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 (kernel_uses_smartmips_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; 174 175 /* 176 * No need to up_read(&mm->mmap_sem) 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 } 184 185 up_read(&mm->mmap_sem); 186 return; 187 188 /* 189 * Something tried to access memory that isn't in our memory map.. 190 * Fix it, but check if it's kernel or user first.. 191 */ 192 bad_area: 193 up_read(&mm->mmap_sem); 194 195 bad_area_nosemaphore: 196 /* User mode accesses just cause a SIGSEGV */ 197 if (user_mode(regs)) { 198 tsk->thread.cp0_badvaddr = address; 199 tsk->thread.error_code = write; 200 #if 0 201 printk("do_page_fault() #2: sending SIGSEGV to %s for " 202 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 203 tsk->comm, 204 write ? "write access to" : "read access from", 205 field, address, 206 field, (unsigned long) regs->cp0_epc, 207 field, (unsigned long) regs->regs[31]); 208 #endif 209 info.si_signo = SIGSEGV; 210 info.si_errno = 0; 211 /* info.si_code has been set above */ 212 info.si_addr = (void __user *) address; 213 force_sig_info(SIGSEGV, &info, tsk); 214 return; 215 } 216 217 no_context: 218 /* Are we prepared to handle this kernel fault? */ 219 if (fixup_exception(regs)) { 220 current->thread.cp0_baduaddr = address; 221 return; 222 } 223 224 /* 225 * Oops. The kernel tried to access some bad page. We'll have to 226 * terminate things with extreme prejudice. 227 */ 228 bust_spinlocks(1); 229 230 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 231 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 232 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 233 field, regs->regs[31]); 234 die("Oops", regs); 235 236 out_of_memory: 237 /* 238 * We ran out of memory, call the OOM killer, and return the userspace 239 * (which will retry the fault, or kill us if we got oom-killed). 240 */ 241 up_read(&mm->mmap_sem); 242 pagefault_out_of_memory(); 243 return; 244 245 do_sigbus: 246 up_read(&mm->mmap_sem); 247 248 /* Kernel mode? Handle exceptions or die */ 249 if (!user_mode(regs)) 250 goto no_context; 251 else 252 /* 253 * Send a sigbus, regardless of whether we were in kernel 254 * or user mode. 255 */ 256 #if 0 257 printk("do_page_fault() #3: sending SIGBUS to %s for " 258 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 259 tsk->comm, 260 write ? "write access to" : "read access from", 261 field, address, 262 field, (unsigned long) regs->cp0_epc, 263 field, (unsigned long) regs->regs[31]); 264 #endif 265 tsk->thread.cp0_badvaddr = address; 266 info.si_signo = SIGBUS; 267 info.si_errno = 0; 268 info.si_code = BUS_ADRERR; 269 info.si_addr = (void __user *) address; 270 force_sig_info(SIGBUS, &info, tsk); 271 272 return; 273 #ifndef CONFIG_64BIT 274 vmalloc_fault: 275 { 276 /* 277 * Synchronize this task's top level page-table 278 * with the 'reference' page table. 279 * 280 * Do _not_ use "tsk" here. We might be inside 281 * an interrupt in the middle of a task switch.. 282 */ 283 int offset = __pgd_offset(address); 284 pgd_t *pgd, *pgd_k; 285 pud_t *pud, *pud_k; 286 pmd_t *pmd, *pmd_k; 287 pte_t *pte_k; 288 289 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 290 pgd_k = init_mm.pgd + offset; 291 292 if (!pgd_present(*pgd_k)) 293 goto no_context; 294 set_pgd(pgd, *pgd_k); 295 296 pud = pud_offset(pgd, address); 297 pud_k = pud_offset(pgd_k, address); 298 if (!pud_present(*pud_k)) 299 goto no_context; 300 301 pmd = pmd_offset(pud, address); 302 pmd_k = pmd_offset(pud_k, address); 303 if (!pmd_present(*pmd_k)) 304 goto no_context; 305 set_pmd(pmd, *pmd_k); 306 307 pte_k = pte_offset_kernel(pmd_k, address); 308 if (!pte_present(*pte_k)) 309 goto no_context; 310 return; 311 } 312 #endif 313 } 314