xref: /openbmc/linux/arch/s390/kernel/signal.c (revision 171f1bc7) 
1 /*
2  *  arch/s390/kernel/signal.c
3  *
4  *    Copyright (C) IBM Corp. 1999,2006
5  *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
6  *
7  *    Based on Intel version
8  *
9  *  Copyright (C) 1991, 1992  Linus Torvalds
10  *
11  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
12  */
13 
14 #include <linux/sched.h>
15 #include <linux/mm.h>
16 #include <linux/smp.h>
17 #include <linux/kernel.h>
18 #include <linux/signal.h>
19 #include <linux/errno.h>
20 #include <linux/wait.h>
21 #include <linux/ptrace.h>
22 #include <linux/unistd.h>
23 #include <linux/stddef.h>
24 #include <linux/tty.h>
25 #include <linux/personality.h>
26 #include <linux/binfmts.h>
27 #include <linux/tracehook.h>
28 #include <linux/syscalls.h>
29 #include <linux/compat.h>
30 #include <asm/ucontext.h>
31 #include <asm/uaccess.h>
32 #include <asm/lowcore.h>
33 #include <asm/compat.h>
34 #include "entry.h"
35 
36 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
37 
38 
39 typedef struct
40 {
41 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
42 	struct sigcontext sc;
43 	_sigregs sregs;
44 	int signo;
45 	__u8 retcode[S390_SYSCALL_SIZE];
46 } sigframe;
47 
48 typedef struct
49 {
50 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
51 	__u8 retcode[S390_SYSCALL_SIZE];
52 	struct siginfo info;
53 	struct ucontext uc;
54 } rt_sigframe;
55 
56 /*
57  * Atomically swap in the new signal mask, and wait for a signal.
58  */
59 SYSCALL_DEFINE3(sigsuspend, int, history0, int, history1, old_sigset_t, mask)
60 {
61 	sigset_t blocked;
62 
63 	current->saved_sigmask = current->blocked;
64 	mask &= _BLOCKABLE;
65 	siginitset(&blocked, mask);
66 	set_current_blocked(&blocked);
67 	set_current_state(TASK_INTERRUPTIBLE);
68 	schedule();
69 	set_restore_sigmask();
70 	return -ERESTARTNOHAND;
71 }
72 
73 SYSCALL_DEFINE3(sigaction, int, sig, const struct old_sigaction __user *, act,
74 		struct old_sigaction __user *, oact)
75 {
76 	struct k_sigaction new_ka, old_ka;
77 	int ret;
78 
79 	if (act) {
80 		old_sigset_t mask;
81 		if (!access_ok(VERIFY_READ, act, sizeof(*act)) ||
82 		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
83 		    __get_user(new_ka.sa.sa_restorer, &act->sa_restorer) ||
84 		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
85 		    __get_user(mask, &act->sa_mask))
86 			return -EFAULT;
87 		siginitset(&new_ka.sa.sa_mask, mask);
88 	}
89 
90 	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
91 
92 	if (!ret && oact) {
93 		if (!access_ok(VERIFY_WRITE, oact, sizeof(*oact)) ||
94 		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
95 		    __put_user(old_ka.sa.sa_restorer, &oact->sa_restorer) ||
96 		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
97 		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
98 			return -EFAULT;
99 	}
100 
101 	return ret;
102 }
103 
104 SYSCALL_DEFINE2(sigaltstack, const stack_t __user *, uss,
105 		stack_t __user *, uoss)
106 {
107 	struct pt_regs *regs = task_pt_regs(current);
108 	return do_sigaltstack(uss, uoss, regs->gprs[15]);
109 }
110 
111 /* Returns non-zero on fault. */
112 static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
113 {
114 	_sigregs user_sregs;
115 
116 	save_access_regs(current->thread.acrs);
117 
118 	/* Copy a 'clean' PSW mask to the user to avoid leaking
119 	   information about whether PER is currently on.  */
120 	user_sregs.regs.psw.mask = psw_user_bits |
121 		(regs->psw.mask & PSW_MASK_USER);
122 	user_sregs.regs.psw.addr = regs->psw.addr;
123 	memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
124 	memcpy(&user_sregs.regs.acrs, current->thread.acrs,
125 	       sizeof(sregs->regs.acrs));
126 	/*
127 	 * We have to store the fp registers to current->thread.fp_regs
128 	 * to merge them with the emulated registers.
