1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/arch/sh/kernel/signal.c
4  *
5  *  Copyright (C) 1991, 1992  Linus Torvalds
6  *
7  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
8  *
9  *  SuperH version:  Copyright (C) 1999, 2000  Niibe Yutaka & Kaz Kojima
10  *
11  */
12 #include <linux/sched.h>
13 #include <linux/sched/task_stack.h>
14 #include <linux/mm.h>
15 #include <linux/smp.h>
16 #include <linux/kernel.h>
17 #include <linux/signal.h>
18 #include <linux/errno.h>
19 #include <linux/wait.h>
20 #include <linux/ptrace.h>
21 #include <linux/unistd.h>
22 #include <linux/stddef.h>
23 #include <linux/tty.h>
24 #include <linux/elf.h>
25 #include <linux/personality.h>
26 #include <linux/binfmts.h>
27 #include <linux/io.h>
28 #include <linux/resume_user_mode.h>
29 #include <asm/ucontext.h>
30 #include <linux/uaccess.h>
31 #include <asm/cacheflush.h>
32 #include <asm/syscalls.h>
33 #include <asm/fpu.h>
34 
35 struct fdpic_func_descriptor {
36 	unsigned long	text;
37 	unsigned long	GOT;
38 };
39 
40 /*
41  * The following define adds a 64 byte gap between the signal
42  * stack frame and previous contents of the stack.  This allows
43  * frame unwinding in a function epilogue but only if a frame
44  * pointer is used in the function.  This is necessary because
45  * current gcc compilers (<4.3) do not generate unwind info on
46  * SH for function epilogues.
47  */
48 #define UNWINDGUARD 64
49 
50 /*
51  * Do a signal return; undo the signal stack.
52  */
53 
54 #define MOVW(n)	 (0x9300|((n)-2))	/* Move mem word at PC+n to R3 */
55 #if defined(CONFIG_CPU_SH2)
56 #define TRAP_NOARG 0xc320		/* Syscall w/no args (NR in R3) */
57 #else
58 #define TRAP_NOARG 0xc310		/* Syscall w/no args (NR in R3) */
59 #endif
60 #define OR_R0_R0 0x200b			/* or r0,r0 (insert to avoid hardware bug) */
61 
62 struct sigframe
63 {
64 	struct sigcontext sc;
65 	unsigned long extramask[_NSIG_WORDS-1];
66 	u16 retcode[8];
67 };
68 
69 struct rt_sigframe
70 {
71 	struct siginfo info;
72 	struct ucontext uc;
73 	u16 retcode[8];
74 };
75 
76 #ifdef CONFIG_SH_FPU
restore_sigcontext_fpu(struct sigcontext __user * sc)77 static inline int restore_sigcontext_fpu(struct sigcontext __user *sc)
78 {
79 	struct task_struct *tsk = current;
80 
81 	if (!(boot_cpu_data.flags & CPU_HAS_FPU))
82 		return 0;
83 
84 	set_used_math();
85 	return __copy_from_user(&tsk->thread.xstate->hardfpu, &sc->sc_fpregs[0],
86 				sizeof(long)*(16*2+2));
87 }
88 
save_sigcontext_fpu(struct sigcontext __user * sc,struct pt_regs * regs)89 static inline int save_sigcontext_fpu(struct sigcontext __user *sc,
90 				      struct pt_regs *regs)
91 {
92 	struct task_struct *tsk = current;
93 
94 	if (!(boot_cpu_data.flags & CPU_HAS_FPU))
95 		return 0;
96 
97 	if (!used_math())
98 		return __put_user(0, &sc->sc_ownedfp);
99 
100 	if (__put_user(1, &sc->sc_ownedfp))
101 		return -EFAULT;
102 
103 	/* This will cause a "finit" to be triggered by the next
104 	   attempted FPU operation by the 'current' process.
