summaryrefslogtreecommitdiff
path: root/arch/x86/kernel/signal.c
blob: ea794a083c44ebab56183e3ea100453abffeb154 (plain)
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
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 *  2000-2002   x86-64 support by Andi Kleen
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/tracehook.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/uaccess.h>
#include <linux/user-return-notifier.h>
#include <linux/uprobes.h>
#include <linux/context_tracking.h>
#include <linux/entry-common.h>
#include <linux/syscalls.h>

#include <asm/processor.h>
#include <asm/ucontext.h>
#include <asm/fpu/internal.h>
#include <asm/fpu/signal.h>
#include <asm/vdso.h>
#include <asm/mce.h>
#include <asm/sighandling.h>
#include <asm/vm86.h>

#ifdef CONFIG_X86_64
#include <linux/compat.h>
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#endif /* CONFIG_X86_64 */

#include <asm/syscall.h>
#include <asm/sigframe.h>
#include <asm/signal.h>

#ifdef CONFIG_X86_64
/*
 * If regs->ss will cause an IRET fault, change it.  Otherwise leave it
 * alone.  Using this generally makes no sense unless
 * user_64bit_mode(regs) would return true.
 */
static void force_valid_ss(struct pt_regs *regs)
{
	u32 ar;
	asm volatile ("lar %[old_ss], %[ar]\n\t"
		      "jz 1f\n\t"		/* If invalid: */
		      "xorl %[ar], %[ar]\n\t"	/* set ar = 0 */
		      "1:"
		      : [ar] "=r" (ar)
		      : [old_ss] "rm" ((u16)regs->ss));

	/*
	 * For a valid 64-bit user context, we need DPL 3, type
	 * read-write data or read-write exp-down data, and S and P
	 * set.  We can't use VERW because VERW doesn't check the
	 * P bit.
	 */
	ar &= AR_DPL_MASK | AR_S | AR_P | AR_TYPE_MASK;
	if (ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA) &&
	    ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
		regs->ss = __USER_DS;
}
# define CONTEXT_COPY_SIZE	offsetof(struct sigcontext, reserved1)
#else
# define CONTEXT_COPY_SIZE	sizeof(struct sigcontext)
#endif

static int restore_sigcontext(struct pt_regs *regs,
			      struct sigcontext __user *usc,
			      unsigned long uc_flags)
{
	struct sigcontext sc;

	/* Always make any pending restarted system calls return -EINTR */
	current->restart_block.fn = do_no_restart_syscall;

	if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
		return -EFAULT;

#ifdef CONFIG_X86_32
	set_user_gs(regs, sc.gs);
	regs->fs = sc.fs;
	regs->es = sc.es;
	regs->ds = sc.ds;
#endif /* CONFIG_X86_32 */

	regs->bx = sc.bx;
	regs->cx = sc.cx;
	regs->dx = sc.dx;
	regs->si = sc.si;
	regs->di = sc.di;
	regs->bp = sc.bp;
	regs->ax = sc.ax;
	regs->sp = sc.sp;
	regs->ip = sc.ip;

#ifdef CONFIG_X86_64
	regs->r8 = sc.r8;
	regs->r9 = sc.r9;
	regs->r10 = sc.r10;
	regs->r11 = sc.r11;
	regs->r12 = sc.r12;
	regs->r13 = sc.r13;
	regs->r14 = sc.r14;
	regs->r15 = sc.r15;
#endif /* CONFIG_X86_64 */

	/* Get CS/SS and force CPL3 */
	regs->cs = sc.cs | 0x03;
	regs->ss = sc.ss | 0x03;

	regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
	/* disable syscall checks */
	regs->orig_ax = -1;

