1 /* 2 * linux/arch/m68k/mm/fault.c 3 * 4 * Copyright (C) 1995 Hamish Macdonald 5 */ 6 7 #include <linux/mman.h> 8 #include <linux/mm.h> 9 #include <linux/kernel.h> 10 #include <linux/ptrace.h> 11 #include <linux/interrupt.h> 12 #include <linux/module.h> 13 14 #include <asm/setup.h> 15 #include <asm/traps.h> 16 #include <asm/uaccess.h> 17 #include <asm/pgalloc.h> 18 19 extern void die_if_kernel(char *, struct pt_regs *, long); 20 21 int send_fault_sig(struct pt_regs *regs) 22 { 23 siginfo_t siginfo = { 0, 0, 0, }; 24 25 siginfo.si_signo = current->thread.signo; 26 siginfo.si_code = current->thread.code; 27 siginfo.si_addr = (void *)current->thread.faddr; 28 #ifdef DEBUG 29 printk("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, siginfo.si_signo, siginfo.si_code); 30 #endif 31 32 if (user_mode(regs)) { 33 force_sig_info(siginfo.si_signo, 34 &siginfo, current); 35 } else { 36 if (handle_kernel_fault(regs)) 37 return -1; 38 39 //if (siginfo.si_signo == SIGBUS) 40 // force_sig_info(siginfo.si_signo, 41 // &siginfo, current); 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)siginfo.si_addr < PAGE_SIZE) 48 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference"); 49 else 50 printk(KERN_ALERT "Unable to handle kernel access"); 51 printk(" at virtual address %p\n", siginfo.si_addr); 52 die_if_kernel("Oops", regs, 0 /*error_code*/); 53 do_exit(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 int fault; 76 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 77 78 #ifdef DEBUG 79 printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 80 regs->sr, regs->pc, address, error_code, 81 current->mm->pgd); 82 #endif 83 84 /* 85 * If we're in an interrupt or have no user 86 * context, we must not take the fault.. 87 */ 88 if (in_atomic() || !mm) 89 goto no_context; 90 91 if (user_mode(regs)) 92 flags |= FAULT_FLAG_USER; 93 retry: 94 down_read(&mm->mmap_sem); 95 96 vma = find_vma(mm, address); 97 if (!vma) 98 goto map_err; 99 if (vma->vm_flags & VM_IO) 100 goto acc_err; 101 if (vma->vm_start <= address) 102 goto good_area; 103 if (!(vma->vm_flags & VM_GROWSDOWN)) 104 goto map_err; 105 if (user_mode(regs)) { 106 /* Accessing the stack below usp is always a bug. The 107 "+ 256" is there due to some instructions doing 108 pre-decrement on the stack and that doesn't show up 109 until later. */ 110 if (address + 256 < rdusp()) 111 goto map_err; 112 } 113 if (expand_stack(vma, address)) 114 goto map_err; 115 116 /* 117 * Ok, we have a good vm_area for this memory access, so 118 * we can handle it.. 119 */ 120 good_area: 121 #ifdef DEBUG 122 printk("do_page_fault: good_area\n"); 123 #endif 124 switch (error_code & 3) { 125 default: /* 3: write, present */ 126 /* fall through */ 127 case 2: /* write, not present */ 128 if (!(vma->vm_flags & VM_WRITE)) 129 goto acc_err; 130 flags |= FAULT_FLAG_WRITE; 131 break; 132 case 1: /* read, present */ 133 goto acc_err; 134 case 0: /* read, not present */ 135 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 136 goto acc_err; 137 } 138 139 /* 140 * If for any reason at all we couldn't handle the fault, 141 * make sure we exit gracefully rather than endlessly redo 142 * the fault. 143 */ 144 145 fault = handle_mm_fault(mm, vma, address, flags); 146 #ifdef DEBUG 147 printk("handle_mm_fault returns %d\n",fault); 148 #endif 149 150 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 151 return 0; 152 153 if (unlikely(fault & VM_FAULT_ERROR)) { 154 if (fault & VM_FAULT_OOM) 155 goto out_of_memory; 156 else if (fault & VM_FAULT_SIGBUS) 157 goto bus_err; 158 BUG(); 159 } 160 161 /* 162 * Major/minor page fault accounting is only done on the 163 * initial attempt. If we go through a retry, it is extremely 164 * likely that the page will be found in page cache at that point. 165 */ 166 if (flags & FAULT_FLAG_ALLOW_RETRY) { 167 if (fault & VM_FAULT_MAJOR) 168 current->maj_flt++; 169 else 170 current->min_flt++; 171 if (fault & VM_FAULT_RETRY) { 172 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 173 * of starvation. */ 174 flags &= ~FAULT_FLAG_ALLOW_RETRY; 175 flags |= FAULT_FLAG_TRIED; 176 177 /* 178 * No need to up_read(&mm->mmap_sem) as we would 179 * have already released it in __lock_page_or_retry 180 * in mm/filemap.c. 181 */ 182 183 goto retry; 184 } 185 } 186 187 up_read(&mm->mmap_sem); 188 return 0; 189 190 /* 191 * We ran out of memory, or some other thing happened to us that made 192 * us unable to handle the page fault gracefully. 193 */ 194 out_of_memory: 195 up_read(&mm->mmap_sem); 196 if (!user_mode(regs)) 197 goto no_context; 198 pagefault_out_of_memory(); 199 return 0; 200 201 no_context: 202 current->thread.signo = SIGBUS; 203 current->thread.faddr = address; 204 return send_fault_sig(regs); 205 206 bus_err: 207 current->thread.signo = SIGBUS; 208 current->thread.code = BUS_ADRERR; 209 current->thread.faddr = address; 210 goto send_sig; 211 212 map_err: 213 current->thread.signo = SIGSEGV; 214 current->thread.code = SEGV_MAPERR; 215 current->thread.faddr = address; 216 goto send_sig; 217 218 acc_err: 219 current->thread.signo = SIGSEGV; 220 current->thread.code = SEGV_ACCERR; 221 current->thread.faddr = address; 222 223 send_sig: 224 up_read(&mm->mmap_sem); 225 return send_fault_sig(regs); 226 } 227