1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/arch/arm/kernel/signal.c
5 * Copyright (C) 1995-2009 Russell King
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>
17 #include <asm/cacheflush.h>
18 #include <asm/traps.h>
19 #include <asm/unistd.h>
24 extern const unsigned long sigreturn_codes[17];
26 static unsigned long signal_return_offset;
30 static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame)
32 char kbuf[sizeof(*frame) + 8];
33 struct iwmmxt_sigframe *kframe;
36 /* the iWMMXt context must be 64 bit aligned */
37 kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7);
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);
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:
50 *kframe = (struct iwmmxt_sigframe) {
52 .size = IWMMXT_STORAGE_SIZE,
56 err = __copy_to_user(frame, kframe, sizeof(*kframe));
61 static int restore_iwmmxt_context(char __user **auxp)
63 struct iwmmxt_sigframe __user *frame =
64 (struct iwmmxt_sigframe __user *)*auxp;
65 char kbuf[sizeof(*frame) + 8];
66 struct iwmmxt_sigframe *kframe;
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)))
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:
79 if (!test_thread_flag(TIF_USING_IWMMXT) &&
80 kframe->magic != DUMMY_MAGIC)
83 if (kframe->size != IWMMXT_STORAGE_SIZE)
86 if (test_thread_flag(TIF_USING_IWMMXT)) {
87 if (kframe->magic != IWMMXT_MAGIC)
90 iwmmxt_task_restore(current_thread_info(), &kframe->storage);
93 *auxp += IWMMXT_STORAGE_SIZE;
101 static int preserve_vfp_context(struct vfp_sigframe __user *frame)
103 struct vfp_sigframe kframe;
106 memset(&kframe, 0, sizeof(kframe));
107 kframe.magic = VFP_MAGIC;
108 kframe.size = VFP_STORAGE_SIZE;
110 err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc);
114 return __copy_to_user(frame, &kframe, sizeof(kframe));
117 static int restore_vfp_context(char __user **auxp)
119 struct vfp_sigframe frame;
122 err = __copy_from_user(&frame, *auxp, sizeof(frame));
126 if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE)
129 *auxp += sizeof(frame);
130 return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc);
136 * Do a signal return; undo the signal stack. These are aligned to 64-bit.
139 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
141 struct sigcontext context;
146 err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
148 set_current_blocked(&set);
150 err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context));
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;
171 err |= !valid_user_regs(regs);
173 aux = (char __user *) sf->uc.uc_regspace;
176 err |= restore_iwmmxt_context(&aux);
180 err |= restore_vfp_context(&aux);
186 asmlinkage int sys_sigreturn(struct pt_regs *regs)
188 struct sigframe __user *frame;
190 /* Always make any pending restarted system calls return -EINTR */
191 current->restart_block.fn = do_no_restart_syscall;
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.
198 if (regs->ARM_sp & 7)
201 frame = (struct sigframe __user *)regs->ARM_sp;
203 if (!access_ok(frame, sizeof (*frame)))
206 if (restore_sigframe(regs, frame))
216 asmlinkage int sys_rt_sigreturn(struct pt_regs *regs)
218 struct rt_sigframe __user *frame;
220 /* Always make any pending restarted system calls return -EINTR */
221 current->restart_block.fn = do_no_restart_syscall;
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.
228 if (regs->ARM_sp & 7)
231 frame = (struct rt_sigframe __user *)regs->ARM_sp;
233 if (!access_ok(frame, sizeof (*frame)))
236 if (restore_sigframe(regs, &frame->sig))
239 if (restore_altstack(&frame->sig.uc.uc_stack))
250 setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set)
252 struct aux_sigframe __user *aux;
253 struct sigcontext context;
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,
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],
281 err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context));
283 err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
285 aux = (struct aux_sigframe __user *) sf->uc.uc_regspace;
288 err |= preserve_iwmmxt_context(&aux->iwmmxt);
292 err |= preserve_vfp_context(&aux->vfp);
294 err |= __put_user(0, &aux->end_magic);
299 static inline void __user *
300 get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize)
302 unsigned long sp = sigsp(regs->ARM_sp, ksig);
306 * ATPCS B01 mandates 8-byte alignment
308 frame = (void __user *)((sp - framesize) & ~7);
311 * Check that we can actually write to the signal frame.
