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/resume_user_mode.h>
23#include <linux/sched/task_stack.h>
24
25#include <asm/ucontext.h>
26#include <linux/uaccess.h>
27#include <asm/cacheflush.h>
28#include <asm/coprocessor.h>
29#include <asm/processor.h>
30#include <asm/syscall.h>
31#include <asm/unistd.h>
32
33extern struct task_struct *coproc_owners[];
34
35struct rt_sigframe
36{
37	struct siginfo info;
38	struct ucontext uc;
39	struct {
40		xtregs_opt_t opt;
41		xtregs_user_t user;
42#if XTENSA_HAVE_COPROCESSORS
43		xtregs_coprocessor_t cp;
44#endif
45	} xtregs;
46	unsigned char retcode[6];
47	unsigned int window[4];
48};
49
50#if defined(USER_SUPPORT_WINDOWED)
51/*
52 * Flush register windows stored in pt_regs to stack.
53 * Returns 1 for errors.
54 */
55
56static int
57flush_window_regs_user(struct pt_regs *regs)
58{
59	const unsigned long ws = regs->windowstart;
60	const unsigned long wb = regs->windowbase;
61	unsigned long sp = 0;
62	unsigned long wm;
63	int err = 1;
64	int base;
65
66	/* Return if no other frames. */
67
68	if (regs->wmask == 1)
69		return 0;
70
71	/* Rotate windowmask and skip empty frames. */
72
73	wm = (ws >> wb) | (ws << (XCHAL_NUM_AREGS / 4 - wb));
74	base = (XCHAL_NUM_AREGS / 4) - (regs->wmask >> 4);
75
76	/* For call8 or call12 frames, we need the previous stack pointer. */
77
78	if ((regs->wmask & 2) == 0)
79		if (__get_user(sp, (int*)(regs->areg[base * 4 + 1] - 12)))
80			goto errout;
81
82	/* Spill frames to stack. */
83
84	while (base < XCHAL_NUM_AREGS / 4) {
85
86		int m = (wm >> base);
87		int inc = 0;
88
89		/* Save registers a4..a7 (call8) or a4...a11 (call12) */
90
91		if (m & 2) {			/* call4 */
92			inc = 1;
93
94		} else if (m & 4) {		/* call8 */
95			if (copy_to_user(&SPILL_SLOT_CALL8(sp, 4),
96					 &regs->areg[(base + 1) * 4], 16))
97				goto errout;
98			inc = 2;
99
100		} else if (m & 8) {	/* call12 */
101			if (copy_to_user(&SPILL_SLOT_CALL12(sp, 4),
102					 &regs->areg[(base + 1) * 4], 32))
103				goto errout;
104			inc = 3;
105		}
106
107		/* Save current frame a0..a3 under next SP */
108
109		sp = regs->areg[((base + inc) * 4 + 1) % XCHAL_NUM_AREGS];
110		if (copy_to_user(&SPILL_SLOT(sp, 0), &regs->areg[base * 4], 16))
111			goto errout;
112
113		/* Get current stack pointer for next loop iteration. */
114
115		sp = regs->areg[base * 4 + 1];
116		base += inc;
117	}
118
119	regs->wmask = 1;
120	regs->windowstart = 1 << wb;
121
122	return 0;
123
124errout:
125	return err;
126}
127#else
128static int
129flush_window_regs_user(struct pt_regs *regs)
130{
131	return 0;
132}
133#endif
134
135/*
136 * Note: We don't copy double exception 'regs', we have to finish double exc.
137 * first before we return to signal handler! This dbl.exc.handler might cause
138 * another double exception, but I think we are fine as the situation is the
139 * same as if we had returned to the signal handerl and got an interrupt
140 * immediately...
