334	struct task_struct *tsk = current;
335	int state_size = xstate_size;
336	u64 xstate_bv = 0;
337	int fx_only = 0;
338
339	ia32_fxstate &= (config_enabled(CONFIG_X86_32) ||
340			 config_enabled(CONFIG_IA32_EMULATION));
341
342	if (!buf) {
343		drop_init_fpu(tsk);
344		return 0;
345	}
346
347	if (!access_ok(VERIFY_READ, buf, size))
348		return -EACCES;
349
350	if (!used_math() && init_fpu(tsk))
351		return -1;
352
353	if (!static_cpu_has(X86_FEATURE_FPU))
354		return fpregs_soft_set(current, NULL,
355				       0, sizeof(struct user_i387_ia32_struct),
356				       NULL, buf) != 0;
357
358	if (use_xsave()) {
359		struct _fpx_sw_bytes fx_sw_user;
360		if (unlikely(check_for_xstate(buf_fx, buf_fx, &fx_sw_user))) {
361			/*
362			 * Couldn't find the extended state information in the
363			 * memory layout. Restore just the FP/SSE and init all
364			 * the other extended state.
365			 */
366			state_size = sizeof(struct i387_fxsave_struct);
367			fx_only = 1;
368		} else {
369			state_size = fx_sw_user.xstate_size;
370			xstate_bv = fx_sw_user.xstate_bv;
371		}
372	}
373
374	if (ia32_fxstate) {
375		/*
376		 * For 32-bit frames with fxstate, copy the user state to the
377		 * thread's fpu state, reconstruct fxstate from the fsave
378		 * header. Sanitize the copied state etc.
379		 */
380		struct xsave_struct *xsave = &tsk->thread.fpu.state->xsave;
381		struct user_i387_ia32_struct env;
382		int err = 0;
383
384		/*
385		 * Drop the current fpu which clears used_math(). This ensures
386		 * that any context-switch during the copy of the new state,
387		 * avoids the intermediate state from getting restored/saved.
388		 * Thus avoiding the new restored state from getting corrupted.
389		 * We will be ready to restore/save the state only after
390		 * set_used_math() is again set.
391		 */
392		drop_fpu(tsk);
393
394		if (__copy_from_user(xsave, buf_fx, state_size) ||
395		    __copy_from_user(&env, buf, sizeof(env))) {
396			err = -1;
397		} else {
398			sanitize_restored_xstate(tsk, &env, xstate_bv, fx_only);
399			set_used_math();
400		}
401
402		if (use_eager_fpu())
403			math_state_restore();
404
405		return err;
406	} else {
407		/*
408		 * For 64-bit frames and 32-bit fsave frames, restore the user
409		 * state to the registers directly (with exceptions handled).
410		 */
411		user_fpu_begin();
412		if (restore_user_xstate(buf_fx, xstate_bv, fx_only)) {
413			drop_init_fpu(tsk);
414			return -1;
415		}
416	}
417
418	return 0;
419}
420
421/*
422 * Prepare the SW reserved portion of the fxsave memory layout, indicating
423 * the presence of the extended state information in the memory layout
424 * pointed by the fpstate pointer in the sigcontext.
425 * This will be saved when ever the FP and extended state context is
426 * saved on the user stack during the signal handler delivery to the user.
427 */
428static void prepare_fx_sw_frame(void)
429{
430	int fsave_header_size = sizeof(struct i387_fsave_struct);
431	int size = xstate_size + FP_XSTATE_MAGIC2_SIZE;
432
433	if (config_enabled(CONFIG_X86_32))
434		size += fsave_header_size;
435
436	fx_sw_reserved.magic1 = FP_XSTATE_MAGIC1;
437	fx_sw_reserved.extended_size = size;
438	fx_sw_reserved.xstate_bv = pcntxt_mask;
439	fx_sw_reserved.xstate_size = xstate_size;
440
441	if (config_enabled(CONFIG_IA32_EMULATION)) {
442		fx_sw_reserved_ia32 = fx_sw_reserved;
443		fx_sw_reserved_ia32.extended_size += fsave_header_size;
444	}
445}
446
447/*
448 * Enable the extended processor state save/restore feature
449 */
450static inline void xstate_enable(void)
451{
452	set_in_cr4(X86_CR4_OSXSAVE);
453	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);
454}
455
456/*
457 * Record the offsets and sizes of different state managed by the xsave
458 * memory layout.
