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/ptrace.h>
23#include <arch/hwregs/cpu_vect.h>
24
25extern unsigned long cris_signal_return_page;
26
27/*
28 * A syscall in CRIS is really a "break 13" instruction, which is 2
29 * bytes. The registers is manipulated so upon return the instruction
30 * will be executed again.
31 *
32 * This relies on that PC points to the instruction after the break call.
33 */
34#define RESTART_CRIS_SYS(regs) regs->r10 = regs->orig_r10; regs->erp -= 2;
35
36/* Signal frames. */
37struct signal_frame {
38	struct sigcontext sc;
39	unsigned long extramask[_NSIG_WORDS - 1];
40	unsigned char retcode[8];	/* Trampoline code. */
41};
42
43struct rt_signal_frame {
44	struct siginfo *pinfo;
45	void *puc;
46	struct siginfo info;
47	struct ucontext uc;
48	unsigned char retcode[8];	/* Trampoline code. */
49};
50
51void do_signal(int restart, struct pt_regs *regs);
52void keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
53		      struct pt_regs *regs);
54
55static int
56restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
57{
58	unsigned int err = 0;
59	unsigned long old_usp;
60
61        /* Always make any pending restarted system calls return -EINTR */
62	current->restart_block.fn = do_no_restart_syscall;
63
64	/*
65	 * Restore the registers from &sc->regs. sc is already checked
66	 * for VERIFY_READ since the signal_frame was previously
67	 * checked in sys_sigreturn().
68	 */
69	if (__copy_from_user(regs, sc, sizeof(struct pt_regs)))
70		goto badframe;
71
72	/* Make that the user-mode flag is set. */
73	regs->ccs |= (1 << (U_CCS_BITNR + CCS_SHIFT));
74
75	/* Don't perform syscall restarting */
76	regs->exs = -1;
77
78	/* Restore the old USP. */
79	err |= __get_user(old_usp, &sc->usp);
80	wrusp(old_usp);
81
82	return err;
83
84badframe:
85	return 1;
86}
87
88asmlinkage int sys_sigreturn(void)
89{
90	struct pt_regs *regs = current_pt_regs();
91	sigset_t set;
92	struct signal_frame __user *frame;
93	unsigned long oldspc = regs->spc;
94	unsigned long oldccs = regs->ccs;
95
96	frame = (struct signal_frame *) rdusp();
97
98	/*
99	 * Since the signal is stacked on a dword boundary, the frame
100	 * should be dword aligned here as well. It it's not, then the
101	 * user is trying some funny business.
102	 */
103	if (((long)frame) & 3)
104		goto badframe;
105
106	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
107		goto badframe;
108
109	if (__get_user(set.sig[0], &frame->sc.oldmask) ||
110	    (_NSIG_WORDS > 1 && __copy_from_user(&set.sig[1],
111						 frame->extramask,
112						 sizeof(frame->extramask))))
113		goto badframe;
114
115	set_current_blocked(&set);
116
117	if (restore_sigcontext(regs, &frame->sc))
118		goto badframe;
119
120	keep_debug_flags(oldccs, oldspc, regs);
121
122	return regs->r10;
123
124badframe:
125	force_sig(SIGSEGV, current);
126	return 0;
127}
128
129asmlinkage int sys_rt_sigreturn(void)
130{
131	struct pt_regs *regs = current_pt_regs();
132	sigset_t set;
133	struct rt_signal_frame __user *frame;
134	unsigned long oldspc = regs->spc;
135	unsigned long oldccs = regs->ccs;
136
137	frame = (struct rt_signal_frame *) rdusp();
138
139	/*
140	 * Since the signal is stacked on a dword boundary, the frame
141	 * should be dword aligned here as well. It it's not, then the
142	 * user is trying some funny business.
