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