313 if (!access_ok(frame, framesize))
320 setup_return(struct pt_regs *regs, struct ksignal *ksig,
321 unsigned long __user *rc, void __user *frame)
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);
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]))
339 cpsr |= PSR_ENDSTATE;
342 * Maybe we need to deliver a 32-bit signal to a 26-bit task.
344 if (ksig->ka.sa.sa_flags & SA_THIRTYTWO)
345 cpsr = (cpsr & ~MODE_MASK) | USR_MODE;
347 #ifdef CONFIG_ARM_THUMB
348 if (elf_hwcap & HWCAP_THUMB) {
350 * The LSB of the handler determines if we're going to
351 * be using THUMB or ARM mode for this signal handler.
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
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.
366 cpsr &= ~PSR_IT_MASK;
375 if (ksig->ka.sa.sa_flags & SA_RESTORER) {
376 retcode = (unsigned long)ksig->ka.sa.sa_restorer;
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.
386 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
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))
397 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
401 * Put the sigreturn code on the stack no matter which return
402 * mechanism we use in order to remain ABI compliant
404 if (__put_user(sigreturn_codes[idx], rc) ||
405 __put_user(sigreturn_codes[idx+1], rc+1))
410 if (cpsr & MODE32_BIT) {
411 struct mm_struct *mm = current->mm;
414 * 32-bit code can use the signal return page
415 * except when the MPU has protected the vectors
418 retcode = mm->context.sigpage + signal_return_offset +
424 * Ensure that the instruction cache sees
425 * the return code written onto the stack.
427 flush_icache_range((unsigned long)rc,
428 (unsigned long)(rc + 3));
430 retcode = ((unsigned long)rc) + thumb;
434 regs->ARM_r0 = ksig->sig;
435 regs->ARM_sp = (unsigned long)frame;
436 regs->ARM_lr = retcode;
437 regs->ARM_pc = handler;
439 regs->ARM_r9 = handler_fdpic_GOT;
440 regs->ARM_cpsr = cpsr;
446 setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
448 struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
455 * Set uc.uc_flags to a value which sc.trap_no would never have.
457 err = __put_user(0x5ac3c35a, &frame->uc.uc_flags);
459 err |= setup_sigframe(frame, regs, set);
461 err = setup_return(regs, ksig, frame->retcode, frame);
467 setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)
469 struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame));
475 err |= copy_siginfo_to_user(&frame->info, &ksig->info);
477 err |= __put_user(0, &frame->sig.uc.uc_flags);
478 err |= __put_user(NULL, &frame->sig.uc.uc_link);
480 err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp);
481 err |= setup_sigframe(&frame->sig, regs, set);
483 err = setup_return(regs, ksig, frame->sig.retcode, frame);
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
491 regs->ARM_r1 = (unsigned long)&frame->info;
492 regs->ARM_r2 = (unsigned long)&frame->sig.uc;
499 * OK, we're invoking a handler
501 static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
503 sigset_t *oldset = sigmask_to_save();
507 * Perform fixup for the pre-signal frame.
509 rseq_signal_deliver(ksig, regs);
512 * Set up the stack frame
514 if (ksig->ka.sa.sa_flags & SA_SIGINFO)
515 ret = setup_rt_frame(ksig, oldset, regs);
517 ret = setup_frame(ksig, oldset, regs);
520 * Check that the resulting registers are actually sane.
522 ret |= !valid_user_regs(regs);
524 signal_setup_done(ret, ksig, 0);
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
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.
536 static int do_signal(struct pt_regs *regs, int syscall)
538 unsigned int retval = 0, continue_addr = 0, restart_addr = 0;
543 * If we were from a system call, check for system call restarting...
546 continue_addr = regs->ARM_pc;
547 restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4);
548 retval = regs->ARM_r0;
551 * Prepare for system call restart. We do this here so that a
552 * debugger will see the already changed PSW.
555 case -ERESTART_RESTARTBLOCK:
558 case -ERESTARTNOHAND:
560 case -ERESTARTNOINTR:
562 regs->ARM_r0 = regs->ARM_ORIG_r0;
563 regs->ARM_pc = restart_addr;
569 * Get the signal to deliver. When running under ptrace, at this
570 * point the debugger may change all our registers ...
