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