// SPDX-License-Identifier: GPL-2.0 /* * linux/arch/m68k/mm/fault.c * * Copyright (C) 1995 Hamish Macdonald */ #include <linux/mman.h> #include <linux/mm.h> #include <linux/kernel.h> #include <linux/ptrace.h> #include <linux/interrupt.h> #include <linux/module.h> #include <linux/uaccess.h> #include <linux/perf_event.h> #include <asm/setup.h> #include <asm/traps.h> #include "fault.h" extern void die_if_kernel(char *, struct pt_regs *, long); int send_fault_sig(struct pt_regs *regs) { int signo, si_code; void __user *addr; signo = current->thread.signo; si_code = current->thread.code; addr = (void __user *)current->thread.faddr; pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code); if (user_mode(regs)) { force_sig_fault(signo, si_code, addr); } else { if (fixup_exception(regs)) return -1; //if (signo == SIGBUS) // force_sig_fault(si_signo, si_code, addr); /* * Oops. The kernel tried to access some bad page. We'll have to * terminate things with extreme prejudice. */ if ((unsigned long)addr < PAGE_SIZE) pr_alert("Unable to handle kernel NULL pointer dereference"); else pr_alert("Unable to handle kernel access"); pr_cont(" at virtual address %p\n", addr); die_if_kernel("Oops", regs, 0 /*error_code*/); make_task_dead(SIGKILL); } return 1; } /* * This routine handles page faults. It determines the problem, and * then passes it off to one of the appropriate routines. * * error_code: * bit 0 == 0 means no page found, 1 means protection fault * bit 1 == 0 means read, 1 means write * * If this routine detects a bad access, it returns 1, otherwise it * returns 0. */ int do_page_fault(struct pt_regs *regs, unsigned long address, unsigned long error_code) { struct mm_struct *mm = current->mm; struct vm_area_struct * vma; vm_fault_t fault; unsigned int flags = FAULT_FLAG_DEFAULT; pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); /* * If we're in an interrupt or have no user * context, we must not take the fault.. */ if (faulthandler_disabled() || !mm) goto no_context; if (user_mode(regs)) flags |= FAULT_FLAG_USER; perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); retry: mmap_read_lock(mm); vma = find_vma(mm, address); if (!vma) goto map_err; if (vma->vm_start <= address) goto good_area; if (!(vma->vm_flags & VM_GROWSDOWN)) goto map_err; if (user_mode(regs)) { /* Accessing the stack below usp is always a bug. The "+ 256" is there due to some instructions doing pre-decrement on the stack and that doesn't show up until later. */ if (address + 256 < rdusp()) goto map_err; } vma = expand_stack(mm, address); if (!vma) goto map_err_nosemaphore; /* * Ok, we have a good vm_area for this memory access, so * we can handle it.. */ good_area: pr_debug("do_page_fault: good_area\n"); switch (error_code & 3) { default: /* 3: write, present */ fallthrough; case 2: /* write, not present */ if (!(vma->vm_flags & VM_WRITE)) goto acc_err; flags |= FAULT_FLAG_WRITE; break; case 1: /* read, present */ goto acc_err; case 0: /* read, not present */ if (unlikely(!vma_is_accessible(vma))) goto acc_err; } /* * If for any reason at all we couldn't handle the fault, * make sure we exit gracefully rather than endlessly redo * the fault. */ fault = handle_mm_fault(vma, address, flags, regs); pr_debug("handle_mm_fault returns %x\n", fault); if (fault_signal_pending(fault, regs)) { if (!user_mode(regs)) goto no_context; return 0; } /* The fault is fully completed (including releasing mmap lock) */ if (fault & VM_FAULT_COMPLETED) return 0; if (unlikely(fault & VM_FAULT_ERROR)) { if (fault & VM_FAULT_OOM) goto out_of_memory; else if (fault & VM_FAULT_SIGSEGV) goto map_err; else if (fault & VM_FAULT_SIGBUS) goto bus_err; BUG(); } if (fault & VM_FAULT_RETRY) { flags |= FAULT_FLAG_TRIED; /* * No need to mmap_read_unlock(mm) as we would * have already released it in __lock_page_or_retry * in mm/filemap.c. */ goto retry; } mmap_read_unlock(mm); return 0; /* * We ran out of memory, or some other thing happened to us that made * us unable to handle the page fault gracefully. */ out_of_memory: mmap_read_unlock(mm); if (!user_mode(regs)) goto no_context; pagefault_out_of_memory(); return 0; no_context: current->thread.signo = SIGBUS; current->thread.faddr = address; return send_fault_sig(regs); bus_err: current->thread.signo = SIGBUS; current->thread.code = BUS_ADRERR; current->thread.faddr = address; goto send_sig; map_err: mmap_read_unlock(mm); map_err_nosemaphore: current->thread.signo = SIGSEGV; current->thread.code = SEGV_MAPERR; current->thread.faddr = address; return send_fault_sig(regs); acc_err: current->thread.signo = SIGSEGV; current->thread.code = SEGV_ACCERR; current->thread.faddr = address; send_sig: mmap_read_unlock(mm); return send_fault_sig(regs); }