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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/arch/arm/kernel/signal.c
4 *
5 * Copyright (C) 1995-2009 Russell King
6 */
7#include <linux/errno.h>
8#include <linux/random.h>
9#include <linux/signal.h>
10#include <linux/personality.h>
11#include <linux/uaccess.h>
12#include <linux/tracehook.h>
13#include <linux/uprobes.h>
14#include <linux/syscalls.h>
15
16#include <asm/elf.h>
17#include <asm/cacheflush.h>
18#include <asm/traps.h>
19#include <asm/unistd.h>
20#include <asm/vfp.h>
21
22#include "signal.h"
23
24extern const unsigned long sigreturn_codes[17];
25
26static unsigned long signal_return_offset;
27
28#ifdef CONFIG_CRUNCH
29static int preserve_crunch_context(struct crunch_sigframe __user *frame)
30{
31 char kbuf[sizeof(*frame) + 8];
32 struct crunch_sigframe *kframe;
33
34 /* the crunch context must be 64 bit aligned */
35 kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
36 kframe->magic = CRUNCH_MAGIC;
37 kframe->size = CRUNCH_STORAGE_SIZE;
38 crunch_task_copy(current_thread_info(), &kframe->storage);
39 return __copy_to_user(frame, kframe, sizeof(*frame));
40}
41
42static int restore_crunch_context(char __user **auxp)
43{
44 struct crunch_sigframe __user *frame =
45 (struct crunch_sigframe __user *)*auxp;
46 char kbuf[sizeof(*frame) + 8];
47 struct crunch_sigframe *kframe;
48
49 /* the crunch context must be 64 bit aligned */
50 kframe = (struct crunch_sigframe *)((unsigned long)(kbuf + 8) & ~7);
51 if (__copy_from_user(kframe, frame, sizeof(*frame)))
52 return -1;
53 if (kframe->magic != CRUNCH_MAGIC ||
54 kframe->size != CRUNCH_STORAGE_SIZE)
55 return -1;
56 *auxp += CRUNCH_STORAGE_SIZE;
57 crunch_task_restore(current_thread_info(), &kframe->storage);
58 return 0;
59}
60#endif
61
62#ifdef CONFIG_IWMMXT
63
64static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
65{
66 char kbuf[sizeof(*frame) + 8];
67 struct iwmmxt_sigframe *kframe;
68 int err = 0;
69
70 /* the iWMMXt context must be 64 bit aligned */
71 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
72
73 if (test_thread_flag(TIF_USING_IWMMXT)) {
74 kframe->magic = IWMMXT_MAGIC;
75 kframe->size = IWMMXT_STORAGE_SIZE;
76 iwmmxt_task_copy(current_thread_info(), &kframe->storage);
77 } else {
78 /*
79 * For bug-compatibility with older kernels, some space
80 * has to be reserved for iWMMXt even if it's not used.
81 * Set the magic and size appropriately so that properly
82 * written userspace can skip it reliably:
83 */
84 *kframe = (struct iwmmxt_sigframe) {
85 .magic = DUMMY_MAGIC,
86 .size = IWMMXT_STORAGE_SIZE,
87 };
88 }
89
90 err = __copy_to_user(frame, kframe, sizeof(*kframe));
91
92 return err;
93}
94
95static int restore_iwmmxt_context(char __user **auxp)
96{
97 struct iwmmxt_sigframe __user *frame =
98 (struct iwmmxt_sigframe __user *)*auxp;
99 char kbuf[sizeof(*frame) + 8];
100 struct iwmmxt_sigframe *kframe;
101
102 /* the iWMMXt context must be 64 bit aligned */
103 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
104 if (__copy_from_user(kframe, frame, sizeof(*frame)))
105 return -1;
106
107 /*
108 * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
109 * block is discarded for compatibility with setup_sigframe() if
110 * present, but we don't mandate its presence. If some other
111 * magic is here, it's not for us:
112 */
113 if (!test_thread_flag(TIF_USING_IWMMXT) &&
114 kframe->magic != DUMMY_MAGIC)
115 return 0;
116
117 if (kframe->size != IWMMXT_STORAGE_SIZE)
118 return -1;
119
120 if (test_thread_flag(TIF_USING_IWMMXT)) {
121 if (kframe->magic != IWMMXT_MAGIC)
122 return -1;
123
124 iwmmxt_task_restore(current_thread_info(), &kframe->storage);
125 }
126
127 *auxp += IWMMXT_STORAGE_SIZE;
128 return 0;
129}
130
131#endif
132
133#ifdef CONFIG_VFP
134
135static int preserve_vfp_context(struct vfp_sigframe __user *frame)
136{
137 struct vfp_sigframe kframe;
138 int err = 0;
139
140 memset(&kframe, 0, sizeof(kframe));
141 kframe.magic = VFP_MAGIC;
142 kframe.size = VFP_STORAGE_SIZE;
143
144 err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
145 if (err)
146 return err;
147
148 return __copy_to_user(frame, &kframe, sizeof(kframe));
149}
150
151static int restore_vfp_context(char __user **auxp)
152{
153 struct vfp_sigframe frame;
154 int err;
155
156 err = __copy_from_user(&frame, *auxp, sizeof(frame));
157 if (err)
158 return err;
159
160 if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
161 return -EINVAL;
162
163 *auxp += sizeof(frame);
164 return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
165}
166
167#endif
168
169/*
170 * Do a signal return; undo the signal stack. These are aligned to 64-bit.