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.
577 if (get_signal(&ksig)) {
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;
588 handle_signal(&ksig, regs);
591 restore_saved_sigmask();
592 if (unlikely(restart) && regs->ARM_pc == restart_addr) {
593 regs->ARM_pc = continue_addr;
601 do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)
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.
608 trace_hardirqs_off();
610 if (likely(thread_flags & _TIF_NEED_RESCHED)) {
613 if (unlikely(!user_mode(regs)))
616 if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) {
617 int restart = do_signal(regs, syscall);
618 if (unlikely(restart)) {
620 * Restart without handlers.
621 * Deal with it without leaving
627 } else if (thread_flags & _TIF_UPROBE) {
628 uprobe_notify_resume(regs);
630 resume_user_mode_work(regs);
634 thread_flags = read_thread_flags();
635 } while (thread_flags & _TIF_WORK_MASK);
639 struct page *get_signal_page(void)
646 page = alloc_pages(GFP_KERNEL, 0);
651 addr = page_address(page);
653 /* Poison the entire page */
654 memset32(addr, __opcode_to_mem_arm(0xe7fddef1),
655 PAGE_SIZE / sizeof(u32));
657 /* Give the signal return code some randomness */
658 offset = 0x200 + (get_random_int() & 0x7fc);
659 signal_return_offset = offset;
661 /* Copy signal return handlers into the page */
662 memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes));
664 /* Flush out all instructions in this page */
665 ptr = (unsigned long)addr;
666 flush_icache_range(ptr, ptr + PAGE_SIZE);
671 #ifdef CONFIG_DEBUG_RSEQ
672 asmlinkage void do_rseq_syscall(struct pt_regs *regs)
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.
682 static_assert(NSIGILL == 11);
683 static_assert(NSIGFPE == 15);
684 static_assert(NSIGSEGV == 9);
685 static_assert(NSIGBUS == 5);
686 static_assert(NSIGTRAP == 6);
687 static_assert(NSIGCHLD == 6);
688 static_assert(NSIGSYS == 2);
689 static_assert(sizeof(siginfo_t) == 128);
690 static_assert(__alignof__(siginfo_t) == 4);
691 static_assert(offsetof(siginfo_t, si_signo) == 0x00);
692 static_assert(offsetof(siginfo_t, si_errno) == 0x04);
693 static_assert(offsetof(siginfo_t, si_code) == 0x08);
694 static_assert(offsetof(siginfo_t, si_pid) == 0x0c);
695 static_assert(offsetof(siginfo_t, si_uid) == 0x10);
696 static_assert(offsetof(siginfo_t, si_tid) == 0x0c);
697 static_assert(offsetof(siginfo_t, si_overrun) == 0x10);
698 static_assert(offsetof(siginfo_t, si_status) == 0x14);
699 static_assert(offsetof(siginfo_t, si_utime) == 0x18);
700 static_assert(offsetof(siginfo_t, si_stime) == 0x1c);
701 static_assert(offsetof(siginfo_t, si_value) == 0x14);
702 static_assert(offsetof(siginfo_t, si_int) == 0x14);
703 static_assert(offsetof(siginfo_t, si_ptr) == 0x14);
704 static_assert(offsetof(siginfo_t, si_addr) == 0x0c);
705 static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10);
706 static_assert(offsetof(siginfo_t, si_lower) == 0x14);
707 static_assert(offsetof(siginfo_t, si_upper) == 0x18);
708 static_assert(offsetof(siginfo_t, si_pkey) == 0x14);
709 static_assert(offsetof(siginfo_t, si_perf_data) == 0x10);
710 static_assert(offsetof(siginfo_t, si_perf_type) == 0x14);
711 static_assert(offsetof(siginfo_t, si_perf_flags) == 0x18);
712 static_assert(offsetof(siginfo_t, si_band) == 0x0c);
713 static_assert(offsetof(siginfo_t, si_fd) == 0x10);
714 static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c);
715 static_assert(offsetof(siginfo_t, si_syscall) == 0x10);
716 static_assert(offsetof(siginfo_t, si_arch) == 0x14);