1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/arch/alpha/mm/fault.c 4 * 5 * Copyright (C) 1995 Linus Torvalds 6 */ 7 8 #include <linux/sched/signal.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/interrupt.h> 26 #include <linux/extable.h> 27 #include <linux/uaccess.h> 28 #include <linux/perf_event.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)+10 : (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 si_code = SEGV_MAPERR; 92 vm_fault_t fault; 93 unsigned int flags = FAULT_FLAG_DEFAULT; 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 || faulthandler_disabled()) 112 goto no_context; 113 114 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 115 if (address >= TASK_SIZE) 116 goto vmalloc_fault; 117 #endif 118 if (user_mode(regs)) 119 flags |= FAULT_FLAG_USER; 120 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 121 retry: 122 mmap_read_lock(mm); 123 vma = find_vma(mm, address); 124 if (!vma) 125 goto bad_area; 126 if (vma->vm_start <= address) 127 goto good_area; 128 if (!(vma->vm_flags & VM_GROWSDOWN)) 129 goto bad_area; 130 if (expand_stack(vma, address)) 131 goto bad_area; 132 133 /* Ok, we have a good vm_area for this memory access, so 134 we can handle it. */ 135 good_area: 136 si_code = SEGV_ACCERR; 137 if (cause < 0) { 138 if (!(vma->vm_flags & VM_EXEC)) 139 goto bad_area; 140 } else if (!cause) { 141 /* Allow reads even for write-only mappings */ 142 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) 143 goto bad_area; 144 } else { 145 if (!(vma->vm_flags & VM_WRITE)) 146 goto bad_area; 147 flags |= FAULT_FLAG_WRITE; 148 } 149 150 /* If for any reason at all we couldn't handle the fault, 151 make sure we exit gracefully rather than endlessly redo 152 the fault. */ 153 fault = handle_mm_fault(vma, address, flags, regs); 154 155 if (fault_signal_pending(fault, regs)) { 156 if (!user_mode(regs)) 157 goto no_context; 158 return; 159 } 160 161 /* The fault is fully completed (including releasing mmap lock) */ 162 if (fault & VM_FAULT_COMPLETED) 163 return; 164 165 if (unlikely(fault & VM_FAULT_ERROR)) { 166 if (fault & VM_FAULT_OOM) 167 goto out_of_memory; 168 else if (fault & VM_FAULT_SIGSEGV) 169 goto bad_area; 170 else if (fault & VM_FAULT_SIGBUS) 171 goto do_sigbus; 172 BUG(); 173 } 174 175 if (fault & VM_FAULT_RETRY) { 176 flags |= FAULT_FLAG_TRIED; 177 178 /* No need to mmap_read_unlock(mm) as we would 179 * have already released it in __lock_page_or_retry 180 * in mm/filemap.c. 181 */ 182 183 goto retry; 184 } 185 186 mmap_read_unlock(mm); 187 188 return; 189 190 /* Something tried to access memory that isn't in our memory map. 191 Fix it, but check if it's kernel or user first. */ 192 bad_area: 193 mmap_read_unlock(mm); 194 195 if (user_mode(regs)) 196 goto do_sigsegv; 197 198 no_context: 199 /* Are we prepared to handle this fault as an exception? */ 200 if ((fixup = search_exception_tables(regs->pc)) != 0) { 201 unsigned long newpc; 202 newpc = fixup_exception(dpf_reg, fixup, regs->pc); 203 regs->pc = newpc; 204 return; 205 } 206 207 /* Oops. The kernel tried to access some bad page. We'll have to 208 terminate things with extreme prejudice. */ 209 printk(KERN_ALERT "Unable to handle kernel paging request at " 210 "virtual address %016lx\n", address); 211 die_if_kernel("Oops", regs, cause, (unsigned long*)regs - 16); 212 make_task_dead(SIGKILL); 213 214 /* We ran out of memory, or some other thing happened to us that 215 made us unable to handle the page fault gracefully. */ 216 out_of_memory: 217 mmap_read_unlock(mm); 218 if (!user_mode(regs)) 219 goto no_context; 220 pagefault_out_of_memory(); 221 return; 222 223 do_sigbus: 224 mmap_read_unlock(mm); 225 /* Send a sigbus, regardless of whether we were in kernel 226 or user mode. */ 227 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *) address); 228 if (!user_mode(regs)) 229 goto no_context; 230 return; 231 232 do_sigsegv: 233 force_sig_fault(SIGSEGV, si_code, (void __user *) address); 234 return; 235 236 #ifdef CONFIG_ALPHA_LARGE_VMALLOC 237 vmalloc_fault: 238 if (user_mode(regs)) 239 goto do_sigsegv; 240 else { 241 /* Synchronize this task's top level page-table 242 with the "reference" page table from init. */ 243 long index = pgd_index(address); 244 pgd_t *pgd, *pgd_k; 245 246 pgd = current->active_mm->pgd + index; 247 pgd_k = swapper_pg_dir + index; 248 if (!pgd_present(*pgd) && pgd_present(*pgd_k)) { 249 pgd_val(*pgd) = pgd_val(*pgd_k); 250 return; 251 } 252 goto no_context; 253 } 254 #endif 255 } 256