xref: /openbmc/linux/arch/s390/kernel/signal.c (revision 4725c86055f5bbdcdfe47199c0715881893a2c79)
1 /*
2  *    Copyright IBM Corp. 1999, 2006
3  *    Author(s): Denis Joseph Barrow (djbarrow@de.ibm.com,barrow_dj@yahoo.com)
4  *
5  *    Based on Intel version
6  *
7  *  Copyright (C) 1991, 1992  Linus Torvalds
8  *
9  *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
10  */
11 
12 #include <linux/sched.h>
13 #include <linux/mm.h>
14 #include <linux/smp.h>
15 #include <linux/kernel.h>
16 #include <linux/signal.h>
17 #include <linux/errno.h>
18 #include <linux/wait.h>
19 #include <linux/ptrace.h>
20 #include <linux/unistd.h>
21 #include <linux/stddef.h>
22 #include <linux/tty.h>
23 #include <linux/personality.h>
24 #include <linux/binfmts.h>
25 #include <linux/tracehook.h>
26 #include <linux/syscalls.h>
27 #include <linux/compat.h>
28 #include <asm/ucontext.h>
29 #include <asm/uaccess.h>
30 #include <asm/lowcore.h>
31 #include <asm/switch_to.h>
32 #include "entry.h"
33 
34 typedef struct
35 {
36 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
37 	struct sigcontext sc;
38 	_sigregs sregs;
39 	int signo;
40 	__u8 retcode[S390_SYSCALL_SIZE];
41 } sigframe;
42 
43 typedef struct
44 {
45 	__u8 callee_used_stack[__SIGNAL_FRAMESIZE];
46 	__u8 retcode[S390_SYSCALL_SIZE];
47 	struct siginfo info;
48 	struct ucontext uc;
49 } rt_sigframe;
50 
51 /* Returns non-zero on fault. */
52 static int save_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
53 {
54 	_sigregs user_sregs;
55 
56 	save_access_regs(current->thread.acrs);
57 
58 	/* Copy a 'clean' PSW mask to the user to avoid leaking
59 	   information about whether PER is currently on.  */
60 	user_sregs.regs.psw.mask = PSW_USER_BITS |
61 		(regs->psw.mask & PSW_MASK_USER);
62 	user_sregs.regs.psw.addr = regs->psw.addr;
63 	memcpy(&user_sregs.regs.gprs, &regs->gprs, sizeof(sregs->regs.gprs));
64 	memcpy(&user_sregs.regs.acrs, current->thread.acrs,
65 	       sizeof(user_sregs.regs.acrs));
66 	/*
67 	 * We have to store the fp registers to current->thread.fp_regs
68 	 * to merge them with the emulated registers.
69 	 */
70 	save_fp_ctl(&current->thread.fp_regs.fpc);
71 	save_fp_regs(current->thread.fp_regs.fprs);
72 	memcpy(&user_sregs.fpregs, &current->thread.fp_regs,
73 	       sizeof(user_sregs.fpregs));
74 	if (__copy_to_user(sregs, &user_sregs, sizeof(_sigregs)))
75 		return -EFAULT;
76 	return 0;
77 }
78 
79 static int restore_sigregs(struct pt_regs *regs, _sigregs __user *sregs)
80 {
81 	_sigregs user_sregs;
82 
83 	/* Alwys make any pending restarted system call return -EINTR */
84 	current_thread_info()->restart_block.fn = do_no_restart_syscall;
85 
86 	if (__copy_from_user(&user_sregs, sregs, sizeof(user_sregs)))
87 		return -EFAULT;
88 
89 	/* Loading the floating-point-control word can fail. Do that first. */
90 	if (restore_fp_ctl(&user_sregs.fpregs.fpc))
91 		return -EINVAL;
92 
93 	/* Use regs->psw.mask instead of PSW_USER_BITS to preserve PER bit. */
94 	regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
95 		(user_sregs.regs.psw.mask & PSW_MASK_USER);
96 	/* Check for invalid user address space control. */
97 	if ((regs->psw.mask & PSW_MASK_ASC) == PSW_ASC_HOME)
98 		regs->psw.mask = PSW_ASC_PRIMARY |
99 			(regs->psw.mask & ~PSW_MASK_ASC);
100 	/* Check for invalid amode */
101 	if (regs->psw.mask & PSW_MASK_EA)
102 		regs->psw.mask |= PSW_MASK_BA;
103 	regs->psw.addr = user_sregs.regs.psw.addr;
104 	memcpy(&regs->gprs, &user_sregs.regs.gprs, sizeof(sregs->regs.gprs));
105 	memcpy(&current->thread.acrs, &user_sregs.regs.acrs,
106 	       sizeof(current->thread.acrs));
107 	restore_access_regs(current->thread.acrs);
108 
109 	memcpy(&current->thread.fp_regs, &user_sregs.fpregs,
110 	       sizeof(current->thread.fp_regs));
111 
112 	restore_fp_regs(current->thread.fp_regs.fprs);
