1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/cris/kernel/signal.c
4 *
5 * Based on arch/i386/kernel/signal.c by
6 * Copyright (C) 1991, 1992 Linus Torvalds
7 * 1997-11-28 Modified for POSIX.1b signals by Richard Henderson *
8 *
9 * Ideas also taken from arch/arm.
10 *
11 * Copyright (C) 2000-2007 Axis Communications AB
12 *
13 * Authors: Bjorn Wesen (bjornw@axis.com)
14 *
15 */
16
17 #include <linux/sched.h>
18 #include <linux/sched/task_stack.h>
19 #include <linux/mm.h>
20 #include <linux/smp.h>
21 #include <linux/kernel.h>
22 #include <linux/signal.h>
23 #include <linux/errno.h>
24 #include <linux/wait.h>
25 #include <linux/ptrace.h>
26 #include <linux/unistd.h>
27 #include <linux/stddef.h>
28
29 #include <asm/processor.h>
30 #include <asm/ucontext.h>
31 #include <linux/uaccess.h>
32 #include <arch/system.h>
33
34 #define DEBUG_SIG 0
35
36 /* a syscall in Linux/CRIS is a break 13 instruction which is 2 bytes */
37 /* manipulate regs so that upon return, it will be re-executed */
38
39 /* We rely on that pc points to the instruction after "break 13", so the
40 * library must never do strange things like putting it in a delay slot.
41 */
42 #define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->irp -= 2;
43
44 void do_signal(int canrestart, struct pt_regs *regs);
45
46 /*
47 * Do a signal return; undo the signal stack.
48 */
49
50 struct sigframe {
51 struct sigcontext sc;
52 unsigned long extramask[_NSIG_WORDS-1];
53 unsigned char retcode[8]; /* trampoline code */
54 };
55
56 struct rt_sigframe {
57 struct siginfo *pinfo;
58 void *puc;
59 struct siginfo info;
60 struct ucontext uc;
61 unsigned char retcode[8]; /* trampoline code */
62 };
63
64
65 static int
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)66 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
67 {
68 unsigned int err = 0;
69 unsigned long old_usp;
70
71 /* Always make any pending restarted system calls return -EINTR */
72 current->restart_block.fn = do_no_restart_syscall;
73
74 /* restore the regs from &sc->regs (same as sc, since regs is first)
75 * (sc is already checked for VERIFY_READ since the sigframe was
76 * checked in sys_sigreturn previously)
77 */
78
79 if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
80 goto badframe;
81
82 /* make sure the U-flag is set so user-mode cannot fool us */
83
84 regs->dccr |= 1 << 8;
85
86 /* restore the old USP as it was before we stacked the sc etc.
87 * (we cannot just pop the sigcontext since we aligned the sp and
88 * stuff after pushing it)
89 */
90
91 err |= __get_user(old_usp, &sc->usp);
92
93 wrusp(old_usp);
94
95 /* TODO: the other ports use regs->orig_XX to disable syscall checks
96 * after this completes, but we don't use that mechanism. maybe we can
97 * use it now ?
98 */
99
100 return err;
101
102 badframe:
103 return 1;
104 }
105
sys_sigreturn(void)106 asmlinkage int sys_sigreturn(void)
107 {
108 struct pt_regs *regs = current_pt_regs();
109 struct sigframe __user *frame = (struct sigframe *)rdusp();
110 sigset_t set;
111
112 /*
113 * Since we stacked the signal on a dword boundary,
114 * then frame should be dword aligned here. If it's
115 * not, then the user is trying to mess with us.
116 */
117 if (((long)frame) & 3)
118 goto badframe;
119
120 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
121 goto badframe;
122 if (__get_user(set.sig[0], &frame->sc.oldmask)
123 || (_NSIG_WORDS > 1
124 && __copy_from_user(&set.sig[1], frame->extramask,
125 sizeof(frame->extramask))))
126 goto badframe;
127
128 set_current_blocked(&set);
129
130 if (restore_sigcontext(regs, &frame->sc))
131 goto badframe;
132
133 /* TODO: SIGTRAP when single-stepping as in arm ? */
134
135 return regs->r10;
136
137 badframe:
138 force_sig(SIGSEGV, current);
139 return 0;
140 }
141
sys_rt_sigreturn(void)142 asmlinkage int sys_rt_sigreturn(void)
143 {
144 struct pt_regs *regs = current_pt_regs();
145 struct rt_sigframe __user *frame = (struct rt_sigframe *)rdusp();
146 sigset_t set;
147
148 /*
149 * Since we stacked the signal on a dword boundary,
150 * then frame should be dword aligned here. If it's
151 * not, then the user is trying to mess with us.
