1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/arch/alpha/mm/fault.c 4 * 5 * Copyright (C) 1995 Linus Torvalds 6 */ 7 8 #include <linux/sched/signal.h> 9 #include <linux/kernel.h> 10 #include <linux/mm.h> 11 #include <asm/io.h> 12 13 #define __EXTERN_INLINE inline 14 #include <asm/mmu_context.h> 15 #include <asm/tlbflush.h> 16 #undef __EXTERN_INLINE 17 18 #include <linux/signal.h> 19 #include <linux/errno.h> 20 #include <linux/string.h> 21 #include <linux/types.h> 22 #include <linux/ptrace.h> 23 #include <linux/mman.h> 24 #include <linux/smp.h> 25 #include <linux/interrupt.h> 26 #include <linux/extable.h> 27 #include <linux/uaccess.h> 28 29 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *); 30 31 32 /* 33 * Force a new ASN for a task. 34 */ 35 36 #ifndef CONFIG_SMP 37 unsigned long last_asn = ASN_FIRST_VERSION; 38 #endif 39 40 void 41 __load_new_mm_context(struct mm_struct *next_mm) 42 { 43 unsigned long mmc; 44 struct pcb_struct *pcb; 45 46 mmc = __get_new_mm_context(next_mm, smp_processor_id()); 47 next_mm->context[smp_processor_id()] = mmc; 48 49 pcb = ¤t_thread_info()->pcb; 50 pcb->asn = mmc & HARDWARE_ASN_MASK; 51 pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT; 52 53 __reload_thread(pcb); 54 } 55 56 57 /* 58 * This routine handles page faults. It determines the address, 59 * and the problem, and then passes it off to handle_mm_fault(). 60 * 61 * mmcsr: 62 * 0 = translation not valid 63 * 1 = access violation 64 * 2 = fault-on-read 65 * 3 = fault-on-execute 66 * 4 = fault-on-write 67 * 68 * cause: 69 * -1 = instruction fetch 70 * 0 = load 71 * 1 = store 72 * 73 * Registers $9 through $15 are saved in a block just prior to `regs' and 74 * are saved and restored around the call to allow exception code to 75 * modify them. 76 */ 77 78 /* Macro for exception fixup code to access integer registers. */ 79 #define dpf_reg(r) \ 80 (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 : \ 81 (r) <= 18 ? (r)+10 : (r)-10]) 82 83 asmlinkage void 84 do_page_fault(unsigned long address, unsigned long mmcsr, 85 long cause, struct pt_regs *regs) 86 { 87 struct vm_area_struct * vma; 88 struct mm_struct *mm = current->mm; 89 const struct exception_table_entry *fixup; 90 int si_code = SEGV_MAPERR; 91 vm_fault_t fault; 92 unsigned int flags = FAULT_FLAG_DEFAULT; 93 94 /* As of EV6, a load into $31/$f31 is a prefetch, and never faults 95 (or is suppressed by the PALcode). Support that for older CPUs 96 by ignoring such an instruction. */ 97 if (cause == 0) { 98 unsigned int insn; 99 __get_user(insn, (unsigned int __user *)regs->pc); 100 if ((insn >> 21 & 0x1f) == 0x1f && 101 /* ldq ldl ldt lds ldg ldf ldwu ldbu */ 102 (1ul << (insn >> 26) & 0x30f00001400ul)) { 103 regs->pc += 4; 104 return; 105 } 106 } 107 108 /* If we're in an interrupt context, or have no user context, 109 we must not take the fault. */ 110 if (!mm || faulthandler_disabled()) 111 goto no_context; 112 113 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 114 if (address >= TASK_SIZE) 115 goto vmalloc_fault; 116 #endif 117 if (user_mode(regs)) 118 flags |= FAULT_FLAG_USER; 119 retry: 120 down_read(&mm->mmap_sem); 121 vma = find_vma(mm, address); 122 if (!vma) 123 goto bad_area; 124 if (vma->vm_start <= address) 125 goto good_area; 126 if (!