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