1 /*
2 * Copyright (C) 2003, Axis Communications AB.
3 */
4
5 #include <linux/sched.h>
6 #include <linux/mm.h>
7 #include <linux/slab.h>
8 #include <linux/kernel.h>
9 #include <linux/signal.h>
10 #include <linux/errno.h>
11 #include <linux/wait.h>
12 #include <linux/ptrace.h>
13 #include <linux/unistd.h>
14 #include <linux/stddef.h>
15 #include <linux/syscalls.h>
16 #include <linux/vmalloc.h>
17
18 #include <asm/io.h>
19 #include <asm/processor.h>
20 #include <asm/ucontext.h>
21 #include <asm/uaccess.h>
22 #include <arch/hwregs/cpu_vect.h>
23
24 extern unsigned long cris_signal_return_page;
25
26 /*
27 * A syscall in CRIS is really a "break 13" instruction, which is 2
28 * bytes. The registers is manipulated so upon return the instruction
29 * will be executed again.
30 *
31 * This relies on that PC points to the instruction after the break call.
32 */
33 #define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->erp -= 2;
34
35 /* Signal frames. */
36 struct signal_frame {
37 struct sigcontext sc;
38 unsigned long extramask[_NSIG_WORDS - 1];
39 unsigned char retcode[8]; /* Trampoline code. */
40 };
41
42 struct rt_signal_frame {
43 struct siginfo *pinfo;
44 void *puc;
45 struct siginfo info;
46 struct ucontext uc;
47 unsigned char retcode[8]; /* Trampoline code. */
48 };
49
50 void do_signal(int restart, struct pt_regs *regs);
51 void keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
52 struct pt_regs *regs);
53
54 static int
55 restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
56 {
57 unsigned int err = 0;
58 unsigned long old_usp;
59
60 /* Always make any pending restarted system calls return -EINTR */
61 current->restart_block.fn = do_no_restart_syscall;
62
63 /*
64 * Restore the registers from &sc->regs. sc is already checked
65 * for VERIFY_READ since the signal_frame was previously
66 * checked in sys_sigreturn().
67 */
68 if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
69 goto badframe;
70
71 /* Make that the user-mode flag is set. */
72 regs->ccs |= (1 << (U_CCS_BITNR + CCS_SHIFT));
73
74 /* Don't perform syscall restarting */
75 regs->exs = -1;
76
77 /* Restore the old USP. */
78 err |= __get_user(old_usp, &sc->usp);
79 wrusp(old_usp);
80
81 return err;
82
83 badframe:
84 return 1;
85 }
86
87 asmlinkage int sys_sigreturn(void)
88 {
89 struct pt_regs *regs = current_pt_regs();
90 sigset_t set;
91 struct signal_frame __user *frame;
92 unsigned long oldspc = regs->spc;
93 unsigned long oldccs = regs->ccs;
94
95 frame = (struct signal_frame *) rdusp();
96
97 /*
98 * Since the signal is stacked on a dword boundary, the frame
99 * should be dword aligned here as well. It it's not, then the
100 * user is trying some funny business.
101 */
102 if (((long)frame) & 3)
103 goto badframe;
104
105 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
106 goto badframe;
107
108 if (__get_user(set.sig[0], &frame->sc.oldmask) ||
109 (_NSIG_WORDS > 1 && __copy_from_user(&set.sig[1],
110 frame->extramask,
111 sizeof(frame->extramask))))
112 goto badframe;
113
114 set_current_blocked(&set);
115
116 if (restore_sigcontext(regs, &frame->sc))
117 goto badframe;
118
119 keep_debug_flags(oldccs, oldspc, regs);
120
121 return regs->r10;
122
123 badframe:
124 force_sig(SIGSEGV, current);
125 return 0;
126 }
127
128 asmlinkage int sys_rt_sigreturn(void)
129 {
130 struct pt_regs *regs = current_pt_regs();
131 sigset_t set;
132 struct rt_signal_frame __user *frame;
133 unsigned long oldspc = regs->spc;
134 unsigned long oldccs = regs->ccs;
135
136 frame = (struct rt_signal_frame *) rdusp();
137
138 /*
139 * Since the signal is stacked on a dword boundary, the frame
140 * should be dword aligned here as well. It it's not, then the
141 * user is trying some funny business.
142 */
143 if (((long)frame) & 3)
144 goto badframe;
145
146 if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
147 goto badframe;
148
149 if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
150 goto badframe;
151
152 set_current_blocked(&set);
153
154 if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
155 goto badframe;
156
157 if (restore_altstack(&frame->uc.uc_stack))
158 goto badframe;
159
160 keep_debug_flags(oldccs, oldspc, regs);
161
162 return regs->r10;
163
164 badframe:
165 force_sig(SIGSEGV, current);
166 return 0;
167 }
168
169 /* Setup a signal frame. */
170 static int
171 setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
172 unsigned long mask)
173 {
174 int err;
175 unsigned long usp;
176
177 err = 0;
178 usp = rdusp();
179
180 /*
181 * Copy the registers. They are located first in sc, so it's
182 * possible to use sc directly.
