1 /* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Copyright (C) 1995 - 2000 by Ralf Baechle 7 */ 8 #include <linux/context_tracking.h> 9 #include <linux/signal.h> 10 #include <linux/sched.h> 11 #include <linux/interrupt.h> 12 #include <linux/kernel.h> 13 #include <linux/errno.h> 14 #include <linux/string.h> 15 #include <linux/types.h> 16 #include <linux/ptrace.h> 17 #include <linux/ratelimit.h> 18 #include <linux/mman.h> 19 #include <linux/mm.h> 20 #include <linux/smp.h> 21 #include <linux/kprobes.h> 22 #include <linux/perf_event.h> 23 #include <linux/uaccess.h> 24 25 #include <asm/branch.h> 26 #include <asm/mmu_context.h> 27 #include <asm/ptrace.h> 28 #include <asm/highmem.h> /* For VMALLOC_END */ 29 #include <linux/kdebug.h> 30 31 int show_unhandled_signals = 1; 32 33 /* 34 * This routine handles page faults. It determines the address, 35 * and the problem, and then passes it off to one of the appropriate 36 * routines. 37 */ 38 static void __do_page_fault(struct pt_regs *regs, unsigned long write, 39 unsigned long address) 40 { 41 struct vm_area_struct * vma = NULL; 42 struct task_struct *tsk = current; 43 struct mm_struct *mm = tsk->mm; 44 const int field = sizeof(unsigned long) * 2; 45 int si_code; 46 vm_fault_t fault; 47 unsigned int flags = FAULT_FLAG_DEFAULT; 48 49 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); 50 51 #if 0 52 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(), 53 current->comm, current->pid, field, address, write, 54 field, regs->cp0_epc); 55 #endif 56 57 #ifdef CONFIG_KPROBES 58 /* 59 * This is to notify the fault handler of the kprobes. 60 */ 61 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1, 62 current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) 63 return; 64 #endif 65 66 si_code = SEGV_MAPERR; 67 68 /* 69 * We fault-in kernel-space virtual memory on-demand. The 70 * 'reference' page table is init_mm.pgd. 71 * 72 * NOTE! We MUST NOT take any locks for this case. We may 73 * be in an interrupt or a critical region, and should 74 * only copy the information from the master page table, 75 * nothing more. 76 */ 77 #ifdef CONFIG_64BIT 78 # define VMALLOC_FAULT_TARGET no_context 79 #else 80 # define VMALLOC_FAULT_TARGET vmalloc_fault 81 #endif 82 83 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 84 goto VMALLOC_FAULT_TARGET; 85 #ifdef MODULE_START 86 if (unlikely(address >= MODULE_START && address < MODULE_END)) 87 goto VMALLOC_FAULT_TARGET; 88 #endif 89 90 /* 91 * If we're in an interrupt or have no user 92 * context, we must not take the fault.. 93 */ 94 if (faulthandler_disabled() || !mm) 95 goto bad_area_nosemaphore; 96 97 if (user_mode(regs)) 98 flags |= FAULT_FLAG_USER; 99 100 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 101 retry: 102 vma = lock_mm_and_find_vma(mm, address, regs); 103 if (!vma) 104 goto bad_area_nosemaphore; 105 /* 106 * Ok, we have a good vm_area for this memory access, so 107 * we can handle it.. 108 */ 109 si_code = SEGV_ACCERR; 110 111 if (write) { 112 if (!(vma->vm_flags & VM_WRITE)) 113 goto bad_area; 114 flags |= FAULT_FLAG_WRITE; 115 } else { 116 if (cpu_has_rixi) { 117 if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { 118 #if 0 119 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n", 120 raw_smp_processor_id(), 121 current->comm, current->pid, 122 field, address, write, 123 field, regs->cp0_epc); 124 #endif 125 goto bad_area; 126 } 127 if (!(vma->vm_flags & VM_READ) && 128 exception_epc(regs) != address) { 129 #if 0 130 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n", 131 raw_smp_processor_id(), 132 current->comm, current->pid, 133 field, address, write, 134 field, regs->cp0_epc); 135 #endif 136 goto bad_area; 137 } 138 } else { 139 if (unlikely(!vma_is_accessible(vma))) 140 goto bad_area; 141 } 142 } 143 144 /* 145 * If for any reason at all we couldn't handle the fault, 146 * make sure we exit gracefully rather than endlessly redo 147 * the fault. 148 */ 149 fault = handle_mm_fault(vma, address, flags, regs); 150 151 if (fault_signal_pending(fault, regs)) { 152 if (!user_mode(regs)) 153 goto no_context; 154 return; 155 } 156 157 /* The fault is fully completed (including releasing mmap lock) */ 158 if (fault & VM_FAULT_COMPLETED) 159 return; 160 161 if (unlikely(fault & VM_FAULT_ERROR)) { 162 if (fault & VM_FAULT_OOM) 163 goto out_of_memory; 164 else if (fault & VM_FAULT_SIGSEGV) 165 goto bad_area; 166 else if (fault & VM_FAULT_SIGBUS) 167 goto do_sigbus; 168 BUG(); 169 } 170 171 if (fault & VM_FAULT_RETRY) { 172 flags |= FAULT_FLAG_TRIED; 173 174 /* 175 * No need to mmap_read_unlock(mm) as we would 176 * have already released it in __lock_page_or_retry 177 * in mm/filemap.c. 178 */ 179 180 goto retry; 181 } 182 183 mmap_read_unlock(mm); 184 return; 185 186 /* 187 * Something tried to access memory that isn't in our memory map.. 188 * Fix it, but check if it's kernel or user first.. 