xref: /openbmc/linux/arch/s390/kernel/signal.c (revision f4356947)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *    Copyright IBM Corp. 1999, 2006
4  *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
5  *
6  *    Based on Intel version
7  *
8  *  Copyright (C) 1991, 1992  Linus Torvalds
9  *
10  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
11  */
12 
13 #include <linux/sched.h>
14 #include <linux/sched/task_stack.h>
15 #include <linux/mm.h>
16 #include <linux/smp.h>
17 #include <linux/kernel.h>
18 #include <linux/signal.h>
19 #include <linux/entry-common.h>
20 #include <linux/errno.h>
21 #include <linux/wait.h>
22 #include <linux/ptrace.h>
23 #include <linux/unistd.h>
24 #include <linux/stddef.h>
25 #include <linux/tty.h>
26 #include <linux/personality.h>
27 #include <linux/binfmts.h>
28 #include <linux/syscalls.h>
29 #include <linux/compat.h>
30 #include <asm/ucontext.h>
31 #include <linux/uaccess.h>
32 #include <asm/lowcore.h>
33 #include <asm/switch_to.h>
34 #include <asm/vdso.h>
35 #include "entry.h"
36 
37 /*
38  * Layout of an old-style signal-frame:
39  *	-----------------------------------------
40  *	| save area (_SIGNAL_FRAMESIZE)		|
41  *	-----------------------------------------
42  *	| struct sigcontext			|
43  *	|	oldmask				|
44  *	|	_sigregs *			|
45  *	-----------------------------------------
46  *	| _sigregs with				|
47  *	|	_s390_regs_common		|
48  *	|	_s390_fp_regs			|
49  *	-----------------------------------------
50  *	| int signo				|
51  *	-----------------------------------------
52  *	| _sigregs_ext with			|
53  *	|	gprs_high 64 byte (opt)		|
54  *	|	vxrs_low 128 byte (opt)		|
55  *	|	vxrs_high 256 byte (opt)	|
56  *	|	reserved 128 byte (opt)		|
57  *	-----------------------------------------
58  *	| __u16 svc_insn			|
59  *	-----------------------------------------
60  * The svc_insn entry with the sigreturn system call opcode does not
61  * have a fixed position and moves if gprs_high or vxrs exist.
62  * Future extensions will be added to _sigregs_ext.
63  */
64 struct sigframe
65 {
66 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
67 	struct sigcontext sc;
68 	_sigregs sregs;
69 	int signo;
70 	_sigregs_ext sregs_ext;
71 	__u16 svc_insn;		/* Offset of svc_insn is NOT fixed! */
72 };
73 
74 /*
75  * Layout of an rt signal-frame:
76  *	-----------------------------------------
77  *	| save area (_SIGNAL_FRAMESIZE)		|
78  *	-----------------------------------------
79  *	| svc __NR_rt_sigreturn 2 byte		|
80  *	-----------------------------------------
81  *	| struct siginfo			|
82  *	-----------------------------------------
83  *	| struct ucontext_extended with		|
84  *	|	unsigned long uc_flags		|
85  *	|	struct ucontext *uc_link	|
86  *	|	stack_t uc_stack		|
87  *	|	_sigregs uc_mcontext with	|
88  *	|		_s390_regs_common	|
89  *	|		_s390_fp_regs		|
90  *	|	sigset_t uc_sigmask		|
91  *	|	_sigregs_ext uc_mcontext_ext	|
92  *	|		gprs_high 64 byte (opt)	|
93  *	|		vxrs_low 128 byte (opt)	|
94  *	|		vxrs_high 256 byte (opt)|
95  *	|		reserved 128 byte (opt)	|
96  *	-----------------------------------------
97  * Future extensions will be added to _sigregs_ext.
