1/*
2 * arch/xtensa/kernel/signal.c
3 *
4 * Default platform functions.
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License.  See the file "COPYING" in the main directory of this archive
8 * for more details.
9 *
10 * Copyright (C) 2005, 2006 Tensilica Inc.
11 * Copyright (C) 1991, 1992  Linus Torvalds
12 * 1997-11-28  Modified for POSIX.1b signals by Richard Henderson
13 *
14 * Chris Zankel <chris@zankel.net>
15 * Joe Taylor <joe@tensilica.com>
16 */
17
18#include <linux/signal.h>
19#include <linux/errno.h>
20#include <linux/ptrace.h>
21#include <linux/personality.h>
22#include <linux/tracehook.h>
23
24#include <asm/ucontext.h>
25#include <asm/uaccess.h>
26#include <asm/cacheflush.h>
27#include <asm/coprocessor.h>
28#include <asm/unistd.h>
29
30#define DEBUG_SIG  0
31
32extern struct task_struct *coproc_owners[];
33
34struct rt_sigframe
35{
36	struct siginfo info;
37	struct ucontext uc;
38	struct {
39		xtregs_opt_t opt;
40		xtregs_user_t user;
41#if XTENSA_HAVE_COPROCESSORS
42		xtregs_coprocessor_t cp;
43#endif
44	} xtregs;
45	unsigned char retcode[6];
46	unsigned int window[4];
47};
48
49/*
50 * Flush register windows stored in pt_regs to stack.
51 * Returns 1 for errors.
52 */
53
54int
55flush_window_regs_user(struct pt_regs *regs)
56{
57	const unsigned long ws = regs->windowstart;
58	const unsigned long wb = regs->windowbase;
59	unsigned long sp = 0;
60	unsigned long wm;
61	int err = 1;
62	int base;
63
64	/* Return if no other frames. */
65
66	if (regs->wmask == 1)
67		return 0;
68
69	/* Rotate windowmask and skip empty frames. */
70
71	wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
72	base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
73
74	/* For call8 or call12 frames, we need the previous stack pointer. */
75
76	if ((regs->wmask & 2) == 0)
77		if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
78			goto errout;
79
80	/* Spill frames to stack. */
81
82	while (base < XCHAL_NUM_AREGS / 4) {
83
84		int m = (wm >> base);
85		int inc = 0;
86
87		/* Save registers a4..a7 (call8) or a4...a11 (call12) */
88
89		if (m & 2) {			/* call4 */
90			inc = 1;
91
92		} else if (m & 4) {		/* call8 */
93			if (copy_to_user((void*)(sp - 32),
94					   &regs->areg[(base + 1) * 4], 16))
95				goto errout;
96			inc = 2;
97
98		} else if (m & 8) {	/* call12 */
99			if (copy_to_user((void*)(sp - 48),
100					   &regs->areg[(base + 1) * 4], 32))
101				goto errout;
102			inc = 3;
103		}
104
105		/* Save current frame a0..a3 under next SP */
106
107		sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
108		if (copy_to_user((void*)(sp - 16), &regs->areg[base * 4], 16))
109			goto errout;
110
111		/* Get current stack pointer for next loop iteration. */
112
113		sp = regs->areg[base * 4 + 1];
114		base += inc;
115	}
116
117	regs->wmask = 1;
118	regs->windowstart = 1 << wb;
119
120	return 0;
121
122errout:
123	return err;
124}
125
126/*
127 * Note: We don't copy double exception 'regs', we have to finish double exc.
128 * first before we return to signal handler! This dbl.exc.handler might cause
129 * another double exception, but I think we are fine as the situation is the
130 * same as if we had returned to the signal handerl and got an interrupt
131 * immediately...
132 */
133
134static int
135setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
136{
137	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
138	struct thread_info *ti = current_thread_info();
139	int err = 0;
140
141#define COPY(x)	err |= __put_user(regs->x, &sc->sc_##x)
142	COPY(pc);
143	COPY(ps);
144	COPY(lbeg);
145	COPY(lend);
146	COPY(lcount);
147	COPY(sar);
148#undef COPY
149
150	err |= flush_window_regs_user(regs);
151	err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
152	err |= __put_user(0, &sc->sc_xtregs);
153
154	if (err)
155		return err;
156
157#if XTENSA_HAVE_COPROCESSORS
158	coprocessor_flush_all(ti);
159	coprocessor_release_all(ti);
160	err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
161			      sizeof (frame->xtregs.cp));
162#endif
163	err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
164			      sizeof (xtregs_opt_t));
165	err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
166			      sizeof (xtregs_user_t));
167
168	err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
169
170	return err;
171}
172
173static int
174restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
175{
176	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
177	struct thread_info *ti = current_thread_info();
178	unsigned int err = 0;
179	unsigned long ps;
180
181#define COPY(x)	err |= __get_user(regs->x, &sc->sc_##x)
182	COPY(pc);
183	COPY(lbeg);
184	COPY(lend);
185	COPY(lcount);
186	COPY(sar);
187#undef COPY
188
189	/* All registers were flushed to stack. Start with a prestine frame. */
190
191	regs->wmask = 1;
192	regs->windowbase = 0;
193	regs->windowstart = 1;
194
195	regs->syscall = -1;		/* disable syscall checks */
196
197	/* For PS, restore only PS.CALLINC.
