1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/arch/alpha/kernel/signal.c
4  *
5  *  Copyright (C) 1995  Linus Torvalds
6  *
7  *  1997-11-02  Modified for POSIX.1b signals by Richard Henderson
8  */
9 
10 #include <linux/sched/signal.h>
11 #include <linux/sched/task_stack.h>
12 #include <linux/kernel.h>
13 #include <linux/signal.h>
14 #include <linux/errno.h>
15 #include <linux/wait.h>
16 #include <linux/ptrace.h>
17 #include <linux/unistd.h>
18 #include <linux/mm.h>
19 #include <linux/smp.h>
20 #include <linux/stddef.h>
21 #include <linux/tty.h>
22 #include <linux/binfmts.h>
23 #include <linux/bitops.h>
24 #include <linux/syscalls.h>
25 #include <linux/resume_user_mode.h>
26 
27 #include <linux/uaccess.h>
28 #include <asm/sigcontext.h>
29 #include <asm/ucontext.h>
30 
31 #include "proto.h"
32 
33 
34 #define DEBUG_SIG 0
35 
36 #define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))
37 
38 asmlinkage void ret_from_sys_call(void);
39 
40 /*
41  * The OSF/1 sigprocmask calling sequence is different from the
42  * C sigprocmask() sequence..
43  */
SYSCALL_DEFINE2(osf_sigprocmask,int,how,unsigned long,newmask)44 SYSCALL_DEFINE2(osf_sigprocmask, int, how, unsigned long, newmask)
45 {
46 	sigset_t oldmask;
47 	sigset_t mask;
48 	unsigned long res;
49 
50 	siginitset(&mask, newmask & _BLOCKABLE);
51 	res = sigprocmask(how, &mask, &oldmask);
52 	if (!res) {
53 		force_successful_syscall_return();
54 		res = oldmask.sig[0];
55 	}
56 	return res;
57 }
58 
SYSCALL_DEFINE3(osf_sigaction,int,sig,const struct osf_sigaction __user *,act,struct osf_sigaction __user *,oact)59 SYSCALL_DEFINE3(osf_sigaction, int, sig,
60 		const struct osf_sigaction __user *, act,
61 		struct osf_sigaction __user *, oact)
62 {
63 	struct k_sigaction new_ka, old_ka;
64 	int ret;
65 
66 	if (act) {
67 		old_sigset_t mask;
68 		if (!access_ok(act, sizeof(*act)) ||
69 		    __get_user(new_ka.sa.sa_handler, &act->sa_handler) ||
70 		    __get_user(new_ka.sa.sa_flags, &act->sa_flags) ||
71 		    __get_user(mask, &act->sa_mask))
72 			return -EFAULT;
73 		siginitset(&new_ka.sa.sa_mask, mask);
74 		new_ka.ka_restorer = NULL;
75 	}
76 
77 	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
78 
79 	if (!ret && oact) {
80 		if (!access_ok(oact, sizeof(*oact)) ||
81 		    __put_user(old_ka.sa.sa_handler, &oact->sa_handler) ||
82 		    __put_user(old_ka.sa.sa_flags, &oact->sa_flags) ||
83 		    __put_user(old_ka.sa.sa_mask.sig[0], &oact->sa_mask))
84 			return -EFAULT;
85 	}
86 
87 	return ret;
88 }
89 
SYSCALL_DEFINE5(rt_sigaction,int,sig,const struct sigaction __user *,act,struct sigaction __user *,oact,size_t,sigsetsize,void __user *,restorer)90 SYSCALL_DEFINE5(rt_sigaction, int, sig, const struct sigaction __user *, act,
91 		struct sigaction __user *, oact,
92 		size_t, sigsetsize, void __user *, restorer)
93 {
94 	struct k_sigaction new_ka, old_ka;
95 	int ret;
96 
97 	/* XXX: Don't preclude handling different sized sigset_t's.  */
98 	if (sigsetsize != sizeof(sigset_t))
99 		return -EINVAL;
100 
101 	if (act) {
102 		new_ka.ka_restorer = restorer;
103 		if (copy_from_user(&new_ka.sa, act, sizeof(*act)))
104 			return -EFAULT;
105 	}
106 
107 	ret = do_sigaction(sig, act ? &new_ka : NULL, oact ? &old_ka : NULL);
108 
109 	if (!ret && oact) {
110 		if (copy_to_user(oact, &old_ka.sa, sizeof(*oact)))
111 			return -EFAULT;
112 	}
113 
114 	return ret;
115 }
116 
117 /*
118  * Do a signal return; undo the signal stack.