#ifdef CONFIG_X86_64
	/*
	 * Fix up SS if needed for the benefit of old DOSEMU and
	 * CRIU.
	 */
	if (unlikely(!(uc_flags & UC_STRICT_RESTORE_SS) && user_64bit_mode(regs)))
		force_valid_ss(regs);
#endif

	return fpu__restore_sig((void __user *)sc.fpstate,
			       IS_ENABLED(CONFIG_X86_32));
}

static __always_inline int
__unsafe_setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
		     struct pt_regs *regs, unsigned long mask)
{
#ifdef CONFIG_X86_32
	unsafe_put_user(get_user_gs(regs),
				  (unsigned int __user *)&sc->gs, Efault);
	unsafe_put_user(regs->fs, (unsigned int __user *)&sc->fs, Efault);
	unsafe_put_user(regs->es, (unsigned int __user *)&sc->es, Efault);
	unsafe_put_user(regs->ds, (unsigned int __user *)&sc->ds, Efault);
#endif /* CONFIG_X86_32 */

	unsafe_put_user(regs->di, &sc->di, Efault);
	unsafe_put_user(regs->si, &sc->si, Efault);
	unsafe_put_user(regs->bp, &sc->bp, Efault);
	unsafe_put_user(regs->sp, &sc->sp, Efault);
	unsafe_put_user(regs->bx, &sc->bx, Efault);
	unsafe_put_user(regs->dx, &sc->dx, Efault);
	unsafe_put_user(regs->cx, &sc->cx, Efault);
	unsafe_put_user(regs->ax, &sc->ax, Efault);
#ifdef CONFIG_X86_64
	unsafe_put_user(regs->r8, &sc->r8, Efault);
	unsafe_put_user(regs->r9, &sc->r9, Efault);
	unsafe_put_user(regs->r10, &sc->r10, Efault);
	unsafe_put_user(regs->r11, &sc->r11, Efault);
	unsafe_put_user(regs->r12, &sc->r12, Efault);
	unsafe_put_user(regs->r13, &sc->r13, Efault);
	unsafe_put_user(regs->r14, &sc->r14, Efault);
	unsafe_put_user(regs->r15, &sc->r15, Efault);
#endif /* CONFIG_X86_64 */

	unsafe_put_user(current->thread.trap_nr, &sc->trapno, Efault);
	unsafe_put_user(current->thread.error_code, &sc->err, Efault);
	unsafe_put_user(regs->ip, &sc->ip, Efault);
#ifdef CONFIG_X86_32
	unsafe_put_user(regs->cs, (unsigned int __user *)&sc->cs, Efault);
	unsafe_put_user(regs->flags, &sc->flags, Efault);
	unsafe_put_user(regs->sp, &sc->sp_at_signal, Efault);
	unsafe_put_user(regs->ss, (unsigned int __user *)&sc->ss, Efault);
#else /* !CONFIG_X86_32 */
	unsafe_put_user(regs->flags, &sc->flags, Efault);
	unsafe_put_user(regs->cs, &sc->cs, Efault);
	unsafe_put_user(0, &sc->gs, Efault);
	unsafe_put_user(0, &sc->fs, Efault);
	unsafe_put_user(regs->ss, &sc->ss, Efault);
#endif /* CONFIG_X86_32 */

	unsafe_put_user(fpstate, (unsigned long __user *)&sc->fpstate, Efault);

	/* non-iBCS2 extensions.. */
	unsafe_put_user(mask, &sc->oldmask, Efault);
	unsafe_put_user(current->thread.cr2, &sc->cr2, Efault);
	return 0;
Efault:
	return -EFAULT;
}

#define unsafe_put_sigcontext(sc, fp, regs, set, label)			\
do {									\
	if (__unsafe_setup_sigcontext(sc, fp, regs, set->sig[0]))	\
		goto label;						\
} while(0);

#define unsafe_put_sigmask(set, frame, label) \
	unsafe_put_user(*(__u64 *)(set), \
			(__u64 __user *)&(frame)->uc.uc_sigmask, \
			label)

/*
 * Set up a signal frame.
 */

/*
 * Determine which stack to use..
 */
static unsigned long align_sigframe(unsigned long sp)
{
#ifdef CONFIG_X86_32
	/*
	 * Align the stack pointer according to the i386 ABI,
	 * i.e. so that on function entry ((sp + 4) & 15) == 0.
	 */
	sp = ((sp + 4) & -16ul) - 4;
#else /* !CONFIG_X86_32 */
	sp = round_down(sp, 16) - 8;
#endif
	return sp;
}

static void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
	     void __user **fpstate)
{
	/* Default to using normal stack */
	unsigned long math_size = 0;
	unsigned long sp = regs->sp;
	unsigned long buf_fx = 0;
	int onsigstack = on_sig_stack(sp);
	int ret;

