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/signal.h> 9 #include <linux/sched.h> 10 #include <linux/interrupt.h> 11 #include <linux/kernel.h> 12 #include <linux/errno.h> 13 #include <linux/string.h> 14 #include <linux/types.h> 15 #include <linux/ptrace.h> 16 #include <linux/mman.h> 17 #include <linux/mm.h> 18 #include <linux/smp.h> 19 #include <linux/module.h> 20 #include <linux/kprobes.h> 21 #include <linux/perf_event.h> 22 23 #include <asm/branch.h> 24 #include <asm/mmu_context.h> 25 #include <asm/uaccess.h> 26 #include <asm/ptrace.h> 27 #include <asm/highmem.h> /* For VMALLOC_END */ 28 #include <linux/kdebug.h> 29 30 /* 31 * This routine handles page faults. It determines the address, 32 * and the problem, and then passes it off to one of the appropriate 33 * routines. 34 */ 35 asmlinkage void __kprobes do_page_fault(struct pt_regs *regs, unsigned long write, 36 unsigned long address) 37 { 38 struct vm_area_struct * vma = NULL; 39 struct task_struct *tsk = current; 40 struct mm_struct *mm = tsk->mm; 41 const int field = sizeof(unsigned long) * 2; 42 siginfo_t info; 43 int fault; 44 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 45 (write ? FAULT_FLAG_WRITE : 0); 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 retry: 96 down_read(&mm->mmap_sem); 97 vma = find_vma(mm, address); 98 if (!vma) 99 goto bad_area; 100 if (vma->vm_start <= address) 101 goto good_area; 102 if (!(vma->vm_flags & VM_GROWSDOWN)) 103 goto bad_area; 104 if (expand_stack(vma, address)) 105 goto bad_area; 106 /* 107 * Ok, we have a good vm_area for this memory access, so 108 * we can handle it.. 109 */ 110 good_area: 111 info.si_code = SEGV_ACCERR; 112 113 if (write) { 114 if (!(vma->vm_flags & VM_WRITE)) 115 goto bad_area; 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 #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 (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 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(mm, vma, address, flags); 150 151 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 152 return; 153 154 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 155 if (unlikely(fault & VM_FAULT_ERROR)) { 156 if (fault & VM_FAULT_OOM) 157 goto out_of_memory; 158 else if (fault & VM_FAULT_SIGBUS) 159 goto do_sigbus; 160 BUG(); 161 } 162 if (flags & FAULT_FLAG_ALLOW_RETRY) { 163 if (fault & VM_FAULT_MAJOR) { 164 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 165 regs, address); 166 tsk->maj_flt++; 167 } else { 168 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 169 regs, address); 170 tsk->min_flt++; 171 } 172 if (fault & VM_FAULT_RETRY) { 173 flags &= ~FAULT_FLAG_ALLOW_RETRY; 174 flags |= FAULT_FLAG_TRIED; 175 176 /* 177 * No need to up_read(&mm->mmap_sem) as we would 178 * have already released it in __lock_page_or_retry 179 * in mm/filemap.c. 180 */ 181 182 goto retry; 183 } 184 } 185 186 up_read(&mm->mmap_sem); 187 return; 188 189 /* 190 * Something tried to access memory that isn't in our memory map.. 191 * Fix it, but check if it's kernel or user first.. 192 */ 193 bad_area: 194 up_read(&mm->mmap_sem); 195 196 bad_area_nosemaphore: 197 /* User mode accesses just cause a SIGSEGV */ 198 if (user_mode(regs)) { 199 tsk->thread.cp0_badvaddr = address; 200 tsk->thread.error_code = write; 201 #if 0 202 printk("do_page_fault() #2: sending SIGSEGV to %s for " 203 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 204 tsk->comm, 205 write ? "write access to" : "read access from", 206 field, address, 207 field, (unsigned long) regs->cp0_epc, 208 field, (unsigned long) regs->regs[31]); 209 #endif 210 info.si_signo = SIGSEGV; 211 info.si_errno = 0; 212 /* info.si_code has been set above */ 213 info.si_addr = (void __user *) address; 214 force_sig_info(SIGSEGV, &info, tsk); 215 return; 216 } 217 218 no_context: 219 /* Are we prepared to handle this kernel fault? */ 220 if (fixup_exception(regs)) { 221 current->thread.cp0_baduaddr = address; 222 return; 223 } 224 225 /* 226 * Oops. The kernel tried to access some bad page. We'll have to 227 * terminate things with extreme prejudice. 228 */ 229 bust_spinlocks(1); 230 231 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 232 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 233 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 234 field, regs->regs[31]); 235 die("Oops", regs); 236 237 out_of_memory: 238 /* 239 * We ran out of memory, call the OOM killer, and return the userspace 240 * (which will retry the fault, or kill us if we got oom-killed). 241 */ 242 up_read(&mm->mmap_sem); 243 pagefault_out_of_memory(); 244 return; 245 246 do_sigbus: 247 up_read(&mm->mmap_sem); 248 249 /* Kernel mode? Handle exceptions or die */ 250 if (!user_mode(regs)) 251 goto no_context; 252 else 253 /* 254 * Send a sigbus, regardless of whether we were in kernel 255 * or user mode. 256 */ 257 #if 0 258 printk("do_page_fault() #3: sending SIGBUS to %s for " 259 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 260 tsk->comm, 261 write ? "write access to" : "read access from", 262 field, address, 263 field, (unsigned long) regs->cp0_epc, 264 field, (unsigned long) regs->regs[31]); 265 #endif 266 tsk->thread.cp0_badvaddr = address; 267 info.si_signo = SIGBUS; 268 info.si_errno = 0; 269 info.si_code = BUS_ADRERR; 270 info.si_addr = (void __user *) address; 271 force_sig_info(SIGBUS, &info, tsk); 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_offset(address); 285 pgd_t *pgd, *pgd_k; 286 pud_t *pud, *pud_k; 287 pmd_t *pmd, *pmd_k; 288 pte_t *pte_k; 289 290 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 291 pgd_k = init_mm.pgd + offset; 292 293 if (!pgd_present(*pgd_k)) 294 goto no_context; 295 set_pgd(pgd, *pgd_k); 296 297 pud = pud_offset(pgd, address); 298 pud_k = pud_offset(pgd_k, address); 299 if (!pud_present(*pud_k)) 300 goto no_context; 301 302 pmd = pmd_offset(pud, address); 303 pmd_k = pmd_offset(pud_k, address); 304 if (!pmd_present(*pmd_k)) 305 goto no_context; 306 set_pmd(pmd, *pmd_k); 307 308 pte_k = pte_offset_kernel(pmd_k, address); 309 if (!pte_present(*pte_k)) 310 goto no_context; 311 return; 312 } 313 #endif 314 } 315