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 <asm/traps.h> 30 #include <linux/kdebug.h> 31 32 int show_unhandled_signals = 1; 33 34 /* 35 * This routine handles page faults. It determines the address, 36 * and the problem, and then passes it off to one of the appropriate 37 * routines. 38 */ 39 static void __do_page_fault(struct pt_regs *regs, unsigned long write, 40 unsigned long address) 41 { 42 struct vm_area_struct * vma = NULL; 43 struct task_struct *tsk = current; 44 struct mm_struct *mm = tsk->mm; 45 const int field = sizeof(unsigned long) * 2; 46 int si_code; 47 vm_fault_t fault; 48 unsigned int flags = FAULT_FLAG_DEFAULT; 49 50 static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10); 51 52 #if 0 53 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(), 54 current->comm, current->pid, field, address, write, 55 field, regs->cp0_epc); 56 #endif 57 58 #ifdef CONFIG_KPROBES 59 /* 60 * This is to notify the fault handler of the kprobes. 61 */ 62 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1, 63 current->thread.trap_nr, SIGSEGV) == NOTIFY_STOP) 64 return; 65 #endif 66 67 si_code = SEGV_MAPERR; 68 69 /* 70 * We fault-in kernel-space virtual memory on-demand. The 71 * 'reference' page table is init_mm.pgd. 72 * 73 * NOTE! We MUST NOT take any locks for this case. We may 74 * be in an interrupt or a critical region, and should 75 * only copy the information from the master page table, 76 * nothing more. 77 */ 78 #ifdef CONFIG_64BIT 79 # define VMALLOC_FAULT_TARGET no_context 80 #else 81 # define VMALLOC_FAULT_TARGET vmalloc_fault 82 #endif 83 84 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 85 goto VMALLOC_FAULT_TARGET; 86 #ifdef MODULE_START 87 if (unlikely(address >= MODULE_START && address < MODULE_END)) 88 goto VMALLOC_FAULT_TARGET; 89 #endif 90 91 /* 92 * If we're in an interrupt or have no user 93 * context, we must not take the fault.. 94 */ 95 if (faulthandler_disabled() || !mm) 96 goto bad_area_nosemaphore; 97 98 if (user_mode(regs)) 99 flags |= FAULT_FLAG_USER; 100 101 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 102 retry: 103 vma = lock_mm_and_find_vma(mm, address, regs); 104 if (!vma) 105 goto bad_area_nosemaphore; 106 /* 107 * Ok, we have a good vm_area for this memory access, so 108 * we can handle it.. 109 */ 110 si_code = SEGV_ACCERR; 111 112 if (write) { 113 if (!(vma->vm_flags & VM_WRITE)) 114 goto bad_area; 115 flags |= FAULT_FLAG_WRITE; 116 } else { 117 if (cpu_has_rixi) { 118 if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { 119 #if 0 120 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n", 121 raw_smp_processor_id(), 122 current->comm, current->pid, 123 field, address, write, 124 field, regs->cp0_epc); 125 #endif 126 goto bad_area; 127 } 128 if (!(vma->vm_flags & VM_READ) && 129 exception_epc(regs) != address) { 130 #if 0 131 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n", 132 raw_smp_processor_id(), 133 current->comm, current->pid, 134 field, address, write, 135 field, regs->cp0_epc); 136 #endif 137 goto bad_area; 138 } 139 } else { 140 if (unlikely(!vma_is_accessible(vma))) 141 goto bad_area; 142 } 143 } 144 145 /* 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 */ 150 fault = handle_mm_fault(vma, address, flags, regs); 151 152 if (fault_signal_pending(fault, regs)) { 153 if (!user_mode(regs)) 154 goto no_context; 155 return; 156 } 157 158 /* The fault is fully completed (including releasing mmap lock) */ 159 if (fault & VM_FAULT_COMPLETED) 160 return; 161 162 if (unlikely(fault & VM_FAULT_ERROR)) { 163 if (fault & VM_FAULT_OOM) 164 goto out_of_memory; 165 else if (fault & VM_FAULT_SIGSEGV) 166 goto bad_area; 167 else if (fault & VM_FAULT_SIGBUS) 168 goto do_sigbus; 169 BUG(); 170 } 171 172 if (fault & VM_FAULT_RETRY) { 173 flags |= FAULT_FLAG_TRIED; 174 175 /* 176 * No need to mmap_read_unlock(mm) as we would 177 * have already released it in __lock_page_or_retry 178 * in mm/filemap.c. 179 */ 180 181 goto retry; 182 } 183 184 mmap_read_unlock(mm); 185 return; 186 187 /* 188 * Something tried to access memory that isn't in our memory map.. 189 * Fix it, but check if it's kernel or user first.. 