	/* redzone */
	if (IS_ENABLED(CONFIG_X86_64))
		sp -= 128;

	/* This is the X/Open sanctioned signal stack switching.  */
	if (ka->sa.sa_flags & SA_ONSTACK) {
		if (sas_ss_flags(sp) == 0)
			sp = current->sas_ss_sp + current->sas_ss_size;
	} else if (IS_ENABLED(CONFIG_X86_32) &&
		   !onsigstack &&
		   regs->ss != __USER_DS &&
		   !(ka->sa.sa_flags & SA_RESTORER) &&
		   ka->sa.sa_restorer) {
		/* This is the legacy signal stack switching. */
		sp = (unsigned long) ka->sa.sa_restorer;
	}

	sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
				  &buf_fx, &math_size);
	*fpstate = (void __user *)sp;

	sp = align_sigframe(sp - frame_size);

	/*
	 * If we are on the alternate signal stack and would overflow it, don't.
	 * Return an always-bogus address instead so we will die with SIGSEGV.
	 */
	if (onsigstack && !likely(on_sig_stack(sp)))
		return (void __user *)-1L;

	/* save i387 and extended state */
	ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
	if (ret < 0)
		return (void __user *)-1L;

	return (void __user *)sp;
}

#ifdef CONFIG_X86_32
static const struct {
	u16 poplmovl;
	u32 val;
	u16 int80;
} __attribute__((packed)) retcode = {
	0xb858,		/* popl %eax; movl $..., %eax */
	__NR_sigreturn,
	0x80cd,		/* int $0x80 */
};

static const struct {
	u8  movl;
	u32 val;
	u16 int80;
	u8  pad;
} __attribute__((packed)) rt_retcode = {
	0xb8,		/* movl $..., %eax */
	__NR_rt_sigreturn,
	0x80cd,		/* int $0x80 */
	0
};

static int
__setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
	      struct pt_regs *regs)
{
	struct sigframe __user *frame;
	void __user *restorer;
	void __user *fp = NULL;

	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

	if (!user_access_begin(frame, sizeof(*frame)))
		return -EFAULT;

	unsafe_put_user(sig, &frame->sig, Efault);
	unsafe_put_sigcontext(&frame->sc, fp, regs, set, Efault);
	unsafe_put_user(set->sig[1], &frame->extramask[0], Efault);
	if (current->mm->context.vdso)
		restorer = current->mm->context.vdso +
			vdso_image_32.sym___kernel_sigreturn;
	else
		restorer = &frame->retcode;
	if (ksig->ka.sa.sa_flags & SA_RESTORER)
		restorer = ksig->ka.sa.sa_restorer;

	/* Set up to return from userspace.  */
	unsafe_put_user(restorer, &frame->pretcode, Efault);

	/*
	 * This is popl %eax ; movl $__NR_sigreturn, %eax ; int $0x80
	 *
	 * WE DO NOT USE IT ANY MORE! It's only left here for historical
	 * reasons and because gdb uses it as a signature to notice
	 * signal handler stack frames.
	 */
	unsafe_put_user(*((u64 *)&retcode), (u64 *)frame->retcode, Efault);
	user_access_end();

	/* Set up registers for signal handler */
	regs->sp = (unsigned long)frame;
	regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
	regs->ax = (unsigned long)sig;
	regs->dx = 0;
	regs->cx = 0;

	regs->ds = __USER_DS;
	regs->es = __USER_DS;
	regs->ss = __USER_DS;
	regs->cs = __USER_CS;

	return 0;

Efault:
	user_access_end();
	return -EFAULT;
}

static int __setup_rt_frame(int sig, struct ksignal *ksig,
			    sigset_t *set, struct pt_regs *regs)
{
	struct rt_sigframe __user *frame;
	void __user *restorer;
	void __user *fp = NULL;

