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 #include "fault.h" 21 22 extern void die_if_kernel(char *, struct pt_regs *, long); 23 24 int send_fault_sig(struct pt_regs *regs) 25 { 26 int signo, si_code; 27 void __user *addr; 28 29 signo = current->thread.signo; 30 si_code = current->thread.code; 31 addr = (void __user *)current->thread.faddr; 32 pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code); 33 34 if (user_mode(regs)) { 35 force_sig_fault(signo, si_code, addr); 36 } else { 37 if (fixup_exception(regs)) 38 return -1; 39 40 //if (signo == SIGBUS) 41 // force_sig_fault(si_signo, si_code, addr); 42 43 /* 44 * Oops. The kernel tried to access some bad page. We'll have to 45 * terminate things with extreme prejudice. 46 */ 47 if ((unsigned long)addr < PAGE_SIZE) 48 pr_alert("Unable to handle kernel NULL pointer dereference"); 49 else 50 pr_alert("Unable to handle kernel access"); 51 pr_cont(" at virtual address %p\n", addr); 52 die_if_kernel("Oops", regs, 0 /*error_code*/); 53 make_task_dead(SIGKILL); 54 } 55 56 return 1; 57 } 58 59 /* 60 * This routine handles page faults. It determines the problem, and 61 * then passes it off to one of the appropriate routines. 62 * 63 * error_code: 64 * bit 0 == 0 means no page found, 1 means protection fault 65 * bit 1 == 0 means read, 1 means write 66 * 67 * If this routine detects a bad access, it returns 1, otherwise it 68 * returns 0. 69 */ 70 int do_page_fault(struct pt_regs *regs, unsigned long address, 71 unsigned long error_code) 72 { 73 struct mm_struct *mm = current->mm; 74 struct vm_area_struct * vma; 75 vm_fault_t fault; 76 unsigned int flags = FAULT_FLAG_DEFAULT; 77 78 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 79 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); 80 81 /* 82 * If we're in an interrupt or have no user 83 * context, we must not take the fault.. 84 */ 85 if (faulthandler_disabled() || !mm) 86 goto no_context; 87 88 if (user_mode(regs)) 89 flags |= FAULT_FLAG_USER; 90 91 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 92 retry: 93 mmap_read_lock(mm); 94 95 vma = find_vma(mm, address); 96 if (!vma) 97 goto map_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 vma = expand_stack(mm, address); 111 if (!vma) 112 goto map_err_nosemaphore; 113 114 /* 115 * Ok, we have a good vm_area for this memory access, so 116 * we can handle it.. 117 */ 118 good_area: 119 pr_debug("do_page_fault: good_area\n"); 120 switch (error_code & 3) { 121 default: /* 3: write, present */ 122 fallthrough; 123 case 2: /* write, not present */ 124 if (!(vma->vm_flags & VM_WRITE)) 125 goto acc_err; 126 flags |= FAULT_FLAG_WRITE; 127 break; 128 case 1: /* read, present */ 129 goto acc_err; 130 case 0: /* read, not present */ 131 if (unlikely(!vma_is_accessible(vma))) 132 goto acc_err; 133 } 134 135 /* 136 * If for any reason at all we couldn't handle the fault, 137 * make sure we exit gracefully rather than endlessly redo 138 * the fault. 139 */ 140 141 fault = handle_mm_fault(vma, address, flags, regs); 142 pr_debug("handle_mm_fault returns %x\n", fault); 143 144 if (fault_signal_pending(fault, regs)) { 145 if (!user_mode(regs)) 146 goto no_context; 147 return 0; 148 } 149 150 /* The fault is fully completed (including releasing mmap lock) */ 151 if (fault & VM_FAULT_COMPLETED) 152 return 0; 153 154 if (unlikely(fault & VM_FAULT_ERROR)) { 155 if (fault & VM_FAULT_OOM) 156 goto out_of_memory; 157 else if (fault & VM_FAULT_SIGSEGV) 158 goto map_err; 159 else if (fault & VM_FAULT_SIGBUS) 160 goto bus_err; 161 BUG(); 162 } 163 164 if (fault & VM_FAULT_RETRY) { 165 flags |= FAULT_FLAG_TRIED; 166 167 /* 168 * No need to mmap_read_unlock(mm) as we would 169 * have already released it in __lock_page_or_retry 170 * in mm/filemap.c. 171 */ 172 173 goto retry; 174 } 175 176 mmap_read_unlock(mm); 177 return 0; 178 179 /* 180 * We ran out of memory, or some other thing happened to us that made 181 * us unable to handle the page fault gracefully. 182 */ 183 out_of_memory: 184 mmap_read_unlock(mm); 185 if (!user_mode(regs)) 186 goto no_context; 187 pagefault_out_of_memory(); 188 return 0; 189 190 no_context: 191 current->thread.signo = SIGBUS; 192 current->thread.faddr = address; 193 return send_fault_sig(regs); 194 195 bus_err: 196 current->thread.signo = SIGBUS; 197 current->thread.code = BUS_ADRERR; 198 current->thread.faddr = address; 199 goto send_sig; 200 201 map_err: 202 mmap_read_unlock(mm); 203 map_err_nosemaphore: 204 current->thread.signo = SIGSEGV; 205 current->thread.code = SEGV_MAPERR; 206 current->thread.faddr = address; 207 return send_fault_sig(regs); 208 209 acc_err: 210 current->thread.signo = SIGSEGV; 211 current->thread.code = SEGV_ACCERR; 212 current->thread.faddr = address; 213 214 send_sig: 215 mmap_read_unlock(mm); 216 return send_fault_sig(regs); 217 } 218