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 pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, 29 siginfo.si_signo, siginfo.si_code); 30 31 if (user_mode(regs)) { 32 force_sig_info(siginfo.si_signo, 33 &siginfo, current); 34 } else { 35 if (handle_kernel_fault(regs)) 36 return -1; 37 38 //if (siginfo.si_signo == SIGBUS) 39 // force_sig_info(siginfo.si_signo, 40 // &siginfo, current); 41 42 /* 43 * Oops. The kernel tried to access some bad page. We'll have to 44 * terminate things with extreme prejudice. 45 */ 46 if ((unsigned long)siginfo.si_addr < PAGE_SIZE) 47 pr_alert("Unable to handle kernel NULL pointer dereference"); 48 else 49 pr_alert("Unable to handle kernel access"); 50 pr_cont(" at virtual address %p\n", siginfo.si_addr); 51 die_if_kernel("Oops", regs, 0 /*error_code*/); 52 do_exit(SIGKILL); 53 } 54 55 return 1; 56 } 57 58 /* 59 * This routine handles page faults. It determines the problem, and 60 * then passes it off to one of the appropriate routines. 61 * 62 * error_code: 63 * bit 0 == 0 means no page found, 1 means protection fault 64 * bit 1 == 0 means read, 1 means write 65 * 66 * If this routine detects a bad access, it returns 1, otherwise it 67 * returns 0. 68 */ 69 int do_page_fault(struct pt_regs *regs, unsigned long address, 70 unsigned long error_code) 71 { 72 struct mm_struct *mm = current->mm; 73 struct vm_area_struct * vma; 74 int fault; 75 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 76 77 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 78 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); 79 80 /* 81 * If we're in an interrupt or have no user 82 * context, we must not take the fault.. 83 */ 84 if (in_atomic() || !mm) 85 goto no_context; 86 87 if (user_mode(regs)) 88 flags |= FAULT_FLAG_USER; 89 retry: 90 down_read(&mm->mmap_sem); 91 92 vma = find_vma(mm, address); 93 if (!vma) 94 goto map_err; 95 if (vma->vm_flags & VM_IO) 96 goto acc_err; 97 if (vma->vm_start <= address) 98 goto good_area; 99 if (!(vma->vm_flags & VM_GROWSDOWN)) 100 goto map_err; 101 if (user_mode(regs)) { 102 /* Accessing the stack below usp is always a bug. The 103 "+ 256" is there due to some instructions doing 104 pre-decrement on the stack and that doesn't show up 105 until later. */ 106 if (address + 256 < rdusp()) 107 goto map_err; 108 } 109 if (expand_stack(vma, address)) 110 goto map_err; 111 112 /* 113 * Ok, we have a good vm_area for this memory access, so 114 * we can handle it.. 115 */ 116 good_area: 117 pr_debug("do_page_fault: good_area\n"); 118 switch (error_code & 3) { 119 default: /* 3: write, present */ 120 /* fall through */ 121 case 2: /* write, not present */ 122 if (!(vma->vm_flags & VM_WRITE)) 123 goto acc_err; 124 flags |= FAULT_FLAG_WRITE; 125 break; 126 case 1: /* read, present */ 127 goto acc_err; 128 case 0: /* read, not present */ 129 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 130 goto acc_err; 131 } 132 133 /* 134 * If for any reason at all we couldn't handle the fault, 135 * make sure we exit gracefully rather than endlessly redo 136 * the fault. 137 */ 138 139 fault = handle_mm_fault(mm, vma, address, flags); 140 pr_debug("handle_mm_fault returns %d\n", fault); 141 142 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 143 return 0; 144 145 if (unlikely(fault & VM_FAULT_ERROR)) { 146 if (fault & VM_FAULT_OOM) 147 goto out_of_memory; 148 else if (fault & VM_FAULT_SIGSEGV) 149 goto map_err; 150 else if (fault & VM_FAULT_SIGBUS) 151 goto bus_err; 152 BUG(); 153 } 154 155 /* 156 * Major/minor page fault accounting is only done on the 157 * initial attempt. If we go through a retry, it is extremely 158 * likely that the page will be found in page cache at that point. 159 */ 160 if (flags & FAULT_FLAG_ALLOW_RETRY) { 161 if (fault & VM_FAULT_MAJOR) 162 current->maj_flt++; 163 else 164 current->min_flt++; 165 if (fault & VM_FAULT_RETRY) { 166 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 167 * of starvation. */ 168 flags &= ~FAULT_FLAG_ALLOW_RETRY; 169 flags |= FAULT_FLAG_TRIED; 170 171 /* 172 * No need to up_read(&mm->mmap_sem) as we would 173 * have already released it in __lock_page_or_retry 174 * in mm/filemap.c. 175 */ 176 177 goto retry; 178 } 179 } 180 181 up_read(&mm->mmap_sem); 182 return 0; 183 184 /* 185 * We ran out of memory, or some other thing happened to us that made 186 * us unable to handle the page fault gracefully. 187 */ 188 out_of_memory: 189 up_read(&mm->mmap_sem); 190 if (!user_mode(regs)) 191 goto no_context; 192 pagefault_out_of_memory(); 193 return 0; 194 195 no_context: 196 current->thread.signo = SIGBUS; 197 current->thread.faddr = address; 198 return send_fault_sig(regs); 199 200 bus_err: 201 current->thread.signo = SIGBUS; 202 current->thread.code = BUS_ADRERR; 203 current->thread.faddr = address; 204 goto send_sig; 205 206 map_err: 207 current->thread.signo = SIGSEGV; 208 current->thread.code = SEGV_MAPERR; 209 current->thread.faddr = address; 210 goto send_sig; 211 212 acc_err: 213 current->thread.signo = SIGSEGV; 214 current->thread.code = SEGV_ACCERR; 215 current->thread.faddr = address; 216 217 send_sig: 218 up_read(&mm->mmap_sem); 219 return send_fault_sig(regs); 220 } 221