	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

	if (!user_access_begin(frame, sizeof(*frame)))
		return -EFAULT;

	unsafe_put_user(sig, &frame->sig, Efault);
	unsafe_put_user(&frame->info, &frame->pinfo, Efault);
	unsafe_put_user(&frame->uc, &frame->puc, Efault);

	/* Create the ucontext.  */
	if (static_cpu_has(X86_FEATURE_XSAVE))
		unsafe_put_user(UC_FP_XSTATE, &frame->uc.uc_flags, Efault);
	else
		unsafe_put_user(0, &frame->uc.uc_flags, Efault);
	unsafe_put_user(0, &frame->uc.uc_link, Efault);
	unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);

	/* Set up to return from userspace.  */
	restorer = current->mm->context.vdso +
		vdso_image_32.sym___kernel_rt_sigreturn;
	if (ksig->ka.sa.sa_flags & SA_RESTORER)
		restorer = ksig->ka.sa.sa_restorer;
	unsafe_put_user(restorer, &frame->pretcode, Efault);

	/*
	 * This is movl $__NR_rt_sigreturn, %ax ; int $0x80
	 *
	 * WE DO NOT USE IT ANY MORE! It's only left here for historical
	 * reasons and because gdb uses it as a signature to notice
	 * signal handler stack frames.
	 */
	unsafe_put_user(*((u64 *)&rt_retcode), (u64 *)frame->retcode, Efault);
	unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
	unsafe_put_sigmask(set, frame, Efault);
	user_access_end();
	
	if (copy_siginfo_to_user(&frame->info, &ksig->info))
		return -EFAULT;

	/* Set up registers for signal handler */
	regs->sp = (unsigned long)frame;
	regs->ip = (unsigned long)ksig->ka.sa.sa_handler;
	regs->ax = (unsigned long)sig;
	regs->dx = (unsigned long)&frame->info;
	regs->cx = (unsigned long)&frame->uc;

	regs->ds = __USER_DS;
	regs->es = __USER_DS;
	regs->ss = __USER_DS;
	regs->cs = __USER_CS;

	return 0;
Efault:
	user_access_end();
	return -EFAULT;
}
#else /* !CONFIG_X86_32 */
static unsigned long frame_uc_flags(struct pt_regs *regs)
{
	unsigned long flags;

	if (boot_cpu_has(X86_FEATURE_XSAVE))
		flags = UC_FP_XSTATE | UC_SIGCONTEXT_SS;
	else
		flags = UC_SIGCONTEXT_SS;

	if (likely(user_64bit_mode(regs)))
		flags |= UC_STRICT_RESTORE_SS;

	return flags;
}

static int __setup_rt_frame(int sig, struct ksignal *ksig,
			    sigset_t *set, struct pt_regs *regs)
{
	struct rt_sigframe __user *frame;
	void __user *fp = NULL;
	unsigned long uc_flags;

	/* x86-64 should always use SA_RESTORER. */
	if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
		return -EFAULT;

	frame = get_sigframe(&ksig->ka, regs, sizeof(struct rt_sigframe), &fp);
	uc_flags = frame_uc_flags(regs);

	if (!user_access_begin(frame, sizeof(*frame)))
		return -EFAULT;

	/* Create the ucontext.  */
	unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
	unsafe_put_user(0, &frame->uc.uc_link, Efault);
	unsafe_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	unsafe_put_user(ksig->ka.sa.sa_restorer, &frame->pretcode, Efault);
	unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
	unsafe_put_sigmask(set, frame, Efault);
	user_access_end();

	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
		if (copy_siginfo_to_user(&frame->info, &ksig->info))
			return -EFAULT;
	}

	/* Set up registers for signal handler */
	regs->di = sig;
	/* In case the signal handler was declared without prototypes */
	regs->ax = 0;

	/* This also works for non SA_SIGINFO handlers because they expect the
	   next argument after the signal number on the stack. */
	regs->si = (unsigned long)&frame->info;
	regs->dx = (unsigned long)&frame->uc;
	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;

	regs->sp = (unsigned long)frame;