98  */
99 struct rt_sigframe
100 {
101 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
102 	__u16 svc_insn;
103 	struct siginfo info;
104 	struct ucontext_extended uc;
105 };
106 
107 /* Store registers needed to create the signal frame */
108 static void store_sigregs(void)
109 {
110 	save_access_regs(current->thread.acrs);
111 	save_fpu_regs();
112 }
113 
114 /* Load registers after signal return */
115 static void load_sigregs(void)
116 {
117 	restore_access_regs(current->thread.acrs);
118 }
119 
120 /* Returns non-zero on fault. */
121 static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
122 {
123 	_sigregs user_sregs;
124 
125 	/* Copy a 'clean' PSW mask to the user to avoid leaking
126 	   information about whether PER is currently on.  */
127 	user_sregs.regs.psw.mask = PSW_USER_BITS |
128 		(regs->psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
129 	user_sregs.regs.psw.addr = regs->psw.addr;
130 	memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
131 	memcpy(&user_sregs.regs.acrs, current->thread.acrs,
132 	       sizeof(user_sregs.regs.acrs));
133 	fpregs_store(&user_sregs.fpregs, &current->thread.fpu);
134 	if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
135 		return -EFAULT;
136 	return 0;
137 }
138 
139 static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
140 {
141 	_sigregs user_sregs;
142 
143 	/* Always make any pending restarted system call return -EINTR */
144 	current->restart_block.fn = do_no_restart_syscall;
145 
146 	if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
147 		return -EFAULT;
148 
149 	if (!is_ri_task(current) && (user_sregs.regs.psw.mask & PSW_MASK_RI))
150 		return -EINVAL;
151 
152 	/* Test the floating-point-control word. */
153 	if (test_fp_ctl(user_sregs.fpregs.fpc))
154 		return -EINVAL;
155 
156 	/* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
157 	regs->psw.mask = (regs->psw.mask & ~(PSW_MASK_USER | PSW_MASK_RI)) |
158 		(user_sregs.regs.psw.mask & (PSW_MASK_USER | PSW_MASK_RI));
159 	/* Check for invalid user address space control. */
160 	if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME)
161 		regs->psw.mask = PSW_ASC_PRIMARY |
162 			(regs->psw.mask & ~PSW_MASK_ASC);
163 	/* Check for invalid amode */
164 	if (regs->psw.mask & PSW_MASK_EA)
165 		regs->psw.mask |= PSW_MASK_BA;
166 	regs->psw.addr = user_sregs.regs.psw.addr;
167 	memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
168 	memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
169 	       sizeof(current->thread.acrs));
170 
171 	fpregs_load(&user_sregs.fpregs, &current->thread.fpu);
172 
173 	clear_pt_regs_flag(regs, PIF_SYSCALL); /* No longer in a system call */
174 	return 0;
175 }
176 
177 /* Returns non-zero on fault. */
178 static int save_sigregs_ext(struct pt_regs *regs,
179 			    _sigregs_ext __user *sregs_ext)
180 {
181 	__u64 vxrs[__NUM_VXRS_LOW];
182 	int i;
183 
184 	/* Save vector registers to signal stack */
185 	if (MACHINE_HAS_VX) {
186 		for (i = 0; i < __NUM_VXRS_LOW; i++)
187 			vxrs[i] = current->thread.fpu.vxrs[i].low;
188 		if (__copy_to_user(&sregs_ext->vxrs_low, vxrs,
189 				   sizeof(sregs_ext->vxrs_low)) ||
190 		    __copy_to_user(&sregs_ext->vxrs_high,
191 				   current->thread.fpu.vxrs + __NUM_VXRS_LOW,
192 				   sizeof(sregs_ext->vxrs_high)))
193 			return -EFAULT;
194 	}
195 	return 0;
196 }
197 
198 static int restore_sigregs_ext(struct pt_regs *regs,
199 			       _sigregs_ext __user *sregs_ext)
200 {
201 	__u64 vxrs[__NUM_VXRS_LOW];
202 	int i;
203 
204 	/* Restore vector registers from signal stack */
205 	if (MACHINE_HAS_VX) {
206 		if (__copy_from_user(vxrs, &sregs_ext->vxrs_low,
207 				     sizeof(sregs_ext->vxrs_low)) ||
208 		    __copy_from_user(current->thread.fpu.vxrs + __NUM_VXRS_LOW,
209 				     &sregs_ext->vxrs_high,
210 				     sizeof(sregs_ext->vxrs_high)))
211 			return -EFAULT;
212 		for (i = 0; i < __NUM_VXRS_LOW; i++)
213 			current->thread.fpu.vxrs[i].low = vxrs[i];
214 	}
215 	return 0;
216 }
217 
218 SYSCALL_DEFINE0(sigreturn)
219 {
220 	struct pt_regs *regs = task_pt_regs(current);
221 	struct sigframe __user *frame =
222 		(struct sigframe __user *) regs->gprs[15];
223 	sigset_t set;