105 	   */
106 	clear_used_math();
107 
108 	unlazy_fpu(tsk, regs);
109 	return __copy_to_user(&sc->sc_fpregs[0], &tsk->thread.xstate->hardfpu,
110 			      sizeof(long)*(16*2+2));
111 }
112 #endif /* CONFIG_SH_FPU */
113 
114 static int
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc,int * r0_p)115 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, int *r0_p)
116 {
117 	unsigned int err = 0;
118 
119 #define COPY(x)		err |= __get_user(regs->x, &sc->sc_##x)
120 			COPY(regs[1]);
121 	COPY(regs[2]);	COPY(regs[3]);
122 	COPY(regs[4]);	COPY(regs[5]);
123 	COPY(regs[6]);	COPY(regs[7]);
124 	COPY(regs[8]);	COPY(regs[9]);
125 	COPY(regs[10]);	COPY(regs[11]);
126 	COPY(regs[12]);	COPY(regs[13]);
127 	COPY(regs[14]);	COPY(regs[15]);
128 	COPY(gbr);	COPY(mach);
129 	COPY(macl);	COPY(pr);
130 	COPY(sr);	COPY(pc);
131 #undef COPY
132 
133 #ifdef CONFIG_SH_FPU
134 	if (boot_cpu_data.flags & CPU_HAS_FPU) {
135 		int owned_fp;
136 		struct task_struct *tsk = current;
137 
138 		regs->sr |= SR_FD; /* Release FPU */
139 		clear_fpu(tsk, regs);
140 		clear_used_math();
141 		err |= __get_user (owned_fp, &sc->sc_ownedfp);
142 		if (owned_fp)
143 			err |= restore_sigcontext_fpu(sc);
144 	}
145 #endif
146 
147 	regs->tra = -1;		/* disable syscall checks */
148 	err |= __get_user(*r0_p, &sc->sc_regs[0]);
149 	return err;
150 }
151 
sys_sigreturn(void)152 asmlinkage int sys_sigreturn(void)
153 {
154 	struct pt_regs *regs = current_pt_regs();
155 	struct sigframe __user *frame = (struct sigframe __user *)regs->regs[15];
156 	sigset_t set;
157 	int r0;
158 
159         /* Always make any pending restarted system calls return -EINTR */
160 	current->restart_block.fn = do_no_restart_syscall;
161 
162 	if (!access_ok(frame, sizeof(*frame)))
163 		goto badframe;
164 
165 	if (__get_user(set.sig[0], &frame->sc.oldmask)
166 	    || (_NSIG_WORDS > 1
167 		&& __copy_from_user(&set.sig[1], &frame->extramask,
168 				    sizeof(frame->extramask))))
169 		goto badframe;
170 
171 	set_current_blocked(&set);
172 
173 	if (restore_sigcontext(regs, &frame->sc, &r0))
174 		goto badframe;
175 	return r0;
176 
177 badframe:
178 	force_sig(SIGSEGV);
179 	return 0;
180 }
181 
sys_rt_sigreturn(void)182 asmlinkage int sys_rt_sigreturn(void)
183 {
184 	struct pt_regs *regs = current_pt_regs();
185 	struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->regs[15];
186 	sigset_t set;
187 	int r0;
188 
189 	/* Always make any pending restarted system calls return -EINTR */
190 	current->restart_block.fn = do_no_restart_syscall;
191 
192 	if (!access_ok(frame, sizeof(*frame)))
193 		goto badframe;
194 
195 	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
196 		goto badframe;
197 
198 	set_current_blocked(&set);
199 
200 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
201 		goto badframe;
202 
203 	if (restore_altstack(&frame->uc.uc_stack))
204 		goto badframe;
205 
206 	return r0;
207 
208 badframe:
209 	force_sig(SIGSEGV);
210 	return 0;
211 }
212 
213 /*
214  * Set up a signal frame.
215  */
216 
217 static int
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs,unsigned long mask)218 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
219 		 unsigned long mask)
220 {
221 	int err = 0;
222 
223 #define COPY(x)		err |= __put_user(regs->x, &sc->sc_##x)
224 	COPY(regs[0]);	COPY(regs[1]);
225 	COPY(regs[2]);	COPY(regs[3]);
226 	COPY(regs[4]);	COPY(regs[5]);
227 	COPY(regs[6]);	COPY(regs[7]);
228 	COPY(regs[8]);	COPY(regs[9]);
229 	COPY(regs[10]);	COPY(regs[11]);
230 	COPY(regs[12]);	COPY(regs[13]);
231 	COPY(regs[14]);	COPY(regs[15]);
232 	COPY(gbr);	COPY(mach);
233 	COPY(macl);	COPY(pr);
234 	COPY(sr);	COPY(pc);
235 #undef COPY
236 
237 #ifdef CONFIG_SH_FPU
238 	err |= save_sigcontext_fpu(sc, regs);
239 #endif
240 
241 	/* non-iBCS2 extensions.. */
242 	err |= __put_user(mask, &sc->oldmask);
243 
244 	return err;
245 }
246 
247 /*
248  * Determine which stack to use..
249  */
250 static inline void __user *
get_sigframe(struct k_sigaction * ka,unsigned long sp,size_t frame_size)251 get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
252 {
253 	if (ka->sa.sa_flags & SA_ONSTACK) {
254 		if (sas_ss_flags(sp) == 0)
255 			sp = current->sas_ss_sp + current->sas_ss_size;
256 	}
257 
258 	return (void __user *)((sp - (frame_size+UNWINDGUARD)) & -8ul);
259 }
260 
261 /* These symbols are defined with the addresses in the vsyscall page.