171 */
172
173static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
174{
175 struct sigcontext context;
176 char __user *aux;
177 sigset_t set;
178 int err;
179
180 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
181 if (err == 0)
182 set_current_blocked(&set);
183
184 err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
185 if (err == 0) {
186 regs->ARM_r0 = context.arm_r0;
187 regs->ARM_r1 = context.arm_r1;
188 regs->ARM_r2 = context.arm_r2;
189 regs->ARM_r3 = context.arm_r3;
190 regs->ARM_r4 = context.arm_r4;
191 regs->ARM_r5 = context.arm_r5;
192 regs->ARM_r6 = context.arm_r6;
193 regs->ARM_r7 = context.arm_r7;
194 regs->ARM_r8 = context.arm_r8;
195 regs->ARM_r9 = context.arm_r9;
196 regs->ARM_r10 = context.arm_r10;
197 regs->ARM_fp = context.arm_fp;
198 regs->ARM_ip = context.arm_ip;
199 regs->ARM_sp = context.arm_sp;
200 regs->ARM_lr = context.arm_lr;
201 regs->ARM_pc = context.arm_pc;
202 regs->ARM_cpsr = context.arm_cpsr;
203 }
204
205 err |= !valid_user_regs(regs);
206
207 aux = (char __user *) sf->uc.uc_regspace;
208#ifdef CONFIG_CRUNCH
209 if (err == 0)
210 err |= restore_crunch_context(&aux);
211#endif
212#ifdef CONFIG_IWMMXT
213 if (err == 0)
214 err |= restore_iwmmxt_context(&aux);
215#endif
216#ifdef CONFIG_VFP
217 if (err == 0)
218 err |= restore_vfp_context(&aux);
219#endif
220
221 return err;
222}
223
224asmlinkage int sys_sigreturn(struct pt_regs *regs)
225{
226 struct sigframe __user *frame;
227
228 /* Always make any pending restarted system calls return -EINTR */
229 current->restart_block.fn = do_no_restart_syscall;
230
231 /*
232 * Since we stacked the signal on a 64-bit boundary,
233 * then 'sp' should be word aligned here. If it's
234 * not, then the user is trying to mess with us.
235 */
236 if (regs->ARM_sp & 7)
237 goto badframe;
238
239 frame = (struct sigframe __user *)regs->ARM_sp;
240
241 if (!access_ok(frame, sizeof (*frame)))
242 goto badframe;
243
244 if (restore_sigframe(regs, frame))
245 goto badframe;
246
247 return regs->ARM_r0;
248
249badframe:
250 force_sig(SIGSEGV);
251 return 0;
252}
253
254asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
255{
256 struct rt_sigframe __user *frame;
257
258 /* Always make any pending restarted system calls return -EINTR */
259 current->restart_block.fn = do_no_restart_syscall;
260
261 /*
262 * Since we stacked the signal on a 64-bit boundary,
263 * then 'sp' should be word aligned here. If it's
264 * not, then the user is trying to mess with us.
265 */
266 if (regs->ARM_sp & 7)
267 goto badframe;
268
269 frame = (struct rt_sigframe __user *)regs->ARM_sp;
270
271 if (!access_ok(frame, sizeof (*frame)))
272 goto badframe;
273
274 if (restore_sigframe(regs, &frame->sig))
275 goto badframe;
276
277 if (restore_altstack(&frame->sig.uc.uc_stack))
278 goto badframe;
279
280 return regs->ARM_r0;
281
282badframe:
283 force_sig(SIGSEGV);
284 return 0;
285}
286
287static int
288setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
289{
290 struct aux_sigframe __user *aux;
291 struct sigcontext context;
292 int err = 0;
293
294 context = (struct sigcontext) {
295 .arm_r0 = regs->ARM_r0,
296 .arm_r1 = regs->ARM_r1,
297 .arm_r2 = regs->ARM_r2,
298 .arm_r3 = regs->ARM_r3,
299 .arm_r4 = regs->ARM_r4,
300 .arm_r5 = regs->ARM_r5,
301 .arm_r6 = regs->ARM_r6,
302 .arm_r7 = regs->ARM_r7,
303 .arm_r8 = regs->ARM_r8,
304 .arm_r9 = regs->ARM_r9,
305 .arm_r10 = regs->ARM_r10,
306 .arm_fp = regs->ARM_fp,
307 .arm_ip = regs->ARM_ip,
308 .arm_sp = regs->ARM_sp,
309 .arm_lr = regs->ARM_lr,
310 .arm_pc = regs->ARM_pc,
311 .arm_cpsr = regs->ARM_cpsr,
312
313 .trap_no = current->thread.trap_no,
314 .error_code = current->thread.error_code,
315 .fault_address = current->thread.address,
316 .oldmask = set->sig[0],
317 };
318
319 err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
320
321 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
322
323 aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
324#ifdef CONFIG_CRUNCH
325 if (err == 0)
326 err |= preserve_crunch_context(&aux->crunch);
327#endif
328#ifdef CONFIG_IWMMXT
329 if (err == 0)
330 err |= preserve_iwmmxt_context(&aux->iwmmxt);
331#endif
332#ifdef CONFIG_VFP
333 if (err == 0)
334 err |= preserve_vfp_context(&aux->vfp);
335#endif
336 err |= __put_user(0, &aux->end_magic);
337
338 return err;
339}
340
341static inline void __user *
342get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
343{
344 unsigned long sp = sigsp(regs->ARM_sp, ksig);
345 void __user *frame;
346
347 /*
348 * ATPCS B01 mandates 8-byte alignment
349 */
350 frame = (void __user *)((sp - framesize) & ~7);
351
352 /*
353 * Check that we can actually write to the signal frame.