224 
225 	if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
226 		goto badframe;
227 	set_current_blocked(&set);
228 	save_fpu_regs();
229 	if (restore_sigregs(regs, &frame->sregs))
230 		goto badframe;
231 	if (restore_sigregs_ext(regs, &frame->sregs_ext))
232 		goto badframe;
233 	load_sigregs();
234 	return regs->gprs[2];
235 badframe:
236 	force_sig(SIGSEGV);
237 	return 0;
238 }
239 
240 SYSCALL_DEFINE0(rt_sigreturn)
241 {
242 	struct pt_regs *regs = task_pt_regs(current);
243 	struct rt_sigframe __user *frame =
244 		(struct rt_sigframe __user *)regs->gprs[15];
245 	sigset_t set;
246 
247 	if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
248 		goto badframe;
249 	set_current_blocked(&set);
250 	if (restore_altstack(&frame->uc.uc_stack))
251 		goto badframe;
252 	save_fpu_regs();
253 	if (restore_sigregs(regs, &frame->uc.uc_mcontext))
254 		goto badframe;
255 	if (restore_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
256 		goto badframe;
257 	load_sigregs();
258 	return regs->gprs[2];
259 badframe:
260 	force_sig(SIGSEGV);
261 	return 0;
262 }
263 
264 /*
265  * Determine which stack to use..
266  */
267 static inline void __user *
268 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
269 {
270 	unsigned long sp;
271 
272 	/* Default to using normal stack */
273 	sp = regs->gprs[15];
274 
275 	/* Overflow on alternate signal stack gives SIGSEGV. */
276 	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
277 		return (void __user *) -1UL;
278 
279 	/* This is the X/Open sanctioned signal stack switching.  */
280 	if (ka->sa.sa_flags & SA_ONSTACK) {
281 		if (! sas_ss_flags(sp))
282 			sp = current->sas_ss_sp + current->sas_ss_size;
283 	}
284 
285 	return (void __user *)((sp - frame_size) & -8ul);
286 }
287 
288 static int setup_frame(int sig, struct k_sigaction *ka,
289 		       sigset_t *set, struct pt_regs * regs)
290 {
291 	struct sigframe __user *frame;
292 	struct sigcontext sc;
293 	unsigned long restorer;
294 	size_t frame_size;
295 
296 	/*
297 	 * gprs_high are only present for a 31-bit task running on
298 	 * a 64-bit kernel (see compat_signal.c) but the space for
299 	 * gprs_high need to be allocated if vector registers are
300 	 * included in the signal frame on a 31-bit system.
301 	 */
302 	frame_size = sizeof(*frame) - sizeof(frame->sregs_ext);
303 	if (MACHINE_HAS_VX)
304 		frame_size += sizeof(frame->sregs_ext);
305 	frame = get_sigframe(ka, regs, frame_size);
306 	if (frame == (void __user *) -1UL)
307 		return -EFAULT;
308 
309 	/* Set up backchain. */
310 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
311 		return -EFAULT;
312 
313 	/* Create struct sigcontext on the signal stack */
314 	memcpy(&sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE);
315 	sc.sregs = (_sigregs __user __force *) &frame->sregs;
316 	if (__copy_to_user(&frame->sc, &sc, sizeof(frame->sc)))
317 		return -EFAULT;
318 
319 	/* Store registers needed to create the signal frame */
320 	store_sigregs();
321 
322 	/* Create _sigregs on the signal stack */
323 	if (save_sigregs(regs, &frame->sregs))
324 		return -EFAULT;
325 
326 	/* Place signal number on stack to allow backtrace from handler.  */
327 	if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
328 		return -EFAULT;
329 
330 	/* Create _sigregs_ext on the signal stack */
331 	if (save_sigregs_ext(regs, &frame->sregs_ext))
332 		return -EFAULT;
333 
334 	/* Set up to return from userspace.  If provided, use a stub
335 	   already in userspace.  */
336 	if (ka->sa.sa_flags & SA_RESTORER)
337 		restorer = (unsigned long) ka->sa.sa_restorer;
338 	else
339 		restorer = VDSO64_SYMBOL(current, sigreturn);
340 
341 	/* Set up registers for signal handler */
342 	regs->gprs[14] = restorer;
343 	regs->gprs[15] = (unsigned long) frame;
344 	/* Force default amode and default user address space control. */
345 	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
346 		(PSW_USER_BITS & PSW_MASK_ASC) |
347 		(regs->psw.mask & ~PSW_MASK_ASC);
348 	regs->psw.addr = (unsigned long) ka->sa.sa_handler;
349 
350 	regs->gprs[2] = sig;
351 	regs->gprs[3] = (unsigned long) &frame->sc;
352 
353 	/* We forgot to include these in the sigcontext.