129 	 */
130 	save_fp_regs(&current->thread.fp_regs);
131 	memcpy(&user_sregs.fpregs, &current->thread.fp_regs,
132 	       sizeof(s390_fp_regs));
133 	return __copy_to_user(sregs, &user_sregs, sizeof(_sigregs));
134 }
135 
136 /* Returns positive number on error */
137 static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
138 {
139 	int err;
140 	_sigregs user_sregs;
141 
142 	/* Alwys make any pending restarted system call return -EINTR */
143 	current_thread_info()->restart_block.fn = do_no_restart_syscall;
144 
145 	err = __copy_from_user(&user_sregs, sregs, sizeof(_sigregs));
146 	if (err)
147 		return err;
148 	/* Use regs->psw.mask instead of psw_user_bits to preserve PER bit. */
149 	regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
150 		(user_sregs.regs.psw.mask & PSW_MASK_USER);
151 	/* Check for invalid amode */
152 	if (regs->psw.mask & PSW_MASK_EA)
153 		regs->psw.mask |= PSW_MASK_BA;
154 	regs->psw.addr = user_sregs.regs.psw.addr;
155 	memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
156 	memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
157 	       sizeof(sregs->regs.acrs));
158 	restore_access_regs(current->thread.acrs);
159 
160 	memcpy(&current->thread.fp_regs, &user_sregs.fpregs,
161 	       sizeof(s390_fp_regs));
162 	current->thread.fp_regs.fpc &= FPC_VALID_MASK;
163 
164 	restore_fp_regs(&current->thread.fp_regs);
165 	clear_thread_flag(TIF_SYSCALL);	/* No longer in a system call */
166 	return 0;
167 }
168 
169 SYSCALL_DEFINE0(sigreturn)
170 {
171 	struct pt_regs *regs = task_pt_regs(current);
172 	sigframe __user *frame = (sigframe __user *)regs->gprs[15];
173 	sigset_t set;
174 
175 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
176 		goto badframe;
177 	if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
178 		goto badframe;
179 	sigdelsetmask(&set, ~_BLOCKABLE);
180 	set_current_blocked(&set);
181 	if (restore_sigregs(regs, &frame->sregs))
182 		goto badframe;
183 	return regs->gprs[2];
184 badframe:
185 	force_sig(SIGSEGV, current);
186 	return 0;
187 }
188 
189 SYSCALL_DEFINE0(rt_sigreturn)
190 {
191 	struct pt_regs *regs = task_pt_regs(current);
192 	rt_sigframe __user *frame = (rt_sigframe __user *)regs->gprs[15];
193 	sigset_t set;
194 
195 	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
196 		goto badframe;
197 	if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
198 		goto badframe;
199 	sigdelsetmask(&set, ~_BLOCKABLE);
200 	set_current_blocked(&set);
201 	if (restore_sigregs(regs, &frame->uc.uc_mcontext))
202 		goto badframe;
203 	if (do_sigaltstack(&frame->uc.uc_stack, NULL,
204 			   regs->gprs[15]) == -EFAULT)
205 		goto badframe;
206 	return regs->gprs[2];
207 badframe:
208 	force_sig(SIGSEGV, current);
209 	return 0;
210 }
211 
212 /*
213  * Set up a signal frame.
214  */
215 
216 
217 /*
218  * Determine which stack to use..