113 	clear_thread_flag(TIF_SYSCALL);	/* No longer in a system call */
114 	return 0;
115 }
116 
117 SYSCALL_DEFINE0(sigreturn)
118 {
119 	struct pt_regs *regs = task_pt_regs(current);
120 	sigframe __user *frame = (sigframe __user *)regs->gprs[15];
121 	sigset_t set;
122 
123 	if (__copy_from_user(&set.sig, &frame->sc.oldmask, _SIGMASK_COPY_SIZE))
124 		goto badframe;
125 	set_current_blocked(&set);
126 	if (restore_sigregs(regs, &frame->sregs))
127 		goto badframe;
128 	return regs->gprs[2];
129 badframe:
130 	force_sig(SIGSEGV, current);
131 	return 0;
132 }
133 
134 SYSCALL_DEFINE0(rt_sigreturn)
135 {
136 	struct pt_regs *regs = task_pt_regs(current);
137 	rt_sigframe __user *frame = (rt_sigframe __user *)regs->gprs[15];
138 	sigset_t set;
139 
140 	if (__copy_from_user(&set.sig, &frame->uc.uc_sigmask, sizeof(set)))
141 		goto badframe;
142 	set_current_blocked(&set);
143 	if (restore_sigregs(regs, &frame->uc.uc_mcontext))
144 		goto badframe;
145 	if (restore_altstack(&frame->uc.uc_stack))
146 		goto badframe;
147 	return regs->gprs[2];
148 badframe:
149 	force_sig(SIGSEGV, current);
150 	return 0;
151 }
152 
153 /*
154  * Set up a signal frame.
155  */
156 
157 
158 /*
159  * Determine which stack to use..
160  */
161 static inline void __user *
162 get_sigframe(struct k_sigaction *ka, struct pt_regs * regs, size_t frame_size)
163 {
164 	unsigned long sp;
165 
166 	/* Default to using normal stack */
167 	sp = regs->gprs[15];
168 
169 	/* Overflow on alternate signal stack gives SIGSEGV. */
170 	if (on_sig_stack(sp) && !on_sig_stack((sp - frame_size) & -8UL))
171 		return (void __user *) -1UL;
172 
173 	/* This is the X/Open sanctioned signal stack switching.  */
174 	if (ka->sa.sa_flags & SA_ONSTACK) {
175 		if (! sas_ss_flags(sp))
176 			sp = current->sas_ss_sp + current->sas_ss_size;
177 	}
178 
179 	return (void __user *)((sp - frame_size) & -8ul);
180 }
181 
182 static inline int map_signal(int sig)
183 {
184 	if (current_thread_info()->exec_domain
185 	    && current_thread_info()->exec_domain->signal_invmap
186 	    && sig < 32)
187 		return current_thread_info()->exec_domain->signal_invmap[sig];
188 	else
189 		return sig;
190 }
191 
192 static int setup_frame(int sig, struct k_sigaction *ka,
193 		       sigset_t *set, struct pt_regs * regs)
194 {
195 	sigframe __user *frame;
196 
197 	frame = get_sigframe(ka, regs, sizeof(sigframe));
198 
199 	if (frame == (void __user *) -1UL)
200 		goto give_sigsegv;
201 
202 	if (__copy_to_user(&frame->sc.oldmask, &set->sig, _SIGMASK_COPY_SIZE))
203 		goto give_sigsegv;
204 
205 	if (save_sigregs(regs, &frame->sregs))
206 		goto give_sigsegv;
207 	if (__put_user(&frame->sregs, &frame->sc.sregs))
208 		goto give_sigsegv;
209 
210 	/* Set up to return from userspace.  If provided, use a stub
211 	   already in userspace.  */
212 	if (ka->sa.sa_flags & SA_RESTORER) {
213                 regs->gprs[14] = (unsigned long)
214 			ka->sa.sa_restorer | PSW_ADDR_AMODE;
215 	} else {
216                 regs->gprs[14] = (unsigned long)
217 			frame->retcode | PSW_ADDR_AMODE;
218 		if (__put_user(S390_SYSCALL_OPCODE | __NR_sigreturn,
219 	                       (u16 __user *)(frame->retcode)))
220 			goto give_sigsegv;
221 	}
222 
223 	/* Set up backchain. */
224 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
225 		goto give_sigsegv;
226 
227 	/* Set up registers for signal handler */
228 	regs->gprs[15] = (unsigned long) frame;
229 	/* Force default amode and default user address space control. */
230 	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
231 		(PSW_USER_BITS & PSW_MASK_ASC) |
232 		(regs->psw.mask & ~PSW_MASK_ASC);
233 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
234 
235 	regs->gprs[2] = map_signal(sig);
236 	regs->gprs[3] = (unsigned long) &frame->sc;
237 
238 	/* We forgot to include these in the sigcontext.