354 	   To avoid breaking binary compatibility, they are passed as args. */
355 	if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
356 	    sig == SIGTRAP || sig == SIGFPE) {
357 		/* set extra registers only for synchronous signals */
358 		regs->gprs[4] = regs->int_code & 127;
359 		regs->gprs[5] = regs->int_parm_long;
360 		regs->gprs[6] = current->thread.last_break;
361 	}
362 	return 0;
363 }
364 
365 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
366 			  struct pt_regs *regs)
367 {
368 	struct rt_sigframe __user *frame;
369 	unsigned long uc_flags, restorer;
370 	size_t frame_size;
371 
372 	frame_size = sizeof(struct rt_sigframe) - sizeof(_sigregs_ext);
373 	/*
374 	 * gprs_high are only present for a 31-bit task running on
375 	 * a 64-bit kernel (see compat_signal.c) but the space for
376 	 * gprs_high need to be allocated if vector registers are
377 	 * included in the signal frame on a 31-bit system.
378 	 */
379 	uc_flags = 0;
380 	if (MACHINE_HAS_VX) {
381 		frame_size += sizeof(_sigregs_ext);
382 		uc_flags |= UC_VXRS;
383 	}
384 	frame = get_sigframe(&ksig->ka, regs, frame_size);
385 	if (frame == (void __user *) -1UL)
386 		return -EFAULT;
387 
388 	/* Set up backchain. */
389 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
390 		return -EFAULT;
391 
392 	/* Set up to return from userspace.  If provided, use a stub
393 	   already in userspace.  */
394 	if (ksig->ka.sa.sa_flags & SA_RESTORER)
395 		restorer = (unsigned long) ksig->ka.sa.sa_restorer;
396 	else
397 		restorer = VDSO64_SYMBOL(current, rt_sigreturn);
398 
399 	/* Create siginfo on the signal stack */
400 	if (copy_siginfo_to_user(&frame->info, &ksig->info))
401 		return -EFAULT;
402 
403 	/* Store registers needed to create the signal frame */
404 	store_sigregs();
405 
406 	/* Create ucontext on the signal stack. */
407 	if (__put_user(uc_flags, &frame->uc.uc_flags) ||
408 	    __put_user(NULL, &frame->uc.uc_link) ||
409 	    __save_altstack(&frame->uc.uc_stack, regs->gprs[15]) ||
410 	    save_sigregs(regs, &frame->uc.uc_mcontext) ||
411 	    __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)) ||
412 	    save_sigregs_ext(regs, &frame->uc.uc_mcontext_ext))
413 		return -EFAULT;
414 
415 	/* Set up registers for signal handler */
416 	regs->gprs[14] = restorer;
417 	regs->gprs[15] = (unsigned long) frame;
418 	/* Force default amode and default user address space control. */
419 	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
420 		(PSW_USER_BITS & PSW_MASK_ASC) |
421 		(regs->psw.mask & ~PSW_MASK_ASC);
422 	regs->psw.addr = (unsigned long) ksig->ka.sa.sa_handler;
423 
424 	regs->gprs[2] = ksig->sig;
425 	regs->gprs[3] = (unsigned long) &frame->info;
426 	regs->gprs[4] = (unsigned long) &frame->uc;
427 	regs->gprs[5] = current->thread.last_break;
428 	return 0;
429 }
430 
431 static void handle_signal(struct ksignal *ksig, sigset_t *oldset,
432 			  struct pt_regs *regs)
433 {
434 	int ret;
435 
436 	/* Set up the stack frame */
437 	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
438 		ret = setup_rt_frame(ksig, oldset, regs);
439 	else
440 		ret = setup_frame(ksig->sig, &ksig->ka, oldset, regs);
441 
442 	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLE_STEP));
443 }
444 
445 /*
446  * Note that 'init' is a special process: it doesn't get signals it doesn't
447  * want to handle. Thus you cannot kill init even with a SIGKILL even by
448  * mistake.
