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