xref: /openbmc/linux/arch/sh/kernel/signal_32.c (revision 573b22cc)
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 	unsigned int sr = regs->sr & ~SR_USER_MASK;
119 
120 #define COPY(x)		err |= __get_user(regs->x, &sc->sc_##x)
121 			COPY(regs[1]);
122 	COPY(regs[2]);	COPY(regs[3]);
123 	COPY(regs[4]);	COPY(regs[5]);
124 	COPY(regs[6]);	COPY(regs[7]);
125 	COPY(regs[8]);	COPY(regs[9]);
126 	COPY(regs[10]);	COPY(regs[11]);
127 	COPY(regs[12]);	COPY(regs[13]);
128 	COPY(regs[14]);	COPY(regs[15]);
129 	COPY(gbr);	COPY(mach);
130 	COPY(macl);	COPY(pr);
131 	COPY(sr);	COPY(pc);
132 #undef COPY
133 
134 	regs->sr = (regs->sr & SR_USER_MASK) | sr;
135 
136 #ifdef CONFIG_SH_FPU
137 	if (boot_cpu_data.flags & CPU_HAS_FPU) {
138 		int owned_fp;
139 		struct task_struct *tsk = current;
140 
141 		regs->sr |= SR_FD; /* Release FPU */
142 		clear_fpu(tsk, regs);
143 		clear_used_math();
144 		err |= __get_user (owned_fp, &sc->sc_ownedfp);
145 		if (owned_fp)
146 			err |= restore_sigcontext_fpu(sc);
147 	}
148 #endif
149 
150 	regs->tra = -1;		/* disable syscall checks */
151 	err |= __get_user(*r0_p, &sc->sc_regs[0]);
152 	return err;
153 }
154 
sys_sigreturn(void)155 asmlinkage int sys_sigreturn(void)
156 {
157 	struct pt_regs *regs = current_pt_regs();
158 	struct sigframe __user *frame = (struct sigframe __user *)regs->regs[15];
159 	sigset_t set;
160 	int r0;
161 
162         /* Always make any pending restarted system calls return -EINTR */
163 	current->restart_block.fn = do_no_restart_syscall;
164 
165 	if (!access_ok(frame, sizeof(*frame)))
166 		goto badframe;
167 
168 	if (__get_user(set.sig[0], &frame->sc.oldmask)
169 	    || (_NSIG_WORDS > 1
170 		&& __copy_from_user(&set.sig[1], &frame->extramask,
171 				    sizeof(frame->extramask))))
172 		goto badframe;
173 
174 	set_current_blocked(&set);
175 
176 	if (restore_sigcontext(regs, &frame->sc, &r0))
177 		goto badframe;
178 	return r0;
179 
180 badframe:
181 	force_sig(SIGSEGV);
182 	return 0;
183 }
184 
sys_rt_sigreturn(void)185 asmlinkage int sys_rt_sigreturn(void)
186 {
187 	struct pt_regs *regs = current_pt_regs();
188 	struct rt_sigframe __user *frame = (struct rt_sigframe __user *)regs->regs[15];
189 	sigset_t set;
190 	int r0;
191 
192 	/* Always make any pending restarted system calls return -EINTR */
193 	current->restart_block.fn = do_no_restart_syscall;
194 
195 	if (!access_ok(frame, sizeof(*frame)))
196 		goto badframe;
197 
198 	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
199 		goto badframe;
200 
201 	set_current_blocked(&set);
202 
203 	if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &r0))
204 		goto badframe;
205 
206 	if (restore_altstack(&frame->uc.uc_stack))
207 		goto badframe;
208 
209 	return r0;
210 
211 badframe:
212 	force_sig(SIGSEGV);
213 	return 0;
214 }
215 
216 /*
217  * Set up a signal frame.
