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 retry: 92 down_read(&mm->mmap_sem); 93 94 vma = find_vma(mm, address); 95 if (!vma) 96 goto map_err; 97 if (vma->vm_flags & VM_IO) 98 goto acc_err; 99 if (vma->vm_start <= address) 100 goto good_area; 101 if (!(vma->vm_flags & VM_GROWSDOWN)) 102 goto map_err; 103 if (user_mode(regs)) { 104 /* Accessing the stack below usp is always a bug. The 105 "+ 256" is there due to some instructions doing 106 pre-decrement on the stack and that doesn't show up 107 until later. */ 108 if (address + 256 < rdusp()) 109 goto map_err; 110 } 111 if (expand_stack(vma, address)) 112 goto map_err; 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 #ifdef DEBUG 120 printk("do_page_fault: good_area\n"); 121 #endif 122 switch (error_code & 3) { 123 default: /* 3: write, present */ 124 /* fall through */ 125 case 2: /* write, not present */ 126 if (!(vma->vm_flags & VM_WRITE)) 127 goto acc_err; 128 flags |= FAULT_FLAG_WRITE; 129 break; 130 case 1: /* read, present */ 131 goto acc_err; 132 case 0: /* read, not present */ 133 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 134 goto acc_err; 135 } 136 137 /* 138 * If for any reason at all we couldn't handle the fault, 139 * make sure we exit gracefully rather than endlessly redo 140 * the fault. 141 */ 142 143 fault = handle_mm_fault(mm, vma, address, flags); 144 #ifdef DEBUG 145 printk("handle_mm_fault returns %d\n",fault); 146 #endif 147 148 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 149 return 0; 150 151 if (unlikely(fault & VM_FAULT_ERROR)) { 152 if (fault & VM_FAULT_OOM) 153 goto out_of_memory; 154 else if (fault & VM_FAULT_SIGBUS) 155 goto bus_err; 156 BUG(); 157 } 158 159 /* 160 * Major/minor page fault accounting is only done on the 161 * initial attempt. If we go through a retry, it is extremely 162 * likely that the page will be found in page cache at that point. 163 */ 164 if (flags & FAULT_FLAG_ALLOW_RETRY) { 165 if (fault & VM_FAULT_MAJOR) 166 current->maj_flt++; 167 else 168 current->min_flt++; 169 if (fault & VM_FAULT_RETRY) { 170 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 171 * of starvation. */ 172 flags &= ~FAULT_FLAG_ALLOW_RETRY; 173 174 /* 175 * No need to up_read(&mm->mmap_sem) as we would 176 * have already released it in __lock_page_or_retry 177 * in mm/filemap.c. 178 */ 179 180 goto retry; 181 } 182 } 183 184 up_read(&mm->mmap_sem); 185 return 0; 186 187 /* 188 * We ran out of memory, or some other thing happened to us that made 189 * us unable to handle the page fault gracefully. 190 */ 191 out_of_memory: 192 up_read(&mm->mmap_sem); 193 if (!user_mode(regs)) 194 goto no_context; 195 pagefault_out_of_memory(); 196 return 0; 197 198 no_context: 199 current->thread.signo = SIGBUS; 200 current->thread.faddr = address; 201 return send_fault_sig(regs); 202 203 bus_err: 204 current->thread.signo = SIGBUS; 205 current->thread.code = BUS_ADRERR; 206 current->thread.faddr = address; 207 goto send_sig; 208 209 map_err: 210 current->thread.signo = SIGSEGV; 211 current->thread.code = SEGV_MAPERR; 212 current->thread.faddr = address; 213 goto send_sig; 214 215 acc_err: 216 current->thread.signo = SIGSEGV; 217 current->thread.code = SEGV_ACCERR; 218 current->thread.faddr = address; 219 220 send_sig: 221 up_read(&mm->mmap_sem); 222 return send_fault_sig(regs); 223 } 224