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/module.h> 22 #include <linux/kprobes.h> 23 #include <linux/perf_event.h> 24 #include <linux/uaccess.h> 25 26 #include <asm/branch.h> 27 #include <asm/mmu_context.h> 28 #include <asm/ptrace.h> 29 #include <asm/highmem.h> /* For VMALLOC_END */ 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 __kprobes __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 siginfo_t info; 47 int fault; 48 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 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. The 61 * exception code is redundant as it is also carried in REGS, 62 * but we pass it anyhow. 63 */ 64 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1, 65 (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP) 66 return; 67 #endif 68 69 info.si_code = SEGV_MAPERR; 70 71 /* 72 * We fault-in kernel-space virtual memory on-demand. The 73 * 'reference' page table is init_mm.pgd. 74 * 75 * NOTE! We MUST NOT take any locks for this case. We may 76 * be in an interrupt or a critical region, and should 77 * only copy the information from the master page table, 78 * nothing more. 79 */ 80 #ifdef CONFIG_64BIT 81 # define VMALLOC_FAULT_TARGET no_context 82 #else 83 # define VMALLOC_FAULT_TARGET vmalloc_fault 84 #endif 85 86 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 87 goto VMALLOC_FAULT_TARGET; 88 #ifdef MODULE_START 89 if (unlikely(address >= MODULE_START && address < MODULE_END)) 90 goto VMALLOC_FAULT_TARGET; 91 #endif 92 93 /* 94 * If we're in an interrupt or have no user 95 * context, we must not take the fault.. 96 */ 97 if (faulthandler_disabled() || !mm) 98 goto bad_area_nosemaphore; 99 100 if (user_mode(regs)) 101 flags |= FAULT_FLAG_USER; 102 retry: 103 down_read(&mm->mmap_sem); 104 vma = find_vma(mm, address); 105 if (!vma) 106 goto bad_area; 107 if (vma->vm_start <= address) 108 goto good_area; 109 if (!(vma->vm_flags & VM_GROWSDOWN)) 110 goto bad_area; 111 if (expand_stack(vma, address)) 112 goto bad_area; 113 /* 114 * Ok, we have a good vm_area for this memory access, so 115 * we can handle it.. 116 */ 117 good_area: 118 info.si_code = SEGV_ACCERR; 119 120 if (write) { 121 if (!(vma->vm_flags & VM_WRITE)) 122 goto bad_area; 123 flags |= FAULT_FLAG_WRITE; 124 } else { 125 if (cpu_has_rixi) { 126 if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { 127 #if 0 128 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n", 129 raw_smp_processor_id(), 130 current->comm, current->pid, 131 field, address, write, 132 field, regs->cp0_epc); 133 #endif 134 goto bad_area; 135 } 136 if (!(vma->vm_flags & VM_READ) && 137 exception_epc(regs) != address) { 138 #if 0 139 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n", 140 raw_smp_processor_id(), 141 current->comm, current->pid, 142 field, address, write, 143 field, regs->cp0_epc); 144 #endif 145 goto bad_area; 146 } 147 } else { 148 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 149 goto bad_area; 150 } 151 } 152 153 /* 154 * If for any reason at all we couldn't handle the fault, 155 * make sure we exit gracefully rather than endlessly redo 156 * the fault. 157 */ 158 fault = handle_mm_fault(mm, vma, address, flags); 159 160 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 161 return; 162 163 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 164 if (unlikely(fault & VM_FAULT_ERROR)) { 165 if (fault & VM_FAULT_OOM) 166 goto out_of_memory; 167 else if (fault & VM_FAULT_SIGSEGV) 168 goto bad_area; 169 else if (fault & VM_FAULT_SIGBUS) 170 goto do_sigbus; 171 BUG(); 172 } 173 if (flags & FAULT_FLAG_ALLOW_RETRY) { 174 if (fault & VM_FAULT_MAJOR) { 175 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 176 regs, address); 177 tsk->maj_flt++; 178 } else { 179 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 180 regs, address); 181 tsk->min_flt++; 182 } 183 if (fault & VM_FAULT_RETRY) { 184 flags &= ~FAULT_FLAG_ALLOW_RETRY; 185 flags |= FAULT_FLAG_TRIED; 186 187 /* 188 * No need to up_read(&mm->mmap_sem) as we would 189 * have already released it in __lock_page_or_retry 190 * in mm/filemap.c. 191 */ 192 193 goto retry; 194 } 195 } 196 197 up_read(&mm->mmap_sem); 198 return; 199 200 /* 201 * Something tried to access memory that isn't in our memory map.. 202 * Fix it, but check if it's kernel or user first.. 