218  */
219 
220 static int
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs,unsigned long mask)221 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
222 		 unsigned long mask)
223 {
224 	int err = 0;
225 
226 #define COPY(x)		err |= __put_user(regs->x, &sc->sc_##x)
227 	COPY(regs[0]);	COPY(regs[1]);
228 	COPY(regs[2]);	COPY(regs[3]);
229 	COPY(regs[4]);	COPY(regs[5]);
230 	COPY(regs[6]);	COPY(regs[7]);
231 	COPY(regs[8]);	COPY(regs[9]);
232 	COPY(regs[10]);	COPY(regs[11]);
233 	COPY(regs[12]);	COPY(regs[13]);
234 	COPY(regs[14]);	COPY(regs[15]);
235 	COPY(gbr);	COPY(mach);
236 	COPY(macl);	COPY(pr);
237 	COPY(sr);	COPY(pc);
238 #undef COPY
239 
240 #ifdef CONFIG_SH_FPU
241 	err |= save_sigcontext_fpu(sc, regs);
242 #endif
243 
244 	/* non-iBCS2 extensions.. */
245 	err |= __put_user(mask, &sc->oldmask);
246 
247 	return err;
248 }
249 
250 /*
251  * Determine which stack to use..
252  */
253 static inline void __user *
get_sigframe(struct k_sigaction * ka,unsigned long sp,size_t frame_size)254 get_sigframe(struct k_sigaction *ka, unsigned long sp, size_t frame_size)
255 {
256 	if (ka->sa.sa_flags & SA_ONSTACK) {
257 		if (sas_ss_flags(sp) == 0)
258 			sp = current->sas_ss_sp + current->sas_ss_size;
259 	}
260 
261 	return (void __user *)((sp - (frame_size+UNWINDGUARD)) & -8ul);
262 }
263 
264 /* These symbols are defined with the addresses in the vsyscall page.
265    See vsyscall-trapa.S.  */
266 extern void __kernel_sigreturn(void);
267 extern void __kernel_rt_sigreturn(void);
268 
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)269 static int setup_frame(struct ksignal *ksig, sigset_t *set,
270 		       struct pt_regs *regs)
271 {
272 	struct sigframe __user *frame;
273 	int err = 0, sig = ksig->sig;
274 
275 	frame = get_sigframe(&ksig->ka, regs->regs[15], sizeof(*frame));
276 
277 	if (!access_ok(frame, sizeof(*frame)))
278 		return -EFAULT;
279 
280 	err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
281 
282 	if (_NSIG_WORDS > 1)
283 		err |= __copy_to_user(frame->extramask, &set->sig[1],
284 				      sizeof(frame->extramask));
285 
286 	/* Set up to return from userspace.  If provided, use a stub
287 	   already in userspace.  */
288 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
289 		regs->pr = (unsigned long) ksig->ka.sa.sa_restorer;
290 #ifdef CONFIG_VSYSCALL
291 	} else if (likely(current->mm->context.vdso)) {
292 		regs->pr = VDSO_SYM(&__kernel_sigreturn);
293 #endif
294 	} else {
295 		/* Generate return code (system call to sigreturn) */
296 		err |= __put_user(MOVW(7), &frame->retcode[0]);
297 		err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
298 		err |= __put_user(OR_R0_R0, &frame->retcode[2]);
299 		err |= __put_user(OR_R0_R0, &frame->retcode[3]);
300 		err |= __put_user(OR_R0_R0, &frame->retcode[4]);
301 		err |= __put_user(OR_R0_R0, &frame->retcode[5]);
302 		err |= __put_user(OR_R0_R0, &frame->retcode[6]);
303 		err |= __put_user((__NR_sigreturn), &frame->retcode[7]);
304 		regs->pr = (unsigned long) frame->retcode;
305 		flush_icache_range(regs->pr, regs->pr + sizeof(frame->retcode));
306 	}
307 
308 	if (err)
309 		return -EFAULT;
310 
311 	/* Set up registers for signal handler */
312 	regs->regs[15] = (unsigned long) frame;
313 	regs->regs[4] = sig; /* Arg for signal handler */
314 	regs->regs[5] = 0;
315 	regs->regs[6] = (unsigned long) &frame->sc;
316 