198	 * Assume that all other bits are either the same as for the signal
199	 * handler, or the user mode value doesn't matter (e.g. PS.OWB).
200	 */
201	err |= __get_user(ps, &sc->sc_ps);
202	regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
203
204	/* Additional corruption checks */
205
206	if ((regs->lcount > 0)
207	    && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
208		err = 1;
209
210	err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
211
212	if (err)
213		return err;
214
215	/* The signal handler may have used coprocessors in which
216	 * case they are still enabled.  We disable them to force a
217	 * reloading of the original task's CP state by the lazy
218	 * context-switching mechanisms of CP exception handling.
219	 * Also, we essentially discard any coprocessor state that the
220	 * signal handler created. */
221
222#if XTENSA_HAVE_COPROCESSORS
223	coprocessor_release_all(ti);
224	err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
225				sizeof (frame->xtregs.cp));
226#endif
227	err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
228				sizeof (xtregs_user_t));
229	err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
230				sizeof (xtregs_opt_t));
231
232	return err;
233}
234
235
236/*
237 * Do a signal return; undo the signal stack.
238 */
239
240asmlinkage long xtensa_rt_sigreturn(long a0, long a1, long a2, long a3,
241				    long a4, long a5, struct pt_regs *regs)
242{
243	struct rt_sigframe __user *frame;
244	sigset_t set;
245	int ret;
246
247	/* Always make any pending restarted system calls return -EINTR */
248	current->restart_block.fn = do_no_restart_syscall;
249
250	if (regs->depc > 64)
251		panic("rt_sigreturn in double exception!\n");
252
253	frame = (struct rt_sigframe __user *) regs->areg[1];
254
255	if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
256		goto badframe;
257
258	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
259		goto badframe;
260
261	set_current_blocked(&set);
262
263	if (restore_sigcontext(regs, frame))
264		goto badframe;
265
266	ret = regs->areg[2];
267
268	if (restore_altstack(&frame->uc.uc_stack))
269		goto badframe;
270
271	return ret;
272
273badframe:
274	force_sig(SIGSEGV, current);
275	return 0;
276}
277
278
279
280/*
281 * Set up a signal frame.
282 */
283
284static int
285gen_return_code(unsigned char *codemem)
286{
287	int err = 0;
288
289	/*
290	 * The 12-bit immediate is really split up within the 24-bit MOVI
291	 * instruction.  As long as the above system call numbers fit within
292	 * 8-bits, the following code works fine. See the Xtensa ISA for
293	 * details.
294	 */
295
296#if __NR_rt_sigreturn > 255
297# error Generating the MOVI instruction below breaks!
298#endif
299
300#ifdef __XTENSA_EB__   /* Big Endian version */
301	/* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
302	err |= __put_user(0x22, &codemem[0]);
303	err |= __put_user(0x0a, &codemem[1]);
304	err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
305	/* Generate instruction:  SYSCALL */
306	err |= __put_user(0x00, &codemem[3]);
307	err |= __put_user(0x05, &codemem[4]);
308	err |= __put_user(0x00, &codemem[5]);
309
310#elif defined __XTENSA_EL__   /* Little Endian version */
311	/* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
312	err |= __put_user(0x22, &codemem[0]);
313	err |= __put_user(0xa0, &codemem[1]);
314	err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
315	/* Generate instruction:  SYSCALL */
316	err |= __put_user(0x00, &codemem[3]);
317	err |= __put_user(0x50, &codemem[4]);
318	err |= __put_user(0x00, &codemem[5]);
319#else
320# error Must use compiler for Xtensa processors.
