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 22 #include <asm/branch.h> 23 #include <asm/mmu_context.h> 24 #include <asm/system.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 45 #if 0 46 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(), 47 current->comm, current->pid, field, address, write, 48 field, regs->cp0_epc); 49 #endif 50 51 #ifdef CONFIG_KPROBES 52 /* 53 * This is to notify the fault handler of the kprobes. The 54 * exception code is redundant as it is also carried in REGS, 55 * but we pass it anyhow. 56 */ 57 if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1, 58 (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP) 59 return; 60 #endif 61 62 info.si_code = SEGV_MAPERR; 63 64 /* 65 * We fault-in kernel-space virtual memory on-demand. The 66 * 'reference' page table is init_mm.pgd. 67 * 68 * NOTE! We MUST NOT take any locks for this case. We may 69 * be in an interrupt or a critical region, and should 70 * only copy the information from the master page table, 71 * nothing more. 72 */ 73 #ifdef CONFIG_64BIT 74 # define VMALLOC_FAULT_TARGET no_context 75 #else 76 # define VMALLOC_FAULT_TARGET vmalloc_fault 77 #endif 78 79 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 80 goto VMALLOC_FAULT_TARGET; 81 #ifdef MODULE_START 82 if (unlikely(address >= MODULE_START && address < MODULE_END)) 83 goto VMALLOC_FAULT_TARGET; 84 #endif 85 86 /* 87 * If we're in an interrupt or have no user 88 * context, we must not take the fault.. 89 */ 90 if (in_atomic() || !mm) 91 goto bad_area_nosemaphore; 92 93 down_read(&mm->mmap_sem); 94 vma = find_vma(mm, address); 95 if (!vma) 96 goto bad_area; 97 if (vma->vm_start <= address) 98 goto good_area; 99 if (!(vma->vm_flags & VM_GROWSDOWN)) 100 goto bad_area; 101 if (expand_stack(vma, address)) 102 goto bad_area; 103 /* 104 * Ok, we have a good vm_area for this memory access, so 105 * we can handle it.. 106 */ 107 good_area: 108 info.si_code = SEGV_ACCERR; 109 110 if (write) { 111 if (!(vma->vm_flags & VM_WRITE)) 112 goto bad_area; 113 } else { 114 if (kernel_uses_smartmips_rixi) { 115 if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) { 116 #if 0 117 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation\n", 118 raw_smp_processor_id(), 119 current->comm, current->pid, 120 field, address, write, 121 field, regs->cp0_epc); 122 #endif 123 goto bad_area; 124 } 125 if (!(vma->vm_flags & VM_READ)) { 126 #if 0 127 pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI 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 } else { 136 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 137 goto bad_area; 138 } 139 } 140 141 /* 142 * If for any reason at all we couldn't handle the fault, 143 * make sure we exit gracefully rather than endlessly redo 144 * the fault. 145 */ 146 fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0); 147 if (unlikely(fault & VM_FAULT_ERROR)) { 148 if (fault & VM_FAULT_OOM) 149 goto out_of_memory; 150 else if (fault & VM_FAULT_SIGBUS) 151 goto do_sigbus; 152 BUG(); 153 } 154 if (fault & VM_FAULT_MAJOR) 155 tsk->maj_flt++; 156 else 157 tsk->min_flt++; 158 159 up_read(&mm->mmap_sem); 160 return; 161 162 /* 163 * Something tried to access memory that isn't in our memory map.. 164 * Fix it, but check if it's kernel or user first.. 165 */ 166 bad_area: 167 up_read(&mm->mmap_sem); 168 169 bad_area_nosemaphore: 170 /* User mode accesses just cause a SIGSEGV */ 171 if (user_mode(regs)) { 172 tsk->thread.cp0_badvaddr = address; 173 tsk->thread.error_code = write; 174 #if 0 175 printk("do_page_fault() #2: sending SIGSEGV to %s for " 176 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 177 tsk->comm, 178 write ? "write access to" : "read access from", 179 field, address, 180 field, (unsigned long) regs->cp0_epc, 181 field, (unsigned long) regs->regs[31]); 182 #endif 183 info.si_signo = SIGSEGV; 184 info.si_errno = 0; 185 /* info.si_code has been set above */ 186 info.si_addr = (void __user *) address; 187 force_sig_info(SIGSEGV, &info, tsk); 188 return; 189 } 190 191 no_context: 192 /* Are we prepared to handle this kernel fault? */ 193 if (fixup_exception(regs)) { 194 current->thread.cp0_baduaddr = address; 195 return; 196 } 197 198 /* 199 * Oops. The kernel tried to access some bad page. We'll have to 200 * terminate things with extreme prejudice. 201 */ 202 bust_spinlocks(1); 203 204 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 205 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 206 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 207 field, regs->regs[31]); 208 die("Oops", regs); 209 210 out_of_memory: 211 /* 212 * We ran out of memory, call the OOM killer, and return the userspace 213 * (which will retry the fault, or kill us if we got oom-killed). 214 */ 215 up_read(&mm->mmap_sem); 216 pagefault_out_of_memory(); 217 return; 218 219 do_sigbus: 220 up_read(&mm->mmap_sem); 221 222 /* Kernel mode? Handle exceptions or die */ 223 if (!user_mode(regs)) 224 goto no_context; 225 else 226 /* 227 * Send a sigbus, regardless of whether we were in kernel 228 * or user mode. 229 */ 230 #if 0 231 printk("do_page_fault() #3: sending SIGBUS to %s for " 232 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 233 tsk->comm, 234 write ? "write access to" : "read access from", 235 field, address, 236 field, (unsigned long) regs->cp0_epc, 237 field, (unsigned long) regs->regs[31]); 238 #endif 239 tsk->thread.cp0_badvaddr = address; 240 info.si_signo = SIGBUS; 241 info.si_errno = 0; 242 info.si_code = BUS_ADRERR; 243 info.si_addr = (void __user *) address; 244 force_sig_info(SIGBUS, &info, tsk); 245 246 return; 247 #ifndef CONFIG_64BIT 248 vmalloc_fault: 249 { 250 /* 251 * Synchronize this task's top level page-table 252 * with the 'reference' page table. 253 * 254 * Do _not_ use "tsk" here. We might be inside 255 * an interrupt in the middle of a task switch.. 256 */ 257 int offset = __pgd_offset(address); 258 pgd_t *pgd, *pgd_k; 259 pud_t *pud, *pud_k; 260 pmd_t *pmd, *pmd_k; 261 pte_t *pte_k; 262 263 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 264 pgd_k = init_mm.pgd + offset; 265 266 if (!pgd_present(*pgd_k)) 267 goto no_context; 268 set_pgd(pgd, *pgd_k); 269 270 pud = pud_offset(pgd, address); 271 pud_k = pud_offset(pgd_k, address); 272 if (!pud_present(*pud_k)) 273 goto no_context; 274 275 pmd = pmd_offset(pud, address); 276 pmd_k = pmd_offset(pud_k, address); 277 if (!pmd_present(*pmd_k)) 278 goto no_context; 279 set_pmd(pmd, *pmd_k); 280 281 pte_k = pte_offset_kernel(pmd_k, address); 282 if (!pte_present(*pte_k)) 283 goto no_context; 284 return; 285 } 286 #endif 287 } 288