459 */
460static void __init setup_xstate_features(void)
461{
462	int eax, ebx, ecx, edx, leaf = 0x2;
463
464	xstate_features = fls64(pcntxt_mask);
465	xstate_offsets = alloc_bootmem(xstate_features * sizeof(int));
466	xstate_sizes = alloc_bootmem(xstate_features * sizeof(int));
467
468	do {
469		cpuid_count(XSTATE_CPUID, leaf, &eax, &ebx, &ecx, &edx);
470
471		if (eax == 0)
472			break;
473
474		xstate_offsets[leaf] = ebx;
475		xstate_sizes[leaf] = eax;
476
477		leaf++;
478	} while (1);
479}
480
481/*
482 * setup the xstate image representing the init state
483 */
484static void __init setup_init_fpu_buf(void)
485{
486	/*
487	 * Setup init_xstate_buf to represent the init state of
488	 * all the features managed by the xsave
489	 */
490	init_xstate_buf = alloc_bootmem_align(xstate_size,
491					      __alignof__(struct xsave_struct));
492	fx_finit(&init_xstate_buf->i387);
493
494	if (!cpu_has_xsave)
495		return;
496
497	setup_xstate_features();
498
499	/*
500	 * Init all the features state with header_bv being 0x0
501	 */
502	xrstor_state(init_xstate_buf, -1);
503	/*
504	 * Dump the init state again. This is to identify the init state
505	 * of any feature which is not represented by all zero's.
506	 */
507	xsave_state(init_xstate_buf, -1);
508}
509
510static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO;
511static int __init eager_fpu_setup(char *s)
512{
513	if (!strcmp(s, "on"))
514		eagerfpu = ENABLE;
515	else if (!strcmp(s, "off"))
516		eagerfpu = DISABLE;
517	else if (!strcmp(s, "auto"))
518		eagerfpu = AUTO;
519	return 1;
520}
521__setup("eagerfpu=", eager_fpu_setup);
522
523/*
524 * Enable and initialize the xsave feature.
525 */
526static void __init xstate_enable_boot_cpu(void)
527{
528	unsigned int eax, ebx, ecx, edx;
529
530	if (boot_cpu_data.cpuid_level < XSTATE_CPUID) {
531		WARN(1, KERN_ERR "XSTATE_CPUID missing\n");
532		return;
533	}
534
535	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
536	pcntxt_mask = eax + ((u64)edx << 32);
537
538	if ((pcntxt_mask & XSTATE_FPSSE) != XSTATE_FPSSE) {
539		pr_err("FP/SSE not shown under xsave features 0x%llx\n",
540		       pcntxt_mask);
541		BUG();
542	}
543
544	/*
545	 * Support only the state known to OS.
546	 */
547	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
548
549	xstate_enable();
550
551	/*
552	 * Recompute the context size for enabled features
553	 */
554	cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx);
555	xstate_size = ebx;
556
557	update_regset_xstate_info(xstate_size, pcntxt_mask);
558	prepare_fx_sw_frame();
559	setup_init_fpu_buf();
560
561	/* Auto enable eagerfpu for xsaveopt */
562	if (cpu_has_xsaveopt && eagerfpu != DISABLE)
563		eagerfpu = ENABLE;
564
565	if (pcntxt_mask & XSTATE_EAGER) {
566		if (eagerfpu == DISABLE) {
567			pr_err("eagerfpu not present, disabling some xstate features: 0x%llx\n",
568					pcntxt_mask & XSTATE_EAGER);
569			pcntxt_mask &= ~XSTATE_EAGER;
570		} else {
571			eagerfpu = ENABLE;
572		}
573	}
574
575	pr_info("enabled xstate_bv 0x%llx, cntxt size 0x%x\n",
576		pcntxt_mask, xstate_size);
577}
578
579/*
580 * For the very first instance, this calls xstate_enable_boot_cpu();
581 * for all subsequent instances, this calls xstate_enable().
582 *
583 * This is somewhat obfuscated due to the lack of powerful enough
584 * overrides for the section checks.
585 */
586void xsave_init(void)
587{
588	static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;
589	void (*this_func)(void);
590
591	if (!cpu_has_xsave)
592		return;
593
594	this_func = next_func;
595	next_func = xstate_enable;
596	this_func();
597}
598
599static inline void __init eager_fpu_init_bp(void)
600{
601	current->thread.fpu.state =
602	    alloc_bootmem_align(xstate_size, __alignof__(struct xsave_struct));
603	if (!init_xstate_buf)
604		setup_init_fpu_buf();
605}
606
607void eager_fpu_init(void)
608{
609	static __refdata void (*boot_func)(void) = eager_fpu_init_bp;
610
611	clear_used_math();
612	current_thread_info()->status = 0;
613
614	if (eagerfpu == ENABLE)
615		setup_force_cpu_cap(X86_FEATURE_EAGER_FPU);
616
617	if (!cpu_has_eager_fpu) {
618		stts();
619		return;
620	}
621
622	if (boot_func) {
623		boot_func();
624		boot_func = NULL;
625	}
626
627	/*
628	 * This is same as math_state_restore(). But use_xsave() is
629	 * not yet patched to use math_state_restore().
630	 */
631	init_fpu(current);
632	__thread_fpu_begin(current);
633	if (cpu_has_xsave)
634		xrstor_state(init_xstate_buf, -1);
635	else
636		fxrstor_checking(&init_xstate_buf->i387);
637}