// SPDX-License-Identifier: GPL-2.0-only /* * linux/arch/arm/kernel/signal.c * * Copyright (C) 1995-2009 Russell King */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include "signal.h" extern const unsigned long sigreturn_codes[17]; static unsigned long signal_return_offset; #ifdef CONFIG_IWMMXT static int preserve_iwmmxt_context(struct iwmmxt_sigframe __user *frame) { char kbuf[sizeof(*frame) + 8]; struct iwmmxt_sigframe *kframe; int err = 0; /* the iWMMXt context must be 64 bit aligned */ kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7); if (test_thread_flag(TIF_USING_IWMMXT)) { kframe->magic = IWMMXT_MAGIC; kframe->size = IWMMXT_STORAGE_SIZE; iwmmxt_task_copy(current_thread_info(), &kframe->storage); } else { /* * For bug-compatibility with older kernels, some space * has to be reserved for iWMMXt even if it's not used. * Set the magic and size appropriately so that properly * written userspace can skip it reliably: */ *kframe = (struct iwmmxt_sigframe) { .magic = DUMMY_MAGIC, .size = IWMMXT_STORAGE_SIZE, }; } err = __copy_to_user(frame, kframe, sizeof(*kframe)); return err; } static int restore_iwmmxt_context(char __user **auxp) { struct iwmmxt_sigframe __user *frame = (struct iwmmxt_sigframe __user *)*auxp; char kbuf[sizeof(*frame) + 8]; struct iwmmxt_sigframe *kframe; /* the iWMMXt context must be 64 bit aligned */ kframe = (struct iwmmxt_sigframe *)((unsigned long)(kbuf + 8) & ~7); if (__copy_from_user(kframe, frame, sizeof(*frame))) return -1; /* * For non-iWMMXt threads: a single iwmmxt_sigframe-sized dummy * block is discarded for compatibility with setup_sigframe() if * present, but we don't mandate its presence. If some other * magic is here, it's not for us: */ if (!test_thread_flag(TIF_USING_IWMMXT) && kframe->magic != DUMMY_MAGIC) return 0; if (kframe->size != IWMMXT_STORAGE_SIZE) return -1; if (test_thread_flag(TIF_USING_IWMMXT)) { if (kframe->magic != IWMMXT_MAGIC) return -1; iwmmxt_task_restore(current_thread_info(), &kframe->storage); } *auxp += IWMMXT_STORAGE_SIZE; return 0; } #endif #ifdef CONFIG_VFP static int preserve_vfp_context(struct vfp_sigframe __user *frame) { struct vfp_sigframe kframe; int err = 0; memset(&kframe, 0, sizeof(kframe)); kframe.magic = VFP_MAGIC; kframe.size = VFP_STORAGE_SIZE; err = vfp_preserve_user_clear_hwstate(&kframe.ufp, &kframe.ufp_exc); if (err) return err; return __copy_to_user(frame, &kframe, sizeof(kframe)); } static int restore_vfp_context(char __user **auxp) { struct vfp_sigframe frame; int err; err = __copy_from_user(&frame, *auxp, sizeof(frame)); if (err) return err; if (frame.magic != VFP_MAGIC || frame.size != VFP_STORAGE_SIZE) return -EINVAL; *auxp += sizeof(frame); return vfp_restore_user_hwstate(&frame.ufp, &frame.ufp_exc); } #endif /* * Do a signal return; undo the signal stack. These are aligned to 64-bit. */ static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf) { struct sigcontext context; char __user *aux; sigset_t set; int err; err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set)); if (err == 0) set_current_blocked(&set); err |= __copy_from_user(&context, &sf->uc.uc_mcontext, sizeof(context)); if (err == 0) { regs->ARM_r0 = context.arm_r0; regs->ARM_r1 = context.arm_r1; regs->ARM_r2 = context.arm_r2; regs->ARM_r3 = context.arm_r3; regs->ARM_r4 = context.arm_r4; regs->ARM_r5 = context.arm_r5; regs->ARM_r6 = context.arm_r6; regs->ARM_r7 = context.arm_r7; regs->ARM_r8 = context.arm_r8; regs->ARM_r9 = context.arm_r9; regs->ARM_r10 = context.arm_r10; regs->ARM_fp = context.arm_fp; regs->ARM_ip = context.arm_ip; regs->ARM_sp = context.arm_sp; regs->ARM_lr = context.arm_lr; regs->ARM_pc = context.arm_pc; regs->ARM_cpsr = context.arm_cpsr; } err |= !valid_user_regs(regs); aux = (char __user *) sf->uc.uc_regspace; #ifdef CONFIG_IWMMXT if (err == 0) err |= restore_iwmmxt_context(&aux); #endif #ifdef CONFIG_VFP if (err == 0) err |= restore_vfp_context(&aux); #endif return err; } asmlinkage int sys_sigreturn(struct pt_regs *regs) { struct sigframe __user *frame; /* Always make any pending restarted system calls return -EINTR */ current->restart_block.fn = do_no_restart_syscall; /* * Since we stacked the signal on a 64-bit boundary, * then 'sp' should be word aligned here. If it's * not, then the user is trying to mess with us. */ if (regs->ARM_sp & 7) goto badframe; frame = (struct sigframe __user *)regs->ARM_sp; if (!access_ok(frame, sizeof (*frame))) goto badframe; if (restore_sigframe(regs, frame)) goto badframe; return regs->ARM_r0; badframe: force_sig(SIGSEGV); return 0; } asmlinkage int sys_rt_sigreturn(struct pt_regs *regs) { struct rt_sigframe __user *frame; /* Always make any pending restarted system calls return -EINTR */ current->restart_block.fn = do_no_restart_syscall; /* * Since we stacked the signal on a 64-bit boundary, * then 'sp' should be word aligned here. If it's * not, then the user is trying to mess with us. */ if (regs->ARM_sp & 7) goto badframe; frame = (struct rt_sigframe __user *)regs->ARM_sp; if (!access_ok(frame, sizeof (*frame))) goto badframe; if (restore_sigframe(regs, &frame->sig)) goto badframe; if (restore_altstack(&frame->sig.uc.uc_stack)) goto badframe; return regs->ARM_r0; badframe: force_sig(SIGSEGV); return 0; } static int setup_sigframe(struct sigframe __user *sf, struct pt_regs *regs, sigset_t *set) { struct aux_sigframe __user *aux; struct sigcontext context; int err = 0; context = (struct sigcontext) { .arm_r0 = regs->ARM_r0, .arm_r1 = regs->ARM_r1, .arm_r2 = regs->ARM_r2, .arm_r3 = regs->ARM_r3, .arm_r4 = regs->ARM_r4, .arm_r5 = regs->ARM_r5, .arm_r6 = regs->ARM_r6, .arm_r7 = regs->ARM_r7, .arm_r8 = regs->ARM_r8, .arm_r9 = regs->ARM_r9, .arm_r10 = regs->ARM_r10, .arm_fp = regs->ARM_fp, .arm_ip = regs->ARM_ip, .arm_sp = regs->ARM_sp, .arm_lr = regs->ARM_lr, .arm_pc = regs->ARM_pc, .arm_cpsr = regs->ARM_cpsr, .trap_no = current->thread.trap_no, .error_code = current->thread.error_code, .fault_address = current->thread.address, .oldmask = set->sig[0], }; err |= __copy_to_user(&sf->uc.uc_mcontext, &context, sizeof(context)); err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set)); aux = (struct aux_sigframe __user *) sf->uc.uc_regspace; #ifdef CONFIG_IWMMXT if (err == 0) err |= preserve_iwmmxt_context(&aux->iwmmxt); #endif #ifdef CONFIG_VFP if (err == 0) err |= preserve_vfp_context(&aux->vfp); #endif err |= __put_user(0, &aux->end_magic); return err; } static inline void __user * get_sigframe(struct ksignal *ksig, struct pt_regs *regs, int framesize) { unsigned long sp = sigsp(regs->ARM_sp, ksig); void __user *frame; /* * ATPCS B01 mandates 8-byte alignment */ frame = (void __user *)((sp - framesize) & ~7); /* * Check that we can actually write to the signal frame. */ if (!access_ok(frame, framesize)) frame = NULL; return frame; } static int setup_return(struct pt_regs *regs, struct ksignal *ksig, unsigned long __user *rc, void __user *frame) { unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler; unsigned long handler_fdpic_GOT = 0; unsigned long retcode; unsigned int idx, thumb = 0; unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT); bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) && (current->personality & FDPIC_FUNCPTRS); if (fdpic) { unsigned long __user *fdpic_func_desc = (unsigned long __user *)handler; if (__get_user(handler, &fdpic_func_desc[0]) || __get_user(handler_fdpic_GOT, &fdpic_func_desc[1])) return 1; } cpsr |= PSR_ENDSTATE; /* * Maybe we need to deliver a 32-bit signal to a 26-bit task. */ if (ksig->ka.sa.sa_flags & SA_THIRTYTWO) cpsr = (cpsr & ~MODE_MASK) | USR_MODE; #ifdef CONFIG_ARM_THUMB if (elf_hwcap & HWCAP_THUMB) { /* * The LSB of the handler determines if we're going to * be using THUMB or ARM mode for this signal handler. */ thumb = handler & 1; /* * Clear the If-Then Thumb-2 execution state. ARM spec * requires this to be all 000s in ARM mode. Snapdragon * S4/Krait misbehaves on a Thumb=>ARM signal transition * without this. * * We must do this whenever we are running on a Thumb-2 * capable CPU, which includes ARMv6T2. However, we elect * to always do this to simplify the code; this field is * marked UNK/SBZP for older architectures. */ cpsr &= ~PSR_IT_MASK; if (thumb) { cpsr |= PSR_T_BIT; } else cpsr &= ~PSR_T_BIT; } #endif if (ksig->ka.sa.sa_flags & SA_RESTORER) { retcode = (unsigned long)ksig->ka.sa.sa_restorer; if (fdpic) { /* * We need code to load the function descriptor. * That code follows the standard sigreturn code * (6 words), and is made of 3 + 2 words for each * variant. The 4th copied word is the actual FD * address that the assembly code expects. */ idx = 6 + thumb * 3; if (ksig->ka.sa.sa_flags & SA_SIGINFO) idx += 5; if (__put_user(sigreturn_codes[idx], rc ) || __put_user(sigreturn_codes[idx+1], rc+1) || __put_user(sigreturn_codes[idx+2], rc+2) || __put_user(retcode, rc+3)) return 1; goto rc_finish; } } else { idx = thumb << 1; if (ksig->ka.sa.sa_flags & SA_SIGINFO) idx += 3; /* * Put the sigreturn code on the stack no matter which return * mechanism we use in order to remain ABI compliant */ if (__put_user(sigreturn_codes[idx], rc) || __put_user(sigreturn_codes[idx+1], rc+1)) return 1; rc_finish: #ifdef CONFIG_MMU if (cpsr & MODE32_BIT) { struct mm_struct *mm = current->mm; /* * 32-bit code can use the signal return page * except when the MPU has protected the vectors * page from PL0 */ retcode = mm->context.sigpage + signal_return_offset + (idx << 2) + thumb; } else #endif { /* * Ensure that the instruction cache sees * the return code written onto the stack. */ flush_icache_range((unsigned long)rc, (unsigned long)(rc + 3)); retcode = ((unsigned long)rc) + thumb; } } regs->ARM_r0 = ksig->sig; regs->ARM_sp = (unsigned long)frame; regs->ARM_lr = retcode; regs->ARM_pc = handler; if (fdpic) regs->ARM_r9 = handler_fdpic_GOT; regs->ARM_cpsr = cpsr; return 0; } static int setup_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) { struct sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame)); int err = 0; if (!frame) return 1; /* * Set uc.uc_flags to a value which sc.trap_no would never have. */ err = __put_user(0x5ac3c35a, &frame->uc.uc_flags); err |= setup_sigframe(frame, regs, set); if (err == 0) err = setup_return(regs, ksig, frame->retcode, frame); return err; } static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs) { struct rt_sigframe __user *frame = get_sigframe(ksig, regs, sizeof(*frame)); int err = 0; if (!frame) return 1; err |= copy_siginfo_to_user(&frame->info, &ksig->info); err |= __put_user(0, &frame->sig.uc.uc_flags); err |= __put_user(NULL, &frame->sig.uc.uc_link); err |= __save_altstack(&frame->sig.uc.uc_stack, regs->ARM_sp); err |= setup_sigframe(&frame->sig, regs, set); if (err == 0) err = setup_return(regs, ksig, frame->sig.retcode, frame); if (err == 0) { /* * For realtime signals we must also set the second and third * arguments for the signal handler. * -- Peter Maydell 2000-12-06 */ regs->ARM_r1 = (unsigned long)&frame->info; regs->ARM_r2 = (unsigned long)&frame->sig.uc; } return err; } /* * OK, we're invoking a handler */ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) { sigset_t *oldset = sigmask_to_save(); int ret; /* * Perform fixup for the pre-signal frame. */ rseq_signal_deliver(ksig, regs); /* * Set up the stack frame */ if (ksig->ka.sa.sa_flags & SA_SIGINFO) ret = setup_rt_frame(ksig, oldset, regs); else ret = setup_frame(ksig, oldset, regs); /* * Check that the resulting registers are actually sane. */ ret |= !valid_user_regs(regs); signal_setup_done(ret, ksig, 0); } /* * Note that 'init' is a special process: it doesn't get signals it doesn't * want to handle. Thus you cannot kill init even with a SIGKILL even by * mistake. * * Note that we go through the signals twice: once to check the signals that * the kernel can handle, and then we build all the user-level signal handling * stack-frames in one go after that. */ static int do_signal(struct pt_regs *regs, int syscall) { unsigned int retval = 0, continue_addr = 0, restart_addr = 0; struct ksignal ksig; int restart = 0; /* * If we were from a system call, check for system call restarting... */ if (syscall) { continue_addr = regs->ARM_pc; restart_addr = continue_addr - (thumb_mode(regs) ? 2 : 4); retval = regs->ARM_r0; /* * Prepare for system call restart. We do this here so that a * debugger will see the already changed PSW. */ switch (retval) { case -ERESTART_RESTARTBLOCK: restart -= 2; fallthrough; case -ERESTARTNOHAND: case -ERESTARTSYS: case -ERESTARTNOINTR: restart++; regs->ARM_r0 = regs->ARM_ORIG_r0; regs->ARM_pc = restart_addr; break; } } /* * Get the signal to deliver. When running under ptrace, at this * point the debugger may change all our registers ... */ /* * Depending on the signal settings we may need to revert the * decision to restart the system call. But skip this if a * debugger has chosen to restart at a different PC. */ if (get_signal(&ksig)) { /* handler */ if (unlikely(restart) && regs->ARM_pc == restart_addr) { if (retval == -ERESTARTNOHAND || retval == -ERESTART_RESTARTBLOCK || (retval == -ERESTARTSYS && !