143	 */
144	if (((long)frame) & 3)
145		goto badframe;
146
147	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
148		goto badframe;
149
150	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
151		goto badframe;
152
153	set_current_blocked(&set);
154
155	if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
156		goto badframe;
157
158	if (restore_altstack(&frame->uc.uc_stack))
159		goto badframe;
160
161	keep_debug_flags(oldccs, oldspc, regs);
162
163	return regs->r10;
164
165badframe:
166	force_sig(SIGSEGV, current);
167	return 0;
168}
169
170/* Setup a signal frame. */
171static int
172setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs,
173		 unsigned long mask)
174{
175	int err;
176	unsigned long usp;
177
178	err = 0;
179	usp = rdusp();
180
181	/*
182	 * Copy the registers. They are located first in sc, so it's
183	 * possible to use sc directly.
184	 */
185	err |= __copy_to_user(sc, regs, sizeof(struct pt_regs));
186
187	err |= __put_user(mask, &sc->oldmask);
188	err |= __put_user(usp, &sc->usp);
189
190	return err;
191}
192
193/* Figure out where to put the new signal frame - usually on the stack. */
194static inline void __user *
195get_sigframe(struct ksignal *ksig, size_t frame_size)
196{
197	unsigned long sp = sigsp(rdusp(), ksig);
198
199	/* Make sure the frame is dword-aligned. */
200	sp &= ~3;
201
202	return (void __user *)(sp - frame_size);
203}
204
205/* Grab and setup a signal frame.
206 *
207 * Basically a lot of state-info is stacked, and arranged for the
208 * user-mode program to return to the kernel using either a trampiline
209 * which performs the syscall sigreturn(), or a provided user-mode
210 * trampoline.
211  */
212static int
213setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
214{
215	int err;
216	unsigned long return_ip;
217	struct signal_frame __user *frame;
218
219	err = 0;
220	frame = get_sigframe(ksig, sizeof(*frame));
221
222	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
223		return -EFAULT;
224
225	err |= setup_sigcontext(&frame->sc, regs, set->sig[0]);
226
227	if (err)
228		return -EFAULT;
229
230	if (_NSIG_WORDS > 1) {
231		err |= __copy_to_user(frame->extramask, &set->sig[1],
232				      sizeof(frame->extramask));
233	}
234
235	if (err)
236		return -EFAULT;
237
238	/*
239	 * Set up to return from user-space. If provided, use a stub
240	 * already located in user-space.
241	 */
242	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
243		return_ip = (unsigned long)ksig->ka.sa.sa_restorer;
244	} else {
245		/* Trampoline - the desired return ip is in the signal return page. */
246		return_ip = cris_signal_return_page;
247
248		/*
249		 * This is movu.w __NR_sigreturn, r9; break 13;
250		 *
251		 * WE DO NOT USE IT ANY MORE! It's only left here for historical
252		 * reasons and because gdb uses it as a signature to notice
253		 * signal handler stack frames.
254		 */
255		err |= __put_user(0x9c5f,         (short __user*)(frame->retcode+0));
256		err |= __put_user(__NR_sigreturn, (short __user*)(frame->retcode+2));
257		err |= __put_user(0xe93d,         (short __user*)(frame->retcode+4));
258	}
259
260	if (err)
261		return -EFAULT;
262
263	/*
264	 * Set up registers for signal handler.
265	 *
266	 * Where the code enters now.
267	 * Where the code enter later.
268	 * First argument, signo.
269	 */
270	regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
271	regs->srp = return_ip;
272	regs->r10 = ksig->sig;
273
274	/* Actually move the USP to reflect the stacked frame. */
275	wrusp((unsigned long)frame);
276
277	return 0;
278}
279
280static int
281setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
282{
283	int err;
284	unsigned long return_ip;
285	struct rt_signal_frame __user *frame;
286
287	err = 0;
288	frame = get_sigframe(ksig, sizeof(*frame));
289
290	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
291		return -EFAULT;
292
293	err |= __put_user(&frame->info, &frame->pinfo);
294	err |= __put_user(&frame->uc, &frame->puc);
295	err |= copy_siginfo_to_user(&frame->info, &ksig->info);
296
297	if (err)
298		return -EFAULT;
299
300	/* Clear all the bits of the ucontext we don't use.  */
301	err |= __clear_user(&frame->uc, offsetof(struct ucontext, uc_mcontext));
302	err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0]);
303	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
304	err |= __save_altstack(&frame->uc.uc_stack, rdusp());
305
306	if (err)
307		return -EFAULT;
308
309	/*
310	 * Set up to return from user-space. If provided, use a stub
311	 * already located in user-space.
