1 /* 2 * linux/arch/alpha/mm/fault.c 3 * 4 * Copyright (C) 1995 Linus Torvalds 5 */ 6 7 #include <linux/config.h> 8 #include <linux/sched.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/smp_lock.h> 26 #include <linux/interrupt.h> 27 #include <linux/module.h> 28 29 #include <asm/system.h> 30 #include <asm/uaccess.h> 31 32 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *); 33 34 35 /* 36 * Force a new ASN for a task. 37 */ 38 39 #ifndef CONFIG_SMP 40 unsigned long last_asn = ASN_FIRST_VERSION; 41 #endif 42 43 void 44 __load_new_mm_context(struct mm_struct *next_mm) 45 { 46 unsigned long mmc; 47 struct pcb_struct *pcb; 48 49 mmc = __get_new_mm_context(next_mm, smp_processor_id()); 50 next_mm->context[smp_processor_id()] = mmc; 51 52 pcb = ¤t_thread_info()->pcb; 53 pcb->asn = mmc & HARDWARE_ASN_MASK; 54 pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT; 55 56 __reload_thread(pcb); 57 } 58 59 60 /* 61 * This routine handles page faults. It determines the address, 62 * and the problem, and then passes it off to handle_mm_fault(). 63 * 64 * mmcsr: 65 * 0 = translation not valid 66 * 1 = access violation 67 * 2 = fault-on-read 68 * 3 = fault-on-execute 69 * 4 = fault-on-write 70 * 71 * cause: 72 * -1 = instruction fetch 73 * 0 = load 74 * 1 = store 75 * 76 * Registers $9 through $15 are saved in a block just prior to `regs' and 77 * are saved and restored around the call to allow exception code to 78 * modify them. 79 */ 80 81 /* Macro for exception fixup code to access integer registers. */ 82 #define dpf_reg(r) \ 83 (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 : \ 84 (r) <= 18 ? (r)+8 : (r)-10]) 85 86 asmlinkage void 87 do_page_fault(unsigned long address, unsigned long mmcsr, 88 long cause, struct pt_regs *regs) 89 { 90 struct vm_area_struct * vma; 91 struct mm_struct *mm = current->mm; 92 const struct exception_table_entry *fixup; 93 int fault, si_code = SEGV_MAPERR; 94 siginfo_t info; 95 96 /* As of EV6, a load into $31/$f31 is a prefetch, and never faults 97 (or is suppressed by the PALcode). Support that for older CPUs 98 by ignoring such an instruction. */ 99 if (cause == 0) { 100 unsigned int insn; 101 __get_user(insn, (unsigned int __user *)regs->pc); 102 if ((insn >> 21 & 0x1f) == 0x1f && 103 /* ldq ldl ldt lds ldg ldf ldwu ldbu */ 104 (1ul << (insn >> 26) & 0x30f00001400ul)) { 105 regs->pc += 4; 106 return; 107 } 108 } 109 110 /* If we're in an interrupt context, or have no user context, 111 we must not take the fault. */ 112 if (!mm || in_interrupt()) 113 goto no_context; 114 115 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 116 if (address >= TASK_SIZE) 117 goto vmalloc_fault; 118 #endif 119 120 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 survive: 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(mm, vma, address, cause > 0); 152 up_read(&mm->mmap_sem); 153 154 switch (fault) { 155 case VM_FAULT_MINOR: 156 current->min_flt++; 157 break; 158 case VM_FAULT_MAJOR: 159 current->maj_flt++; 160 break; 161 case VM_FAULT_SIGBUS: 162 goto do_sigbus; 163 case VM_FAULT_OOM: 164 goto out_of_memory; 165 default: 166 BUG(); 167 } 168 return; 169 170 /* Something tried to access memory that isn't in our memory map. 171 Fix it, but check if it's kernel or user first. */ 172 bad_area: 173 up_read(&mm->mmap_sem); 174 175 if (user_mode(regs)) 176 goto do_sigsegv; 177 178 no_context: 179 /* Are we prepared to handle this fault as an exception? */ 180 if ((fixup = search_exception_tables(regs->pc)) != 0) { 181 unsigned long newpc; 182 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 183 regs->pc = newpc; 184 return; 185 } 186 187 /* Oops. The kernel tried to access some bad page. We'll have to 188 terminate things with extreme prejudice. */ 189 printk(KERN_ALERT "Unable to handle kernel paging request at " 190 "virtual address %016lx\n", address); 191 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 192 do_exit(SIGKILL); 193 194 /* We ran out of memory, or some other thing happened to us that 195 made us unable to handle the page fault gracefully. */ 196 out_of_memory: 197 if (current->pid == 1) { 198 yield(); 199 down_read(&mm->mmap_sem); 200 goto survive; 201 } 202 printk(KERN_ALERT "VM: killing process %s(%d)\n", 203 current->comm, current->pid); 204 if (!user_mode(regs)) 205 goto no_context; 206 do_exit(SIGKILL); 207 208 do_sigbus: 209 /* Send a sigbus, regardless of whether we were in kernel 210 or user mode. */ 211 info.si_signo = SIGBUS; 212 info.si_errno = 0; 213 info.si_code = BUS_ADRERR; 214 info.si_addr = (void __user *) address; 215 force_sig_info(SIGBUS, &info, current); 216 if (!user_mode(regs)) 217 goto no_context; 218 return; 219 220 do_sigsegv: 221 info.si_signo = SIGSEGV; 222 info.si_errno = 0; 223 info.si_code = si_code; 224 info.si_addr = (void __user *) address; 225 force_sig_info(SIGSEGV, &info, current); 226 return; 227 228 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 229 vmalloc_fault: 230 if (user_mode(regs)) 231 goto do_sigsegv; 232 else { 233 /* Synchronize this task's top level page-table 234 with the "reference" page table from init. */ 235 long index = pgd_index(address); 236 pgd_t *pgd, *pgd_k; 237 238 pgd = current->active_mm->pgd + index; 239 pgd_k = swapper_pg_dir + index; 240 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 241 pgd_val(*pgd) = pgd_val(*pgd_k); 242 return; 243 } 244 goto no_context; 245 } 246 #endif 247 } 248