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 = { 0, 0, 0, }; 25 26 siginfo.si_signo = current->thread.signo; 27 siginfo.si_code = current->thread.code; 28 siginfo.si_addr = (void *)current->thread.faddr; 29 pr_debug("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, 30 siginfo.si_signo, siginfo.si_code); 31 32 if (user_mode(regs)) { 33 force_sig_info(siginfo.si_signo, 34 &siginfo, current); 35 } else { 36 if (fixup_exception(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 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", 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 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 retry: 91 down_read(&mm->mmap_sem); 92 93 vma = find_vma(mm, address); 94 if (!vma) 95 goto map_err; 96 if (vma->vm_flags & VM_IO) 97 goto acc_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 if (expand_stack(vma, address)) 111 goto map_err; 112 113 /* 114 * Ok, we have a good vm_area for this memory access, so 115 * we can handle it.. 116 */ 117 good_area: 118 pr_debug("do_page_fault: good_area\n"); 119 switch (error_code & 3) { 120 default: /* 3: write, present */ 121 /* fall through */ 122 case 2: /* write, not present */ 123 if (!(vma->vm_flags & VM_WRITE)) 124 goto acc_err; 125 flags |= FAULT_FLAG_WRITE; 126 break; 127 case 1: /* read, present */ 128 goto acc_err; 129 case 0: /* read, not present */ 130 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 131 goto acc_err; 132 } 133 134 /* 135 * If for any reason at all we couldn't handle the fault, 136 * make sure we exit gracefully rather than endlessly redo 137 * the fault. 138 */ 139 140 fault = handle_mm_fault(vma, address, flags); 141 pr_debug("handle_mm_fault returns %d\n", fault); 142 143 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 144 return 0; 145 146 if (unlikely(fault & VM_FAULT_ERROR)) { 147 if (fault & VM_FAULT_OOM) 148 goto out_of_memory; 149 else if (fault & VM_FAULT_SIGSEGV) 150 goto map_err; 151 else if (fault & VM_FAULT_SIGBUS) 152 goto bus_err; 153 BUG(); 154 } 155 156 /* 157 * Major/minor page fault accounting is only done on the 158 * initial attempt. If we go through a retry, it is extremely 159 * likely that the page will be found in page cache at that point. 160 */ 161 if (flags & FAULT_FLAG_ALLOW_RETRY) { 162 if (fault & VM_FAULT_MAJOR) 163 current->maj_flt++; 164 else 165 current->min_flt++; 166 if (fault & VM_FAULT_RETRY) { 167 /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 168 * of starvation. */ 169 flags &= ~FAULT_FLAG_ALLOW_RETRY; 170 flags |= FAULT_FLAG_TRIED; 171 172 /* 173 * No need to up_read(&mm->mmap_sem) as we would 174 * have already released it in __lock_page_or_retry 175 * in mm/filemap.c. 176 */ 177 178 goto retry; 179 } 180 } 181 182 up_read(&mm->mmap_sem); 183 return 0; 184 185 /* 186 * We ran out of memory, or some other thing happened to us that made 187 * us unable to handle the page fault gracefully. 188 */ 189 out_of_memory: 190 up_read(&mm->mmap_sem); 191 if (!user_mode(regs)) 192 goto no_context; 193 pagefault_out_of_memory(); 194 return 0; 195 196 no_context: 197 current->thread.signo = SIGBUS; 198 current->thread.faddr = address; 199 return send_fault_sig(regs); 200 201 bus_err: 202 current->thread.signo = SIGBUS; 203 current->thread.code = BUS_ADRERR; 204 current->thread.faddr = address; 205 goto send_sig; 206 207 map_err: 208 current->thread.signo = SIGSEGV; 209 current->thread.code = SEGV_MAPERR; 210 current->thread.faddr = address; 211 goto send_sig; 212 213 acc_err: 214 current->thread.signo = SIGSEGV; 215 current->thread.code = SEGV_ACCERR; 216 current->thread.faddr = address; 217 218 send_sig: 219 up_read(&mm->mmap_sem); 220 return send_fault_sig(regs); 221 } 222