141 */
142
143static int
144setup_sigcontext(struct rt_sigframe __user *frame, struct pt_regs *regs)
145{
146	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
147	struct thread_info *ti = current_thread_info();
148	int err = 0;
149
150#define COPY(x)	err |= __put_user(regs->x, &sc->sc_##x)
151	COPY(pc);
152	COPY(ps);
153	COPY(lbeg);
154	COPY(lend);
155	COPY(lcount);
156	COPY(sar);
157#undef COPY
158
159	err |= flush_window_regs_user(regs);
160	err |= __copy_to_user (sc->sc_a, regs->areg, 16 * 4);
161	err |= __put_user(0, &sc->sc_xtregs);
162
163	if (err)
164		return err;
165
166#if XTENSA_HAVE_COPROCESSORS
167	coprocessor_flush_release_all(ti);
168	err |= __copy_to_user(&frame->xtregs.cp, &ti->xtregs_cp,
169			      sizeof (frame->xtregs.cp));
170#endif
171	err |= __copy_to_user(&frame->xtregs.opt, &regs->xtregs_opt,
172			      sizeof (xtregs_opt_t));
173	err |= __copy_to_user(&frame->xtregs.user, &ti->xtregs_user,
174			      sizeof (xtregs_user_t));
175
176	err |= __put_user(err ? NULL : &frame->xtregs, &sc->sc_xtregs);
177
178	return err;
179}
180
181static int
182restore_sigcontext(struct pt_regs *regs, struct rt_sigframe __user *frame)
183{
184	struct sigcontext __user *sc = &frame->uc.uc_mcontext;
185	struct thread_info *ti = current_thread_info();
186	unsigned int err = 0;
187	unsigned long ps;
188
189#define COPY(x)	err |= __get_user(regs->x, &sc->sc_##x)
190	COPY(pc);
191	COPY(lbeg);
192	COPY(lend);
193	COPY(lcount);
194	COPY(sar);
195#undef COPY
196
197	/* All registers were flushed to stack. Start with a pristine frame. */
198
199	regs->wmask = 1;
200	regs->windowbase = 0;
201	regs->windowstart = 1;
202
203	regs->syscall = NO_SYSCALL;	/* disable syscall checks */
204
205	/* For PS, restore only PS.CALLINC.
206	 * Assume that all other bits are either the same as for the signal
207	 * handler, or the user mode value doesn't matter (e.g. PS.OWB).
208	 */
209	err |= __get_user(ps, &sc->sc_ps);
210	regs->ps = (regs->ps & ~PS_CALLINC_MASK) | (ps & PS_CALLINC_MASK);
211
212	/* Additional corruption checks */
213
214	if ((regs->lcount > 0)
215	    && ((regs->lbeg > TASK_SIZE) || (regs->lend > TASK_SIZE)) )
216		err = 1;
217
218	err |= __copy_from_user(regs->areg, sc->sc_a, 16 * 4);
219
220	if (err)
221		return err;
222
223	/* The signal handler may have used coprocessors in which
224	 * case they are still enabled.  We disable them to force a
225	 * reloading of the original task's CP state by the lazy
226	 * context-switching mechanisms of CP exception handling.
227	 * Also, we essentially discard any coprocessor state that the
228	 * signal handler created. */
229
230#if XTENSA_HAVE_COPROCESSORS
231	coprocessor_release_all(ti);
232	err |= __copy_from_user(&ti->xtregs_cp, &frame->xtregs.cp,
233				sizeof (frame->xtregs.cp));
234#endif
235	err |= __copy_from_user(&ti->xtregs_user, &frame->xtregs.user,
236				sizeof (xtregs_user_t));
237	err |= __copy_from_user(&regs->xtregs_opt, &frame->xtregs.opt,
238				sizeof (xtregs_opt_t));
239
240	return err;
241}
242
243
244/*
245 * Do a signal return; undo the signal stack.
246 */
247
248asmlinkage long xtensa_rt_sigreturn(void)
249{
250	struct pt_regs *regs = current_pt_regs();
251	struct rt_sigframe __user *frame;
252	sigset_t set;
253	int ret;
254
255	/* Always make any pending restarted system calls return -EINTR */
256	current->restart_block.fn = do_no_restart_syscall;
257
258	if (regs->depc > 64)
259		panic("rt_sigreturn in double exception!\n");
260
261	frame = (struct rt_sigframe __user *) regs->areg[1];
262
263	if (!access_ok(frame, sizeof(*frame)))
264		goto badframe;
265
266	if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
267		goto badframe;
268
269	set_current_blocked(&set);
270
271	if (restore_sigcontext(regs, frame))
272		goto badframe;
273
274	ret = regs->areg[2];
275
276	if (restore_altstack(&frame->uc.uc_stack))
277		goto badframe;
278
279	return ret;
280
281badframe:
282	force_sig(SIGSEGV);
283	return 0;
284}
285
286
287
288/*
289 * Set up a signal frame.