312	 */
313	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
314		return_ip = (unsigned long) ksig->ka.sa.sa_restorer;
315	} else {
316		/* Trampoline - the desired return ip is in the signal return page. */
317		return_ip = cris_signal_return_page + 6;
318
319		/*
320		 * This is movu.w __NR_rt_sigreturn, r9; break 13;
321		 *
322		 * WE DO NOT USE IT ANY MORE! It's only left here for historical
323		 * reasons and because gdb uses it as a signature to notice
324		 * signal handler stack frames.
325		 */
326		err |= __put_user(0x9c5f, (short __user*)(frame->retcode+0));
327
328		err |= __put_user(__NR_rt_sigreturn,
329				  (short __user*)(frame->retcode+2));
330
331		err |= __put_user(0xe93d, (short __user*)(frame->retcode+4));
332	}
333
334	if (err)
335		return -EFAULT;
336
337	/*
338	 * Set up registers for signal handler.
339	 *
340	 * Where the code enters now.
341	 * Where the code enters later.
342	 * First argument is signo.
343	 * Second argument is (siginfo_t *).
344	 * Third argument is unused.
345	 */
346	regs->erp = (unsigned long) ksig->ka.sa.sa_handler;
347	regs->srp = return_ip;
348	regs->r10 = ksig->sig;
349	regs->r11 = (unsigned long) &frame->info;
350	regs->r12 = 0;
351
352	/* Actually move the usp to reflect the stacked frame. */
353	wrusp((unsigned long)frame);
354
355	return 0;
356}
357
358/* Invoke a signal handler to, well, handle the signal. */
359static inline void
360handle_signal(int canrestart, struct ksignal *ksig, struct pt_regs *regs)
361{
362	sigset_t *oldset = sigmask_to_save();
363	int ret;
364
365	/* Check if this got called from a system call. */
366	if (canrestart) {
367		/* If so, check system call restarting. */
368		switch (regs->r10) {
369			case -ERESTART_RESTARTBLOCK:
370			case -ERESTARTNOHAND:
371				/*
372				 * This means that the syscall should
373				 * only be restarted if there was no
374				 * handler for the signal, and since
375				 * this point isn't reached unless
376				 * there is a handler, there's no need
377				 * to restart.
378				 */
379				regs->r10 = -EINTR;
380				break;
381
382                        case -ERESTARTSYS:
383				/*
384				 * This means restart the syscall if
385                                 * there is no handler, or the handler
386                                 * was registered with SA_RESTART.
387				 */
388				if (!(ksig->ka.sa.sa_flags & SA_RESTART)) {
389					regs->r10 = -EINTR;
390					break;
391				}
392
393				/* Fall through. */
394
395			case -ERESTARTNOINTR:
396				/*
397				 * This means that the syscall should
398                                 * be called again after the signal
399                                 * handler returns.
400				 */
401				RESTART_CRIS_SYS(regs);
402				break;
403                }
404        }
405
406	/* Set up the stack frame. */
407	if (ksig->ka.sa.sa_flags & SA_SIGINFO)
408		ret = setup_rt_frame(ksig, oldset, regs);
409	else
410		ret = setup_frame(ksig, oldset, regs);
411
412	signal_setup_done(ret, ksig, 0);
413}
414
415/*
416 * Note that 'init' is a special process: it doesn't get signals it doesn't
417 * want to handle. Thus you cannot kill init even with a SIGKILL even by
418 * mistake.
419 *
420 * Also note that the regs structure given here as an argument, is the latest
421 * pushed pt_regs. It may or may not be the same as the first pushed registers
422 * when the initial usermode->kernelmode transition took place. Therefore
423 * we can use user_mode(regs) to see if we came directly from kernel or user
424 * mode below.
425 */
426void
427do_signal(int canrestart, struct pt_regs *regs)
428{
429	struct ksignal ksig;
430
431	canrestart = canrestart && ((int)regs->exs >= 0);
432
433	/*
434	 * The common case should go fast, which is why this point is
435	 * reached from kernel-mode. If that's the case, just return
436	 * without doing anything.