(ksig.ka.sa.sa_flags & SA_RESTART))) { regs->ARM_r0 = -EINTR; regs->ARM_pc = continue_addr; } } handle_signal(&ksig, regs); } else { /* no handler */ restore_saved_sigmask(); if (unlikely(restart) && regs->ARM_pc == restart_addr) { regs->ARM_pc = continue_addr; return restart; } } return 0; } asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) { /* * The assembly code enters us with IRQs off, but it hasn't * informed the tracing code of that for efficiency reasons. * Update the trace code with the current status. */ trace_hardirqs_off(); do { if (likely(thread_flags & _TIF_NEED_RESCHED)) { schedule(); } else { if (unlikely(!user_mode(regs))) return 0; local_irq_enable(); if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) { int restart = do_signal(regs, syscall); if (unlikely(restart)) { /* * Restart without handlers. * Deal with it without leaving * the kernel space. */ return restart; } syscall = 0; } else if (thread_flags & _TIF_UPROBE) { uprobe_notify_resume(regs); } else { tracehook_notify_resume(regs); rseq_handle_notify_resume(NULL, regs); } } local_irq_disable(); thread_flags = current_thread_info()->flags; } while (thread_flags & _TIF_WORK_MASK); return 0; } struct page *get_signal_page(void) { unsigned long ptr; unsigned offset; struct page *page; void *addr; page = alloc_pages(GFP_KERNEL, 0); if (!page) return NULL; addr = page_address(page); /* Poison the entire page */ memset32(addr, __opcode_to_mem_arm(0xe7fddef1), PAGE_SIZE / sizeof(u32)); /* Give the signal return code some randomness */ offset = 0x200 + (get_random_int() & 0x7fc); signal_return_offset = offset; /* Copy signal return handlers into the page */ memcpy(addr + offset, sigreturn_codes, sizeof(sigreturn_codes)); /* Flush out all instructions in this page */ ptr = (unsigned long)addr; flush_icache_range(ptr, ptr + PAGE_SIZE); return page; } #ifdef CONFIG_DEBUG_RSEQ asmlinkage void do_rseq_syscall(struct pt_regs *regs) { rseq_syscall(regs); } #endif /* * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as * changes likely come with new fields that should be added below. */ static_assert(NSIGILL == 11); static_assert(NSIGFPE == 15); static_assert(NSIGSEGV == 9); static_assert(NSIGBUS == 5); static_assert(NSIGTRAP == 6); static_assert(NSIGCHLD == 6); static_assert(NSIGSYS == 2); static_assert(sizeof(siginfo_t) == 128); static_assert(__alignof__(siginfo_t) == 4); static_assert(offsetof(siginfo_t, si_signo) == 0x00); static_assert(offsetof(siginfo_t, si_errno) == 0x04); static_assert(offsetof(siginfo_t, si_code) == 0x08); static_assert(offsetof(siginfo_t, si_pid) == 0x0c); static_assert(offsetof(siginfo_t, si_uid) == 0x10); static_assert(offsetof(siginfo_t, si_tid) == 0x0c); static_assert(offsetof(siginfo_t, si_overrun) == 0x10); static_assert(offsetof(siginfo_t, si_status) == 0x14); static_assert(offsetof(siginfo_t, si_utime) == 0x18); static_assert(offsetof(siginfo_t, si_stime) == 0x1c); static_assert(offsetof(siginfo_t, si_value) == 0x14); static_assert(offsetof(siginfo_t, si_int) == 0x14); static_assert(offsetof(siginfo_t, si_ptr) == 0x14); static_assert(offsetof(siginfo_t, si_addr) == 0x0c); static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10); static_assert(offsetof(siginfo_t, si_lower) == 0x14); static_assert(offsetof(siginfo_t, si_upper) == 0x18); static_assert(offsetof(siginfo_t, si_pkey) == 0x14); static_assert(offsetof(siginfo_t, si_perf_data) == 0x10); static_assert(offsetof(siginfo_t, si_perf_type) == 0x14); static_assert(offsetof(siginfo_t, si_band) == 0x0c); static_assert(offsetof(siginfo_t, si_fd) == 0x10); static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c); static_assert(offsetof(siginfo_t, si_syscall) == 0x10); static_assert(offsetof(siginfo_t, si_arch) == 0x14);