219  */
220 static inline void __user *
221 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
222 {
223 	unsigned long sp;
224 
225 	/* Default to using normal stack */
226 	sp = regs->gprs[15];
227 
228 	/* Overflow on alternate signal stack gives SIGSEGV. */
229 	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
230 		return (void __user *) -1UL;
231 
232 	/* This is the X/Open sanctioned signal stack switching.  */
233 	if (ka->sa.sa_flags & SA_ONSTACK) {
234 		if (! sas_ss_flags(sp))
235 			sp = current->sas_ss_sp + current->sas_ss_size;
236 	}
237 
238 	/* This is the legacy signal stack switching. */
239 	else if (!user_mode(regs) &&
240 		 !(ka->sa.sa_flags & SA_RESTORER) &&
241 		 ka->sa.sa_restorer) {
242 		sp = (unsigned long) ka->sa.sa_restorer;
243 	}
244 
245 	return (void __user *)((sp - frame_size) & -8ul);
246 }
247 
248 static inline int map_signal(int sig)
249 {
250 	if (current_thread_info()->exec_domain
251 	    && current_thread_info()->exec_domain->signal_invmap
252 	    && sig < 32)
253 		return current_thread_info()->exec_domain->signal_invmap[sig];
254 	else
255 		return sig;
256 }
257 
258 static int setup_frame(int sig, struct k_sigaction *ka,
259 		       sigset_t *set, struct pt_regs * regs)
260 {
261 	sigframe __user *frame;
262 
263 	frame = get_sigframe(ka, regs, sizeof(sigframe));
264 	if (!access_ok(VERIFY_WRITE, frame, sizeof(sigframe)))
265 		goto give_sigsegv;
266 
267 	if (frame == (void __user *) -1UL)
268 		goto give_sigsegv;
269 
270 	if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE))
271 		goto give_sigsegv;
272 
273 	if (save_sigregs(regs, &frame->sregs))
274 		goto give_sigsegv;
275 	if (__put_user(&frame->sregs, &frame->sc.sregs))
276 		goto give_sigsegv;
277 
278 	/* Set up to return from userspace.  If provided, use a stub
279 	   already in userspace.  */
280 	if (ka->sa.sa_flags & SA_RESTORER) {
281                 regs->gprs[14] = (unsigned long)
282 			ka->sa.sa_restorer | PSW_ADDR_AMODE;
283 	} else {
284                 regs->gprs[14] = (unsigned long)
285 			frame->retcode | PSW_ADDR_AMODE;
286 		if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn,
287 	                       (u16 __user *)(frame->retcode)))
288 			goto give_sigsegv;
289 	}
290 
291 	/* Set up backchain. */
292 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
293 		goto give_sigsegv;
294 
295 	/* Set up registers for signal handler */
296 	regs->gprs[15] = (unsigned long) frame;
297 	regs->psw.mask |= PSW_MASK_EA | PSW_MASK_BA;	/* 64 bit amode */
298 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
299 
300 	regs->gprs[2] = map_signal(sig);
301 	regs->gprs[3] = (unsigned long) &frame->sc;
302 
303 	/* We forgot to include these in the sigcontext.
