summaryrefslogtreecommitdiff
path: root/arch/s390/kernel/signal.c
blob: e6fca5498e1fda810f0aa3fb7bb3e18f55a81272 (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
// SPDX-License-Identifier: GPL-2.0
/*
 *    Copyright IBM Corp. 1999, 2006
 *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
 *
 *    Based on Intel version
 * 
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 */

#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/tty.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/tracehook.h>
#include <linux/syscalls.h>
#include <linux/compat.h>
#include <asm/ucontext.h>
#include <linux/uaccess.h>
#include <asm/lowcore.h>
#include <asm/switch_to.h>
#include "entry.h"

/*
 * Layout of an old-style signal-frame:
 *	-----------------------------------------
 *	| save area (_SIGNAL_FRAMESIZE)		|
 *	-----------------------------------------
 *	| struct sigcontext			|
 *	|	oldmask				|
 *	|	_sigregs *			|
 *	-----------------------------------------
 *	| _sigregs with				|
 *	|	_s390_regs_common		|
 *	|	_s390_fp_regs			|
 *	-----------------------------------------
 *	| int signo				|
 *	-----------------------------------------
 *	| _sigregs_ext with			|
 *	|	gprs_high 64 byte (opt)		|
 *	|	vxrs_low 128 byte (opt)		|
 *	|	vxrs_high 256 byte (opt)	|
 *	|	reserved 128 byte (opt)		|
 *	-----------------------------------------
 *	| __u16 svc_insn			|
 *	-----------------------------------------
 * The svc_insn entry with the sigreturn system call opcode does not
 * have a fixed position and moves if gprs_high or vxrs exist.
 * Future extensions will be added to _sigregs_ext.
 */
struct sigframe
{
	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
	struct sigcontext sc;
	_sigregs sregs;
	int signo;
	_sigregs_ext sregs_ext;
	__u16 svc_insn;		/* Offset of svc_insn is NOT fixed! */
};

/*
 * Layout of an rt signal-frame:
 *	-----------------------------------------
 *	| save area (_SIGNAL_FRAMESIZE)		|
 *	-----------------------------------------
 *	| svc __NR_rt_sigreturn 2 byte		|
 *	-----------------------------------------
 *	| struct siginfo			|
 *	-----------------------------------------
 *	| struct ucontext_extended with		|
 *	|	unsigned long uc_flags		|
 *	|	struct ucontext *uc_link	|
 *	|	stack_t uc_stack		|
 *	|	_sigregs uc_mcontext with	|
 *	|		_s390_regs_common	|
 *	|		_s390_fp_regs		|
 *	|	sigset_t uc_sigmask		|
 *	|	_sigregs_ext uc_mcontext_ext	|
 *	|		gprs_high 64 byte (opt)	|
 *	|		vxrs_low 128 byte (opt)	|
 *	|		vxrs_high 256 byte (opt)|
 *	|		reserved 128 byte (opt)	|
 *	-----------------------------------------
 * Future extensions will be added to _sigregs_ext.
 */
struct rt_sigframe
{
	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
	__u16 svc_insn;
	struct siginfo info;
	struct ucontext_extended uc;
};

/* Store registers needed to create the signal frame */
static void store_sigregs(void)
{
	save_access_regs(current->thread.acrs);
	save_fpu_regs();
}

/* Load registers after signal return */
static void load_sigregs(void)
{
	restore_access_regs(current->thread.acrs);
}

/* Returns non-zero on fault. */
static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
	_sigregs user_sregs;

	/* Copy a 'clean' PSW mask to the user to avoid leaking
	   information about whether PER is currently on.  */
	user_sregs.regs.psw.mask = PSW_USER_BITS |
		(regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
	user_sregs.regs.psw.addr = regs->psw.addr;
	memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
	memcpy(&user_sregs.regs.acrs, current->thread.acrs,
	       sizeof(user_sregs.regs.acrs));
	fpregs_store(&user_sregs.fpregs, &current->thread.fpu);
	if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
		return -EFAULT;
	return 0;
}

static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
{
	_sigregs user_sregs;

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

	if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
		return -EFAULT;

	if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI))
		return -EINVAL;

