1 /* 2 * linux/arch/alpha/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 */ 6 7 #include <linux/sched.h> 8 #include <linux/kernel.h> 9 #include <linux/mm.h> 10 #include <asm/io.h> 11 12 #define __EXTERN_INLINE inline 13 #include <asm/mmu_context.h> 14 #include <asm/tlbflush.h> 15 #undef __EXTERN_INLINE 16 17 #include <linux/signal.h> 18 #include <linux/errno.h> 19 #include <linux/string.h> 20 #include <linux/types.h> 21 #include <linux/ptrace.h> 22 #include <linux/mman.h> 23 #include <linux/smp.h> 24 #include <linux/interrupt.h> 25 #include <linux/module.h> 26 27 #include <asm/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)+8 : (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 fault, si_code = SEGV_MAPERR; 91 siginfo_t info; 92 unsigned int flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 93 (cause > 0 ? FAULT_FLAG_WRITE : 0)); 94 95 /* As of EV6, a load into $31/$f31 is a prefetch, and never faults 96 (or is suppressed by the PALcode). Support that for older CPUs 97 by ignoring such an instruction. */ 98 if (cause == 0) { 99 unsigned int insn; 100 __get_user(insn, (unsigned int __user *)regs->pc); 101 if ((insn >> 21 & 0x1f) == 0x1f && 102 /* ldq ldl ldt lds ldg ldf ldwu ldbu */ 103 (1ul << (insn >> 26) & 0x30f00001400ul)) { 104 regs->pc += 4; 105 return; 106 } 107 } 108 109 /* If we're in an interrupt context, or have no user context, 110 we must not take the fault. */ 111 if (!mm || in_atomic()) 112 goto no_context; 113 114 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 115 if (address >= TASK_SIZE) 116 goto vmalloc_fault; 117 #endif 118 119 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 } 146 147 /* If for any reason at all we couldn't handle the fault, 148 make sure we exit gracefully rather than endlessly redo 149 the fault. */ 150 fault = handle_mm_fault(mm, vma, address, flags); 151 152 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 153 return; 154 155 if (unlikely(fault & VM_FAULT_ERROR)) { 156 if (fault & VM_FAULT_OOM) 157 goto out_of_memory; 158 else if (fault & VM_FAULT_SIGBUS) 159 goto do_sigbus; 160 BUG(); 161 } 162 163 if (flags & FAULT_FLAG_ALLOW_RETRY) { 164 if (fault & VM_FAULT_MAJOR) 165 current->maj_flt++; 166 else 167 current->min_flt++; 168 if (fault & VM_FAULT_RETRY) { 169 flags &= ~FAULT_FLAG_ALLOW_RETRY; 170 171 /* No need to up_read(&mm->mmap_sem) as we would 172 * have already released it in __lock_page_or_retry 173 * in mm/filemap.c. 174 */ 175 176 goto retry; 177 } 178 } 179 180 up_read(&mm->mmap_sem); 181 182 return; 183 184 /* Something tried to access memory that isn't in our memory map. 185 Fix it, but check if it's kernel or user first. */ 186 bad_area: 187 up_read(&mm->mmap_sem); 188 189 if (user_mode(regs)) 190 goto do_sigsegv; 191 192 no_context: 193 /* Are we prepared to handle this fault as an exception? */ 194 if ((fixup = search_exception_tables(regs->pc)) != 0) { 195 unsigned long newpc; 196 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 197 regs->pc = newpc; 198 return; 199 } 200 201 /* Oops. The kernel tried to access some bad page. We'll have to 202 terminate things with extreme prejudice. */ 203 printk(KERN_ALERT "Unable to handle kernel paging request at " 204 "virtual address %016lx\n", address); 205 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 206 do_exit(SIGKILL); 207 208 /* We ran out of memory, or some other thing happened to us that 209 made us unable to handle the page fault gracefully. */ 210 out_of_memory: 211 up_read(&mm->mmap_sem); 212 if (!user_mode(regs)) 213 goto no_context; 214 pagefault_out_of_memory(); 215 return; 216 217 do_sigbus: 218 up_read(&mm->mmap_sem); 219 /* Send a sigbus, regardless of whether we were in kernel 220 or user mode. */ 221 info.si_signo = SIGBUS; 222 info.si_errno = 0; 223 info.si_code = BUS_ADRERR; 224 info.si_addr = (void __user *) address; 225 force_sig_info(SIGBUS, &info, current); 226 if (!user_mode(regs)) 227 goto no_context; 228 return; 229 230 do_sigsegv: 231 info.si_signo = SIGSEGV; 232 info.si_errno = 0; 233 info.si_code = si_code; 234 info.si_addr = (void __user *) address; 235 force_sig_info(SIGSEGV, &info, current); 236 return; 237 238 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 239 vmalloc_fault: 240 if (user_mode(regs)) 241 goto do_sigsegv; 242 else { 243 /* Synchronize this task's top level page-table 244 with the "reference" page table from init. */ 245 long index = pgd_index(address); 246 pgd_t *pgd, *pgd_k; 247 248 pgd = current->active_mm->pgd + index; 249 pgd_k = swapper_pg_dir + index; 250 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 251 pgd_val(*pgd) = pgd_val(*pgd_k); 252 return; 253 } 254 goto no_context; 255 } 256 #endif 257 } 258