290 */
291
292static int
293gen_return_code(unsigned char *codemem)
294{
295	int err = 0;
296
297	/*
298	 * The 12-bit immediate is really split up within the 24-bit MOVI
299	 * instruction.  As long as the above system call numbers fit within
300	 * 8-bits, the following code works fine. See the Xtensa ISA for
301	 * details.
302	 */
303
304#if __NR_rt_sigreturn > 255
305# error Generating the MOVI instruction below breaks!
306#endif
307
308#ifdef __XTENSA_EB__   /* Big Endian version */
309	/* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
310	err |= __put_user(0x22, &codemem[0]);
311	err |= __put_user(0x0a, &codemem[1]);
312	err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
313	/* Generate instruction:  SYSCALL */
314	err |= __put_user(0x00, &codemem[3]);
315	err |= __put_user(0x05, &codemem[4]);
316	err |= __put_user(0x00, &codemem[5]);
317
318#elif defined __XTENSA_EL__   /* Little Endian version */
319	/* Generate instruction:  MOVI a2, __NR_rt_sigreturn */
320	err |= __put_user(0x22, &codemem[0]);
321	err |= __put_user(0xa0, &codemem[1]);
322	err |= __put_user(__NR_rt_sigreturn, &codemem[2]);
323	/* Generate instruction:  SYSCALL */
324	err |= __put_user(0x00, &codemem[3]);
325	err |= __put_user(0x50, &codemem[4]);
326	err |= __put_user(0x00, &codemem[5]);
327#else
328# error Must use compiler for Xtensa processors.
329#endif
330
331	/* Flush generated code out of the data cache */
332
333	if (err == 0) {
334		__invalidate_icache_range((unsigned long)codemem, 6UL);
335		__flush_invalidate_dcache_range((unsigned long)codemem, 6UL);
336	}
337
338	return err;
339}
340
341
342static int setup_frame(struct ksignal *ksig, sigset_t *set,
343		       struct pt_regs *regs)
344{
345	struct rt_sigframe *frame;
346	int err = 0, sig = ksig->sig;
347	unsigned long sp, ra, tp, ps;
348	unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
349	unsigned long handler_fdpic_GOT = 0;
350	unsigned int base;
351	bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
352		(current->personality & FDPIC_FUNCPTRS);
353
354	if (fdpic) {
355		unsigned long __user *fdpic_func_desc =
356			(unsigned long __user *)handler;
357		if (__get_user(handler, &fdpic_func_desc[0]) ||
358		    __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
359			return -EFAULT;
360	}
361
362	sp = regs->areg[1];
363
364	if ((ksig->ka.sa.sa_flags & SA_ONSTACK) != 0 && sas_ss_flags(sp) == 0) {
365		sp = current->sas_ss_sp + current->sas_ss_size;
366	}
367
368	frame = (void *)((sp - sizeof(*frame)) & -16ul);
369
370	if (regs->depc > 64)
371		panic ("Double exception sys_sigreturn\n");
372
373	if (!access_ok(frame, sizeof(*frame))) {
374		return -EFAULT;
375	}
376
377	if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
378		err |= copy_siginfo_to_user(&frame->info, &ksig->info);
379	}
380
381	/* Create the user context.  */
382
383	err |= __put_user(0, &frame->uc.uc_flags);
384	err |= __put_user(0, &frame->uc.uc_link);
385	err |= __save_altstack(&frame->uc.uc_stack, regs->areg[1]);
386	err |= setup_sigcontext(frame, regs);
387	err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
388
389	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
390		if (fdpic) {
391			unsigned long __user *fdpic_func_desc =
392				(unsigned long __user *)ksig->ka.sa.sa_restorer;
393
394			err |= __get_user(ra, fdpic_func_desc);
395		} else {
396			ra = (unsigned long)ksig->ka.sa.sa_restorer;
397		}
398	} else {
399
400		/* Create sys_rt_sigreturn syscall in stack frame */
401
402		err |= gen_return_code(frame->retcode);
403		ra = (unsigned long) frame->retcode;
404	}
405
406	if (err)
407		return -EFAULT;
408
409	/*
410	 * Create signal handler execution context.
411	 * Return context not modified until this point.