	/* Test the floating-point-control word. */
	if (test_fp_ctl(user_sregs.fpregs.fpc))
		return -EINVAL;

	/* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
	regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) |
		(user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
	/* Check for invalid user address space control. */
	if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME)
		regs->psw.mask = PSW_ASC_PRIMARY |
			(regs->psw.mask & ~PSW_MASK_ASC);
	/* Check for invalid amode */
	if (regs->psw.mask & PSW_MASK_EA)
		regs->psw.mask |= PSW_MASK_BA;
	regs->psw.addr = user_sregs.regs.psw.addr;
	memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
	memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
	       sizeof(current->thread.acrs));

	fpregs_load(&user_sregs.fpregs, &current->thread.fpu);

	clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */
	return 0;
}

/* Returns non-zero on fault. */
static int save_sigregs_ext(struct pt_regs *regs,
			    _sigregs_ext __user *sregs_ext)
{
	__u64 vxrs[__NUM_VXRS_LOW];
	int i;

	/* Save vector registers to signal stack */
	if (MACHINE_HAS_VX) {
		for (i = 0; i < __NUM_VXRS_LOW; i++)
			vxrs[i] = *((__u64 *)(current->thread.fpu.vxrs + i) + 1);
		if (__copy_to_user(&sregs_ext->vxrs_low, vxrs,
				   sizeof(sregs_ext->vxrs_low)) ||
		    __copy_to_user(&sregs_ext->vxrs_high,
				   current->thread.fpu.vxrs + __NUM_VXRS_LOW,
				   sizeof(sregs_ext->vxrs_high)))
			return -EFAULT;
	}
	return 0;
}

static int restore_sigregs_ext(struct pt_regs *regs,
			       _sigregs_ext __user *sregs_ext)
{
	__u64 vxrs[__NUM_VXRS_LOW];
	int i;

	/* Restore vector registers from signal stack */
	if (MACHINE_HAS_VX) {
		if (__copy_from_user(vxrs, &sregs_ext->vxrs_low,
				     sizeof(sregs_ext->vxrs_low)) ||
		    __copy_from_user(current->thread.fpu.vxrs + __NUM_VXRS_LOW,
				     &sregs_ext->vxrs_high,
				     sizeof(sregs_ext->vxrs_high)))
			return -EFAULT;
		for (i = 0; i < __NUM_VXRS_LOW; i++)
			*((__u64 *)(current->thread.fpu.vxrs + i) + 1) = vxrs[i];
	}
	return 0;
}

SYSCALL_DEFINE0(sigreturn)
{
	struct pt_regs *regs = task_pt_regs(current);
	struct sigframe __user *frame =
		(struct sigframe __user *) regs->gprs[15];
	sigset_t set;

	if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
		goto badframe;
	set_current_blocked(&set);
	save_fpu_regs();
	if (restore_sigregs(regs, &frame->sregs))
		goto badframe;
	if (restore_sigregs_ext(regs, &frame->sregs_ext))
		goto badframe;
	load_sigregs();
	return regs->gprs[2];
badframe:
	force_sig(SIGSEGV);
	return 0;
}

SYSCALL_DEFINE0(rt_sigreturn)
{
	struct pt_regs *regs = task_pt_regs(current);
	struct rt_sigframe __user *frame =
		(struct rt_sigframe __user *)regs->gprs[15];
	sigset_t set;

	if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
		goto badframe;
	set_current_blocked(&set);
	if (restore_altstack(&frame->uc.uc_stack))
		goto badframe;
	save_fpu_regs();
	if (restore_sigregs(regs, &frame->uc.uc_mcontext))
		goto badframe;
	if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
		goto badframe;
	load_sigregs();
	return regs->gprs[2];
badframe:
	force_sig(SIGSEGV);
	return 0;
}

/*
 * Determine which stack to use..
 */
static inline void __user *
get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
{
	unsigned long sp;

	/* Default to using normal stack */
	sp = regs->gprs[15];

	/* Overflow on alternate signal stack gives SIGSEGV. */
	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
		return (void __user *) -1UL;

