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/smp_lock.h> 25 #include <linux/interrupt.h> 26 #include <linux/module.h> 27 28 #include <asm/system.h> 29 #include <asm/uaccess.h> 30 31 extern void die_if_kernel(char *,struct pt_regs *,long, unsigned long *); 32 33 34 /* 35 * Force a new ASN for a task. 36 */ 37 38 #ifndef CONFIG_SMP 39 unsigned long last_asn = ASN_FIRST_VERSION; 40 #endif 41 42 void 43 __load_new_mm_context(struct mm_struct *next_mm) 44 { 45 unsigned long mmc; 46 struct pcb_struct *pcb; 47 48 mmc = __get_new_mm_context(next_mm, smp_processor_id()); 49 next_mm->context[smp_processor_id()] = mmc; 50 51 pcb = ¤t_thread_info()->pcb; 52 pcb->asn = mmc & HARDWARE_ASN_MASK; 53 pcb->ptbr = ((unsigned long) next_mm->pgd - IDENT_ADDR) >> PAGE_SHIFT; 54 55 __reload_thread(pcb); 56 } 57 58 59 /* 60 * This routine handles page faults. It determines the address, 61 * and the problem, and then passes it off to handle_mm_fault(). 62 * 63 * mmcsr: 64 * 0 = translation not valid 65 * 1 = access violation 66 * 2 = fault-on-read 67 * 3 = fault-on-execute 68 * 4 = fault-on-write 69 * 70 * cause: 71 * -1 = instruction fetch 72 * 0 = load 73 * 1 = store 74 * 75 * Registers $9 through $15 are saved in a block just prior to `regs' and 76 * are saved and restored around the call to allow exception code to 77 * modify them. 78 */ 79 80 /* Macro for exception fixup code to access integer registers. */ 81 #define dpf_reg(r) \ 82 (((unsigned long *)regs)[(r) <= 8 ? (r) : (r) <= 15 ? (r)-16 : \ 83 (r) <= 18 ? (r)+8 : (r)-10]) 84 85 asmlinkage void 86 do_page_fault(unsigned long address, unsigned long mmcsr, 87 long cause, struct pt_regs *regs) 88 { 89 struct vm_area_struct * vma; 90 struct mm_struct *mm = current->mm; 91 const struct exception_table_entry *fixup; 92 int fault, si_code = SEGV_MAPERR; 93 siginfo_t info; 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 down_read(&mm->mmap_sem); 120 vma = find_vma(mm, address); 121 if (!vma) 122 goto bad_area; 123 if (vma->vm_start <= address) 124 goto good_area; 125 if (!(vma->vm_flags & VM_GROWSDOWN)) 126 goto bad_area; 127 if (expand_stack(vma, address)) 128 goto bad_area; 129 130 /* Ok, we have a good vm_area for this memory access, so 131 we can handle it. */ 132 good_area: 133 si_code = SEGV_ACCERR; 134 if (cause < 0) { 135 if (!(vma->vm_flags & VM_EXEC)) 136 goto bad_area; 137 } else if (!cause) { 138 /* Allow reads even for write-only mappings */ 139 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 140 goto bad_area; 141 } else { 142 if (!(vma->vm_flags & VM_WRITE)) 143 goto bad_area; 144 } 145 146 survive: 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, cause > 0); 151 up_read(&mm->mmap_sem); 152 153 switch (fault) { 154 case VM_FAULT_MINOR: 155 current->min_flt++; 156 break; 157 case VM_FAULT_MAJOR: 158 current->maj_flt++; 159 break; 160 case VM_FAULT_SIGBUS: 161 goto do_sigbus; 162 case VM_FAULT_OOM: 163 goto out_of_memory; 164 default: 165 BUG(); 166 } 167 return; 168 169 /* Something tried to access memory that isn't in our memory map. 170 Fix it, but check if it's kernel or user first. */ 171 bad_area: 172 up_read(&mm->mmap_sem); 173 174 if (user_mode(regs)) 175 goto do_sigsegv; 176 177 no_context: 178 /* Are we prepared to handle this fault as an exception? */ 179 if ((fixup = search_exception_tables(regs->pc)) != 0) { 180 unsigned long newpc; 181 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 182 regs->pc = newpc; 183 return; 184 } 185 186 /* Oops. The kernel tried to access some bad page. We'll have to 187 terminate things with extreme prejudice. */ 188 printk(KERN_ALERT "Unable to handle kernel paging request at " 189 "virtual address %016lx\n", address); 190 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 191 do_exit(SIGKILL); 192 193 /* We ran out of memory, or some other thing happened to us that 194 made us unable to handle the page fault gracefully. */ 195 out_of_memory: 196 if (is_init(current)) { 197 yield(); 198 down_read(&mm->mmap_sem); 199 goto survive; 200 } 201 printk(KERN_ALERT "VM: killing process %s(%d)\n", 202 current->comm, current->pid); 203 if (!user_mode(regs)) 204 goto no_context; 205 do_exit(SIGKILL); 206 207 do_sigbus: 208 /* Send a sigbus, regardless of whether we were in kernel 209 or user mode. */ 210 info.si_signo = SIGBUS; 211 info.si_errno = 0; 212 info.si_code = BUS_ADRERR; 213 info.si_addr = (void __user *) address; 214 force_sig_info(SIGBUS, &info, current); 215 if (!user_mode(regs)) 216 goto no_context; 217 return; 218 219 do_sigsegv: 220 info.si_signo = SIGSEGV; 221 info.si_errno = 0; 222 info.si_code = si_code; 223 info.si_addr = (void __user *) address; 224 force_sig_info(SIGSEGV, &info, current); 225 return; 226 227 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 228 vmalloc_fault: 229 if (user_mode(regs)) 230 goto do_sigsegv; 231 else { 232 /* Synchronize this task's top level page-table 233 with the "reference" page table from init. */ 234 long index = pgd_index(address); 235 pgd_t *pgd, *pgd_k; 236 237 pgd = current->active_mm->pgd + index; 238 pgd_k = swapper_pg_dir + index; 239 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 240 pgd_val(*pgd) = pgd_val(*pgd_k); 241 return; 242 } 243 goto no_context; 244 } 245 #endif 246 } 247