190 */ 191 bad_area: 192 mmap_read_unlock(mm); 193 194 bad_area_nosemaphore: 195 /* User mode accesses just cause a SIGSEGV */ 196 if (user_mode(regs)) { 197 tsk->thread.cp0_badvaddr = address; 198 tsk->thread.error_code = write; 199 if (show_unhandled_signals && 200 unhandled_signal(tsk, SIGSEGV) && 201 __ratelimit(&ratelimit_state)) { 202 pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n", 203 tsk->comm, 204 write ? "write access to" : "read access from", 205 field, address); 206 pr_info("epc = %0*lx in", field, 207 (unsigned long) regs->cp0_epc); 208 print_vma_addr(KERN_CONT " ", regs->cp0_epc); 209 pr_cont("\n"); 210 pr_info("ra = %0*lx in", field, 211 (unsigned long) regs->regs[31]); 212 print_vma_addr(KERN_CONT " ", regs->regs[31]); 213 pr_cont("\n"); 214 } 215 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 216 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 217 return; 218 } 219 220 no_context: 221 /* Are we prepared to handle this kernel fault? */ 222 if (fixup_exception(regs)) { 223 current->thread.cp0_baduaddr = address; 224 return; 225 } 226 227 /* 228 * Oops. The kernel tried to access some bad page. We'll have to 229 * terminate things with extreme prejudice. 230 */ 231 bust_spinlocks(1); 232 233 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 234 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 235 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 236 field, regs->regs[31]); 237 die("Oops", regs); 238 239 out_of_memory: 240 /* 241 * We ran out of memory, call the OOM killer, and return the userspace 242 * (which will retry the fault, or kill us if we got oom-killed). 243 */ 244 mmap_read_unlock(mm); 245 if (!user_mode(regs)) 246 goto no_context; 247 pagefault_out_of_memory(); 248 return; 249 250 do_sigbus: 251 mmap_read_unlock(mm); 252 253 /* Kernel mode? Handle exceptions or die */ 254 if (!user_mode(regs)) 255 goto no_context; 256 257 /* 258 * Send a sigbus, regardless of whether we were in kernel 259 * or user mode. 260 */ 261 #if 0 262 printk("do_page_fault() #3: sending SIGBUS to %s for " 263 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 264 tsk->comm, 265 write ? "write access to" : "read access from", 266 field, address, 267 field, (unsigned long) regs->cp0_epc, 268 field, (unsigned long) regs->regs[31]); 269 #endif 270 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 271 tsk->thread.cp0_badvaddr = address; 272 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 273 274 return; 275 #ifndef CONFIG_64BIT 276 vmalloc_fault: 277 { 278 /* 279 * Synchronize this task's top level page-table 280 * with the 'reference' page table. 281 * 282 * Do _not_ use "tsk" here. We might be inside 283 * an interrupt in the middle of a task switch.. 284 */ 285 int offset = pgd_index(address); 286 pgd_t *pgd, *pgd_k; 287 p4d_t *p4d, *p4d_k; 288 pud_t *pud, *pud_k; 289 pmd_t *pmd, *pmd_k; 290 pte_t *pte_k; 291 292 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 293 pgd_k = init_mm.pgd + offset; 294 295 if (!pgd_present(*pgd_k)) 296 goto no_context; 297 set_pgd(pgd, *pgd_k); 298 299 p4d = p4d_offset(pgd, address); 300 p4d_k = p4d_offset(pgd_k, address); 301 if (!p4d_present(*p4d_k)) 302 goto no_context; 303 304 pud = pud_offset(p4d, address); 305 pud_k = pud_offset(p4d_k, address); 306 if (!pud_present(*pud_k)) 307 goto no_context; 308 309 pmd = pmd_offset(pud, address); 310 pmd_k = pmd_offset(pud_k, address); 311 if (!pmd_present(*pmd_k)) 312 goto no_context; 313 set_pmd(pmd, *pmd_k); 314 315 pte_k = pte_offset_kernel(pmd_k, address); 316 if (!pte_present(*pte_k)) 317 goto no_context; 318 return; 319 } 320 #endif 321 } 322 NOKPROBE_SYMBOL(__do_page_fault); 323 324 asmlinkage void do_page_fault(struct pt_regs *regs, 325 unsigned long write, unsigned long address) 326 { 327 enum ctx_state prev_state; 328 329 prev_state = exception_enter(); 330 __do_page_fault(regs, write, address); 331 exception_exit(prev_state); 332 } 333 NOKPROBE_SYMBOL(do_page_fault); 334