262    See vsyscall-trapa.S.  */
263 extern void __kernel_sigreturn(void);
264 extern void __kernel_rt_sigreturn(void);
265 
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)266 static int setup_frame(struct ksignal *ksig, sigset_t *set,
267 		       struct pt_regs *regs)
268 {
269 	struct sigframe __user *frame;
270 	int err = 0, sig = ksig->sig;
271 
272 	frame = get_sigframe(&ksig->ka, regs->regs[15], sizeof(*frame));
273 
274 	if (!access_ok(frame, sizeof(*frame)))
275 		return -EFAULT;
276 
277 	err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
278 
279 	if (_NSIG_WORDS > 1)
280 		err |= __copy_to_user(frame->extramask, &set->sig[1],
281 				      sizeof(frame->extramask));
282 
283 	/* Set up to return from userspace.  If provided, use a stub
284 	   already in userspace.  */
285 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
286 		regs->pr = (unsigned long) ksig->ka.sa.sa_restorer;
287 #ifdef CONFIG_VSYSCALL
288 	} else if (likely(current->mm->context.vdso)) {
289 		regs->pr = VDSO_SYM(&__kernel_sigreturn);
290 #endif
291 	} else {
292 		/* Generate return code (system call to sigreturn) */
293 		err |= __put_user(MOVW(7), &frame->retcode[0]);
294 		err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
295 		err |= __put_user(OR_R0_R0, &frame->retcode[2]);
296 		err |= __put_user(OR_R0_R0, &frame->retcode[3]);
297 		err |= __put_user(OR_R0_R0, &frame->retcode[4]);
298 		err |= __put_user(OR_R0_R0, &frame->retcode[5]);
299 		err |= __put_user(OR_R0_R0, &frame->retcode[6]);
300 		err |= __put_user((__NR_sigreturn), &frame->retcode[7]);
301 		regs->pr = (unsigned long) frame->retcode;
302 		flush_icache_range(regs->pr, regs->pr + sizeof(frame->retcode));
303 	}
304 
305 	if (err)
306 		return -EFAULT;
307 
308 	/* Set up registers for signal handler */
309 	regs->regs[15] = (unsigned long) frame;
310 	regs->regs[4] = sig; /* Arg for signal handler */
311 	regs->regs[5] = 0;
312 	regs->regs[6] = (unsigned long) &frame->sc;
313 
314 	if (current->personality & FDPIC_FUNCPTRS) {
315 		struct fdpic_func_descriptor __user *funcptr =
316 			(struct fdpic_func_descriptor __user *)ksig->ka.sa.sa_handler;
317 
318 		err |= __get_user(regs->pc, &funcptr->text);
319 		err |= __get_user(regs->regs[12], &funcptr->GOT);
320 	} else
321 		regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
322 
323 	if (err)
324 		return -EFAULT;
325 
326 	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
327 		 current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);
328 
329 	return 0;
330 }
331 
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)332 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
333 			  struct pt_regs *regs)
334 {
335 	struct rt_sigframe __user *frame;
336 	int err = 0, sig = ksig->sig;
337 
338 	frame = get_sigframe(&ksig->ka, regs->regs[15], sizeof(*frame));
339 
340 	if (!access_ok(frame, sizeof(*frame)))
341 		return -EFAULT;
342 
343 	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
344 
345 	/* Create the ucontext.  */
346 	err |= __put_user(0, &frame->uc.uc_flags);
347 	err |= __put_user(NULL, &frame->uc.uc_link);
348 	err |= __save_altstack(&frame->uc.uc_stack, regs->regs[15]);
349 	err |= setup_sigcontext(&frame->uc.uc_mcontext,
350 			        regs, set->sig[0]);
351 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
352 
353 	/* Set up to return from userspace.  If provided, use a stub
354 	   already in userspace.  */
355 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
356 		regs->pr = (unsigned long) ksig->ka.sa.sa_restorer;
357 #ifdef CONFIG_VSYSCALL
358 	} else if (likely(current->mm->context.vdso)) {
359 		regs->pr = VDSO_SYM(&__kernel_rt_sigreturn);
360 #endif
361 	} else {
362 		/* Generate return code (system call to rt_sigreturn) */
363 		err |= __put_user(MOVW(7), &frame->retcode[0]);
364 		err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
365 		err |= __put_user(OR_R0_R0, &frame->retcode[2]);
366 		err |= __put_user(OR_R0_R0, &frame->retcode[3]);
367 		err |= __put_user(OR_R0_R0, &frame->retcode[4]);
368 		err |= __put_user(OR_R0_R0, &frame->retcode[5]);
369 		err |= __put_user(OR_R0_R0, &frame->retcode[6]);
370 		err |= __put_user((__NR_rt_sigreturn), &frame->retcode[7]);
371 		regs->pr = (unsigned long) frame->retcode;
372 		flush_icache_range(regs->pr, regs->pr + sizeof(frame->retcode));
373 	}
374 
