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/system.h> 28 #include <asm/uaccess.h> 29 30 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *); 31 32 33 /* 34 * Force a new ASN for a task. 35 */ 36 37 #ifndef CONFIG_SMP 38 unsigned long last_asn = ASN_FIRST_VERSION; 39 #endif 40 41 void 42 __load_new_mm_context(struct mm_struct *next_mm) 43 { 44 unsigned long mmc; 45 struct pcb_struct *pcb; 46 47 mmc = __get_new_mm_context(next_mm, smp_processor_id()); 48 next_mm->context[smp_processor_id()] = mmc; 49 50 pcb = ¤t_thread_info()->pcb; 51 pcb->asn = mmc & HARDWARE_ASN_MASK; 52 pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT; 53 54 __reload_thread(pcb); 55 } 56 57 58 /* 59 * This routine handles page faults. It determines the address, 60 * and the problem, and then passes it off to handle_mm_fault(). 61 * 62 * mmcsr: 63 * 0 = translation not valid 64 * 1 = access violation 65 * 2 = fault-on-read 66 * 3 = fault-on-execute 67 * 4 = fault-on-write 68 * 69 * cause: 70 * -1 = instruction fetch 71 * 0 = load 72 * 1 = store 73 * 74 * Registers $9 through $15 are saved in a block just prior to `regs' and 75 * are saved and restored around the call to allow exception code to 76 * modify them. 77 */ 78 79 /* Macro for exception fixup code to access integer registers. */ 80 #define dpf_reg(r) \ 81 (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 : \ 82 (r) <= 18 ? (r)+8 : (r)-10]) 83 84 asmlinkage void 85 do_page_fault(unsigned long address, unsigned long mmcsr, 86 long cause, struct pt_regs *regs) 87 { 88 struct vm_area_struct * vma; 89 struct mm_struct *mm = current->mm; 90 const struct exception_table_entry *fixup; 91 int fault, si_code = SEGV_MAPERR; 92 siginfo_t info; 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 || in_atomic()) 111 goto no_context; 112 113 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 114 if (address >= TASK_SIZE) 115 goto vmalloc_fault; 116 #endif 117 118 down_read(&mm->mmap_sem); 119 vma = find_vma(mm, address); 120 if (!vma) 121 goto bad_area; 122 if (vma->vm_start <= address) 123 goto good_area; 124 if (!(vma->vm_flags & VM_GROWSDOWN)) 125 goto bad_area; 126 if (expand_stack(vma, address)) 127 goto bad_area; 128 129 /* Ok, we have a good vm_area for this memory access, so 130 we can handle it. */ 131 good_area: 132 si_code = SEGV_ACCERR; 133 if (cause < 0) { 134 if (!(vma->vm_flags & VM_EXEC)) 135 goto bad_area; 136 } else if (!cause) { 137 /* Allow reads even for write-only mappings */ 138 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 139 goto bad_area; 140 } else { 141 if (!(vma->vm_flags & VM_WRITE)) 142 goto bad_area; 143 } 144 145 survive: 146 /* If for any reason at all we couldn't handle the fault, 147 make sure we exit gracefully rather than endlessly redo 148 the fault. */ 149 fault = handle_mm_fault(mm, vma, address, cause > 0); 150 up_read(&mm->mmap_sem); 151 if (unlikely(fault & VM_FAULT_ERROR)) { 152 if (fault & VM_FAULT_OOM) 153 goto out_of_memory; 154 else if (fault & VM_FAULT_SIGBUS) 155 goto do_sigbus; 156 BUG(); 157 } 158 if (fault & VM_FAULT_MAJOR) 159 current->maj_flt++; 160 else 161 current->min_flt++; 162 return; 163 164 /* Something tried to access memory that isn't in our memory map. 165 Fix it, but check if it's kernel or user first. */ 166 bad_area: 167 up_read(&mm->mmap_sem); 168 169 if (user_mode(regs)) 170 goto do_sigsegv; 171 172 no_context: 173 /* Are we prepared to handle this fault as an exception? */ 174 if ((fixup = search_exception_tables(regs->pc)) != 0) { 175 unsigned long newpc; 176 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 177 regs->pc = newpc; 178 return; 179 } 180 181 /* Oops. The kernel tried to access some bad page. We'll have to 182 terminate things with extreme prejudice. */ 183 printk(KERN_ALERT "Unable to handle kernel paging request at " 184 "virtual address %016lx\n", address); 185 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 186 do_exit(SIGKILL); 187 188 /* We ran out of memory, or some other thing happened to us that 189 made us unable to handle the page fault gracefully. */ 190 out_of_memory: 191 if (is_global_init(current)) { 192 yield(); 193 down_read(&mm->mmap_sem); 194 goto survive; 195 } 196 printk(KERN_ALERT "VM: killing process %s(%d)\n", 197 current->comm, task_pid_nr(current)); 198 if (!user_mode(regs)) 199 goto no_context; 200 do_group_exit(SIGKILL); 201 202 do_sigbus: 203 /* Send a sigbus, regardless of whether we were in kernel 204 or user mode. */ 205 info.si_signo = SIGBUS; 206 info.si_errno = 0; 207 info.si_code = BUS_ADRERR; 208 info.si_addr = (void __user *) address; 209 force_sig_info(SIGBUS, &info, current); 210 if (!user_mode(regs)) 211 goto no_context; 212 return; 213 214 do_sigsegv: 215 info.si_signo = SIGSEGV; 216 info.si_errno = 0; 217 info.si_code = si_code; 218 info.si_addr = (void __user *) address; 219 force_sig_info(SIGSEGV, &info, current); 220 return; 221 222 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 223 vmalloc_fault: 224 if (user_mode(regs)) 225 goto do_sigsegv; 226 else { 227 /* Synchronize this task's top level page-table 228 with the "reference" page table from init. */ 229 long index = pgd_index(address); 230 pgd_t *pgd, *pgd_k; 231 232 pgd = current->active_mm->pgd + index; 233 pgd_k = swapper_pg_dir + index; 234 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 235 pgd_val(*pgd) = pgd_val(*pgd_k); 236 return; 237 } 238 goto no_context; 239 } 240 #endif 241 } 242