354 */
355 if (!access_ok(frame, framesize))
356 frame = NULL;
357
358 return frame;
359}
360
361static int
362setup_return(struct pt_regs *regs, struct ksignal *ksig,
363 unsigned long __user *rc, void __user *frame)
364{
365 unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
366 unsigned long handler_fdpic_GOT = 0;
367 unsigned long retcode;
368 unsigned int idx, thumb = 0;
369 unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
370 bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
371 (current->personality & FDPIC_FUNCPTRS);
372
373 if (fdpic) {
374 unsigned long __user *fdpic_func_desc =
375 (unsigned long __user *)handler;
376 if (__get_user(handler, &fdpic_func_desc[0]) ||
377 __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
378 return 1;
379 }
380
381 cpsr |= PSR_ENDSTATE;
382
383 /*
384 * Maybe we need to deliver a 32-bit signal to a 26-bit task.
385 */
386 if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
387 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
388
389#ifdef CONFIG_ARM_THUMB
390 if (elf_hwcap & HWCAP_THUMB) {
391 /*
392 * The LSB of the handler determines if we're going to
393 * be using THUMB or ARM mode for this signal handler.
394 */
395 thumb = handler & 1;
396
397 /*
398 * Clear the If-Then Thumb-2 execution state. ARM spec
399 * requires this to be all 000s in ARM mode. Snapdragon
400 * S4/Krait misbehaves on a Thumb=>ARM signal transition
401 * without this.
402 *
403 * We must do this whenever we are running on a Thumb-2
404 * capable CPU, which includes ARMv6T2. However, we elect
405 * to always do this to simplify the code; this field is
406 * marked UNK/SBZP for older architectures.
407 */
408 cpsr &= ~PSR_IT_MASK;
409
410 if (thumb) {
411 cpsr |= PSR_T_BIT;
412 } else
413 cpsr &= ~PSR_T_BIT;
414 }
415#endif
416
417 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
418 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
419 if (fdpic) {
420 /*
421 * We need code to load the function descriptor.
422 * That code follows the standard sigreturn code
423 * (6 words), and is made of 3 + 2 words for each
424 * variant. The 4th copied word is the actual FD
425 * address that the assembly code expects.
426 */
427 idx = 6 + thumb * 3;
428 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
429 idx += 5;
430 if (__put_user(sigreturn_codes[idx], rc ) ||
431 __put_user(sigreturn_codes[idx+1], rc+1) ||
432 __put_user(sigreturn_codes[idx+2], rc+2) ||
433 __put_user(retcode, rc+3))
434 return 1;
435 goto rc_finish;
436 }
437 } else {
438 idx = thumb << 1;
439 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
440 idx += 3;
441
442 /*
443 * Put the sigreturn code on the stack no matter which return
444 * mechanism we use in order to remain ABI compliant
445 */
446 if (__put_user(sigreturn_codes[idx], rc) ||
447 __put_user(sigreturn_codes[idx+1], rc+1))
448 return 1;
449
450rc_finish:
451#ifdef CONFIG_MMU
452 if (cpsr & MODE32_BIT) {
453 struct mm_struct *mm = current->mm;
454
455 /*
456 * 32-bit code can use the signal return page
457 * except when the MPU has protected the vectors
458 * page from PL0
459 */
460 retcode = mm->context.sigpage + signal_return_offset +
461 (idx << 2) + thumb;
462 } else
463#endif
464 {
465 /*
466 * Ensure that the instruction cache sees
467 * the return code written onto the stack.
468 */
469 flush_icache_range((unsigned long)rc,
470 (unsigned long)(rc + 3));
471
472 retcode = ((unsigned long)rc) + thumb;
473 }
474 }
475
476 regs->ARM_r0 = ksig->sig;
477 regs->ARM_sp = (unsigned long)frame;
478 regs->ARM_lr = retcode;
479 regs->ARM_pc = handler;
480 if (fdpic)
481 regs->ARM_r9 = handler_fdpic_GOT;
482 regs->ARM_cpsr = cpsr;
483
484 return 0;
485}
486
487static int
488setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
489{
490 struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
491 int err = 0;
492
493 if (!frame)
494 return 1;
495
496 /*
497 * Set uc.uc_flags to a value which sc.trap_no would never have.
498 */
499 err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
500
501 err |= setup_sigframe(frame, regs, set);
502 if (err == 0)
503 err = setup_return(regs, ksig, frame->retcode, frame);
504
505 return err;
506}
507
508static int
509setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
510{
511 struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
512 int err = 0;
513
514 if (!frame)
515 return 1;
516
517 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
518
519 err |= __put_user(0, &frame->sig.uc.uc_flags);
520 err |= __put_user(NULL, &frame->sig.uc.uc_link);
521
522 err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
523 err |= setup_sigframe(&frame->sig, regs, set);
524 if (err == 0)
525 err = setup_return(regs, ksig, frame->sig.retcode, frame);
526
527 if (err == 0) {
528 /*
529 * For realtime signals we must also set the second and third
530 * arguments for the signal handler.
