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