437	 */
438	if (!user_mode(regs))
439		return;
440
441	if (get_signal(&ksig)) {
442		/* Whee!  Actually deliver the signal.  */
443		handle_signal(canrestart, &ksig, regs);
444		return;
445	}
446
447	/* Got here from a system call? */
448	if (canrestart) {
449		/* Restart the system call - no handlers present. */
450		if (regs->r10 == -ERESTARTNOHAND ||
451		    regs->r10 == -ERESTARTSYS ||
452		    regs->r10 == -ERESTARTNOINTR) {
453			RESTART_CRIS_SYS(regs);
454		}
455
456		if (regs->r10 == -ERESTART_RESTARTBLOCK){
457			regs->r9 = __NR_restart_syscall;
458			regs->erp -= 2;
459		}
460	}
461
462	/* if there's no signal to deliver, we just put the saved sigmask
463	 * back */
464	restore_saved_sigmask();
465}
466
467asmlinkage void
468ugdb_trap_user(struct thread_info *ti, int sig)
469{
470	if (((user_regs(ti)->exs & 0xff00) >> 8) != SINGLE_STEP_INTR_VECT) {
471		/* Zero single-step PC if the reason we stopped wasn't a single
472		   step exception. This is to avoid relying on it when it isn't
473		   reliable. */
474		user_regs(ti)->spc = 0;
475	}
476	/* FIXME: Filter out false h/w breakpoint hits (i.e. EDA
477	   not within any configured h/w breakpoint range). Synchronize with
478	   what already exists for kernel debugging.  */
479	if (((user_regs(ti)->exs & 0xff00) >> 8) == BREAK_8_INTR_VECT) {
480		/* Break 8: subtract 2 from ERP unless in a delay slot. */
481		if (!(user_regs(ti)->erp & 0x1))
482			user_regs(ti)->erp -= 2;
483	}
484	sys_kill(ti->task->pid, sig);
485}
486
487void
488keep_debug_flags(unsigned long oldccs, unsigned long oldspc,
489		 struct pt_regs *regs)
490{
491	if (oldccs & (1 << Q_CCS_BITNR)) {
492		/* Pending single step due to single-stepping the break 13
493		   in the signal trampoline: keep the Q flag. */
494		regs->ccs |= (1 << Q_CCS_BITNR);
495		/* S flag should be set - complain if it's not. */
496		if (!(oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT)))) {
497			printk("Q flag but no S flag?");
498		}
499		regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
500		/* Assume the SPC is valid and interesting. */
501		regs->spc = oldspc;
502
503	} else if (oldccs & (1 << (S_CCS_BITNR + CCS_SHIFT))) {
504		/* If a h/w bp was set in the signal handler we need
505		   to keep the S flag. */
506		regs->ccs |= (1 << (S_CCS_BITNR + CCS_SHIFT));
507		/* Don't keep the old SPC though; if we got here due to
508		   a single-step, the Q flag should have been set. */
509	} else if (regs->spc) {
510		/* If we were single-stepping *before* the signal was taken,
511		   we don't want to restore that state now, because GDB will
512		   have forgotten all about it. */
513		regs->spc = 0;
514		regs->ccs &= ~(1 << (S_CCS_BITNR + CCS_SHIFT));
515	}
516}
517
518/* Set up the trampolines on the signal return page. */
519int __init
520cris_init_signal(void)
521{
522	u16* data = kmalloc(PAGE_SIZE, GFP_KERNEL);
523
524	/* This is movu.w __NR_sigreturn, r9; break 13; */
525	data[0] = 0x9c5f;
526	data[1] = __NR_sigreturn;
527	data[2] = 0xe93d;
528	/* This is movu.w __NR_rt_sigreturn, r9; break 13; */
529	data[3] = 0x9c5f;
530	data[4] = __NR_rt_sigreturn;
531	data[5] = 0xe93d;
532
533	/* Map to userspace with appropriate permissions (no write access...) */
534	cris_signal_return_page = (unsigned long)
535          __ioremap_prot(virt_to_phys(data), PAGE_SIZE, PAGE_SIGNAL_TRAMPOLINE);
536
537	return 0;
538}
539
540__initcall(cris_init_signal);
541