412	 */
413
414	/* Set up registers for signal handler; preserve the threadptr */
415	tp = regs->threadptr;
416	ps = regs->ps;
417	start_thread(regs, handler, (unsigned long)frame);
418
419	/* Set up a stack frame for a call4 if userspace uses windowed ABI */
420	if (ps & PS_WOE_MASK) {
421		base = 4;
422		regs->areg[base] =
423			(((unsigned long) ra) & 0x3fffffff) | 0x40000000;
424		ps = (ps & ~(PS_CALLINC_MASK | PS_OWB_MASK)) |
425			(1 << PS_CALLINC_SHIFT);
426	} else {
427		base = 0;
428		regs->areg[base] = (unsigned long) ra;
429	}
430	regs->areg[base + 2] = (unsigned long) sig;
431	regs->areg[base + 3] = (unsigned long) &frame->info;
432	regs->areg[base + 4] = (unsigned long) &frame->uc;
433	regs->threadptr = tp;
434	regs->ps = ps;
435	if (fdpic)
436		regs->areg[base + 11] = handler_fdpic_GOT;
437
438	pr_debug("SIG rt deliver (%s:%d): signal=%d sp=%p pc=%08lx\n",
439		 current->comm, current->pid, sig, frame, regs->pc);
440
441	return 0;
442}
443
444/*
445 * Note that 'init' is a special process: it doesn't get signals it doesn't
446 * want to handle. Thus you cannot kill init even with a SIGKILL even by
447 * mistake.
448 *
449 * Note that we go through the signals twice: once to check the signals that
450 * the kernel can handle, and then we build all the user-level signal handling
451 * stack-frames in one go after that.
452 */
453static void do_signal(struct pt_regs *regs)
454{
455	struct ksignal ksig;
456
457	task_pt_regs(current)->icountlevel = 0;
458
459	if (get_signal(&ksig)) {
460		int ret;
461
462		/* Are we from a system call? */
463
464		if (regs->syscall != NO_SYSCALL) {
465
466			/* If so, check system call restarting.. */
467
468			switch (regs->areg[2]) {
469				case -ERESTARTNOHAND:
470				case -ERESTART_RESTARTBLOCK:
471					regs->areg[2] = -EINTR;
472					break;
473
474				case -ERESTARTSYS:
475					if (!(ksig.ka.sa.sa_flags & SA_RESTART)) {
476						regs->areg[2] = -EINTR;
477						break;
478					}
479					fallthrough;
480				case -ERESTARTNOINTR:
481					regs->areg[2] = regs->syscall;
482					regs->pc -= 3;
483					break;
484
485				default:
486					/* nothing to do */
487					if (regs->areg[2] != 0)
488					break;
489			}
490		}
491
492		/* Whee!  Actually deliver the signal.  */
493		/* Set up the stack frame */
494		ret = setup_frame(&ksig, sigmask_to_save(), regs);
495		signal_setup_done(ret, &ksig, 0);
496		if (test_thread_flag(TIF_SINGLESTEP))
497			task_pt_regs(current)->icountlevel = 1;
498
499		return;
500	}
501
502	/* Did we come from a system call? */
503	if (regs->syscall != NO_SYSCALL) {
504		/* Restart the system call - no handlers present */
505		switch (regs->areg[2]) {
506		case -ERESTARTNOHAND:
507		case -ERESTARTSYS:
508		case -ERESTARTNOINTR:
509			regs->areg[2] = regs->syscall;
510			regs->pc -= 3;
511			break;
512		case -ERESTART_RESTARTBLOCK:
513			regs->areg[2] = __NR_restart_syscall;
514			regs->pc -= 3;
515			break;
516		}
517	}
518
519	/* If there's no signal to deliver, we just restore the saved mask.  */
520	restore_saved_sigmask();
521
522	if (test_thread_flag(TIF_SINGLESTEP))
523		task_pt_regs(current)->icountlevel = 1;
524	return;
525}
526
527void do_notify_resume(struct pt_regs *regs)
528{
529	if (test_thread_flag(TIF_SIGPENDING) ||
530	    test_thread_flag(TIF_NOTIFY_SIGNAL))
531		do_signal(regs);
532
533	if (test_thread_flag(TIF_NOTIFY_RESUME))
534		resume_user_mode_work(regs);
535}
536