304 	   To avoid breaking binary compatibility, they are passed as args. */
305 	regs->gprs[4] = current->thread.trap_no;
306 	regs->gprs[5] = current->thread.prot_addr;
307 	regs->gprs[6] = task_thread_info(current)->last_break;
308 
309 	/* Place signal number on stack to allow backtrace from handler.  */
310 	if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
311 		goto give_sigsegv;
312 	return 0;
313 
314 give_sigsegv:
315 	force_sigsegv(sig, current);
316 	return -EFAULT;
317 }
318 
319 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
320 			   sigset_t *set, struct pt_regs * regs)
321 {
322 	int err = 0;
323 	rt_sigframe __user *frame;
324 
325 	frame = get_sigframe(ka, regs, sizeof(rt_sigframe));
326 	if (!access_ok(VERIFY_WRITE, frame, sizeof(rt_sigframe)))
327 		goto give_sigsegv;
328 
329 	if (frame == (void __user *) -1UL)
330 		goto give_sigsegv;
331 
332 	if (copy_siginfo_to_user(&frame->info, info))
333 		goto give_sigsegv;
334 
335 	/* Create the ucontext.  */
336 	err |= __put_user(0, &frame->uc.uc_flags);
337 	err |= __put_user(NULL, &frame->uc.uc_link);
338 	err |= __put_user((void __user *)current->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
339 	err |= __put_user(sas_ss_flags(regs->gprs[15]),
340 			  &frame->uc.uc_stack.ss_flags);
341 	err |= __put_user(current->sas_ss_size, &frame->uc.uc_stack.ss_size);
342 	err |= save_sigregs(regs, &frame->uc.uc_mcontext);
343 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
344 	if (err)
345 		goto give_sigsegv;
346 
347 	/* Set up to return from userspace.  If provided, use a stub
348 	   already in userspace.  */
349 	if (ka->sa.sa_flags & SA_RESTORER) {
350                 regs->gprs[14] = (unsigned long)
351 			ka->sa.sa_restorer | PSW_ADDR_AMODE;
352 	} else {
353                 regs->gprs[14] = (unsigned long)
354 			frame->retcode | PSW_ADDR_AMODE;
355 		if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn,
356 			       (u16 __user *)(frame->retcode)))
357 			goto give_sigsegv;
358 	}
359 
360 	/* Set up backchain. */
361 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
362 		goto give_sigsegv;
363 
364 	/* Set up registers for signal handler */
365 	regs->gprs[15] = (unsigned long) frame;
366 	regs->psw.mask |= PSW_MASK_EA | PSW_MASK_BA;	/* 64 bit amode */
367 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
368 
369 	regs->gprs[2] = map_signal(sig);
370 	regs->gprs[3] = (unsigned long) &frame->info;
371 	regs->gprs[4] = (unsigned long) &frame->uc;
372 	regs->gprs[5] = task_thread_info(current)->last_break;
373 	return 0;
374 
375 give_sigsegv:
376 	force_sigsegv(sig, current);
377 	return -EFAULT;
378 }
379 
380 static int handle_signal(unsigned long sig, struct k_sigaction *ka,
381 			 siginfo_t *info, sigset_t *oldset,
382 			 struct pt_regs *regs)
383 {
384 	sigset_t blocked;
385 	int ret;
386 
387 	/* Set up the stack frame */
388 	if (ka->sa.sa_flags & SA_SIGINFO)
389 		ret = setup_rt_frame(sig, ka, info, oldset, regs);
390 	else
391 		ret = setup_frame(sig, ka, oldset, regs);
392 	if (ret)
393 		return ret;
394 	sigorsets(&blocked, &current->blocked, &ka->sa.sa_mask);
395 	if (!(ka->sa.sa_flags & SA_NODEFER))
396 		sigaddset(&blocked, sig);
397 	set_current_blocked(&blocked);
398 	return 0;
399 }
400 
401 /*
402  * Note that 'init' is a special process: it doesn't get signals it doesn't
403  * want to handle. Thus you cannot kill init even with a SIGKILL even by
404  * mistake.
405  *
406  * Note that we go through the signals twice: once to check the signals that
407  * the kernel can handle, and then we build all the user-level signal handling
408  * stack-frames in one go after that.
409  */
410 void do_signal(struct pt_regs *regs)
411 {
412 	siginfo_t info;
413 	int signr;
414 	struct k_sigaction ka;
415 	sigset_t *oldset;
416 
417 	/*
418 	 * We want the common case to go fast, which
419 	 * is why we may in certain cases get here from
420 	 * kernel mode. Just return without doing anything
421 	 * if so.