119  */
120 
121 #if _NSIG_WORDS > 1
122 # error "Non SA_SIGINFO frame needs rearranging"
123 #endif
124 
125 struct sigframe
126 {
127 	struct sigcontext sc;
128 	unsigned int retcode[3];
129 };
130 
131 struct rt_sigframe
132 {
133 	struct siginfo info;
134 	struct ucontext uc;
135 	unsigned int retcode[3];
136 };
137 
138 /* If this changes, userland unwinders that Know Things about our signal
139    frame will break.  Do not undertake lightly.  It also implies an ABI
140    change wrt the size of siginfo_t, which may cause some pain.  */
141 extern char compile_time_assert
142         [offsetof(struct rt_sigframe, uc.uc_mcontext) == 176 ? 1 : -1];
143 
144 #define INSN_MOV_R30_R16	0x47fe0410
145 #define INSN_LDI_R0		0x201f0000
146 #define INSN_CALLSYS		0x00000083
147 
148 static long
restore_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs)149 restore_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs)
150 {
151 	unsigned long usp;
152 	struct switch_stack *sw = (struct switch_stack *)regs - 1;
153 	long i, err = __get_user(regs->pc, &sc->sc_pc);
154 
155 	current->restart_block.fn = do_no_restart_syscall;
156 
157 	sw->r26 = (unsigned long) ret_from_sys_call;
158 
159 	err |= __get_user(regs->r0, sc->sc_regs+0);
160 	err |= __get_user(regs->r1, sc->sc_regs+1);
161 	err |= __get_user(regs->r2, sc->sc_regs+2);
162 	err |= __get_user(regs->r3, sc->sc_regs+3);
163 	err |= __get_user(regs->r4, sc->sc_regs+4);
164 	err |= __get_user(regs->r5, sc->sc_regs+5);
165 	err |= __get_user(regs->r6, sc->sc_regs+6);
166 	err |= __get_user(regs->r7, sc->sc_regs+7);
167 	err |= __get_user(regs->r8, sc->sc_regs+8);
168 	err |= __get_user(sw->r9, sc->sc_regs+9);
169 	err |= __get_user(sw->r10, sc->sc_regs+10);
170 	err |= __get_user(sw->r11, sc->sc_regs+11);
171 	err |= __get_user(sw->r12, sc->sc_regs+12);
172 	err |= __get_user(sw->r13, sc->sc_regs+13);
173 	err |= __get_user(sw->r14, sc->sc_regs+14);
174 	err |= __get_user(sw->r15, sc->sc_regs+15);
175 	err |= __get_user(regs->r16, sc->sc_regs+16);
176 	err |= __get_user(regs->r17, sc->sc_regs+17);
177 	err |= __get_user(regs->r18, sc->sc_regs+18);
178 	err |= __get_user(regs->r19, sc->sc_regs+19);
179 	err |= __get_user(regs->r20, sc->sc_regs+20);
180 	err |= __get_user(regs->r21, sc->sc_regs+21);
181 	err |= __get_user(regs->r22, sc->sc_regs+22);
182 	err |= __get_user(regs->r23, sc->sc_regs+23);
183 	err |= __get_user(regs->r24, sc->sc_regs+24);
184 	err |= __get_user(regs->r25, sc->sc_regs+25);
185 	err |= __get_user(regs->r26, sc->sc_regs+26);
186 	err |= __get_user(regs->r27, sc->sc_regs+27);
187 	err |= __get_user(regs->r28, sc->sc_regs+28);
188 	err |= __get_user(regs->gp, sc->sc_regs+29);
189 	err |= __get_user(usp, sc->sc_regs+30);
190 	wrusp(usp);
191 
192 	for (i = 0; i < 31; i++)
193 		err |= __get_user(sw->fp[i], sc->sc_fpregs+i);
194 	err |= __get_user(sw->fp[31], &sc->sc_fpcr);
195 
196 	return err;
197 }
198 
199 /* Note that this syscall is also used by setcontext(3) to install
200    a given sigcontext.  This because it's impossible to set *all*
201    registers and transfer control from userland.  */
202 
203 asmlinkage void
do_sigreturn(struct sigcontext __user * sc)204 do_sigreturn(struct sigcontext __user *sc)
205 {
206 	struct pt_regs *regs = current_pt_regs();
207 	sigset_t set;
208 
209 	/* Verify that it's a good sigcontext before using it */
210 	if (!access_ok(sc, sizeof(*sc)))
211 		goto give_sigsegv;
212 	if (__get_user(set.sig[0], &sc->sc_mask))
213 		goto give_sigsegv;
214 
215 	set_current_blocked(&set);
216 
217 	if (restore_sigcontext(sc, regs))
218 		goto give_sigsegv;
219 
220 	/* Send SIGTRAP if we're single-stepping: */