183 */
184 err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
185
186 err |= __put_user(mask, &sc->oldmask);
187 err |= __put_user(usp, &sc->usp);
188
189 return err;
190 }
191
192 /* Figure out where to put the new signal frame - usually on the stack. */
193 static inline void __user *
194 get_sigframe(struct ksignal *ksig, size_t frame_size)
195 {
196 unsigned long sp = sigsp(rdusp(), ksig);
197
198 /* Make sure the frame is dword-aligned. */
199 sp &= ~3;
200
201 return (void __user *)(sp - frame_size);
202 }
203
204 /* Grab and setup a signal frame.
205 *
206 * Basically a lot of state-info is stacked, and arranged for the
207 * user-mode program to return to the kernel using either a trampiline
208 * which performs the syscall sigreturn(), or a provided user-mode
209 * trampoline.
210 */
211 static int
212 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
213 {
214 int err;
215 unsigned long return_ip;
216 struct signal_frame __user *frame;
217
218 err = 0;
219 frame = get_sigframe(ksig, sizeof(*frame));
220
221 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
222 return -EFAULT;
223
224 err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
225
226 if (err)
227 return -EFAULT;
228
229 if (_NSIG_WORDS > 1) {
230 err |= __copy_to_user(frame->extramask, &set->sig[1],
231 sizeof(frame->extramask));
232 }
233
234 if (err)
235 return -EFAULT;
236
237 /*
238 * Set up to return from user-space. If provided, use a stub
239 * already located in user-space.
240 */
241 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
242 return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
243 } else {
244 /* Trampoline - the desired return ip is in the signal return page. */
245 return_ip = cris_signal_return_page;
246
247 /*
248 * This is movu.w __NR_sigreturn, r9; break 13;
249 *
250 * WE DO NOT USE IT ANY MORE! It's only left here for historical
251 * reasons and because gdb uses it as a signature to notice
252 * signal handler stack frames.
253 */
254 err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));
255 err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
256 err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
257 }
258
259 if (err)
260 return -EFAULT;
261
262 /*
263 * Set up registers for signal handler.
264 *
265 * Where the code enters now.
266 * Where the code enter later.
267 * First argument, signo.
268 */
269 regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
270 regs->srp = return_ip;
271 regs->r10 = ksig->sig;
272
273 /* Actually move the USP to reflect the stacked frame. */
274 wrusp((unsigned long)frame);
275
276 return 0;
277 }
278
279 static int
280 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
281 {
282 int err;
283 unsigned long return_ip;
284 struct rt_signal_frame __user *frame;
285
286 err = 0;
287 frame = get_sigframe(ksig, sizeof(*frame));
288
289 if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
290 return -EFAULT;
291
292 err |= __put_user(&frame->info, &frame->pinfo);
293 err |= __put_user(&frame->uc, &frame->puc);
294 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
295
296 if (err)
297 return -EFAULT;
298
299 /* Clear all the bits of the ucontext we don't use. */
300 err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
301 err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
302 err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
303 err |= __save_altstack(&frame->uc.uc_stack, rdusp());
304
305 if (err)
306 return -EFAULT;
307
308 /*
309 * Set up to return from user-space. If provided, use a stub
310 * already located in user-space.
311 */
312 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
313 return_ip = (unsigned long) ksig->ka.sa.sa_restorer;
314 } else {
315 /* Trampoline - the desired return ip is in the signal return page. */
316 return_ip = cris_signal_return_page + 6;
317
318 /*
319 * This is movu.w __NR_rt_sigreturn, r9; break 13;
320 *
321 * WE DO NOT USE IT ANY MORE! It's only left here for historical
322 * reasons and because gdb uses it as a signature to notice
323 * signal handler stack frames.
324 */
325 err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));
326
327 err |= __put_user(__NR_rt_sigreturn,
328 (short __user*)(frame->retcode+2));
329
330 err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
331 }
332
333 if (err)
334 return -EFAULT;
335
336 /*
337 * Set up registers for signal handler.
338 *
339 * Where the code enters now.
340 * Where the code enters later.
341 * First argument is signo.
342 * Second argument is (siginfo_t *).
343 * Third argument is unused.
344 */
345 regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
346 regs->srp = return_ip;
347 regs->r10 = ksig->sig;
348 regs->r11 = (unsigned long) &frame->info;
349 regs->r12 = 0;
350
351 /* Actually move the usp to reflect the stacked frame. */
352 wrusp((unsigned long)frame);
353
354 return 0;
355 }
356
357 /* Invoke a signal handler to, well, handle the signal. */
358 static inline void
359 handle_signal(int canrestart, struct ksignal *ksig, struct pt_regs *regs)
360 {
361 sigset_t *oldset = sigmask_to_save();
362 int ret;
363
364 /* Check if this got called from a system call. */
365 if (canrestart) {
366 /* If so, check system call restarting. */
367 switch (regs->r10) {
368 case -ERESTART_RESTARTBLOCK:
369 case -ERESTARTNOHAND:
370 /*
371 * This means that the syscall should
372 * only be restarted if there was no
373 * handler for the signal, and since
374 * this point isn't reached unless
375 * there is a handler, there's no need
376 * to restart.