317 	if (current->personality & FDPIC_FUNCPTRS) {
318 		struct fdpic_func_descriptor __user *funcptr =
319 			(struct fdpic_func_descriptor __user *)ksig->ka.sa.sa_handler;
320 
321 		err |= __get_user(regs->pc, &funcptr->text);
322 		err |= __get_user(regs->regs[12], &funcptr->GOT);
323 	} else
324 		regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
325 
326 	if (err)
327 		return -EFAULT;
328 
329 	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
330 		 current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);
331 
332 	return 0;
333 }
334 
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)335 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
336 			  struct pt_regs *regs)
337 {
338 	struct rt_sigframe __user *frame;
339 	int err = 0, sig = ksig->sig;
340 
341 	frame = get_sigframe(&ksig->ka, regs->regs[15], sizeof(*frame));
342 
343 	if (!access_ok(frame, sizeof(*frame)))
344 		return -EFAULT;
345 
346 	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
347 
348 	/* Create the ucontext.  */
349 	err |= __put_user(0, &frame->uc.uc_flags);
350 	err |= __put_user(NULL, &frame->uc.uc_link);
351 	err |= __save_altstack(&frame->uc.uc_stack, regs->regs[15]);
352 	err |= setup_sigcontext(&frame->uc.uc_mcontext,
353 			        regs, set->sig[0]);
354 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
355 
356 	/* Set up to return from userspace.  If provided, use a stub
357 	   already in userspace.  */
358 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
359 		regs->pr = (unsigned long) ksig->ka.sa.sa_restorer;
360 #ifdef CONFIG_VSYSCALL
361 	} else if (likely(current->mm->context.vdso)) {
362 		regs->pr = VDSO_SYM(&__kernel_rt_sigreturn);
363 #endif
364 	} else {
365 		/* Generate return code (system call to rt_sigreturn) */
366 		err |= __put_user(MOVW(7), &frame->retcode[0]);
367 		err |= __put_user(TRAP_NOARG, &frame->retcode[1]);
368 		err |= __put_user(OR_R0_R0, &frame->retcode[2]);
369 		err |= __put_user(OR_R0_R0, &frame->retcode[3]);
370 		err |= __put_user(OR_R0_R0, &frame->retcode[4]);
371 		err |= __put_user(OR_R0_R0, &frame->retcode[5]);
372 		err |= __put_user(OR_R0_R0, &frame->retcode[6]);
373 		err |= __put_user((__NR_rt_sigreturn), &frame->retcode[7]);
374 		regs->pr = (unsigned long) frame->retcode;
375 		flush_icache_range(regs->pr, regs->pr + sizeof(frame->retcode));
376 	}
377 
378 	if (err)
379 		return -EFAULT;
380 
381 	/* Set up registers for signal handler */
382 	regs->regs[15] = (unsigned long) frame;
383 	regs->regs[4] = sig; /* Arg for signal handler */
384 	regs->regs[5] = (unsigned long) &frame->info;
385 	regs->regs[6] = (unsigned long) &frame->uc;
386 
387 	if (current->personality & FDPIC_FUNCPTRS) {
388 		struct fdpic_func_descriptor __user *funcptr =
389 			(struct fdpic_func_descriptor __user *)ksig->ka.sa.sa_handler;
390 
391 		err |= __get_user(regs->pc, &funcptr->text);
392 		err |= __get_user(regs->regs[12], &funcptr->GOT);
393 	} else
394 		regs->pc = (unsigned long)ksig->ka.sa.sa_handler;
395 
396 	if (err)
397 		return -EFAULT;
398 
399 	pr_debug("SIG deliver (%s:%d): sp=%p pc=%08lx pr=%08lx\n",
400 		 current->comm, task_pid_nr(current), frame, regs->pc, regs->pr);
401 
402 	return 0;
403 }
404 
405 static inline void
handle_syscall_restart(unsigned long save_r0,struct pt_regs * regs,struct sigaction * sa)406 handle_syscall_restart(unsigned long save_r0, struct pt_regs *regs,