	/* This is the X/Open sanctioned signal stack switching.  */
	if (ka->sa.sa_flags & SA_ONSTACK) {
		if (! sas_ss_flags(sp))
			sp = current->sas_ss_sp + current->sas_ss_size;
	}

	return (void __user *)((sp - frame_size) & -8ul);
}

static int setup_frame(int sig, struct k_sigaction *ka,
		       sigset_t *set, struct pt_regs * regs)
{
	struct sigframe __user *frame;
	struct sigcontext sc;
	unsigned long restorer;
	size_t frame_size;

	/*
	 * gprs_high are only present for a 31-bit task running on
	 * a 64-bit kernel (see compat_signal.c) but the space for
	 * gprs_high need to be allocated if vector registers are
	 * included in the signal frame on a 31-bit system.
	 */
	frame_size = sizeof(*frame) - sizeof(frame->sregs_ext);
	if (MACHINE_HAS_VX)
		frame_size += sizeof(frame->sregs_ext);
	frame = get_sigframe(ka, regs, frame_size);
	if (frame == (void __user *) -1UL)
		return -EFAULT;

	/* Set up backchain. */
	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
		return -EFAULT;

	/* Create struct sigcontext on the signal stack */
	memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE);
	sc.sregs = (_sigregs __user __force *) &frame->sregs;
	if (__copy_to_user(&frame->sc, &sc, sizeof(frame->sc)))
		return -EFAULT;

	/* Store registers needed to create the signal frame */
	store_sigregs();

	/* Create _sigregs on the signal stack */
	if (save_sigregs(regs, &frame->sregs))
		return -EFAULT;

	/* Place signal number on stack to allow backtrace from handler.  */
	if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
		return -EFAULT;

	/* Create _sigregs_ext on the signal stack */
	if (save_sigregs_ext(regs, &frame->sregs_ext))
		return -EFAULT;

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	if (ka->sa.sa_flags & SA_RESTORER) {
		restorer = (unsigned long) ka->sa.sa_restorer;
	} else {
		/* Signal frame without vector registers are short ! */
		__u16 __user *svc = (void __user *) frame + frame_size - 2;
		if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn, svc))
			return -EFAULT;
		restorer = (unsigned long) svc;
	}

	/* Set up registers for signal handler */
	regs->gprs[14] = restorer;
	regs->gprs[15] = (unsigned long) frame;
	/* Force default amode and default user address space control. */
	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
		(PSW_USER_BITS & PSW_MASK_ASC) |
		(regs->psw.mask & ~PSW_MASK_ASC);
	regs->psw.addr = (unsigned long) ka->sa.sa_handler;

	regs->gprs[2] = sig;
	regs->gprs[3] = (unsigned long) &frame->sc;

	/* We forgot to include these in the sigcontext.
	   To avoid breaking binary compatibility, they are passed as args. */
	if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
	    sig == SIGTRAP || sig == SIGFPE) {
		/* set extra registers only for synchronous signals */
		regs->gprs[4] = regs->int_code & 127;
		regs->gprs[5] = regs->int_parm_long;
		regs->gprs[6] = current->thread.last_break;
	}
	return 0;
}

static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
			  struct pt_regs *regs)
{
	struct rt_sigframe __user *frame;
	unsigned long uc_flags, restorer;
	size_t frame_size;

	frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext);
	/*
	 * gprs_high are only present for a 31-bit task running on
	 * a 64-bit kernel (see compat_signal.c) but the space for
	 * gprs_high need to be allocated if vector registers are
	 * included in the signal frame on a 31-bit system.
	 */
	uc_flags = 0;
	if (MACHINE_HAS_VX) {
		frame_size += sizeof(_sigregs_ext);
		uc_flags |= UC_VXRS;
	}
	frame = get_sigframe(&ksig->ka, regs, frame_size);
	if (frame == (void __user *) -1UL)
		return -EFAULT;

	/* Set up backchain. */
	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
		return -EFAULT;

	/* Set up to return from userspace.  If provided, use a stub
	   already in userspace.  */
	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
		restorer = (unsigned long) ksig->ka.sa.sa_restorer;
	} else {
		__u16 __user *svc = &frame->svc_insn;
		if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn, svc))
			return -EFAULT;
		restorer = (unsigned long) svc;
	}