375 	if (err)
376 		return -EFAULT;
377 
378 	/* Set up registers for signal handler */
379 	regs->regs[15] = (unsigned long) frame;
380 	regs->regs[4] = sig; /* Arg for signal handler */
381 	regs->regs[5] = (unsigned long) &frame->info;
382 	regs->regs[6] = (unsigned long) &frame->uc;
383 
384 	if (current->personality & FDPIC_FUNCPTRS) {
385 		struct fdpic_func_descriptor __user *funcptr =
386 			(struct fdpic_func_descriptor __user *)ksig->ka.sa.sa_handler;
387 
388 		err |= __get_user(regs->pc, &funcptr->text);
389 		err |= __get_user(regs->regs[12], &funcptr->GOT);
390 	} else
391 		regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
392 
393 	if (err)
394 		return -EFAULT;
395 
396 	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
397 		 current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);
398 
399 	return 0;
400 }
401 
402 static inline void
handle_syscall_restart(unsigned long save_r0,struct pt_regs * regs,struct sigaction * sa)403 handle_syscall_restart(unsigned long save_r0, struct pt_regs *regs,
404 		       struct sigaction *sa)
405 {
406 	/* If we're not from a syscall, bail out */
407 	if (regs->tra < 0)
408 		return;
409 
410 	/* check for system call restart.. */
411 	switch (regs->regs[0]) {
412 		case -ERESTART_RESTARTBLOCK:
413 		case -ERESTARTNOHAND:
414 		no_system_call_restart:
415 			regs->regs[0] = -EINTR;
416 			break;
417 
418 		case -ERESTARTSYS:
419 			if (!(sa->sa_flags & SA_RESTART))
420 				goto no_system_call_restart;
421 			fallthrough;
422 		case -ERESTARTNOINTR:
423 			regs->regs[0] = save_r0;
424 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
425 			break;
426 	}
427 }
428 
429 /*
430  * OK, we're invoking a handler
431  */
432 static void
handle_signal(struct ksignal * ksig,struct pt_regs * regs,unsigned int save_r0)433 handle_signal(struct ksignal *ksig, struct pt_regs *regs, unsigned int save_r0)
434 {
435 	sigset_t *oldset = sigmask_to_save();
436 	int ret;
437 
438 	/* Set up the stack frame */
439 	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
440 		ret = setup_rt_frame(ksig, oldset, regs);
441 	else
442 		ret = setup_frame(ksig, oldset, regs);
443 
444 	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
445 }
446 
447 /*
448  * Note that 'init' is a special process: it doesn't get signals it doesn't
449  * want to handle. Thus you cannot kill init even with a SIGKILL even by
450  * mistake.
451  *
452  * Note that we go through the signals twice: once to check the signals that
453  * the kernel can handle, and then we build all the user-level signal handling
454  * stack-frames in one go after that.
455  */
do_signal(struct pt_regs * regs,unsigned int save_r0)456 static void do_signal(struct pt_regs *regs, unsigned int save_r0)
457 {
458 	struct ksignal ksig;
459 
460 	/*
461 	 * We want the common case to go fast, which
462 	 * is why we may in certain cases get here from
463 	 * kernel mode. Just return without doing anything
464 	 * if so.
465 	 */
466 	if (!user_mode(regs))
467 		return;
468 
469 	if (get_signal(&ksig)) {
470 		handle_syscall_restart(save_r0, regs, &ksig.ka.sa);
471 
472 		/* Whee!  Actually deliver the signal.  */
473 		handle_signal(&ksig, regs, save_r0);
474 		return;
475 	}
476 
477 	/* Did we come from a system call? */
478 	if (regs->tra >= 0) {
479 		/* Restart the system call - no handlers present */
480 		if (regs->regs[0] == -ERESTARTNOHAND ||
481 		    regs->regs[0] == -ERESTARTSYS ||
482 		    regs->regs[0] == -ERESTARTNOINTR) {
483 			regs->regs[0] = save_r0;
484 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
485 		} else if (regs->regs[0] == -ERESTART_RESTARTBLOCK) {
486 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
487 			regs->regs[3] = __NR_restart_syscall;
488 		}
489 	}
490 
491 	/*
492 	 * If there's no signal to deliver, we just put the saved sigmask
493 	 * back.
494 	 */
495 	restore_saved_sigmask();
496 }
497 
do_notify_resume(struct pt_regs * regs,unsigned int save_r0,unsigned long thread_info_flags)498 asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned int save_r0,
499 				 unsigned long thread_info_flags)
500 {
501 	/* deal with pending signal delivery */
502 	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
503 		do_signal(regs, save_r0);
504 
505 	if (thread_info_flags & _TIF_NOTIFY_RESUME)
506 		resume_user_mode_work(regs);
507 }
508