239 	   To avoid breaking binary compatibility, they are passed as args. */
240 	if (sig == SIGSEGV || sig == SIGBUS || sig == SIGILL ||
241 	    sig == SIGTRAP || sig == SIGFPE) {
242 		/* set extra registers only for synchronous signals */
243 		regs->gprs[4] = regs->int_code & 127;
244 		regs->gprs[5] = regs->int_parm_long;
245 		regs->gprs[6] = task_thread_info(current)->last_break;
246 	}
247 
248 	/* Place signal number on stack to allow backtrace from handler.  */
249 	if (__put_user(regs->gprs[2], (int __user *) &frame->signo))
250 		goto give_sigsegv;
251 	return 0;
252 
253 give_sigsegv:
254 	force_sigsegv(sig, current);
255 	return -EFAULT;
256 }
257 
258 static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
259 			   sigset_t *set, struct pt_regs * regs)
260 {
261 	int err = 0;
262 	rt_sigframe __user *frame;
263 
264 	frame = get_sigframe(ka, regs, sizeof(rt_sigframe));
265 
266 	if (frame == (void __user *) -1UL)
267 		goto give_sigsegv;
268 
269 	if (copy_siginfo_to_user(&frame->info, info))
270 		goto give_sigsegv;
271 
272 	/* Create the ucontext.  */
273 	err |= __put_user(0, &frame->uc.uc_flags);
274 	err |= __put_user(NULL, &frame->uc.uc_link);
275 	err |= __save_altstack(&frame->uc.uc_stack, regs->gprs[15]);
276 	err |= save_sigregs(regs, &frame->uc.uc_mcontext);
277 	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
278 	if (err)
279 		goto give_sigsegv;
280 
281 	/* Set up to return from userspace.  If provided, use a stub
282 	   already in userspace.  */
283 	if (ka->sa.sa_flags & SA_RESTORER) {
284                 regs->gprs[14] = (unsigned long)
285 			ka->sa.sa_restorer | PSW_ADDR_AMODE;
286 	} else {
287                 regs->gprs[14] = (unsigned long)
288 			frame->retcode | PSW_ADDR_AMODE;
289 		if (__put_user(S390_SYSCALL_OPCODE | __NR_rt_sigreturn,
290 			       (u16 __user *)(frame->retcode)))
291 			goto give_sigsegv;
292 	}
293 
294 	/* Set up backchain. */
295 	if (__put_user(regs->gprs[15], (addr_t __user *) frame))
296 		goto give_sigsegv;
297 
298 	/* Set up registers for signal handler */
299 	regs->gprs[15] = (unsigned long) frame;
300 	/* Force default amode and default user address space control. */
301 	regs->psw.mask = PSW_MASK_EA | PSW_MASK_BA |
302 		(PSW_USER_BITS & PSW_MASK_ASC) |
303 		(regs->psw.mask & ~PSW_MASK_ASC);
304 	regs->psw.addr = (unsigned long) ka->sa.sa_handler | PSW_ADDR_AMODE;
305 
306 	regs->gprs[2] = map_signal(sig);
307 	regs->gprs[3] = (unsigned long) &frame->info;
308 	regs->gprs[4] = (unsigned long) &frame->uc;
309 	regs->gprs[5] = task_thread_info(current)->last_break;
310 	return 0;
311 
312 give_sigsegv:
313 	force_sigsegv(sig, current);
314 	return -EFAULT;
315 }
316 
317 static void handle_signal(unsigned long sig, struct k_sigaction *ka,
318 			 siginfo_t *info, sigset_t *oldset,
319 			 struct pt_regs *regs)
320 {
321 	int ret;
322 
323 	/* Set up the stack frame */
324 	if (ka->sa.sa_flags & SA_SIGINFO)
325 		ret = setup_rt_frame(sig, ka, info, oldset, regs);
326 	else
327 		ret = setup_frame(sig, ka, oldset, regs);
328 	if (ret)
329 		return;
330 	signal_delivered(sig, info, ka, regs,
331 				 test_thread_flag(TIF_SINGLE_STEP));
332 }
333 
334 /*
335  * Note that 'init' is a special process: it doesn't get signals it doesn't
336  * want to handle. Thus you cannot kill init even with a SIGKILL even by
337  * mistake.