	/* Create siginfo on the signal stack */
	if (copy_siginfo_to_user(&frame->info, &ksig->info))
		return -EFAULT;

	/* Store registers needed to create the signal frame */
	store_sigregs();

	/* Create ucontext on the signal stack. */
	if (__put_user(uc_flags, &frame->uc.uc_flags) ||
	    __put_user(NULL, &frame->uc.uc_link) ||
	    __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) ||
	    save_sigregs(regs, &frame->uc.uc_mcontext) ||
	    __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)) ||
	    save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
		return -EFAULT;

	/* Set up registers for signal handler */
	regs->gprs[14] = restorer;
	regs->gprs[15] = (unsigned long) frame;
	/* Force default amode and default user address space control. */
	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
		(PSW_USER_BITS & PSW_MASK_ASC) |
		(regs->psw.mask & ~PSW_MASK_ASC);
	regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler;

	regs->gprs[2] = ksig->sig;
	regs->gprs[3] = (unsigned long) &frame->info;
	regs->gprs[4] = (unsigned long) &frame->uc;
	regs->gprs[5] = current->thread.last_break;
	return 0;
}

static void handle_signal(struct ksignal *ksig, sigset_t *oldset,
			  struct pt_regs *regs)
{
	int ret;

	/* Set up the stack frame */
	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
		ret = setup_rt_frame(ksig, oldset, regs);
	else
		ret = setup_frame(ksig->sig, &ksig->ka, oldset, regs);

	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLE_STEP));
}

/*
 * 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.
 *
 * Note that we go through the signals twice: once to check the signals that
 * the kernel can handle, and then we build all the user-level signal handling
 * stack-frames in one go after that.
 */
void do_signal(struct pt_regs *regs)
{
	struct ksignal ksig;
	sigset_t *oldset = sigmask_to_save();

	/*
	 * Get signal to deliver. When running under ptrace, at this point
	 * the debugger may change all our registers, including the system
	 * call information.
	 */
	current->thread.system_call =
		test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;

	if (get_signal(&ksig)) {
		/* Whee!  Actually deliver the signal.  */
		if (current->thread.system_call) {
			regs->int_code = current->thread.system_call;
			/* Check for system call restarting. */
			switch (regs->gprs[2]) {
			case -ERESTART_RESTARTBLOCK:
			case -ERESTARTNOHAND:
				regs->gprs[2] = -EINTR;
				break;
			case -ERESTARTSYS:
				if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
					regs->gprs[2] = -EINTR;
					break;
				}
			/* fallthrough */
			case -ERESTARTNOINTR:
				regs->gprs[2] = regs->orig_gpr2;
				regs->psw.addr =
					__rewind_psw(regs->psw,
						     regs->int_code >> 16);
				break;
			}
		}
		/* No longer in a system call */
		clear_pt_regs_flag(regs, PIF_SYSCALL);
		rseq_signal_deliver(&ksig, regs);
		if (is_compat_task())
			handle_signal32(&ksig, oldset, regs);
		else
			handle_signal(&ksig, oldset, regs);
		return;
	}

	/* No handlers present - check for system call restart */
	clear_pt_regs_flag(regs, PIF_SYSCALL);
	if (current->thread.system_call) {
		regs->int_code = current->thread.system_call;
		switch (regs->gprs[2]) {
		case -ERESTART_RESTARTBLOCK:
			/* Restart with sys_restart_syscall */
			regs->int_code = __NR_restart_syscall;
		/* fallthrough */
		case -ERESTARTNOHAND:
		case -ERESTARTSYS:
		case -ERESTARTNOINTR:
			/* Restart system call with magic TIF bit. */
			regs->gprs[2] = regs->orig_gpr2;
			set_pt_regs_flag(regs, PIF_SYSCALL);
			if (test_thread_flag(TIF_SINGLE_STEP))
				clear_pt_regs_flag(regs, PIF_PER_TRAP);
			break;
		}
	}

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

void do_notify_resume(struct pt_regs *regs)
{
	clear_thread_flag(TIF_NOTIFY_RESUME);
	tracehook_notify_resume(regs);
	rseq_handle_notify_resume(NULL, regs);
}