	/*
	 * Set up the CS and SS registers to run signal handlers in
	 * 64-bit mode, even if the handler happens to be interrupting
	 * 32-bit or 16-bit code.
	 *
	 * SS is subtle.  In 64-bit mode, we don't need any particular
	 * SS descriptor, but we do need SS to be valid.  It's possible
	 * that the old SS is entirely bogus -- this can happen if the
	 * signal we're trying to deliver is #GP or #SS caused by a bad
	 * SS value.  We also have a compatbility issue here: DOSEMU
	 * relies on the contents of the SS register indicating the
	 * SS value at the time of the signal, even though that code in
	 * DOSEMU predates sigreturn's ability to restore SS.  (DOSEMU
	 * avoids relying on sigreturn to restore SS; instead it uses
	 * a trampoline.)  So we do our best: if the old SS was valid,
	 * we keep it.  Otherwise we replace it.
	 */
	regs->cs = __USER_CS;

	if (unlikely(regs->ss != __USER_DS))
		force_valid_ss(regs);

	return 0;

Efault:
	user_access_end();
	return -EFAULT;
}
#endif /* CONFIG_X86_32 */

#ifdef CONFIG_X86_X32_ABI
static int x32_copy_siginfo_to_user(struct compat_siginfo __user *to,
		const struct kernel_siginfo *from)
{
	struct compat_siginfo new;

	copy_siginfo_to_external32(&new, from);
	if (from->si_signo == SIGCHLD) {
		new._sifields._sigchld_x32._utime = from->si_utime;
		new._sifields._sigchld_x32._stime = from->si_stime;
	}
	if (copy_to_user(to, &new, sizeof(struct compat_siginfo)))
		return -EFAULT;
	return 0;
}

int copy_siginfo_to_user32(struct compat_siginfo __user *to,
			   const struct kernel_siginfo *from)
{
	if (in_x32_syscall())
		return x32_copy_siginfo_to_user(to, from);
	return __copy_siginfo_to_user32(to, from);
}
#endif /* CONFIG_X86_X32_ABI */

static int x32_setup_rt_frame(struct ksignal *ksig,
			      compat_sigset_t *set,
			      struct pt_regs *regs)
{
#ifdef CONFIG_X86_X32_ABI
	struct rt_sigframe_x32 __user *frame;
	unsigned long uc_flags;
	void __user *restorer;
	void __user *fp = NULL;

	if (!(ksig->ka.sa.sa_flags & SA_RESTORER))
		return -EFAULT;

	frame = get_sigframe(&ksig->ka, regs, sizeof(*frame), &fp);

	uc_flags = frame_uc_flags(regs);

	if (!user_access_begin(frame, sizeof(*frame)))
		return -EFAULT;

	/* Create the ucontext.  */
	unsafe_put_user(uc_flags, &frame->uc.uc_flags, Efault);
	unsafe_put_user(0, &frame->uc.uc_link, Efault);
	unsafe_compat_save_altstack(&frame->uc.uc_stack, regs->sp, Efault);
	unsafe_put_user(0, &frame->uc.uc__pad0, Efault);
	restorer = ksig->ka.sa.sa_restorer;
	unsafe_put_user(restorer, (unsigned long __user *)&frame->pretcode, Efault);
	unsafe_put_sigcontext(&frame->uc.uc_mcontext, fp, regs, set, Efault);
	unsafe_put_sigmask(set, frame, Efault);
	user_access_end();

	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
		if (x32_copy_siginfo_to_user(&frame->info, &ksig->info))
			return -EFAULT;
	}

	/* Set up registers for signal handler */
	regs->sp = (unsigned long) frame;
	regs->ip = (unsigned long) ksig->ka.sa.sa_handler;

	/* We use the x32 calling convention here... */
	regs->di = ksig->sig;
	regs->si = (unsigned long) &frame->info;
	regs->dx = (unsigned long) &frame->uc;

	loadsegment(ds, __USER_DS);
	loadsegment(es, __USER_DS);

	regs->cs = __USER_CS;
	regs->ss = __USER_DS;
#endif	/* CONFIG_X86_X32_ABI */

	return 0;
#ifdef CONFIG_X86_X32_ABI
Efault:
	user_access_end();
	return -EFAULT;
#endif
}

