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 #include <linux/perf_event.h> 16 17 #include <asm/setup.h> 18 #include <asm/traps.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 int signo, si_code; 25 void __user *addr; 26 27 signo = current->thread.signo; 28 si_code = current->thread.code; 29 addr = (void __user *)current->thread.faddr; 30 pr_debug("send_fault_sig: %p,%d,%d\n", addr, signo, si_code); 31 32 if (user_mode(regs)) { 33 force_sig_fault(signo, si_code, addr); 34 } else { 35 if (fixup_exception(regs)) 36 return -1; 37 38 //if (signo == SIGBUS) 39 // force_sig_fault(si_signo, si_code, addr); 40 41 /* 42 * Oops. The kernel tried to access some bad page. We'll have to 43 * terminate things with extreme prejudice. 44 */ 45 if ((unsigned long)addr < PAGE_SIZE) 46 pr_alert("Unable to handle kernel NULL pointer dereference"); 47 else 48 pr_alert("Unable to handle kernel access"); 49 pr_cont(" at virtual address %p\n", addr); 50 die_if_kernel("Oops", regs, 0 /*error_code*/); 51 make_task_dead(SIGKILL); 52 } 53 54 return 1; 55 } 56 57 /* 58 * This routine handles page faults. It determines the problem, and 59 * then passes it off to one of the appropriate routines. 60 * 61 * error_code: 62 * bit 0 == 0 means no page found, 1 means protection fault 63 * bit 1 == 0 means read, 1 means write 64 * 65 * If this routine detects a bad access, it returns 1, otherwise it 66 * returns 0. 67 */ 68 int do_page_fault(struct pt_regs *regs, unsigned long address, 69 unsigned long error_code) 70 { 71 struct mm_struct *mm = current->mm; 72 struct vm_area_struct * vma; 73 vm_fault_t fault; 74 unsigned int flags = FAULT_FLAG_DEFAULT; 75 76 pr_debug("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n", 77 regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL); 78 79 /* 80 * If we're in an interrupt or have no user 81 * context, we must not take the fault.. 82 */ 83 if (faulthandler_disabled() || !mm) 84 goto no_context; 85 86 if (user_mode(regs)) 87 flags |= FAULT_FLAG_USER; 88 89 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 90 retry: 91 mmap_read_lock(mm); 92 93 vma = find_vma(mm, address); 94 if (!vma) 95 goto map_err; 96 if (vma->vm_start <= address) 97 goto good_area; 98 if (!(vma->vm_flags & VM_GROWSDOWN)) 99 goto map_err; 100 if (user_mode(regs)) { 101 /* Accessing the stack below usp is always a bug. The 102 "+ 256" is there due to some instructions doing 103 pre-decrement on the stack and that doesn't show up 104 until later. */ 105 if (address + 256 < rdusp()) 106 goto map_err; 107 } 108 if (expand_stack(vma, address)) 109 goto map_err; 110 111 /* 112 * Ok, we have a good vm_area for this memory access, so 113 * we can handle it.. 114 */ 115 good_area: 116 pr_debug("do_page_fault: good_area\n"); 117 switch (error_code & 3) { 118 default: /* 3: write, present */ 119 fallthrough; 120 case 2: /* write, not present */ 121 if (!(vma->vm_flags & VM_WRITE)) 122 goto acc_err; 123 flags |= FAULT_FLAG_WRITE; 124 break; 125 case 1: /* read, present */ 126 goto acc_err; 127 case 0: /* read, not present */ 128 if (unlikely(!vma_is_accessible(vma))) 129 goto acc_err; 130 } 131 132 /* 133 * If for any reason at all we couldn't handle the fault, 134 * make sure we exit gracefully rather than endlessly redo 135 * the fault. 136 */ 137 138 fault = handle_mm_fault(vma, address, flags, regs); 139 pr_debug("handle_mm_fault returns %x\n", fault); 140 141 if (fault_signal_pending(fault, regs)) 142 return 0; 143 144 if (unlikely(fault & VM_FAULT_ERROR)) { 145 if (fault & VM_FAULT_OOM) 146 goto out_of_memory; 147 else if (fault & VM_FAULT_SIGSEGV) 148 goto map_err; 149 else if (fault & VM_FAULT_SIGBUS) 150 goto bus_err; 151 BUG(); 152 } 153 154 if (fault & VM_FAULT_RETRY) { 155 flags |= FAULT_FLAG_TRIED; 156 157 /* 158 * No need to mmap_read_unlock(mm) as we would 159 * have already released it in __lock_page_or_retry 160 * in mm/filemap.c. 161 */ 162 163 goto retry; 164 } 165 166 mmap_read_unlock(mm); 167 return 0; 168 169 /* 170 * We ran out of memory, or some other thing happened to us that made 171 * us unable to handle the page fault gracefully. 172 */ 173 out_of_memory: 174 mmap_read_unlock(mm); 175 if (!user_mode(regs)) 176 goto no_context; 177 pagefault_out_of_memory(); 178 return 0; 179 180 no_context: 181 current->thread.signo = SIGBUS; 182 current->thread.faddr = address; 183 return send_fault_sig(regs); 184 185 bus_err: 186 current->thread.signo = SIGBUS; 187 current->thread.code = BUS_ADRERR; 188 current->thread.faddr = address; 189 goto send_sig; 190 191 map_err: 192 current->thread.signo = SIGSEGV; 193 current->thread.code = SEGV_MAPERR; 194 current->thread.faddr = address; 195 goto send_sig; 196 197 acc_err: 198 current->thread.signo = SIGSEGV; 199 current->thread.code = SEGV_ACCERR; 200 current->thread.faddr = address; 201 202 send_sig: 203 mmap_read_unlock(mm); 204 return send_fault_sig(regs); 205 } 206