152 */
153 if (((long)frame) & 3)
154 goto badframe;
155
156 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
157 goto badframe;
158 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
159 goto badframe;
160
161 set_current_blocked(&set);
162
163 if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
164 goto badframe;
165
166 if (restore_altstack(&frame->uc.uc_stack))
167 goto badframe;
168
169 return regs->r10;
170
171 badframe:
172 force_sig(SIGSEGV, current);
173 return 0;
174 }
175
176 /*
177 * Set up a signal frame.
178 */
179
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs,unsigned long mask)180 static int setup_sigcontext(struct sigcontext __user *sc,
181 struct pt_regs *regs, unsigned long mask)
182 {
183 int err = 0;
184 unsigned long usp = rdusp();
185
186 /* copy the regs. they are first in sc so we can use sc directly */
187
188 err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
189
190 /* Set the frametype to CRIS_FRAME_NORMAL for the execution of
191 the signal handler. The frametype will be restored to its previous
192 value in restore_sigcontext. */
193 regs->frametype = CRIS_FRAME_NORMAL;
194
195 /* then some other stuff */
196
197 err |= __put_user(mask, &sc->oldmask);
198
199 err |= __put_user(usp, &sc->usp);
200
201 return err;
202 }
203
204 /* Figure out where we want to put the new signal frame
205 * - usually on the stack. */
206
207 static inline void __user *
get_sigframe(struct ksignal * ksig,size_t frame_size)208 get_sigframe(struct ksignal *ksig, size_t frame_size)
209 {
210 unsigned long sp = sigsp(rdusp(), ksig);
211
212 /* make sure the frame is dword-aligned */
213
214 sp &= ~3;
215
216 return (void __user*)(sp - frame_size);
217 }
218
219 /* grab and setup a signal frame.
220 *
221 * basically we stack a lot of state info, and arrange for the
222 * user-mode program to return to the kernel using either a
223 * trampoline which performs the syscall sigreturn, or a provided
224 * user-mode trampoline.
225 */
226
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)227 static int setup_frame(struct ksignal *ksig, sigset_t *set,
228 struct pt_regs *regs)
229 {
230 struct sigframe __user *frame;
231 unsigned long return_ip;
232 int err = 0;
233
234 frame = get_sigframe(ksig, sizeof(*frame));
235
236 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
237 return -EFAULT;
238
239 err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
240 if (err)
241 return -EFAULT;
242
243 if (_NSIG_WORDS > 1) {
244 err |= __copy_to_user(frame->extramask, &set->sig[1],
245 sizeof(frame->extramask));
246 }
247 if (err)
248 return -EFAULT;
249
250 /* Set up to return from userspace. If provided, use a stub
251 already in userspace. */
252 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
253 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
254 } else {
255 /* trampoline - the desired return ip is the retcode itself */
256 return_ip = (unsigned long)&frame->retcode;
257 /* This is movu.w __NR_sigreturn, r9; break 13; */
258 err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));
259 err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
260 err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
261 }
262
263 if (err)
264 return -EFAULT;
265
266 /* Set up registers for signal handler */
267
268 regs->irp = (unsigned long) ksig->ka.sa.sa_handler; /* what we enter NOW */
269 regs->srp = return_ip; /* what we enter LATER */
270 regs->r10 = ksig->sig; /* first argument is signo */
271
272 /* actually move the usp to reflect the stacked frame */
273
274 wrusp((unsigned long)frame);
275
276 return 0;
277 }
278
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)279 static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
280 struct pt_regs *regs)
281 {
282 struct rt_sigframe __user *frame;
283 unsigned long return_ip;
284 int err = 0;
285
286 frame = get_sigframe(ksig, sizeof(*frame));
287
288 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
289 return -EFAULT;
290
291 err |= __put_user(&frame->info, &frame->pinfo);
292 err |= __put_user(&frame->uc, &frame->puc);
293 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
294 if (err)
295 return -EFAULT;
296
297 /* Clear all the bits of the ucontext we don't use. */
298 err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
299