189 */ 190 bad_area: 191 mmap_read_unlock(mm); 192 193 bad_area_nosemaphore: 194 /* User mode accesses just cause a SIGSEGV */ 195 if (user_mode(regs)) { 196 tsk->thread.cp0_badvaddr = address; 197 tsk->thread.error_code = write; 198 if (show_unhandled_signals && 199 unhandled_signal(tsk, SIGSEGV) && 200 __ratelimit(&ratelimit_state)) { 201 pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n", 202 tsk->comm, 203 write ? "write access to" : "read access from", 204 field, address); 205 pr_info("epc = %0*lx in", field, 206 (unsigned long) regs->cp0_epc); 207 print_vma_addr(KERN_CONT " ", regs->cp0_epc); 208 pr_cont("\n"); 209 pr_info("ra = %0*lx in", field, 210 (unsigned long) regs->regs[31]); 211 print_vma_addr(KERN_CONT " ", regs->regs[31]); 212 pr_cont("\n"); 213 } 214 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 215 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 216 return; 217 } 218 219 no_context: 220 /* Are we prepared to handle this kernel fault? */ 221 if (fixup_exception(regs)) { 222 current->thread.cp0_baduaddr = address; 223 return; 224 } 225 226 /* 227 * Oops. The kernel tried to access some bad page. We'll have to 228 * terminate things with extreme prejudice. 229 */ 230 bust_spinlocks(1); 231 232 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 233 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 234 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 235 field, regs->regs[31]); 236 die("Oops", regs); 237 238 out_of_memory: 239 /* 240 * We ran out of memory, call the OOM killer, and return the userspace 241 * (which will retry the fault, or kill us if we got oom-killed). 242 */ 243 mmap_read_unlock(mm); 244 if (!user_mode(regs)) 245 goto no_context; 246 pagefault_out_of_memory(); 247 return; 248 249 do_sigbus: 250 mmap_read_unlock(mm); 251 252 /* Kernel mode? Handle exceptions or die */ 253 if (!user_mode(regs)) 254 goto no_context; 255 256 /* 257 * Send a sigbus, regardless of whether we were in kernel 258 * or user mode. 259 */ 260 #if 0 261 printk("do_page_fault() #3: sending SIGBUS to %s for " 262 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 263 tsk->comm, 264 write ? "write access to" : "read access from", 265 field, address, 266 field, (unsigned long) regs->cp0_epc, 267 field, (unsigned long) regs->regs[31]); 268 #endif 269 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 270 tsk->thread.cp0_badvaddr = address; 271 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 272 273 return; 274 #ifndef CONFIG_64BIT 275 vmalloc_fault: 276 { 277 /* 278 * Synchronize this task's top level page-table 279 * with the 'reference' page table. 280 * 281 * Do _not_ use "tsk" here. We might be inside 282 * an interrupt in the middle of a task switch.. 283 */ 284 int offset = pgd_index(address); 285 pgd_t *pgd, *pgd_k; 286 p4d_t *p4d, *p4d_k; 287 pud_t *pud, *pud_k; 288 pmd_t *pmd, *pmd_k; 289 pte_t *pte_k; 290 291 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 292 pgd_k = init_mm.pgd + offset; 293 294 if (!pgd_present(*pgd_k)) 295 goto no_context; 296 set_pgd(pgd, *pgd_k); 297 298 p4d = p4d_offset(pgd, address); 299 p4d_k = p4d_offset(pgd_k, address); 300 if (!p4d_present(*p4d_k)) 301 goto no_context; 302 303 pud = pud_offset(p4d, address); 304 pud_k = pud_offset(p4d_k, address); 305 if (!pud_present(*pud_k)) 306 goto no_context; 307 308 pmd = pmd_offset(pud, address); 309 pmd_k = pmd_offset(pud_k, address); 310 if (!pmd_present(*pmd_k)) 311 goto no_context; 312 set_pmd(pmd, *pmd_k); 313 314 pte_k = pte_offset_kernel(pmd_k, address); 315 if (!pte_present(*pte_k)) 316 goto no_context; 317 return; 318 } 319 #endif 320 } 321 NOKPROBE_SYMBOL(__do_page_fault); 322 323 asmlinkage void do_page_fault(struct pt_regs *regs, 324 unsigned long write, unsigned long address) 325 { 326 enum ctx_state prev_state; 327 328 prev_state = exception_enter(); 329 __do_page_fault(regs, write, address); 330 exception_exit(prev_state); 331 } 332 NOKPROBE_SYMBOL(do_page_fault); 333