221 	if (ptrace_cancel_bpt (current)) {
222 		send_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *) regs->pc,
223 			       current);
224 	}
225 	return;
226 
227 give_sigsegv:
228 	force_sig(SIGSEGV);
229 }
230 
231 asmlinkage void
do_rt_sigreturn(struct rt_sigframe __user * frame)232 do_rt_sigreturn(struct rt_sigframe __user *frame)
233 {
234 	struct pt_regs *regs = current_pt_regs();
235 	sigset_t set;
236 
237 	/* Verify that it's a good ucontext_t before using it */
238 	if (!access_ok(&frame->uc, sizeof(frame->uc)))
239 		goto give_sigsegv;
240 	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
241 		goto give_sigsegv;
242 
243 	set_current_blocked(&set);
244 
245 	if (restore_sigcontext(&frame->uc.uc_mcontext, regs))
246 		goto give_sigsegv;
247 
248 	/* Send SIGTRAP if we're single-stepping: */
249 	if (ptrace_cancel_bpt (current)) {
250 		send_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *) regs->pc,
251 			       current);
252 	}
253 	return;
254 
255 give_sigsegv:
256 	force_sig(SIGSEGV);
257 }
258 
259 
260 /*
261  * Set up a signal frame.
262  */
263 
264 static inline void __user *
get_sigframe(struct ksignal * ksig,unsigned long sp,size_t frame_size)265 get_sigframe(struct ksignal *ksig, unsigned long sp, size_t frame_size)
266 {
267 	return (void __user *)((sigsp(sp, ksig) - frame_size) & -32ul);
268 }
269 
270 static long
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs,unsigned long mask,unsigned long sp)271 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
272 		 unsigned long mask, unsigned long sp)
273 {
274 	struct switch_stack *sw = (struct switch_stack *)regs - 1;
275 	long i, err = 0;
276 
277 	err |= __put_user(on_sig_stack((unsigned long)sc), &sc->sc_onstack);
278 	err |= __put_user(mask, &sc->sc_mask);
279 	err |= __put_user(regs->pc, &sc->sc_pc);
280 	err |= __put_user(8, &sc->sc_ps);
281 
282 	err |= __put_user(regs->r0 , sc->sc_regs+0);
283 	err |= __put_user(regs->r1 , sc->sc_regs+1);
284 	err |= __put_user(regs->r2 , sc->sc_regs+2);
285 	err |= __put_user(regs->r3 , sc->sc_regs+3);
286 	err |= __put_user(regs->r4 , sc->sc_regs+4);
287 	err |= __put_user(regs->r5 , sc->sc_regs+5);
288 	err |= __put_user(regs->r6 , sc->sc_regs+6);
289 	err |= __put_user(regs->r7 , sc->sc_regs+7);
290 	err |= __put_user(regs->r8 , sc->sc_regs+8);
291 	err |= __put_user(sw->r9   , sc->sc_regs+9);
292 	err |= __put_user(sw->r10  , sc->sc_regs+10);
293 	err |= __put_user(sw->r11  , sc->sc_regs+11);
294 	err |= __put_user(sw->r12  , sc->sc_regs+12);
295 	err |= __put_user(sw->r13  , sc->sc_regs+13);
296 	err |= __put_user(sw->r14  , sc->sc_regs+14);
297 	err |= __put_user(sw->r15  , sc->sc_regs+15);
298 	err |= __put_user(regs->r16, sc->sc_regs+16);
299 	err |= __put_user(regs->r17, sc->sc_regs+17);
300 	err |= __put_user(regs->r18, sc->sc_regs+18);
301 	err |= __put_user(regs->r19, sc->sc_regs+19);
302 	err |= __put_user(regs->r20, sc->sc_regs+20);
303 	err |= __put_user(regs->r21, sc->sc_regs+21);
304 	err |= __put_user(regs->r22, sc->sc_regs+22);
305 	err |= __put_user(regs->r23, sc->sc_regs+23);
306 	err |= __put_user(regs->r24, sc->sc_regs+24);
307 	err |= __put_user(regs->r25, sc->sc_regs+25);
308 	err |= __put_user(regs->r26, sc->sc_regs+26);
309 	err |= __put_user(regs->r27, sc->sc_regs+27);
310 	err |= __put_user(regs->r28, sc->sc_regs+28);
311 	err |= __put_user(regs->gp , sc->sc_regs+29);
312 	err |= __put_user(sp, sc->sc_regs+30);
313 	err |= __put_user(0, sc->sc_regs+31);
314 
315 	for (i = 0; i < 31; i++)
316 		err |= __put_user(sw->fp[i], sc->sc_fpregs+i);
317 	err |= __put_user(0, sc->sc_fpregs+31);
318 	err |= __put_user(sw->fp[31], &sc->sc_fpcr);
