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
33 extern struct task_struct *coproc_owners[];
34
35 struct 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
56 static int
57 flush_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 ®s->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 ®s->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), ®s->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
124 errout:
125 return err;
126 }
127 #else
128 static int
129 flush_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
143 static int
144 setup_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, ®s->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
181 static int
182 restore_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(®s->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
248 asmlinkage 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
281 badframe:
282 force_sig(SIGSEGV);
283 return 0;
284 }
285
286
287
288 /*
289 * Set up a signal frame.
290 */
291
292 static int
293 gen_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
342 static 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 */
453 static 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
527 void 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
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