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
42 void do_signal(int canrestart, struct pt_regs *regs);
43
44 /*
45 * Do a signal return; undo the signal stack.
46 */
47
48 struct sigframe {
49 struct sigcontext sc;
50 unsigned long extramask[_NSIG_WORDS-1];
51 unsigned char retcode[8]; /* trampoline code */
52 };
53
54 struct 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
63 static int
restore_sigcontext(struct pt_regs * regs,struct sigcontext __user * sc)64 restore_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
100 badframe:
101 return 1;
102 }
103
sys_sigreturn(void)104 asmlinkage 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
135 badframe:
136 force_sig(SIGSEGV, current);
137 return 0;
138 }
139
sys_rt_sigreturn(void)140 asmlinkage 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
169 badframe:
170 force_sig(SIGSEGV, current);
171 return 0;
172 }
173
174 /*
175 * Set up a signal frame.
176 */
177
setup_sigcontext(struct sigcontext __user * sc,struct pt_regs * regs,unsigned long mask)178 static 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
205 static inline void __user *
get_sigframe(struct ksignal * ksig,size_t frame_size)206 get_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
setup_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)225 static 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
setup_rt_frame(struct ksignal * ksig,sigset_t * set,struct pt_regs * regs)277 static 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
handle_signal(int canrestart,struct ksignal * ksig,struct pt_regs * regs)347 static 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
do_signal(int canrestart,struct pt_regs * regs)402 void 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