319 
320 	err |= __put_user(regs->trap_a0, &sc->sc_traparg_a0);
321 	err |= __put_user(regs->trap_a1, &sc->sc_traparg_a1);
322 	err |= __put_user(regs->trap_a2, &sc->sc_traparg_a2);
323 
324 	return err;
325 }
326 
327 static int
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)328 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
329 {
330 	unsigned long oldsp, r26, err = 0;
331 	struct sigframe __user *frame;
332 
333 	oldsp = rdusp();
334 	frame = get_sigframe(ksig, oldsp, sizeof(*frame));
335 	if (!access_ok(frame, sizeof(*frame)))
336 		return -EFAULT;
337 
338 	err |= setup_sigcontext(&frame->sc, regs, set->sig[0], oldsp);
339 	if (err)
340 		return -EFAULT;
341 
342 	/* Set up to return from userspace.  If provided, use a stub
343 	   already in userspace.  */
344 	r26 = (unsigned long) ksig->ka.ka_restorer;
345 	if (!r26) {
346 		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
347 		err |= __put_user(INSN_LDI_R0+__NR_sigreturn, frame->retcode+1);
348 		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
349 		imb();
350 		r26 = (unsigned long) frame->retcode;
351 	}
352 
353 	/* Check that everything was written properly.  */
354 	if (err)
355 		return err;
356 
357 	/* "Return" to the handler */
358 	regs->r26 = r26;
359 	regs->r27 = regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
360 	regs->r16 = ksig->sig;			/* a0: signal number */
361 	regs->r17 = 0;				/* a1: exception code */
362 	regs->r18 = (unsigned long) &frame->sc;	/* a2: sigcontext pointer */
363 	wrusp((unsigned long) frame);
364 
365 #if DEBUG_SIG
366 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
367 		current->comm, current->pid, frame, regs->pc, regs->r26);
368 #endif
369 	return 0;
370 }
371 
372 static int
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)373 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
374 {
375 	unsigned long oldsp, r26, err = 0;
376 	struct rt_sigframe __user *frame;
377 
378 	oldsp = rdusp();
379 	frame = get_sigframe(ksig, oldsp, sizeof(*frame));
380 	if (!access_ok(frame, sizeof(*frame)))
381 		return -EFAULT;
382 
383 	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
384 
385 	/* Create the ucontext.  */
386 	err |= __put_user(0, &frame->uc.uc_flags);
387 	err |= __put_user(0, &frame->uc.uc_link);
388 	err |= __put_user(set->sig[0], &frame->uc.uc_osf_sigmask);
389 	err |= __save_altstack(&frame->uc.uc_stack, oldsp);
390 	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs,
391 				set->sig[0], oldsp);
392 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
393 	if (err)
394 		return -EFAULT;
395 
396 	/* Set up to return from userspace.  If provided, use a stub
397 	   already in userspace.  */
398 	r26 = (unsigned long) ksig->ka.ka_restorer;
399 	if (!r26) {
400 		err |= __put_user(INSN_MOV_R30_R16, frame->retcode+0);
401 		err |= __put_user(INSN_LDI_R0+__NR_rt_sigreturn,
402 				  frame->retcode+1);
403 		err |= __put_user(INSN_CALLSYS, frame->retcode+2);
404 		imb();
405 		r26 = (unsigned long) frame->retcode;
406 	}
407 
408 	if (err)
409 		return -EFAULT;
410 
411 	/* "Return" to the handler */
412 	regs->r26 = r26;
413 	regs->r27 = regs->pc = (unsigned long) ksig->ka.sa.sa_handler;
414 	regs->r16 = ksig->sig;			  /* a0: signal number */
415 	regs->r17 = (unsigned long) &frame->info; /* a1: siginfo pointer */
416 	regs->r18 = (unsigned long) &frame->uc;	  /* a2: ucontext pointer */
417 	wrusp((unsigned long) frame);
418 
419 #if DEBUG_SIG
420 	printk("SIG deliver (%s:%d): sp=%p pc=%p ra=%p\n",
421 		current->comm, current->pid, frame, regs->pc, regs->r26);
422 #endif
423 
424 	return 0;
425 }
426 
427 
428 /*
429  * OK, we're invoking a handler.
