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 __kprobes __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 mmap_read_lock(mm); 103 vma = find_vma(mm, address); 104 if (!vma) 105 goto bad_area; 106 if (vma->vm_start <= address) 107 goto good_area; 108 if (!(vma->vm_flags & VM_GROWSDOWN)) 109 goto bad_area; 110 if (expand_stack(vma, address)) 111 goto bad_area; 112 /* 113 * Ok, we have a good vm_area for this memory access, so 114 * we can handle it.. 115 */ 116 good_area: 117 si_code = SEGV_ACCERR; 118 119 if (write) { 120 if (!(vma->vm_flags & VM_WRITE)) 121 goto bad_area; 122 flags |= FAULT_FLAG_WRITE; 123 } else { 124 if (cpu_has_rixi) { 125 if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { 126 #if 0 127 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n", 128 raw_smp_processor_id(), 129 current->comm, current->pid, 130 field, address, write, 131 field, regs->cp0_epc); 132 #endif 133 goto bad_area; 134 } 135 if (!(vma->vm_flags & VM_READ) && 136 exception_epc(regs) != address) { 137 #if 0 138 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation\n", 139 raw_smp_processor_id(), 140 current->comm, current->pid, 141 field, address, write, 142 field, regs->cp0_epc); 143 #endif 144 goto bad_area; 145 } 146 } else { 147 if (unlikely(!vma_is_accessible(vma))) 148 goto bad_area; 149 } 150 } 151 152 /* 153 * If for any reason at all we couldn't handle the fault, 154 * make sure we exit gracefully rather than endlessly redo 155 * the fault. 156 */ 157 fault = handle_mm_fault(vma, address, flags, regs); 158 159 if (fault_signal_pending(fault, regs)) { 160 if (!user_mode(regs)) 161 goto no_context; 162 return; 163 } 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 if (flags & FAULT_FLAG_ALLOW_RETRY) { 175 if (fault & VM_FAULT_RETRY) { 176 flags |= FAULT_FLAG_TRIED; 177 178 /* 179 * No need to mmap_read_unlock(mm) as we would 180 * have already released it in __lock_page_or_retry 181 * in mm/filemap.c. 182 */ 183 184 goto retry; 185 } 186 } 187 188 mmap_read_unlock(mm); 189 return; 190 191 /* 192 * Something tried to access memory that isn't in our memory map.. 193 * Fix it, but check if it's kernel or user first.. 194 */ 195 bad_area: 196 mmap_read_unlock(mm); 197 198 bad_area_nosemaphore: 199 /* User mode accesses just cause a SIGSEGV */ 200 if (user_mode(regs)) { 201 tsk->thread.cp0_badvaddr = address; 202 tsk->thread.error_code = write; 203 if (show_unhandled_signals && 204 unhandled_signal(tsk, SIGSEGV) && 205 __ratelimit(&ratelimit_state)) { 206 pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n", 207 tsk->comm, 208 write ? "write access to" : "read access from", 209 field, address); 210 pr_info("epc = %0*lx in", field, 211 (unsigned long) regs->cp0_epc); 212 print_vma_addr(KERN_CONT " ", regs->cp0_epc); 213 pr_cont("\n"); 214 pr_info("ra = %0*lx in", field, 215 (unsigned long) regs->regs[31]); 216 print_vma_addr(KERN_CONT " ", regs->regs[31]); 217 pr_cont("\n"); 218 } 219 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 220 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 221 return; 222 } 223 224 no_context: 225 /* Are we prepared to handle this kernel fault? */ 226 if (fixup_exception(regs)) { 227 current->thread.cp0_baduaddr = address; 228 return; 229 } 230 231 /* 232 * Oops. The kernel tried to access some bad page. We'll have to 233 * terminate things with extreme prejudice. 234 */ 235 bust_spinlocks(1); 236 237 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 238 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 239 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 240 field, regs->regs[31]); 241 die("Oops", regs); 242 243 out_of_memory: 244 /* 245 * We ran out of memory, call the OOM killer, and return the userspace 246 * (which will retry the fault, or kill us if we got oom-killed). 247 */ 248 mmap_read_unlock(mm); 249 if (!user_mode(regs)) 250 goto no_context; 251 pagefault_out_of_memory(); 252 return; 253 254 do_sigbus: 255 mmap_read_unlock(mm); 256 257 /* Kernel mode? Handle exceptions or die */ 258 if (!user_mode(regs)) 259 goto no_context; 260 261 /* 262 * Send a sigbus, regardless of whether we were in kernel 263 * or user mode. 264 */ 265 #if 0 266 printk("do_page_fault() #3: sending SIGBUS to %s for " 267 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 268 tsk->comm, 269 write ? "write access to" : "read access from", 270 field, address, 271 field, (unsigned long) regs->cp0_epc, 272 field, (unsigned long) regs->regs[31]); 273 #endif 274 current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f; 275 tsk->thread.cp0_badvaddr = address; 276 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 277 278 return; 279 #ifndef CONFIG_64BIT 280 vmalloc_fault: 281 { 282 /* 283 * Synchronize this task's top level page-table 284 * with the 'reference' page table. 285 * 286 * Do _not_ use "tsk" here. We might be inside 287 * an interrupt in the middle of a task switch.. 288 */ 289 int offset = pgd_index(address); 290 pgd_t *pgd, *pgd_k; 291 p4d_t *p4d, *p4d_k; 292 pud_t *pud, *pud_k; 293 pmd_t *pmd, *pmd_k; 294 pte_t *pte_k; 295 296 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 297 pgd_k = init_mm.pgd + offset; 298 299 if (!pgd_present(*pgd_k)) 300 goto no_context; 301 set_pgd(pgd, *pgd_k); 302 303 p4d = p4d_offset(pgd, address); 304 p4d_k = p4d_offset(pgd_k, address); 305 if (!p4d_present(*p4d_k)) 306 goto no_context; 307 308 pud = pud_offset(p4d, address); 309 pud_k = pud_offset(p4d_k, address); 310 if (!pud_present(*pud_k)) 311 goto no_context; 312 313 pmd = pmd_offset(pud, address); 314 pmd_k = pmd_offset(pud_k, address); 315 if (!pmd_present(*pmd_k)) 316 goto no_context; 317 set_pmd(pmd, *pmd_k); 318 319 pte_k = pte_offset_kernel(pmd_k, address); 320 if (!pte_present(*pte_k)) 321 goto no_context; 322 return; 323 } 324 #endif 325 } 326 327 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, 328 unsigned long write, unsigned long address) 329 { 330 enum ctx_state prev_state; 331 332 prev_state = exception_enter(); 333 __do_page_fault(regs, write, address); 334 exception_exit(prev_state); 335 } 336