531 * -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
532 */
533 regs->ARM_r1 = (unsigned long)&frame->info;
534 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
535 }
536
537 return err;
538}
539
540/*
541 * OK, we're invoking a handler
542 */
543static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
544{
545 sigset_t *oldset = sigmask_to_save();
546 int ret;
547
548 /*
549 * Perform fixup for the pre-signal frame.
550 */
551 rseq_signal_deliver(ksig, regs);
552
553 /*
554 * Set up the stack frame
555 */
556 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
557 ret = setup_rt_frame(ksig, oldset, regs);
558 else
559 ret = setup_frame(ksig, oldset, regs);
560
561 /*
562 * Check that the resulting registers are actually sane.
563 */
564 ret |= !valid_user_regs(regs);
565
566 signal_setup_done(ret, ksig, 0);
567}
568
569/*
570 * Note that 'init' is a special process: it doesn't get signals it doesn't
571 * want to handle. Thus you cannot kill init even with a SIGKILL even by
572 * mistake.
573 *
574 * Note that we go through the signals twice: once to check the signals that
575 * the kernel can handle, and then we build all the user-level signal handling
576 * stack-frames in one go after that.
577 */
578static int do_signal(struct pt_regs *regs, int syscall)
579{
580 unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
581 struct ksignal ksig;
582 int restart = 0;
583
584 /*
585 * If we were from a system call, check for system call restarting...
586 */
587 if (syscall) {
588 continue_addr = regs->ARM_pc;
589 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
590 retval = regs->ARM_r0;
591
592 /*
593 * Prepare for system call restart. We do this here so that a
594 * debugger will see the already changed PSW.
595 */
596 switch (retval) {
597 case -ERESTART_RESTARTBLOCK:
598 restart -= 2;
599 fallthrough;
600 case -ERESTARTNOHAND:
601 case -ERESTARTSYS:
602 case -ERESTARTNOINTR:
603 restart++;
604 regs->ARM_r0 = regs->ARM_ORIG_r0;
605 regs->ARM_pc = restart_addr;
606 break;
607 }
608 }
609
610 /*
611 * Get the signal to deliver. When running under ptrace, at this
612 * point the debugger may change all our registers ...
613 */
614 /*
615 * Depending on the signal settings we may need to revert the
616 * decision to restart the system call. But skip this if a
617 * debugger has chosen to restart at a different PC.
618 */
619 if (get_signal(&ksig)) {
620 /* handler */
621 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
622 if (retval == -ERESTARTNOHAND ||
623 retval == -ERESTART_RESTARTBLOCK
624 || (retval == -ERESTARTSYS
625 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
626 regs->ARM_r0 = -EINTR;
627 regs->ARM_pc = continue_addr;
628 }
629 }
630 handle_signal(&ksig, regs);
631 } else {
632 /* no handler */
633 restore_saved_sigmask();
634 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
635 regs->ARM_pc = continue_addr;
636 return restart;
637 }
638 }
639 return 0;
640}
641
642asmlinkage int
643do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
644{
645 /*
646 * The assembly code enters us with IRQs off, but it hasn't
647 * informed the tracing code of that for efficiency reasons.
648 * Update the trace code with the current status.
649 */
650 trace_hardirqs_off();
651 do {
652 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
653 schedule();
654 } else {
655 if (unlikely(!user_mode(regs)))
656 return 0;
657 local_irq_enable();
658 if (thread_flags & _TIF_SIGPENDING) {
659 int restart = do_signal(regs, syscall);
660 if (unlikely(restart)) {
661 /*
662 * Restart without handlers.
663 * Deal with it without leaving
664 * the kernel space.
665 */
666 return restart;
667 }
668 syscall = 0;
669 } else if (thread_flags & _TIF_UPROBE) {
670 uprobe_notify_resume(regs);
671 } else {
672 clear_thread_flag(TIF_NOTIFY_RESUME);
673 tracehook_notify_resume(regs);
674 rseq_handle_notify_resume(NULL, regs);
675 }
676 }
677 local_irq_disable();
678 thread_flags = current_thread_info()->flags;
679 } while (thread_flags & _TIF_WORK_MASK);
680 return 0;
681}
682
683struct page *get_signal_page(void)
684{
685 unsigned long ptr;
686 unsigned offset;
687 struct page *page;
688 void *addr;
689
690 page = alloc_pages(GFP_KERNEL, 0);
691
692 if (!page)
693 return NULL;
694
695 addr = page_address(page);
696
697 /* Give the signal return code some randomness */
698 offset = 0x200 + (get_random_int() & 0x7fc);
699 signal_return_offset = offset;
700
701 /*
702 * Copy signal return handlers into the vector page, and
703 * set sigreturn to be a pointer to these.