449  *
450  * Note that we go through the signals twice: once to check the signals that
451  * the kernel can handle, and then we build all the user-level signal handling
452  * stack-frames in one go after that.
453  */
454 
455 void arch_do_signal_or_restart(struct pt_regs *regs)
456 {
457 	struct ksignal ksig;
458 	sigset_t *oldset = sigmask_to_save();
459 
460 	/*
461 	 * Get signal to deliver. When running under ptrace, at this point
462 	 * the debugger may change all our registers, including the system
463 	 * call information.
464 	 */
465 	current->thread.system_call =
466 		test_pt_regs_flag(regs, PIF_SYSCALL) ? regs->int_code : 0;
467 
468 	if (get_signal(&ksig)) {
469 		/* Whee!  Actually deliver the signal.  */
470 		if (current->thread.system_call) {
471 			regs->int_code = current->thread.system_call;
472 			/* Check for system call restarting. */
473 			switch (regs->gprs[2]) {
474 			case -ERESTART_RESTARTBLOCK:
475 			case -ERESTARTNOHAND:
476 				regs->gprs[2] = -EINTR;
477 				break;
478 			case -ERESTARTSYS:
479 				if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
480 					regs->gprs[2] = -EINTR;
481 					break;
482 				}
483 				fallthrough;
484 			case -ERESTARTNOINTR:
485 				regs->gprs[2] = regs->orig_gpr2;
486 				regs->psw.addr =
487 					__rewind_psw(regs->psw,
488 						     regs->int_code >> 16);
489 				break;
490 			}
491 		}
492 		/* No longer in a system call */
493 		clear_pt_regs_flag(regs, PIF_SYSCALL);
494 
495 		rseq_signal_deliver(&ksig, regs);
496 		if (is_compat_task())
497 			handle_signal32(&ksig, oldset, regs);
498 		else
499 			handle_signal(&ksig, oldset, regs);
500 		return;
501 	}
502 
503 	/* No handlers present - check for system call restart */
504 	clear_pt_regs_flag(regs, PIF_SYSCALL);
505 	if (current->thread.system_call) {
506 		regs->int_code = current->thread.system_call;
507 		switch (regs->gprs[2]) {
508 		case -ERESTART_RESTARTBLOCK:
509 			/* Restart with sys_restart_syscall */
510 			regs->gprs[2] = regs->orig_gpr2;
511 			current->restart_block.arch_data = regs->psw.addr;
512 			if (is_compat_task())
513 				regs->psw.addr = VDSO32_SYMBOL(current, restart_syscall);
514 			else
515 				regs->psw.addr = VDSO64_SYMBOL(current, restart_syscall);
516 			if (test_thread_flag(TIF_SINGLE_STEP))
517 				clear_thread_flag(TIF_PER_TRAP);
518 			break;
519 		case -ERESTARTNOHAND:
520 		case -ERESTARTSYS:
521 		case -ERESTARTNOINTR:
522 			regs->gprs[2] = regs->orig_gpr2;
523 			regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16);
524 			if (test_thread_flag(TIF_SINGLE_STEP))
525 				clear_thread_flag(TIF_PER_TRAP);
526 			break;
527 		}
528 	}
529 
530 	/*
531 	 * If there's no signal to deliver, we just put the saved sigmask back.
532 	 */
533 	restore_saved_sigmask();
534 }
535