/*
 * Do a signal return; undo the signal stack.
 */
#ifdef CONFIG_X86_32
SYSCALL_DEFINE0(sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct sigframe __user *frame;
	sigset_t set;

	frame = (struct sigframe __user *)(regs->sp - 8);

	if (!access_ok(frame, sizeof(*frame)))
		goto badframe;
	if (__get_user(set.sig[0], &frame->sc.oldmask) ||
	    __get_user(set.sig[1], &frame->extramask[0]))
		goto badframe;

	set_current_blocked(&set);

	/*
	 * x86_32 has no uc_flags bits relevant to restore_sigcontext.
	 * Save a few cycles by skipping the __get_user.
	 */
	if (restore_sigcontext(regs, &frame->sc, 0))
		goto badframe;
	return regs->ax;

badframe:
	signal_fault(regs, frame, "sigreturn");

	return 0;
}
#endif /* CONFIG_X86_32 */

SYSCALL_DEFINE0(rt_sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct rt_sigframe __user *frame;
	sigset_t set;
	unsigned long uc_flags;

	frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
	if (!access_ok(frame, sizeof(*frame)))
		goto badframe;
	if (__get_user(*(__u64 *)&set, (__u64 __user *)&frame->uc.uc_sigmask))
		goto badframe;
	if (__get_user(uc_flags, &frame->uc.uc_flags))
		goto badframe;

	set_current_blocked(&set);

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
		goto badframe;

	if (restore_altstack(&frame->uc.uc_stack))
		goto badframe;

	return regs->ax;

badframe:
	signal_fault(regs, frame, "rt_sigreturn");
	return 0;
}

static inline int is_ia32_compat_frame(struct ksignal *ksig)
{
	return IS_ENABLED(CONFIG_IA32_EMULATION) &&
		ksig->ka.sa.sa_flags & SA_IA32_ABI;
}

static inline int is_ia32_frame(struct ksignal *ksig)
{
	return IS_ENABLED(CONFIG_X86_32) || is_ia32_compat_frame(ksig);
}

static inline int is_x32_frame(struct ksignal *ksig)
{
	return IS_ENABLED(CONFIG_X86_X32_ABI) &&
		ksig->ka.sa.sa_flags & SA_X32_ABI;
}

static int
setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
{
	int usig = ksig->sig;
	sigset_t *set = sigmask_to_save();
	compat_sigset_t *cset = (compat_sigset_t *) set;

	/* Perform fixup for the pre-signal frame. */
	rseq_signal_deliver(ksig, regs);

	/* Set up the stack frame */
	if (is_ia32_frame(ksig)) {
		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
			return ia32_setup_rt_frame(usig, ksig, cset, regs);
		else
			return ia32_setup_frame(usig, ksig, cset, regs);
	} else if (is_x32_frame(ksig)) {
		return x32_setup_rt_frame(ksig, cset, regs);
	} else {
		return __setup_rt_frame(ksig->sig, ksig, set, regs);
	}
}

static void
handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
	bool stepping, failed;
	struct fpu *fpu = &current->thread.fpu;

	if (v8086_mode(regs))
		save_v86_state((struct kernel_vm86_regs *) regs, VM86_SIGNAL);

	/* Are we from a system call? */
	if (syscall_get_nr(current, regs) >= 0) {
		/* If so, check system call restarting.. */
		switch (syscall_get_error(current, regs)) {
		case -ERESTART_RESTARTBLOCK:
		case -ERESTARTNOHAND:
			regs->ax = -EINTR;
			break;

		case -ERESTARTSYS:
			if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
				regs->ax = -EINTR;
				break;
			}
			fallthrough;
		case -ERESTARTNOINTR:
			regs->ax = regs->orig_ax;
			regs->ip -= 2;
			break;
		}
	}