704 */
705 memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
706
707 ptr = (unsigned long)addr + offset;
708 flush_icache_range(ptr, ptr + sizeof(sigreturn_codes));
709
710 return page;
711}
712
713/* Defer to generic check */
714asmlinkage void addr_limit_check_failed(void)
715{
716#ifdef CONFIG_MMU
717 addr_limit_user_check();
718#endif
719}
720
721#ifdef CONFIG_DEBUG_RSEQ
722asmlinkage void do_rseq_syscall(struct pt_regs *regs)
723{
724 rseq_syscall(regs);
725}
726#endif
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/arch/arm/kernel/signal.c
4 *
5 * Copyright (C) 1995-2009 Russell King
6 */
7#include <linux/errno.h>
8#include <linux/random.h>
9#include <linux/signal.h>
10#include <linux/personality.h>
11#include <linux/uaccess.h>
12#include <linux/resume_user_mode.h>
13#include <linux/uprobes.h>
14#include <linux/syscalls.h>
15
16#include <asm/elf.h>
17#include <asm/cacheflush.h>
18#include <asm/traps.h>
19#include <asm/unistd.h>
20#include <asm/vfp.h>
21
22#include "signal.h"
23
24extern const unsigned long sigreturn_codes[17];
25
26static unsigned long signal_return_offset;
27
28#ifdef CONFIG_IWMMXT
29
30static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
31{
32 char kbuf[sizeof(*frame) + 8];
33 struct iwmmxt_sigframe *kframe;
34 int err = 0;
35
36 /* the iWMMXt context must be 64 bit aligned */
37 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
38
39 if (test_thread_flag(TIF_USING_IWMMXT)) {
40 kframe->magic = IWMMXT_MAGIC;
41 kframe->size = IWMMXT_STORAGE_SIZE;
42 iwmmxt_task_copy(current_thread_info(), &kframe->storage);
43 } else {
44 /*
45 * For bug-compatibility with older kernels, some space
46 * has to be reserved for iWMMXt even if it's not used.
47 * Set the magic and size appropriately so that properly
48 * written userspace can skip it reliably:
49 */
50 *kframe = (struct iwmmxt_sigframe) {
51 .magic = DUMMY_MAGIC,
52 .size = IWMMXT_STORAGE_SIZE,
53 };
54 }
55
56 err = __copy_to_user(frame, kframe, sizeof(*kframe));
57
58 return err;
59}
60
61static int restore_iwmmxt_context(char __user **auxp)
62{
63 struct iwmmxt_sigframe __user *frame =
64 (struct iwmmxt_sigframe __user *)*auxp;
65 char kbuf[sizeof(*frame) + 8];
66 struct iwmmxt_sigframe *kframe;
67
68 /* the iWMMXt context must be 64 bit aligned */
69 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
70 if (__copy_from_user(kframe, frame, sizeof(*frame)))
71 return -1;
72
73 /*
74 * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy
75 * block is discarded for compatibility with setup_sigframe() if
76 * present, but we don't mandate its presence. If some other
77 * magic is here, it's not for us:
78 */
79 if (!test_thread_flag(TIF_USING_IWMMXT) &&
80 kframe->magic != DUMMY_MAGIC)
81 return 0;
82
83 if (kframe->size != IWMMXT_STORAGE_SIZE)
84 return -1;
85
86 if (test_thread_flag(TIF_USING_IWMMXT)) {
87 if (kframe->magic != IWMMXT_MAGIC)
88 return -1;
89
90 iwmmxt_task_restore(current_thread_info(), &kframe->storage);
91 }
92
93 *auxp += IWMMXT_STORAGE_SIZE;
94 return 0;
95}
96
97#endif
98
99#ifdef CONFIG_VFP
100
101static int preserve_vfp_context(struct vfp_sigframe __user *frame)
102{
103 struct vfp_sigframe kframe;
104 int err = 0;
105
106 memset(&kframe, 0, sizeof(kframe));
107 kframe.magic = VFP_MAGIC;
108 kframe.size = VFP_STORAGE_SIZE;
109
110 err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
111 if (err)
112 return err;
113
114 return __copy_to_user(frame, &kframe, sizeof(kframe));
115}
116
117static int restore_vfp_context(char __user **auxp)
118{
119 struct vfp_sigframe frame;
120 int err;
121
122 err = __copy_from_user(&frame, *auxp, sizeof(frame));
123 if (err)
124 return err;
125
126 if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
127 return -EINVAL;
128
129 *auxp += sizeof(frame);
130 return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
131}
132
133#endif
134
135/*
136 * Do a signal return; undo the signal stack. These are aligned to 64-bit.
137 */
138
139static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
140{
141 struct sigcontext context;
142 char __user *aux;
143 sigset_t set;
144 int err;
145
146 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
147 if (err == 0)
148 set_current_blocked(&set);
149
150 err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
151 if (err == 0) {
152 regs->ARM_r0 = context.arm_r0;
153 regs->ARM_r1 = context.arm_r1;
154 regs->ARM_r2 = context.arm_r2;
155 regs->ARM_r3 = context.arm_r3;
156 regs->ARM_r4 = context.arm_r4;
157 regs->ARM_r5 = context.arm_r5;
158 regs->ARM_r6 = context.arm_r6;
159 regs->ARM_r7 = context.arm_r7;
160 regs->ARM_r8 = context.arm_r8;
161 regs->ARM_r9 = context.arm_r9;
162 regs->ARM_r10 = context.arm_r10;
163 regs->ARM_fp = context.arm_fp;
164 regs->ARM_ip = context.arm_ip;
165 regs->ARM_sp = context.arm_sp;
166 regs->ARM_lr = context.arm_lr;
167 regs->ARM_pc = context.arm_pc;
168 regs->ARM_cpsr = context.arm_cpsr;
169 }
170
171 err |= !valid_user_regs(regs);
172
173 aux = (char __user *) sf->uc.uc_regspace;
174#ifdef CONFIG_IWMMXT
175 if (err == 0)
176 err |= restore_iwmmxt_context(&aux);
177#endif
178#ifdef CONFIG_VFP
179 if (err == 0)
180 err |= restore_vfp_context(&aux);
181#endif
182
183 return err;
184}
185
186asmlinkage int sys_sigreturn(struct pt_regs *regs)
187{
188 struct sigframe __user *frame;
189
190 /* Always make any pending restarted system calls return -EINTR */
191 current->restart_block.fn = do_no_restart_syscall;
192
193 /*
194 * Since we stacked the signal on a 64-bit boundary,
195 * then 'sp' should be word aligned here. If it's
196 * not, then the user is trying to mess with us.