338  *
339  * Note that we go through the signals twice: once to check the signals that
340  * the kernel can handle, and then we build all the user-level signal handling
341  * stack-frames in one go after that.
342  */
343 void do_signal(struct pt_regs *regs)
344 {
345 	siginfo_t info;
346 	int signr;
347 	struct k_sigaction ka;
348 	sigset_t *oldset = sigmask_to_save();
349 
350 	/*
351 	 * Get signal to deliver. When running under ptrace, at this point
352 	 * the debugger may change all our registers, including the system
353 	 * call information.
354 	 */
355 	current_thread_info()->system_call =
356 		test_thread_flag(TIF_SYSCALL) ? regs->int_code : 0;
357 	signr = get_signal_to_deliver(&info, &ka, regs, NULL);
358 
359 	if (signr > 0) {
360 		/* Whee!  Actually deliver the signal.  */
361 		if (current_thread_info()->system_call) {
362 			regs->int_code = current_thread_info()->system_call;
363 			/* Check for system call restarting. */
364 			switch (regs->gprs[2]) {
365 			case -ERESTART_RESTARTBLOCK:
366 			case -ERESTARTNOHAND:
367 				regs->gprs[2] = -EINTR;
368 				break;
369 			case -ERESTARTSYS:
370 				if (!(ka.sa.sa_flags & SA_RESTART)) {
371 					regs->gprs[2] = -EINTR;
372 					break;
373 				}
374 			/* fallthrough */
375 			case -ERESTARTNOINTR:
376 				regs->gprs[2] = regs->orig_gpr2;
377 				regs->psw.addr =
378 					__rewind_psw(regs->psw,
379 						     regs->int_code >> 16);
380 				break;
381 			}
382 		}
383 		/* No longer in a system call */
384 		clear_thread_flag(TIF_SYSCALL);
385 
386 		if (is_compat_task())
387 			handle_signal32(signr, &ka, &info, oldset, regs);
388 		else
389 			handle_signal(signr, &ka, &info, oldset, regs);
390 		return;
391 	}
392 
393 	/* No handlers present - check for system call restart */
394 	clear_thread_flag(TIF_SYSCALL);
395 	if (current_thread_info()->system_call) {
396 		regs->int_code = current_thread_info()->system_call;
397 		switch (regs->gprs[2]) {
398 		case -ERESTART_RESTARTBLOCK:
399 			/* Restart with sys_restart_syscall */
400 			regs->int_code = __NR_restart_syscall;
401 		/* fallthrough */
402 		case -ERESTARTNOHAND:
403 		case -ERESTARTSYS:
404 		case -ERESTARTNOINTR:
405 			/* Restart system call with magic TIF bit. */
406 			regs->gprs[2] = regs->orig_gpr2;
407 			set_thread_flag(TIF_SYSCALL);
408 			if (test_thread_flag(TIF_SINGLE_STEP))
409 				set_thread_flag(TIF_PER_TRAP);
410 			break;
411 		}
412 	}
413 
414 	/*
415 	 * If there's no signal to deliver, we just put the saved sigmask back.
416 	 */
417 	restore_saved_sigmask();
418 }
419 
420 void do_notify_resume(struct pt_regs *regs)
421 {
422 	clear_thread_flag(TIF_NOTIFY_RESUME);
423 	tracehook_notify_resume(regs);
424 }
425