1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/arch/m68k/mm/fault.c 4 * 5 * Copyright (C) 1995 Hamish Macdonald 6 */ 7 8 #include <linux/mman.h> 9 #include <linux/mm.h> 10 #include <linux/kernel.h> 11 #include <linux/ptrace.h> 12 #include <linux/interrupt.h> 13 #include <linux/module.h> 14 #include <linux/uaccess.h> 15 #include <linux/perf_event.h> 16 17 #include <asm/setup.h> 18 #include <asm/traps.h> 19 20 extern void die_if_kernel(char *, struct pt_regs *, long); 21 22 int send_fault_sig(struct pt_regs *regs) 23 { 24 int signo, si_code; 25 void __user *addr; 26 27 signo = current->thread.signo; 28 si_code = current->thread.code; 29 addr = (void __user *)current->thread.faddr; 30 pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code); 31 32 if (user_mode(regs)) { 33 force_sig_fault(signo, si_code, addr); 34 } else { 35 if (fixup_exception(regs)) 36 return -1; 37 38 //if (signo == SIGBUS) 39 // force_sig_fault(si_signo, si_code, addr); 40 41 /* 42 * Oops. The kernel tried to access some bad page. We'll have to 43 * terminate things with extreme prejudice. 44 */ 45 if ((unsigned long)addr < PAGE_SIZE) 46 pr_alert("Unable to handle kernel NULL pointer dereference"); 47 else 48 pr_alert("Unable to handle kernel access"); 49 pr_cont(" at virtual address %p\n", addr); 50 die_if_kernel("Oops", regs, 0 /*error_code*/); 51 make_task_dead(SIGKILL); 52 } 53 54 return 1; 55 } 56 57 /* 58 * This routine handles page faults. It determines the problem, and 59 * then passes it off to one of the appropriate routines. 60 * 61 * error_code: 62 * bit 0 == 0 means no page found, 1 means protection fault 63 * bit 1 == 0 means read, 1 means write 64 * 65 * If this routine detects a bad access, it returns 1, otherwise it 66 * returns 0. 67 */ 68 int do_page_fault(struct pt_regs *regs, unsigned long address, 69 unsigned long error_code) 70 { 71 struct mm_struct *mm = current->mm; 72 struct vm_area_struct * vma; 73 vm_fault_t fault; 74 unsigned int flags = FAULT_FLAG_DEFAULT; 75 76 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 77 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); 78 79 /* 80 * If we're in an interrupt or have no user 81 * context, we must not take the fault.. 82 */ 83 if (faulthandler_disabled() || !mm) 84 goto no_context; 85 86 if (user_mode(regs)) 87 flags |= FAULT_FLAG_USER; 88 89 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 90 retry: 91 mmap_read_lock(mm); 92 93 vma = find_vma(mm, address); 94 if (!vma) 95 goto map_err; 96 if (vma->vm_flags & VM_IO) 97 goto acc_err; 98 if (vma->vm_start <= address) 99 goto good_area; 100 if (!(vma->vm_flags & VM_GROWSDOWN)) 101 goto map_err; 102 if (user_mode(regs)) { 103 /* Accessing the stack below usp is always a bug. The 104 "+ 256" is there due to some instructions doing 105 pre-decrement on the stack and that doesn't show up 106 until later. */ 107 if (address + 256 < rdusp()) 108 goto map_err; 109 } 110 if (expand_stack(vma, address)) 111 goto map_err; 112 113 /* 114 * Ok, we have a good vm_area for this memory access, so 115 * we can handle it.. 116 */ 117 good_area: 118 pr_debug("do_page_fault: good_area\n"); 119 switch (error_code & 3) { 120 default: /* 3: write, present */ 121 fallthrough; 122 case 2: /* write, not present */ 123 if (!(vma->vm_flags & VM_WRITE)) 124 goto acc_err; 125 flags |= FAULT_FLAG_WRITE; 126 break; 127 case 1: /* read, present */ 128 goto acc_err; 129 case 0: /* read, not present */ 130 if (unlikely(!vma_is_accessible(vma))) 131 goto acc_err; 132 } 133 134 /* 135 * If for any reason at all we couldn't handle the fault, 136 * make sure we exit gracefully rather than endlessly redo 137 * the fault. 138 */ 139 140 fault = handle_mm_fault(vma, address, flags, regs); 141 pr_debug("handle_mm_fault returns %x\n", fault); 142 143 if (fault_signal_pending(fault, regs)) 144 return 0; 145 146 if (unlikely(fault & VM_FAULT_ERROR)) { 147 if (fault & VM_FAULT_OOM) 148 goto out_of_memory; 149 else if (fault & VM_FAULT_SIGSEGV) 150 goto map_err; 151 else if (fault & VM_FAULT_SIGBUS) 152 goto bus_err; 153 BUG(); 154 } 155 156 if (fault & VM_FAULT_RETRY) { 157 flags |= FAULT_FLAG_TRIED; 158 159 /* 160 * No need to mmap_read_unlock(mm) as we would 161 * have already released it in __lock_page_or_retry 162 * in mm/filemap.c. 163 */ 164 165 goto retry; 166 } 167 168 mmap_read_unlock(mm); 169 return 0; 170 171 /* 172 * We ran out of memory, or some other thing happened to us that made 173 * us unable to handle the page fault gracefully. 174 */ 175 out_of_memory: 176 mmap_read_unlock(mm); 177 if (!user_mode(regs)) 178 goto no_context; 179 pagefault_out_of_memory(); 180 return 0; 181 182 no_context: 183 current->thread.signo = SIGBUS; 184 current->thread.faddr = address; 185 return send_fault_sig(regs); 186 187 bus_err: 188 current->thread.signo = SIGBUS; 189 current->thread.code = BUS_ADRERR; 190 current->thread.faddr = address; 191 goto send_sig; 192 193 map_err: 194 current->thread.signo = SIGSEGV; 195 current->thread.code = SEGV_MAPERR; 196 current->thread.faddr = address; 197 goto send_sig; 198 199 acc_err: 200 current->thread.signo = SIGSEGV; 201 current->thread.code = SEGV_ACCERR; 202 current->thread.faddr = address; 203 204 send_sig: 205 mmap_read_unlock(mm); 206 return send_fault_sig(regs); 207 } 208