197 */
198 if (regs->ARM_sp & 7)
199 goto badframe;
200
201 frame = (struct sigframe __user *)regs->ARM_sp;
202
203 if (!access_ok(frame, sizeof (*frame)))
204 goto badframe;
205
206 if (restore_sigframe(regs, frame))
207 goto badframe;
208
209 return regs->ARM_r0;
210
211badframe:
212 force_sig(SIGSEGV);
213 return 0;
214}
215
216asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
217{
218 struct rt_sigframe __user *frame;
219
220 /* Always make any pending restarted system calls return -EINTR */
221 current->restart_block.fn = do_no_restart_syscall;
222
223 /*
224 * Since we stacked the signal on a 64-bit boundary,
225 * then 'sp' should be word aligned here. If it's
226 * not, then the user is trying to mess with us.
227 */
228 if (regs->ARM_sp & 7)
229 goto badframe;
230
231 frame = (struct rt_sigframe __user *)regs->ARM_sp;
232
233 if (!access_ok(frame, sizeof (*frame)))
234 goto badframe;
235
236 if (restore_sigframe(regs, &frame->sig))
237 goto badframe;
238
239 if (restore_altstack(&frame->sig.uc.uc_stack))
240 goto badframe;
241
242 return regs->ARM_r0;
243
244badframe:
245 force_sig(SIGSEGV);
246 return 0;
247}
248
249static int
250setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
251{
252 struct aux_sigframe __user *aux;
253 struct sigcontext context;
254 int err = 0;
255
256 context = (struct sigcontext) {
257 .arm_r0 = regs->ARM_r0,
258 .arm_r1 = regs->ARM_r1,
259 .arm_r2 = regs->ARM_r2,
260 .arm_r3 = regs->ARM_r3,
261 .arm_r4 = regs->ARM_r4,
262 .arm_r5 = regs->ARM_r5,
263 .arm_r6 = regs->ARM_r6,
264 .arm_r7 = regs->ARM_r7,
265 .arm_r8 = regs->ARM_r8,
266 .arm_r9 = regs->ARM_r9,
267 .arm_r10 = regs->ARM_r10,
268 .arm_fp = regs->ARM_fp,
269 .arm_ip = regs->ARM_ip,
270 .arm_sp = regs->ARM_sp,
271 .arm_lr = regs->ARM_lr,
272 .arm_pc = regs->ARM_pc,
273 .arm_cpsr = regs->ARM_cpsr,
274
275 .trap_no = current->thread.trap_no,
276 .error_code = current->thread.error_code,
277 .fault_address = current->thread.address,
278 .oldmask = set->sig[0],
279 };
280
281 err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
282
283 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
284
285 aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
286#ifdef CONFIG_IWMMXT
287 if (err == 0)
288 err |= preserve_iwmmxt_context(&aux->iwmmxt);
289#endif
290#ifdef CONFIG_VFP
291 if (err == 0)
292 err |= preserve_vfp_context(&aux->vfp);
293#endif
294 err |= __put_user(0, &aux->end_magic);
295
296 return err;
297}
298
299static inline void __user *
300get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
301{
302 unsigned long sp = sigsp(regs->ARM_sp, ksig);
303 void __user *frame;
304
305 /*
306 * ATPCS B01 mandates 8-byte alignment
307 */
308 frame = (void __user *)((sp - framesize) & ~7);
309
310 /*
311 * Check that we can actually write to the signal frame.
312 */
313 if (!access_ok(frame, framesize))
314 frame = NULL;
315
316 return frame;
317}
318
319static int
320setup_return(struct pt_regs *regs, struct ksignal *ksig,
321 unsigned long __user *rc, void __user *frame)
322{
323 unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
324 unsigned long handler_fdpic_GOT = 0;
325 unsigned long retcode;
326 unsigned int idx, thumb = 0;
327 unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
328 bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
329 (current->personality & FDPIC_FUNCPTRS);
330
331 if (fdpic) {
332 unsigned long __user *fdpic_func_desc =
333 (unsigned long __user *)handler;
334 if (__get_user(handler, &fdpic_func_desc[0]) ||
335 __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
336 return 1;
337 }
338
339 cpsr |= PSR_ENDSTATE;
340
341 /*
342 * Maybe we need to deliver a 32-bit signal to a 26-bit task.
343 */
344 if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
345 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
346
347#ifdef CONFIG_ARM_THUMB
348 if (elf_hwcap & HWCAP_THUMB) {
349 /*
350 * The LSB of the handler determines if we're going to
351 * be using THUMB or ARM mode for this signal handler.
352 */
353 thumb = handler & 1;
354
355 /*
356 * Clear the If-Then Thumb-2 execution state. ARM spec
357 * requires this to be all 000s in ARM mode. Snapdragon
358 * S4/Krait misbehaves on a Thumb=>ARM signal transition
359 * without this.
360 *
361 * We must do this whenever we are running on a Thumb-2
362 * capable CPU, which includes ARMv6T2. However, we elect
363 * to always do this to simplify the code; this field is
364 * marked UNK/SBZP for older architectures.
