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 93 /* As of EV6, a load into $31/$f31 is a prefetch, and never faults 94 (or is suppressed by the PALcode). Support that for older CPUs 95 by ignoring such an instruction. */ 96 if (cause == 0) { 97 unsigned int insn; 98 __get_user(insn, (unsigned int __user *)regs->pc); 99 if ((insn >> 21 & 0x1f) == 0x1f && 100 /* ldq ldl ldt lds ldg ldf ldwu ldbu */ 101 (1ul << (insn >> 26) & 0x30f00001400ul)) { 102 regs->pc += 4; 103 return; 104 } 105 } 106 107 /* If we're in an interrupt context, or have no user context, 108 we must not take the fault. */ 109 if (!mm || in_atomic()) 110 goto no_context; 111 112 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 113 if (address >= TASK_SIZE) 114 goto vmalloc_fault; 115 #endif 116 117 down_read(&mm->mmap_sem); 118 vma = find_vma(mm, address); 119 if (!vma) 120 goto bad_area; 121 if (vma->vm_start <= address) 122 goto good_area; 123 if (!(vma->vm_flags & VM_GROWSDOWN)) 124 goto bad_area; 125 if (expand_stack(vma, address)) 126 goto bad_area; 127 128 /* Ok, we have a good vm_area for this memory access, so 129 we can handle it. */ 130 good_area: 131 si_code = SEGV_ACCERR; 132 if (cause < 0) { 133 if (!(vma->vm_flags & VM_EXEC)) 134 goto bad_area; 135 } else if (!cause) { 136 /* Allow reads even for write-only mappings */ 137 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 138 goto bad_area; 139 } else { 140 if (!(vma->vm_flags & VM_WRITE)) 141 goto bad_area; 142 } 143 144 /* If for any reason at all we couldn't handle the fault, 145 make sure we exit gracefully rather than endlessly redo 146 the fault. */ 147 fault = handle_mm_fault(mm, vma, address, cause > 0 ? FAULT_FLAG_WRITE : 0); 148 up_read(&mm->mmap_sem); 149 if (unlikely(fault & VM_FAULT_ERROR)) { 150 if (fault & VM_FAULT_OOM) 151 goto out_of_memory; 152 else if (fault & VM_FAULT_SIGBUS) 153 goto do_sigbus; 154 BUG(); 155 } 156 if (fault & VM_FAULT_MAJOR) 157 current->maj_flt++; 158 else 159 current->min_flt++; 160 return; 161 162 /* Something tried to access memory that isn't in our memory map. 163 Fix it, but check if it's kernel or user first. */ 164 bad_area: 165 up_read(&mm->mmap_sem); 166 167 if (user_mode(regs)) 168 goto do_sigsegv; 169 170 no_context: 171 /* Are we prepared to handle this fault as an exception? */ 172 if ((fixup = search_exception_tables(regs->pc)) != 0) { 173 unsigned long newpc; 174 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 175 regs->pc = newpc; 176 return; 177 } 178 179 /* Oops. The kernel tried to access some bad page. We'll have to 180 terminate things with extreme prejudice. */ 181 printk(KERN_ALERT "Unable to handle kernel paging request at " 182 "virtual address %016lx\n", address); 183 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 184 do_exit(SIGKILL); 185 186 /* We ran out of memory, or some other thing happened to us that 187 made us unable to handle the page fault gracefully. */ 188 out_of_memory: 189 if (!user_mode(regs)) 190 goto no_context; 191 pagefault_out_of_memory(); 192 return; 193 194 do_sigbus: 195 /* Send a sigbus, regardless of whether we were in kernel 196 or user mode. */ 197 info.si_signo = SIGBUS; 198 info.si_errno = 0; 199 info.si_code = BUS_ADRERR; 200 info.si_addr = (void __user *) address; 201 force_sig_info(SIGBUS, &info, current); 202 if (!user_mode(regs)) 203 goto no_context; 204 return; 205 206 do_sigsegv: 207 info.si_signo = SIGSEGV; 208 info.si_errno = 0; 209 info.si_code = si_code; 210 info.si_addr = (void __user *) address; 211 force_sig_info(SIGSEGV, &info, current); 212 return; 213 214 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 215 vmalloc_fault: 216 if (user_mode(regs)) 217 goto do_sigsegv; 218 else { 219 /* Synchronize this task's top level page-table 220 with the "reference" page table from init. */ 221 long index = pgd_index(address); 222 pgd_t *pgd, *pgd_k; 223 224 pgd = current->active_mm->pgd + index; 225 pgd_k = swapper_pg_dir + index; 226 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 227 pgd_val(*pgd) = pgd_val(*pgd_k); 228 return; 229 } 230 goto no_context; 231 } 232 #endif 233 } 234