430  */
431 static inline void
handle_signal(struct ksignal * ksig,struct pt_regs * regs)432 handle_signal(struct ksignal *ksig, struct pt_regs *regs)
433 {
434 	sigset_t *oldset = sigmask_to_save();
435 	int ret;
436 
437 	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
438 		ret = setup_rt_frame(ksig, oldset, regs);
439 	else
440 		ret = setup_frame(ksig, oldset, regs);
441 
442 	signal_setup_done(ret, ksig, 0);
443 }
444 
445 static inline void
syscall_restart(unsigned long r0,unsigned long r19,struct pt_regs * regs,struct k_sigaction * ka)446 syscall_restart(unsigned long r0, unsigned long r19,
447 		struct pt_regs *regs, struct k_sigaction *ka)
448 {
449 	switch (regs->r0) {
450 	case ERESTARTSYS:
451 		if (!(ka->sa.sa_flags & SA_RESTART)) {
452 		case ERESTARTNOHAND:
453 			regs->r0 = EINTR;
454 			break;
455 		}
456 		fallthrough;
457 	case ERESTARTNOINTR:
458 		regs->r0 = r0;	/* reset v0 and a3 and replay syscall */
459 		regs->r19 = r19;
460 		regs->pc -= 4;
461 		break;
462 	case ERESTART_RESTARTBLOCK:
463 		regs->r0 = EINTR;
464 		break;
465 	}
466 }
467 
468 
469 /*
470  * Note that 'init' is a special process: it doesn't get signals it doesn't
471  * want to handle. Thus you cannot kill init even with a SIGKILL even by
472  * mistake.
473  *
474  * Note that we go through the signals twice: once to check the signals that
475  * the kernel can handle, and then we build all the user-level signal handling
476  * stack-frames in one go after that.
477  *
478  * "r0" and "r19" are the registers we need to restore for system call
479  * restart. "r0" is also used as an indicator whether we can restart at
480  * all (if we get here from anything but a syscall return, it will be 0)
481  */
482 static void
do_signal(struct pt_regs * regs,unsigned long r0,unsigned long r19)483 do_signal(struct pt_regs *regs, unsigned long r0, unsigned long r19)
484 {
485 	unsigned long single_stepping = ptrace_cancel_bpt(current);
486 	struct ksignal ksig;
487 
488 	/* This lets the debugger run, ... */
489 	if (get_signal(&ksig)) {
490 		/* ... so re-check the single stepping. */
491 		single_stepping |= ptrace_cancel_bpt(current);
492 		/* Whee!  Actually deliver the signal.  */
493 		if (r0)
494 			syscall_restart(r0, r19, regs, &ksig.ka);
495 		handle_signal(&ksig, regs);
496 	} else {
497 		single_stepping |= ptrace_cancel_bpt(current);
498 		if (r0) {
499 			switch (regs->r0) {
500 			case ERESTARTNOHAND:
501 			case ERESTARTSYS:
502 			case ERESTARTNOINTR:
503 				/* Reset v0 and a3 and replay syscall.  */
504 				regs->r0 = r0;
505 				regs->r19 = r19;
506 				regs->pc -= 4;
507 				break;
508 			case ERESTART_RESTARTBLOCK:
509 				/* Set v0 to the restart_syscall and replay */
510 				regs->r0 = __NR_restart_syscall;
511 				regs->pc -= 4;
512 				break;
513 			}
514 		}
515 		restore_saved_sigmask();
516 	}
517 	if (single_stepping)
518 		ptrace_set_bpt(current);	/* re-set breakpoint */
519 }
520 
521 void
do_work_pending(struct pt_regs * regs,unsigned long thread_flags,unsigned long r0,unsigned long r19)522 do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
523 		 unsigned long r0, unsigned long r19)
524 {
525 	do {
526 		if (thread_flags & _TIF_NEED_RESCHED) {
527 			schedule();
528 		} else {
529 			local_irq_enable();
530 			if (thread_flags & (_TIF_SIGPENDING|_TIF_NOTIFY_SIGNAL)) {
531 				do_signal(regs, r0, r19);
532 				r0 = 0;
533 			} else {
534 				resume_user_mode_work(regs);
535 			}
536 		}
537 		local_irq_disable();
538 		thread_flags = read_thread_flags();
539 	} while (thread_flags & _TIF_WORK_MASK);
540 }
541