365 */
366 cpsr &= ~PSR_IT_MASK;
367
368 if (thumb) {
369 cpsr |= PSR_T_BIT;
370 } else
371 cpsr &= ~PSR_T_BIT;
372 }
373#endif
374
375 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
376 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
377 if (fdpic) {
378 /*
379 * We need code to load the function descriptor.
380 * That code follows the standard sigreturn code
381 * (6 words), and is made of 3 + 2 words for each
382 * variant. The 4th copied word is the actual FD
383 * address that the assembly code expects.
384 */
385 idx = 6 + thumb * 3;
386 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
387 idx += 5;
388 if (__put_user(sigreturn_codes[idx], rc ) ||
389 __put_user(sigreturn_codes[idx+1], rc+1) ||
390 __put_user(sigreturn_codes[idx+2], rc+2) ||
391 __put_user(retcode, rc+3))
392 return 1;
393 goto rc_finish;
394 }
395 } else {
396 idx = thumb << 1;
397 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
398 idx += 3;
399
400 /*
401 * Put the sigreturn code on the stack no matter which return
402 * mechanism we use in order to remain ABI compliant
403 */
404 if (__put_user(sigreturn_codes[idx], rc) ||
405 __put_user(sigreturn_codes[idx+1], rc+1))
406 return 1;
407
408rc_finish:
409#ifdef CONFIG_MMU
410 if (cpsr & MODE32_BIT) {
411 struct mm_struct *mm = current->mm;
412
413 /*
414 * 32-bit code can use the signal return page
415 * except when the MPU has protected the vectors
416 * page from PL0
417 */
418 retcode = mm->context.sigpage + signal_return_offset +
419 (idx << 2) + thumb;
420 } else
421#endif
422 {
423 /*
424 * Ensure that the instruction cache sees
425 * the return code written onto the stack.
426 */
427 flush_icache_range((unsigned long)rc,
428 (unsigned long)(rc + 3));
429
430 retcode = ((unsigned long)rc) + thumb;
431 }
432 }
433
434 regs->ARM_r0 = ksig->sig;
435 regs->ARM_sp = (unsigned long)frame;
436 regs->ARM_lr = retcode;
437 regs->ARM_pc = handler;
438 if (fdpic)
439 regs->ARM_r9 = handler_fdpic_GOT;
440 regs->ARM_cpsr = cpsr;
441
442 return 0;
443}
444
445static int
446setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
447{
448 struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
449 int err = 0;
450
451 if (!frame)
452 return 1;
453
454 /*
455 * Set uc.uc_flags to a value which sc.trap_no would never have.
456 */
457 err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
458
459 err |= setup_sigframe(frame, regs, set);
460 if (err == 0)
461 err = setup_return(regs, ksig, frame->retcode, frame);
462
463 return err;
464}
465
466static int
467setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
468{
469 struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
470 int err = 0;
471
472 if (!frame)
473 return 1;
474
475 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
476
477 err |= __put_user(0, &frame->sig.uc.uc_flags);
478 err |= __put_user(NULL, &frame->sig.uc.uc_link);
479
480 err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
481 err |= setup_sigframe(&frame->sig, regs, set);
482 if (err == 0)
483 err = setup_return(regs, ksig, frame->sig.retcode, frame);
484
485 if (err == 0) {
486 /*
487 * For realtime signals we must also set the second and third
488 * arguments for the signal handler.
489 * -- Peter Maydell <pmaydell@chiark.greenend.org.uk> 2000-12-06
490 */
491 regs->ARM_r1 = (unsigned long)&frame->info;
492 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
493 }
494
495 return err;
496}
497
498/*
499 * OK, we're invoking a handler
500 */
501static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
502{
503 sigset_t *oldset = sigmask_to_save();
504 int ret;
505
506 /*
507 * Perform fixup for the pre-signal frame.
508 */
509 rseq_signal_deliver(ksig, regs);
510
511 /*
512 * Set up the stack frame
513 */
514 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
515 ret = setup_rt_frame(ksig, oldset, regs);
516 else
517 ret = setup_frame(ksig, oldset, regs);
518
519 /*
520 * Check that the resulting registers are actually sane.
521 */
522 ret |= !valid_user_regs(regs);
523
524 signal_setup_done(ret, ksig, 0);
525}
526
527/*
528 * Note that 'init' is a special process: it doesn't get signals it doesn't
529 * want to handle. Thus you cannot kill init even with a SIGKILL even by
530 * mistake.
531 *
532 * Note that we go through the signals twice: once to check the signals that
533 * the kernel can handle, and then we build all the user-level signal handling
534 * stack-frames in one go after that.
535 */
536static int do_signal(struct pt_regs *regs, int syscall)
537{
538 unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
539 struct ksignal ksig;
540 int restart = 0;
541
542 /*
543 * If we were from a system call, check for system call restarting...
544 */
545 if (syscall) {
546 continue_addr = regs->ARM_pc;
547 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
548 retval = regs->ARM_r0;
549
550 /*
551 * Prepare for system call restart. We do this here so that a
552 * debugger will see the already changed PSW.
553 */
554 switch (retval) {
555 case -ERESTART_RESTARTBLOCK:
556 restart -= 2;
557 fallthrough;
558 case -ERESTARTNOHAND:
559 case -ERESTARTSYS:
560 case -ERESTARTNOINTR:
561 restart++;
562 regs->ARM_r0 = regs->ARM_ORIG_r0;
563 regs->ARM_pc = restart_addr;
564 break;
565 }
566 }
567
568 /*
569 * Get the signal to deliver. When running under ptrace, at this
570 * point the debugger may change all our registers ...