(vma->vm_flags & VM_GROWSDOWN)) 127 goto bad_area; 128 if (expand_stack(vma, address)) 129 goto bad_area; 130 131 /* Ok, we have a good vm_area for this memory access, so 132 we can handle it. */ 133 good_area: 134 si_code = SEGV_ACCERR; 135 if (cause < 0) { 136 if (!(vma->vm_flags & VM_EXEC)) 137 goto bad_area; 138 } else if (!cause) { 139 /* Allow reads even for write-only mappings */ 140 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 141 goto bad_area; 142 } else { 143 if (!(vma->vm_flags & VM_WRITE)) 144 goto bad_area; 145 flags |= FAULT_FLAG_WRITE; 146 } 147 148 /* If for any reason at all we couldn't handle the fault, 149 make sure we exit gracefully rather than endlessly redo 150 the fault. */ 151 fault = handle_mm_fault(vma, address, flags); 152 153 if (fault_signal_pending(fault, regs)) 154 return; 155 156 if (unlikely(fault & VM_FAULT_ERROR)) { 157 if (fault & VM_FAULT_OOM) 158 goto out_of_memory; 159 else if (fault & VM_FAULT_SIGSEGV) 160 goto bad_area; 161 else if (fault & VM_FAULT_SIGBUS) 162 goto do_sigbus; 163 BUG(); 164 } 165 166 if (flags & FAULT_FLAG_ALLOW_RETRY) { 167 if (fault & VM_FAULT_MAJOR) 168 current->maj_flt++; 169 else 170 current->min_flt++; 171 if (fault & VM_FAULT_RETRY) { 172 flags |= FAULT_FLAG_TRIED; 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); 184 185 return; 186 187 /* Something tried to access memory that isn't in our memory map. 188 Fix it, but check if it's kernel or user first. */ 189 bad_area: 190 up_read(&mm->mmap_sem); 191 192 if (user_mode(regs)) 193 goto do_sigsegv; 194 195 no_context: 196 /* Are we prepared to handle this fault as an exception? */ 197 if ((fixup = search_exception_tables(regs->pc)) != 0) { 198 unsigned long newpc; 199 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 200 regs->pc = newpc; 201 return; 202 } 203 204 /* Oops. The kernel tried to access some bad page. We'll have to 205 terminate things with extreme prejudice. */ 206 printk(KERN_ALERT "Unable to handle kernel paging request at " 207 "virtual address %016lx\n", address); 208 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 209 do_exit(SIGKILL); 210 211 /* We ran out of memory, or some other thing happened to us that 212 made us unable to handle the page fault gracefully. */ 213 out_of_memory: 214 up_read(&mm->mmap_sem); 215 if (!user_mode(regs)) 216 goto no_context; 217 pagefault_out_of_memory(); 218 return; 219 220 do_sigbus: 221 up_read(&mm->mmap_sem); 222 /* Send a sigbus, regardless of whether we were in kernel 223 or user mode. */ 224 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address, 0); 225 if (!user_mode(regs)) 226 goto no_context; 227 return; 228 229 do_sigsegv: 230 force_sig_fault(SIGSEGV, si_code, (void __user *) address, 0); 231 return; 232 233 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 234 vmalloc_fault: 235 if (user_mode(regs)) 236 goto do_sigsegv; 237 else { 238 /* Synchronize this task's top level page-table 239 with the "reference" page table from init. */ 240 long index = pgd_index(address); 241 pgd_t *pgd, *pgd_k; 242 243 pgd = current->active_mm->pgd + index; 244 pgd_k = swapper_pg_dir + index; 245 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 246 pgd_val(*pgd) = pgd_val(*pgd_k); 247 return; 248 } 249 goto no_context; 250 } 251 #endif 252 } 253