203 */ 204 bad_area: 205 up_read(&mm->mmap_sem); 206 207 bad_area_nosemaphore: 208 /* User mode accesses just cause a SIGSEGV */ 209 if (user_mode(regs)) { 210 tsk->thread.cp0_badvaddr = address; 211 tsk->thread.error_code = write; 212 if (show_unhandled_signals && 213 unhandled_signal(tsk, SIGSEGV) && 214 __ratelimit(&ratelimit_state)) { 215 pr_info("\ndo_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx", 216 tsk->comm, 217 write ? "write access to" : "read access from", 218 field, address); 219 pr_info("epc = %0*lx in", field, 220 (unsigned long) regs->cp0_epc); 221 print_vma_addr(" ", regs->cp0_epc); 222 pr_info("ra = %0*lx in", field, 223 (unsigned long) regs->regs[31]); 224 print_vma_addr(" ", regs->regs[31]); 225 pr_info("\n"); 226 } 227 info.si_signo = SIGSEGV; 228 info.si_errno = 0; 229 /* info.si_code has been set above */ 230 info.si_addr = (void __user *) address; 231 force_sig_info(SIGSEGV, &info, tsk); 232 return; 233 } 234 235 no_context: 236 /* Are we prepared to handle this kernel fault? */ 237 if (fixup_exception(regs)) { 238 current->thread.cp0_baduaddr = address; 239 return; 240 } 241 242 /* 243 * Oops. The kernel tried to access some bad page. We'll have to 244 * terminate things with extreme prejudice. 245 */ 246 bust_spinlocks(1); 247 248 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 249 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 250 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 251 field, regs->regs[31]); 252 die("Oops", regs); 253 254 out_of_memory: 255 /* 256 * We ran out of memory, call the OOM killer, and return the userspace 257 * (which will retry the fault, or kill us if we got oom-killed). 258 */ 259 up_read(&mm->mmap_sem); 260 if (!user_mode(regs)) 261 goto no_context; 262 pagefault_out_of_memory(); 263 return; 264 265 do_sigbus: 266 up_read(&mm->mmap_sem); 267 268 /* Kernel mode? Handle exceptions or die */ 269 if (!user_mode(regs)) 270 goto no_context; 271 else 272 /* 273 * Send a sigbus, regardless of whether we were in kernel 274 * or user mode. 275 */ 276 #if 0 277 printk("do_page_fault() #3: sending SIGBUS to %s for " 278 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 279 tsk->comm, 280 write ? "write access to" : "read access from", 281 field, address, 282 field, (unsigned long) regs->cp0_epc, 283 field, (unsigned long) regs->regs[31]); 284 #endif 285 tsk->thread.cp0_badvaddr = address; 286 info.si_signo = SIGBUS; 287 info.si_errno = 0; 288 info.si_code = BUS_ADRERR; 289 info.si_addr = (void __user *) address; 290 force_sig_info(SIGBUS, &info, tsk); 291 292 return; 293 #ifndef CONFIG_64BIT 294 vmalloc_fault: 295 { 296 /* 297 * Synchronize this task's top level page-table 298 * with the 'reference' page table. 299 * 300 * Do _not_ use "tsk" here. We might be inside 301 * an interrupt in the middle of a task switch.. 302 */ 303 int offset = __pgd_offset(address); 304 pgd_t *pgd, *pgd_k; 305 pud_t *pud, *pud_k; 306 pmd_t *pmd, *pmd_k; 307 pte_t *pte_k; 308 309 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 310 pgd_k = init_mm.pgd + offset; 311 312 if (!pgd_present(*pgd_k)) 313 goto no_context; 314 set_pgd(pgd, *pgd_k); 315 316 pud = pud_offset(pgd, address); 317 pud_k = pud_offset(pgd_k, address); 318 if (!pud_present(*pud_k)) 319 goto no_context; 320 321 pmd = pmd_offset(pud, address); 322 pmd_k = pmd_offset(pud_k, address); 323 if (!pmd_present(*pmd_k)) 324 goto no_context; 325 set_pmd(pmd, *pmd_k); 326 327 pte_k = pte_offset_kernel(pmd_k, address); 328 if (!pte_present(*pte_k)) 329 goto no_context; 330 return; 331 } 332 #endif 333 } 334 335 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, 336 unsigned long write, unsigned long address) 337 { 338 enum ctx_state prev_state; 339 340 prev_state = exception_enter(); 341 __do_page_fault(regs, write, address); 342 exception_exit(prev_state); 343 } 344