422 	 */
423 	if (!user_mode(regs))
424 		return;
425 
426 	if (test_thread_flag(TIF_RESTORE_SIGMASK))
427 		oldset = &current->saved_sigmask;
428 	else
429 		oldset = &current->blocked;
430 
431 	/*
432 	 * Get signal to deliver. When running under ptrace, at this point
433 	 * the debugger may change all our registers, including the system
434 	 * call information.
435 	 */
436 	current_thread_info()->system_call =
437 		test_thread_flag(TIF_SYSCALL) ? regs->svc_code : 0;
438 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
439 
440 	if (signr > 0) {
441 		/* Whee!  Actually deliver the signal.  */
442 		if (current_thread_info()->system_call) {
443 			regs->svc_code = current_thread_info()->system_call;
444 			/* Check for system call restarting. */
445 			switch (regs->gprs[2]) {
446 			case -ERESTART_RESTARTBLOCK:
447 			case -ERESTARTNOHAND:
448 				regs->gprs[2] = -EINTR;
449 				break;
450 			case -ERESTARTSYS:
451 				if (!(ka.sa.sa_flags & SA_RESTART)) {
452 					regs->gprs[2] = -EINTR;
453 					break;
454 				}
455 			/* fallthrough */
456 			case -ERESTARTNOINTR:
457 				regs->gprs[2] = regs->orig_gpr2;
458 				regs->psw.addr =
459 					__rewind_psw(regs->psw,
460 						     regs->svc_code >> 16);
461 				break;
462 			}
463 			/* No longer in a system call */
464 			clear_thread_flag(TIF_SYSCALL);
465 		}
466 
467 		if ((is_compat_task() ?
468 		     handle_signal32(signr, &ka, &info, oldset, regs) :
469 		     handle_signal(signr, &ka, &info, oldset, regs)) == 0) {
470 			/*
471 			 * A signal was successfully delivered; the saved
472 			 * sigmask will have been stored in the signal frame,
473 			 * and will be restored by sigreturn, so we can simply
474 			 * clear the TIF_RESTORE_SIGMASK flag.
475 			 */
476 			if (test_thread_flag(TIF_RESTORE_SIGMASK))
477 				clear_thread_flag(TIF_RESTORE_SIGMASK);
478 
479 			/*
480 			 * Let tracing know that we've done the handler setup.
481 			 */
482 			tracehook_signal_handler(signr, &info, &ka, regs,
483 					 test_thread_flag(TIF_SINGLE_STEP));
484 		}
485 		return;
486 	}
487 
488 	/* No handlers present - check for system call restart */
489 	if (current_thread_info()->system_call) {
490 		regs->svc_code = current_thread_info()->system_call;
491 		switch (regs->gprs[2]) {
492 		case -ERESTART_RESTARTBLOCK:
493 			/* Restart with sys_restart_syscall */
494 			regs->svc_code = __NR_restart_syscall;
495 		/* fallthrough */
496 		case -ERESTARTNOHAND:
497 		case -ERESTARTSYS:
498 		case -ERESTARTNOINTR:
499 			/* Restart system call with magic TIF bit. */
500 			regs->gprs[2] = regs->orig_gpr2;
501 			set_thread_flag(TIF_SYSCALL);
502 			break;
503 		default:
504 			clear_thread_flag(TIF_SYSCALL);
505 			break;
506 		}
507 	}
508 
509 	/*
510 	 * If there's no signal to deliver, we just put the saved sigmask back.
511 	 */
512 	if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
513 		clear_thread_flag(TIF_RESTORE_SIGMASK);
514 		sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
515 	}
516 }
517 
518 void do_notify_resume(struct pt_regs *regs)
519 {
520 	clear_thread_flag(TIF_NOTIFY_RESUME);
521 	tracehook_notify_resume(regs);
522 	if (current->replacement_session_keyring)
523 		key_replace_session_keyring();
524 }
525