407 		       struct sigaction *sa)
408 {
409 	/* If we're not from a syscall, bail out */
410 	if (regs->tra < 0)
411 		return;
412 
413 	/* check for system call restart.. */
414 	switch (regs->regs[0]) {
415 		case -ERESTART_RESTARTBLOCK:
416 		case -ERESTARTNOHAND:
417 		no_system_call_restart:
418 			regs->regs[0] = -EINTR;
419 			break;
420 
421 		case -ERESTARTSYS:
422 			if (!(sa->sa_flags & SA_RESTART))
423 				goto no_system_call_restart;
424 			fallthrough;
425 		case -ERESTARTNOINTR:
426 			regs->regs[0] = save_r0;
427 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
428 			break;
429 	}
430 }
431 
432 /*
433  * OK, we're invoking a handler
434  */
435 static void
handle_signal(struct ksignal * ksig,struct pt_regs * regs,unsigned int save_r0)436 handle_signal(struct ksignal *ksig, struct pt_regs *regs, unsigned int save_r0)
437 {
438 	sigset_t *oldset = sigmask_to_save();
439 	int ret;
440 
441 	/* Set up the stack frame */
442 	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
443 		ret = setup_rt_frame(ksig, oldset, regs);
444 	else
445 		ret = setup_frame(ksig, oldset, regs);
446 
447 	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
448 }
449 
450 /*
451  * Note that 'init' is a special process: it doesn't get signals it doesn't
452  * want to handle. Thus you cannot kill init even with a SIGKILL even by
453  * mistake.
454  *
455  * Note that we go through the signals twice: once to check the signals that
456  * the kernel can handle, and then we build all the user-level signal handling
457  * stack-frames in one go after that.
458  */
do_signal(struct pt_regs * regs,unsigned int save_r0)459 static void do_signal(struct pt_regs *regs, unsigned int save_r0)
460 {
461 	struct ksignal ksig;
462 
463 	/*
464 	 * We want the common case to go fast, which
465 	 * is why we may in certain cases get here from
466 	 * kernel mode. Just return without doing anything
467 	 * if so.
468 	 */
469 	if (!user_mode(regs))
470 		return;
471 
472 	if (get_signal(&ksig)) {
473 		handle_syscall_restart(save_r0, regs, &ksig.ka.sa);
474 
475 		/* Whee!  Actually deliver the signal.  */
476 		handle_signal(&ksig, regs, save_r0);
477 		return;
478 	}
479 
480 	/* Did we come from a system call? */
481 	if (regs->tra >= 0) {
482 		/* Restart the system call - no handlers present */
483 		if (regs->regs[0] == -ERESTARTNOHAND ||
484 		    regs->regs[0] == -ERESTARTSYS ||
485 		    regs->regs[0] == -ERESTARTNOINTR) {
486 			regs->regs[0] = save_r0;
487 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
488 		} else if (regs->regs[0] == -ERESTART_RESTARTBLOCK) {
489 			regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
490 			regs->regs[3] = __NR_restart_syscall;
491 		}
492 	}
493 
494 	/*
495 	 * If there's no signal to deliver, we just put the saved sigmask
496 	 * back.
497 	 */
498 	restore_saved_sigmask();
499 }
500 
do_notify_resume(struct pt_regs * regs,unsigned int save_r0,unsigned long thread_info_flags)501 asmlinkage void do_notify_resume(struct pt_regs *regs, unsigned int save_r0,
502 				 unsigned long thread_info_flags)
503 {
504 	/* deal with pending signal delivery */
505 	if (thread_info_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
506 		do_signal(regs, save_r0);
507 
508 	if (thread_info_flags & _TIF_NOTIFY_RESUME)
509 		resume_user_mode_work(regs);
510 }
511