	/*
	 * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
	 * so that register information in the sigcontext is correct and
	 * then notify the tracer before entering the signal handler.
	 */
	stepping = test_thread_flag(TIF_SINGLESTEP);
	if (stepping)
		user_disable_single_step(current);

	failed = (setup_rt_frame(ksig, regs) < 0);
	if (!failed) {
		/*
		 * Clear the direction flag as per the ABI for function entry.
		 *
		 * Clear RF when entering the signal handler, because
		 * it might disable possible debug exception from the
		 * signal handler.
		 *
		 * Clear TF for the case when it wasn't set by debugger to
		 * avoid the recursive send_sigtrap() in SIGTRAP handler.
		 */
		regs->flags &= ~(X86_EFLAGS_DF|X86_EFLAGS_RF|X86_EFLAGS_TF);
		/*
		 * Ensure the signal handler starts with the new fpu state.
		 */
		fpu__clear_user_states(fpu);
	}
	signal_setup_done(failed, ksig, stepping);
}

static inline unsigned long get_nr_restart_syscall(const struct pt_regs *regs)
{
	/*
	 * This function is fundamentally broken as currently
	 * implemented.
	 *
	 * The idea is that we want to trigger a call to the
	 * restart_block() syscall and that we want in_ia32_syscall(),
	 * in_x32_syscall(), etc. to match whatever they were in the
	 * syscall being restarted.  We assume that the syscall
	 * instruction at (regs->ip - 2) matches whatever syscall
	 * instruction we used to enter in the first place.
	 *
	 * The problem is that we can get here when ptrace pokes
	 * syscall-like values into regs even if we're not in a syscall
	 * at all.
	 *
	 * For now, we maintain historical behavior and guess based on
	 * stored state.  We could do better by saving the actual
	 * syscall arch in restart_block or (with caveats on x32) by
	 * checking if regs->ip points to 'int $0x80'.  The current
	 * behavior is incorrect if a tracer has a different bitness
	 * than the tracee.
	 */
#ifdef CONFIG_IA32_EMULATION
	if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED))
		return __NR_ia32_restart_syscall;
#endif
#ifdef CONFIG_X86_X32_ABI
	return __NR_restart_syscall | (regs->orig_ax & __X32_SYSCALL_BIT);
#else
	return __NR_restart_syscall;
#endif
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal)
{
	struct ksignal ksig;

	if (has_signal && get_signal(&ksig)) {
		/* Whee! Actually deliver the signal.  */
		handle_signal(&ksig, regs);
		return;
	}

	/* Did we come from a system call? */
	if (syscall_get_nr(current, regs) >= 0) {
		/* Restart the system call - no handlers present */
		switch (syscall_get_error(current, regs)) {
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
			regs->ax = regs->orig_ax;
			regs->ip -= 2;
			break;

		case -ERESTART_RESTARTBLOCK:
			regs->ax = get_nr_restart_syscall(regs);
			regs->ip -= 2;
			break;
		}
	}

	/*
	 * If there's no signal to deliver, we just put the saved sigmask
	 * back.
	 */
	restore_saved_sigmask();
}

void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
{
	struct task_struct *me = current;

	if (show_unhandled_signals && printk_ratelimit()) {
		printk("%s"
		       "%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
		       task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
		       me->comm, me->pid, where, frame,
		       regs->ip, regs->sp, regs->orig_ax);
		print_vma_addr(KERN_CONT " in ", regs->ip);
		pr_cont("\n");
	}

	force_sig(SIGSEGV);
}

#ifdef CONFIG_X86_X32_ABI
COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn)
{
	struct pt_regs *regs = current_pt_regs();
	struct rt_sigframe_x32 __user *frame;
	sigset_t set;
	unsigned long uc_flags;

	frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);

	if (!access_ok(frame, sizeof(*frame)))
		goto badframe;
	if (__get_user(set.sig[0], (__u64 __user *)&frame->uc.uc_sigmask))
		goto badframe;
	if (__get_user(uc_flags, &frame->uc.uc_flags))
		goto badframe;

	set_current_blocked(&set);

	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, uc_flags))
		goto badframe;

	if (compat_restore_altstack(&frame->uc.uc_stack))
		goto badframe;

	return regs->ax;

badframe:
	signal_fault(regs, frame, "x32 rt_sigreturn");
	return 0;
}
#endif