300 err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
301
302 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
303
304 err |= __save_altstack(&frame->uc.uc_stack, rdusp());
305
306 if (err)
307 return -EFAULT;
308
309 /* Set up to return from userspace. If provided, use a stub
310 already in userspace. */
311 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
312 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
313 } else {
314 /* trampoline - the desired return ip is the retcode itself */
315 return_ip = (unsigned long)&frame->retcode;
316 /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
317 err |= __put_user(0x9c5f, (short __user *)(frame->retcode+0));
318 err |= __put_user(__NR_rt_sigreturn,
319 (short __user *)(frame->retcode+2));
320 err |= __put_user(0xe93d, (short __user *)(frame->retcode+4));
321 }
322
323 if (err)
324 return -EFAULT;
325
326 /* Set up registers for signal handler */
327
328 /* What we enter NOW */
329 regs->irp = (unsigned long) ksig->ka.sa.sa_handler;
330 /* What we enter LATER */
331 regs->srp = return_ip;
332 /* First argument is signo */
333 regs->r10 = ksig->sig;
334 /* Second argument is (siginfo_t *) */
335 regs->r11 = (unsigned long)&frame->info;
336 /* Third argument is unused */
337 regs->r12 = 0;
338
339 /* Actually move the usp to reflect the stacked frame */
340 wrusp((unsigned long)frame);
341
342 return 0;
343 }
344
345 /*
346 * OK, we're invoking a handler
347 */
348
handle_signal(int canrestart,struct ksignal * ksig,struct pt_regs * regs)349 static inline void handle_signal(int canrestart, struct ksignal *ksig,
350 struct pt_regs *regs)
351 {
352 sigset_t *oldset = sigmask_to_save();
353 int ret;
354
355 /* Are we from a system call? */
356 if (canrestart) {
357 /* If so, check system call restarting.. */
358 switch (regs->r10) {
359 case -ERESTART_RESTARTBLOCK:
360 case -ERESTARTNOHAND:
361 /* ERESTARTNOHAND means that the syscall should
362 * only be restarted if there was no handler for
363 * the signal, and since we only get here if there
364 * is a handler, we don't restart */
365 regs->r10 = -EINTR;
366 break;
367 case -ERESTARTSYS:
368 /* ERESTARTSYS means to restart the syscall if
369 * there is no handler or the handler was
370 * registered with SA_RESTART */
371 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
372 regs->r10 = -EINTR;
373 break;
374 }
375 /* fallthrough */
376 case -ERESTARTNOINTR:
377 /* ERESTARTNOINTR means that the syscall should
378 * be called again after the signal handler returns. */
379 RESTART_CRIS_SYS(regs);
380 }
381 }
382
383 /* Set up the stack frame */
384 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
385 ret = setup_rt_frame(ksig, oldset, regs);
386 else
387 ret = setup_frame(ksig, oldset, regs);
388
389 signal_setup_done(ret, ksig, 0);
390 }
391
392 /*
393 * Note that 'init' is a special process: it doesn't get signals it doesn't
394 * want to handle. Thus you cannot kill init even with a SIGKILL even by
395 * mistake.
396 *
397 * Also note that the regs structure given here as an argument, is the latest
398 * pushed pt_regs. It may or may not be the same as the first pushed registers
399 * when the initial usermode->kernelmode transition took place. Therefore
400 * we can use user_mode(regs) to see if we came directly from kernel or user
401 * mode below.
402 */
403
do_signal(int canrestart,struct pt_regs * regs)404 void do_signal(int canrestart, struct pt_regs *regs)
405 {
406 struct ksignal ksig;
407
408 /*
409 * We want the common case to go fast, which
410 * is why we may in certain cases get here from
411 * kernel mode. Just return without doing anything
412 * if so.
413 */
414 if (!user_mode(regs))
415 return;
416
417 if (get_signal(&ksig)) {
418 /* Whee! Actually deliver the signal. */
419 handle_signal(canrestart, &ksig, regs);
420 return;
421 }
422
423 /* Did we come from a system call? */
424 if (canrestart) {
425 /* Restart the system call - no handlers present */
426 if (regs->r10 == -ERESTARTNOHAND ||
427 regs->r10 == -ERESTARTSYS ||
428 regs->r10 == -ERESTARTNOINTR) {
429 RESTART_CRIS_SYS(regs);
430 }
431 if (regs->r10 == -ERESTART_RESTARTBLOCK) {
432 regs->r9 = __NR_restart_syscall;
433 regs->irp -= 2;
434 }
435 }
436
437 /* if there's no signal to deliver, we just put the saved sigmask
438 * back */
439 restore_saved_sigmask();
440 }
441