571 */
572 /*
573 * Depending on the signal settings we may need to revert the
574 * decision to restart the system call. But skip this if a
575 * debugger has chosen to restart at a different PC.
576 */
577 if (get_signal(&ksig)) {
578 /* handler */
579 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
580 if (retval == -ERESTARTNOHAND ||
581 retval == -ERESTART_RESTARTBLOCK
582 || (retval == -ERESTARTSYS
583 && !(ksig.ka.sa.sa_flags & SA_RESTART))) {
584 regs->ARM_r0 = -EINTR;
585 regs->ARM_pc = continue_addr;
586 }
587 }
588 handle_signal(&ksig, regs);
589 } else {
590 /* no handler */
591 restore_saved_sigmask();
592 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
593 regs->ARM_pc = continue_addr;
594 return restart;
595 }
596 }
597 return 0;
598}
599
600asmlinkage int
601do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
602{
603 /*
604 * The assembly code enters us with IRQs off, but it hasn't
605 * informed the tracing code of that for efficiency reasons.
606 * Update the trace code with the current status.
607 */
608 trace_hardirqs_off();
609 do {
610 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
611 schedule();
612 } else {
613 if (unlikely(!user_mode(regs)))
614 return 0;
615 local_irq_enable();
616 if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
617 int restart = do_signal(regs, syscall);
618 if (unlikely(restart)) {
619 /*
620 * Restart without handlers.
621 * Deal with it without leaving
622 * the kernel space.
623 */
624 return restart;
625 }
626 syscall = 0;
627 } else if (thread_flags & _TIF_UPROBE) {
628 uprobe_notify_resume(regs);
629 } else {
630 resume_user_mode_work(regs);
631 }
632 }
633 local_irq_disable();
634 thread_flags = read_thread_flags();
635 } while (thread_flags & _TIF_WORK_MASK);
636 return 0;
637}
638
639struct page *get_signal_page(void)
640{
641 unsigned long ptr;
642 unsigned offset;
643 struct page *page;
644 void *addr;
645
646 page = alloc_pages(GFP_KERNEL, 0);
647
648 if (!page)
649 return NULL;
650
651 addr = page_address(page);
652
653 /* Poison the entire page */
654 memset32(addr, __opcode_to_mem_arm(0xe7fddef1),
655 PAGE_SIZE / sizeof(u32));
656
657 /* Give the signal return code some randomness */
658 offset = 0x200 + (get_random_u16() & 0x7fc);
659 signal_return_offset = offset;
660
661 /* Copy signal return handlers into the page */
662 memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
663
664 /* Flush out all instructions in this page */
665 ptr = (unsigned long)addr;
666 flush_icache_range(ptr, ptr + PAGE_SIZE);
667
668 return page;
669}
670
671#ifdef CONFIG_DEBUG_RSEQ
672asmlinkage void do_rseq_syscall(struct pt_regs *regs)
673{
674 rseq_syscall(regs);
675}
676#endif
677
678/*
679 * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
680 * changes likely come with new fields that should be added below.
681 */
682static_assert(NSIGILL == 11);
683static_assert(NSIGFPE == 15);
684static_assert(NSIGSEGV == 9);
685static_assert(NSIGBUS == 5);
686static_assert(NSIGTRAP == 6);
687static_assert(NSIGCHLD == 6);
688static_assert(NSIGSYS == 2);
689static_assert(sizeof(siginfo_t) == 128);
690static_assert(__alignof__(siginfo_t) == 4);
691static_assert(offsetof(siginfo_t, si_signo) == 0x00);
692static_assert(offsetof(siginfo_t, si_errno) == 0x04);
693static_assert(offsetof(siginfo_t, si_code) == 0x08);
694static_assert(offsetof(siginfo_t, si_pid) == 0x0c);
695static_assert(offsetof(siginfo_t, si_uid) == 0x10);
696static_assert(offsetof(siginfo_t, si_tid) == 0x0c);
697static_assert(offsetof(siginfo_t, si_overrun) == 0x10);
698static_assert(offsetof(siginfo_t, si_status) == 0x14);
699static_assert(offsetof(siginfo_t, si_utime) == 0x18);
700static_assert(offsetof(siginfo_t, si_stime) == 0x1c);
701static_assert(offsetof(siginfo_t, si_value) == 0x14);
702static_assert(offsetof(siginfo_t, si_int) == 0x14);
703static_assert(offsetof(siginfo_t, si_ptr) == 0x14);
704static_assert(offsetof(siginfo_t, si_addr) == 0x0c);
705static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10);
706static_assert(offsetof(siginfo_t, si_lower) == 0x14);
707static_assert(offsetof(siginfo_t, si_upper) == 0x18);
708static_assert(offsetof(siginfo_t, si_pkey) == 0x14);
709static_assert(offsetof(siginfo_t, si_perf_data) == 0x10);
710static_assert(offsetof(siginfo_t, si_perf_type) == 0x14);
711static_assert(offsetof(siginfo_t, si_perf_flags) == 0x18);
712static_assert(offsetof(siginfo_t, si_band) == 0x0c);
713static_assert(offsetof(siginfo_t, si_fd) == 0x10);
714static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c);
715static_assert(offsetof(siginfo_t, si_syscall) == 0x10);
716static_assert(offsetof(siginfo_t, si_arch) == 0x14);