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 16 #include <asm/setup.h> 17 #include <asm/traps.h> 18 #include <asm/pgalloc.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 siginfo_t siginfo; 25 26 clear_siginfo(&siginfo); 27 siginfo.si_signo = current->thread.signo; 28 siginfo.si_code = current->thread.code; 29 siginfo.si_addr = (void *)current->thread.faddr; 30 pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, 31 siginfo.si_signo, siginfo.si_code); 32 33 if (user_mode(regs)) { 34 force_sig_info(siginfo.si_signo, 35 &siginfo, current); 36 } else { 37 if (fixup_exception(regs)) 38 return -1; 39 40 //if (siginfo.si_signo == SIGBUS) 41 // force_sig_info(siginfo.si_signo, 42 // &siginfo, current); 43 44 /* 45 * Oops. The kernel tried to access some bad page. We'll have to 46 * terminate things with extreme prejudice. 47 */ 48 if ((unsigned long)siginfo.si_addr < PAGE_SIZE) 49 pr_alert("Unable to handle kernel NULL pointer dereference"); 50 else 51 pr_alert("Unable to handle kernel access"); 52 pr_cont(" at virtual address %p\n", siginfo.si_addr); 53 die_if_kernel("Oops", regs, 0 /*error_code*/); 54 do_exit(SIGKILL); 55 } 56 57 return 1; 58 } 59 60 /* 61 * This routine handles page faults. It determines the problem, and 62 * then passes it off to one of the appropriate routines. 63 * 64 * error_code: 65 * bit 0 == 0 means no page found, 1 means protection fault 66 * bit 1 == 0 means read, 1 means write 67 * 68 * If this routine detects a bad access, it returns 1, otherwise it 69 * returns 0. 70 */ 71 int do_page_fault(struct pt_regs *regs, unsigned long address, 72 unsigned long error_code) 73 { 74 struct mm_struct *mm = current->mm; 75 struct vm_area_struct * vma; 76 int fault; 77 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 78 79 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 80 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); 81 82 /* 83 * If we're in an interrupt or have no user 84 * context, we must not take the fault.. 85 */ 86 if (faulthandler_disabled() || !mm) 87 goto no_context; 88 89 if (user_mode(regs)) 90 flags |= FAULT_FLAG_USER; 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 pr_debug("do_page_fault: good_area\n"); 120 switch (error_code & 3) { 121 default: /* 3: write, present */ 122 /* fall through */ 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 (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 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); 142 pr_debug("handle_mm_fault returns %d\n", fault); 143 144 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 145 return 0; 146 147 if (unlikely(fault & VM_FAULT_ERROR)) { 148 if (fault & VM_FAULT_OOM) 149 goto out_of_memory; 150 else if (fault & VM_FAULT_SIGSEGV) 151 goto map_err; 152 else if (fault & VM_FAULT_SIGBUS) 153 goto bus_err; 154 BUG(); 155 } 156 157 /* 158 * Major/minor page fault accounting is only done on the 159 * initial attempt. If we go through a retry, it is extremely 160 * likely that the page will be found in page cache at that point. 161 */ 162 if (flags & FAULT_FLAG_ALLOW_RETRY) { 163 if (fault & VM_FAULT_MAJOR) 164 current->maj_flt++; 165 else 166 current->min_flt++; 167 if (fault & VM_FAULT_RETRY) { 168 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 169 * of starvation. */ 170 flags &= ~FAULT_FLAG_ALLOW_RETRY; 171 flags |= FAULT_FLAG_TRIED; 172 173 /* 174 * No need to up_read(&mm->mmap_sem) as we would 175 * have already released it in __lock_page_or_retry 176 * in mm/filemap.c. 177 */ 178 179 goto retry; 180 } 181 } 182 183 up_read(&mm->mmap_sem); 184 return 0; 185 186 /* 187 * We ran out of memory, or some other thing happened to us that made 188 * us unable to handle the page fault gracefully. 189 */ 190 out_of_memory: 191 up_read(&mm->mmap_sem); 192 if (!user_mode(regs)) 193 goto no_context; 194 pagefault_out_of_memory(); 195 return 0; 196 197 no_context: 198 current->thread.signo = SIGBUS; 199 current->thread.faddr = address; 200 return send_fault_sig(regs); 201 202 bus_err: 203 current->thread.signo = SIGBUS; 204 current->thread.code = BUS_ADRERR; 205 current->thread.faddr = address; 206 goto send_sig; 207 208 map_err: 209 current->thread.signo = SIGSEGV; 210 current->thread.code = SEGV_MAPERR; 211 current->thread.faddr = address; 212 goto send_sig; 213 214 acc_err: 215 current->thread.signo = SIGSEGV; 216 current->thread.code = SEGV_ACCERR; 217 current->thread.faddr = address; 218 219 send_sig: 220 up_read(&mm->mmap_sem); 221 return send_fault_sig(regs); 222 } 223