321#endif
322
323	/* Flush generated code out of the data cache */
324
325	if (err == 0) {
326		__invalidate_icache_range((unsigned long)codemem, 6UL);
327		__flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
328	}
329
330	return err;
331}
332
333
334static int setup_frame(struct ksignal *ksig, sigset_t *set,
335		       struct pt_regs *regs)
336{
337	struct rt_sigframe *frame;
338	int err = 0, sig = ksig->sig;
339	unsigned long sp, ra, tp;
340
341	sp = regs->areg[1];
342
343	if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
344		sp = current->sas_ss_sp + current->sas_ss_size;
345	}
346
347	frame = (void *)((sp - sizeof(*frame)) & -16ul);
348
349	if (regs->depc > 64)
350		panic ("Double exception sys_sigreturn\n");
351
352	if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame))) {
353		return -EFAULT;
354	}
355
356	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
357		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
358	}
359
360	/* Create the user context.  */
361
362	err |= __put_user(0, &frame->uc.uc_flags);
363	err |= __put_user(0, &frame->uc.uc_link);
364	err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
365	err |= setup_sigcontext(frame, regs);
366	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
367
368	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
369		ra = (unsigned long)ksig->ka.sa.sa_restorer;
370	} else {
371
372		/* Create sys_rt_sigreturn syscall in stack frame */
373
374		err |= gen_return_code(frame->retcode);
375
376		if (err) {
377			return -EFAULT;
378		}
379		ra = (unsigned long) frame->retcode;
380	}
381
382	/*
383	 * Create signal handler execution context.
384	 * Return context not modified until this point.
385	 */
386
387	/* Set up registers for signal handler; preserve the threadptr */
388	tp = regs->threadptr;
389	start_thread(regs, (unsigned long) ksig->ka.sa.sa_handler,
390		     (unsigned long) frame);
391
392	/* Set up a stack frame for a call4
393	 * Note: PS.CALLINC is set to one by start_thread
394	 */
395	regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
396	regs->areg[6] = (unsigned long) sig;
397	regs->areg[7] = (unsigned long) &frame->info;
398	regs->areg[8] = (unsigned long) &frame->uc;
399	regs->threadptr = tp;
400
401#if DEBUG_SIG
402	printk("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08x\n",
403		current->comm, current->pid, sig, frame, regs->pc);
404#endif
405
406	return 0;
407}
408
409/*
410 * Note that 'init' is a special process: it doesn't get signals it doesn't
411 * want to handle. Thus you cannot kill init even with a SIGKILL even by
412 * mistake.
413 *
414 * Note that we go through the signals twice: once to check the signals that
415 * the kernel can handle, and then we build all the user-level signal handling
416 * stack-frames in one go after that.
417 */
418static void do_signal(struct pt_regs *regs)
419{
420	struct ksignal ksig;
421
422	task_pt_regs(current)->icountlevel = 0;
423
424	if (get_signal(&ksig)) {
425		int ret;
426
427		/* Are we from a system call? */
428
429		if ((signed)regs->syscall >= 0) {
430
431			/* If so, check system call restarting.. */
432
433			switch (regs->areg[2]) {
434				case -ERESTARTNOHAND:
435				case -ERESTART_RESTARTBLOCK:
436					regs->areg[2] = -EINTR;
437					break;
438
439				case -ERESTARTSYS:
440					if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
441						regs->areg[2] = -EINTR;
442						break;
443					}
444					/* fallthrough */
445				case -ERESTARTNOINTR:
446					regs->areg[2] = regs->syscall;
447					regs->pc -= 3;
448					break;
449
450				default:
451					/* nothing to do */
452					if (regs->areg[2] != 0)
453					break;
454			}
455		}
456
457		/* Whee!  Actually deliver the signal.  */
458		/* Set up the stack frame */
459		ret = setup_frame(&ksig, sigmask_to_save(), regs);
460		signal_setup_done(ret, &ksig, 0);
461		if (current->ptrace & PT_SINGLESTEP)
462			task_pt_regs(current)->icountlevel = 1;
463
464		return;
465	}
466
467	/* Did we come from a system call? */
468	if ((signed) regs->syscall >= 0) {
469		/* Restart the system call - no handlers present */
470		switch (regs->areg[2]) {
471		case -ERESTARTNOHAND:
472		case -ERESTARTSYS:
473		case -ERESTARTNOINTR:
474			regs->areg[2] = regs->syscall;
475			regs->pc -= 3;
476			break;
477		case -ERESTART_RESTARTBLOCK:
478			regs->areg[2] = __NR_restart_syscall;
479			regs->pc -= 3;
480			break;
481		}
482	}
483
484	/* If there's no signal to deliver, we just restore the saved mask.  */
485	restore_saved_sigmask();
486
487	if (current->ptrace & PT_SINGLESTEP)
488		task_pt_regs(current)->icountlevel = 1;
489	return;
490}
491
492void do_notify_resume(struct pt_regs *regs)
493{
494	if (test_thread_flag(TIF_SIGPENDING))
495		do_signal(regs);
496
497	if (test_and_clear_thread_flag(TIF_NOTIFY_RESUME))
498		tracehook_notify_resume(regs);
499}
500