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/smp_lock.h> 20 #include <linux/vt_kern.h> /* For unblank_screen() */ 21 #include <linux/module.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 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 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 44 #if 0 45 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", smp_processor_id(), 46 current->comm, current->pid, field, address, write, 47 field, regs->cp0_epc); 48 #endif 49 50 info.si_code = SEGV_MAPERR; 51 52 /* 53 * We fault-in kernel-space virtual memory on-demand. The 54 * 'reference' page table is init_mm.pgd. 55 * 56 * NOTE! We MUST NOT take any locks for this case. We may 57 * be in an interrupt or a critical region, and should 58 * only copy the information from the master page table, 59 * nothing more. 60 */ 61 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 62 goto vmalloc_fault; 63 #ifdef MODULE_START 64 if (unlikely(address >= MODULE_START && address < MODULE_END)) 65 goto vmalloc_fault; 66 #endif 67 68 /* 69 * If we're in an interrupt or have no user 70 * context, we must not take the fault.. 71 */ 72 if (in_atomic() || !mm) 73 goto bad_area_nosemaphore; 74 75 down_read(&mm->mmap_sem); 76 vma = find_vma(mm, address); 77 if (!vma) 78 goto bad_area; 79 if (vma->vm_start <= address) 80 goto good_area; 81 if (!(vma->vm_flags & VM_GROWSDOWN)) 82 goto bad_area; 83 if (expand_stack(vma, address)) 84 goto bad_area; 85 /* 86 * Ok, we have a good vm_area for this memory access, so 87 * we can handle it.. 88 */ 89 good_area: 90 info.si_code = SEGV_ACCERR; 91 92 if (write) { 93 if (!(vma->vm_flags & VM_WRITE)) 94 goto bad_area; 95 } else { 96 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 97 goto bad_area; 98 } 99 100 survive: 101 /* 102 * If for any reason at all we couldn't handle the fault, 103 * make sure we exit gracefully rather than endlessly redo 104 * the fault. 105 */ 106 switch (handle_mm_fault(mm, vma, address, write)) { 107 case VM_FAULT_MINOR: 108 tsk->min_flt++; 109 break; 110 case VM_FAULT_MAJOR: 111 tsk->maj_flt++; 112 break; 113 case VM_FAULT_SIGBUS: 114 goto do_sigbus; 115 case VM_FAULT_OOM: 116 goto out_of_memory; 117 default: 118 BUG(); 119 } 120 121 up_read(&mm->mmap_sem); 122 return; 123 124 /* 125 * Something tried to access memory that isn't in our memory map.. 126 * Fix it, but check if it's kernel or user first.. 127 */ 128 bad_area: 129 up_read(&mm->mmap_sem); 130 131 bad_area_nosemaphore: 132 /* User mode accesses just cause a SIGSEGV */ 133 if (user_mode(regs)) { 134 tsk->thread.cp0_badvaddr = address; 135 tsk->thread.error_code = write; 136 #if 0 137 printk("do_page_fault() #2: sending SIGSEGV to %s for " 138 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 139 tsk->comm, 140 write ? "write access to" : "read access from", 141 field, address, 142 field, (unsigned long) regs->cp0_epc, 143 field, (unsigned long) regs->regs[31]); 144 #endif 145 info.si_signo = SIGSEGV; 146 info.si_errno = 0; 147 /* info.si_code has been set above */ 148 info.si_addr = (void __user *) address; 149 force_sig_info(SIGSEGV, &info, tsk); 150 return; 151 } 152 153 no_context: 154 /* Are we prepared to handle this kernel fault? */ 155 if (fixup_exception(regs)) { 156 current->thread.cp0_baduaddr = address; 157 return; 158 } 159 160 /* 161 * Oops. The kernel tried to access some bad page. We'll have to 162 * terminate things with extreme prejudice. 163 */ 164 bust_spinlocks(1); 165 166 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 167 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 168 smp_processor_id(), field, address, field, regs->cp0_epc, 169 field, regs->regs[31]); 170 die("Oops", regs); 171 172 /* 173 * We ran out of memory, or some other thing happened to us that made 174 * us unable to handle the page fault gracefully. 175 */ 176 out_of_memory: 177 up_read(&mm->mmap_sem); 178 if (is_init(tsk)) { 179 yield(); 180 down_read(&mm->mmap_sem); 181 goto survive; 182 } 183 printk("VM: killing process %s\n", tsk->comm); 184 if (user_mode(regs)) 185 do_exit(SIGKILL); 186 goto no_context; 187 188 do_sigbus: 189 up_read(&mm->mmap_sem); 190 191 /* Kernel mode? Handle exceptions or die */ 192 if (!user_mode(regs)) 193 goto no_context; 194 else 195 /* 196 * Send a sigbus, regardless of whether we were in kernel 197 * or user mode. 198 */ 199 #if 0 200 printk("do_page_fault() #3: sending SIGBUS to %s for " 201 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 202 tsk->comm, 203 write ? "write access to" : "read access from", 204 field, address, 205 field, (unsigned long) regs->cp0_epc, 206 field, (unsigned long) regs->regs[31]); 207 #endif 208 tsk->thread.cp0_badvaddr = address; 209 info.si_signo = SIGBUS; 210 info.si_errno = 0; 211 info.si_code = BUS_ADRERR; 212 info.si_addr = (void __user *) address; 213 force_sig_info(SIGBUS, &info, tsk); 214 215 return; 216 vmalloc_fault: 217 { 218 /* 219 * Synchronize this task's top level page-table 220 * with the 'reference' page table. 221 * 222 * Do _not_ use "tsk" here. We might be inside 223 * an interrupt in the middle of a task switch.. 224 */ 225 int offset = __pgd_offset(address); 226 pgd_t *pgd, *pgd_k; 227 pud_t *pud, *pud_k; 228 pmd_t *pmd, *pmd_k; 229 pte_t *pte_k; 230 231 pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset; 232 pgd_k = init_mm.pgd + offset; 233 234 if (!pgd_present(*pgd_k)) 235 goto no_context; 236 set_pgd(pgd, *pgd_k); 237 238 pud = pud_offset(pgd, address); 239 pud_k = pud_offset(pgd_k, address); 240 if (!pud_present(*pud_k)) 241 goto no_context; 242 243 pmd = pmd_offset(pud, address); 244 pmd_k = pmd_offset(pud_k, address); 245 if (!pmd_present(*pmd_k)) 246 goto no_context; 247 set_pmd(pmd, *pmd_k); 248 249 pte_k = pte_offset_kernel(pmd_k, address); 250 if (!pte_present(*pte_k)) 251 goto no_context; 252 return; 253 } 254 } 255