377 */
378 regs->r10 = -EINTR;
379 break;
380
381 case -ERESTARTSYS:
382 /*
383 * This means restart the syscall if
384 * there is no handler, or the handler
385 * was registered with SA_RESTART.
386 */
387 if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
388 regs->r10 = -EINTR;
389 break;
390 }
391
392 /* Fall through. */
393
394 case -ERESTARTNOINTR:
395 /*
396 * This means that the syscall should
397 * be called again after the signal
398 * handler returns.
399 */
400 RESTART_CRIS_SYS(regs);
401 break;
402 }
403 }
404
405 /* Set up the stack frame. */
406 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
407 ret = setup_rt_frame(ksig, oldset, regs);
408 else
409 ret = setup_frame(ksig, oldset, regs);
410
411 signal_setup_done(ret, ksig, 0);
412 }
413
414 /*
415 * Note that 'init' is a special process: it doesn't get signals it doesn't
416 * want to handle. Thus you cannot kill init even with a SIGKILL even by
417 * mistake.
418 *
419 * Also note that the regs structure given here as an argument, is the latest
420 * pushed pt_regs. It may or may not be the same as the first pushed registers
421 * when the initial usermode->kernelmode transition took place. Therefore
422 * we can use user_mode(regs) to see if we came directly from kernel or user
423 * mode below.
424 */
425 void
426 do_signal(int canrestart, struct pt_regs *regs)
427 {
428 struct ksignal ksig;
429
430 canrestart = canrestart && ((int)regs->exs >= 0);
431
432 /*
433 * The common case should go fast, which is why this point is
434 * reached from kernel-mode. If that's the case, just return
435 * without doing anything.
436 */
437 if (!user_mode(regs))
438 return;
439
440 if (get_signal(&ksig)) {
441 /* Whee! Actually deliver the signal. */
442 handle_signal(canrestart, &ksig, regs);
443 return;
444 }
445
446 /* Got here from a system call? */
447 if (canrestart) {
448 /* Restart the system call - no handlers present. */
449 if (regs->r10 == -ERESTARTNOHAND ||
450 regs->r10 == -ERESTARTSYS ||
451 regs->r10 == -ERESTARTNOINTR) {
452 RESTART_CRIS_SYS(regs);
453 }
454
455 if (regs->r10 == -ERESTART_RESTARTBLOCK){
456 regs->r9 = __NR_restart_syscall;
457 regs->erp -= 2;
458 }
459 }
460
461 /* if there's no signal to deliver, we just put the saved sigmask
462 * back */
463 restore_saved_sigmask();
464 }
465
466 asmlinkage void
467 ugdb_trap_user(struct thread_info *ti, int sig)
468 {
469 if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
470 /* Zero single-step PC if the reason we stopped wasn't a single
471 step exception. This is to avoid relying on it when it isn't
472 reliable. */
473 user_regs(ti)->spc = 0;
474 }
475 /* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
476 not within any configured h/w breakpoint range). Synchronize with
477 what already exists for kernel debugging. */
478 if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
479 /* Break 8: subtract 2 from ERP unless in a delay slot. */
480 if (!(user_regs(ti)->erp & 0x1))
481 user_regs(ti)->erp -= 2;
482 }
483 sys_kill(ti->task->pid, sig);
484 }
485
486 void
487 keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
488 struct pt_regs *regs)
489 {
490 if (oldccs & (1 << Q_CCS_BITNR)) {
491 /* Pending single step due to single-stepping the break 13
492 in the signal trampoline: keep the Q flag. */
493 regs->ccs |= (1 << Q_CCS_BITNR);
494 /* S flag should be set - complain if it's not. */
495 if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
496 printk("Q flag but no S flag?");
497 }
498 regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
499 /* Assume the SPC is valid and interesting. */
500 regs->spc = oldspc;
501
502 } else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
503 /* If a h/w bp was set in the signal handler we need
504 to keep the S flag. */
505 regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
506 /* Don't keep the old SPC though; if we got here due to
507 a single-step, the Q flag should have been set. */
508 } else if (regs->spc) {
509 /* If we were single-stepping *before* the signal was taken,
510 we don't want to restore that state now, because GDB will
511 have forgotten all about it. */
512 regs->spc = 0;
513 regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
514 }
515 }
516
517 /* Set up the trampolines on the signal return page. */
518 int __init
519 cris_init_signal(void)
520 {
521 u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);
522
523 /* This is movu.w __NR_sigreturn, r9; break 13; */
524 data[0] = 0x9c5f;
525 data[1] = __NR_sigreturn;
526 data[2] = 0xe93d;
527 /* This is movu.w __NR_rt_sigreturn, r9; break 13; */
528 data[3] = 0x9c5f;
529 data[4] = __NR_rt_sigreturn;
530 data[5] = 0xe93d;
531
532 /* Map to userspace with appropriate permissions (no write access...) */
533 cris_signal_return_page = (unsigned long)
534 __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);
535
536 return 0;
537 }
538
539 __initcall(cris_init_signal);
540
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