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 64 /* 65 * If we're in an interrupt or have no user 66 * context, we must not take the fault.. 67 */ 68 if (in_atomic() || !mm) 69 goto bad_area_nosemaphore; 70 71 down_read(&mm->mmap_sem); 72 vma = find_vma(mm, address); 73 if (!vma) 74 goto bad_area; 75 if (vma->vm_start <= address) 76 goto good_area; 77 if (!(vma->vm_flags & VM_GROWSDOWN)) 78 goto bad_area; 79 if (expand_stack(vma, address)) 80 goto bad_area; 81 /* 82 * Ok, we have a good vm_area for this memory access, so 83 * we can handle it.. 84 */ 85 good_area: 86 info.si_code = SEGV_ACCERR; 87 88 if (write) { 89 if (!(vma->vm_flags & VM_WRITE)) 90 goto bad_area; 91 } else { 92 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 93 goto bad_area; 94 } 95 96 survive: 97 /* 98 * If for any reason at all we couldn't handle the fault, 99 * make sure we exit gracefully rather than endlessly redo 100 * the fault. 101 */ 102 switch (handle_mm_fault(mm, vma, address, write)) { 103 case VM_FAULT_MINOR: 104 tsk->min_flt++; 105 break; 106 case VM_FAULT_MAJOR: 107 tsk->maj_flt++; 108 break; 109 case VM_FAULT_SIGBUS: 110 goto do_sigbus; 111 case VM_FAULT_OOM: 112 goto out_of_memory; 113 default: 114 BUG(); 115 } 116 117 up_read(&mm->mmap_sem); 118 return; 119 120 /* 121 * Something tried to access memory that isn't in our memory map.. 122 * Fix it, but check if it's kernel or user first.. 123 */ 124 bad_area: 125 up_read(&mm->mmap_sem); 126 127 bad_area_nosemaphore: 128 /* User mode accesses just cause a SIGSEGV */ 129 if (user_mode(regs)) { 130 tsk->thread.cp0_badvaddr = address; 131 tsk->thread.error_code = write; 132 #if 0 133 printk("do_page_fault() #2: sending SIGSEGV to %s for " 134 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 135 tsk->comm, 136 write ? "write access to" : "read access from", 137 field, address, 138 field, (unsigned long) regs->cp0_epc, 139 field, (unsigned long) regs->regs[31]); 140 #endif 141 info.si_signo = SIGSEGV; 142 info.si_errno = 0; 143 /* info.si_code has been set above */ 144 info.si_addr = (void __user *) address; 145 force_sig_info(SIGSEGV, &info, tsk); 146 return; 147 } 148 149 no_context: 150 /* Are we prepared to handle this kernel fault? */ 151 if (fixup_exception(regs)) { 152 current->thread.cp0_baduaddr = address; 153 return; 154 } 155 156 /* 157 * Oops. The kernel tried to access some bad page. We'll have to 158 * terminate things with extreme prejudice. 159 */ 160 bust_spinlocks(1); 161 162 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 163 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 164 smp_processor_id(), field, address, field, regs->cp0_epc, 165 field, regs->regs[31]); 166 die("Oops", regs); 167 168 /* 169 * We ran out of memory, or some other thing happened to us that made 170 * us unable to handle the page fault gracefully. 171 */ 172 out_of_memory: 173 up_read(&mm->mmap_sem); 174 if (is_init(tsk)) { 175 yield(); 176 down_read(&mm->mmap_sem); 177 goto survive; 178 } 179 printk("VM: killing process %s\n", tsk->comm); 180 if (user_mode(regs)) 181 do_exit(SIGKILL); 182 goto no_context; 183 184 do_sigbus: 185 up_read(&mm->mmap_sem); 186 187 /* Kernel mode? Handle exceptions or die */ 188 if (!user_mode(regs)) 189 goto no_context; 190 else 191 /* 192 * Send a sigbus, regardless of whether we were in kernel 193 * or user mode. 194 */ 195 #if 0 196 printk("do_page_fault() #3: sending SIGBUS to %s for " 197 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 198 tsk->comm, 199 write ? "write access to" : "read access from", 200 field, address, 201 field, (unsigned long) regs->cp0_epc, 202 field, (unsigned long) regs->regs[31]); 203 #endif 204 tsk->thread.cp0_badvaddr = address; 205 info.si_signo = SIGBUS; 206 info.si_errno = 0; 207 info.si_code = BUS_ADRERR; 208 info.si_addr = (void __user *) address; 209 force_sig_info(SIGBUS, &info, tsk); 210 211 return; 212 vmalloc_fault: 213 { 214 /* 215 * Synchronize this task's top level page-table 216 * with the 'reference' page table. 217 * 218 * Do _not_ use "tsk" here. We might be inside 219 * an interrupt in the middle of a task switch.. 220 */ 221 int offset = __pgd_offset(address); 222 pgd_t *pgd, *pgd_k; 223 pud_t *pud, *pud_k; 224 pmd_t *pmd, *pmd_k; 225 pte_t *pte_k; 226 227 pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset; 228 pgd_k = init_mm.pgd + offset; 229 230 if (!pgd_present(*pgd_k)) 231 goto no_context; 232 set_pgd(pgd, *pgd_k); 233 234 pud = pud_offset(pgd, address); 235 pud_k = pud_offset(pgd_k, address); 236 if (!pud_present(*pud_k)) 237 goto no_context; 238 239 pmd = pmd_offset(pud, address); 240 pmd_k = pmd_offset(pud_k, address); 241 if (!pmd_present(*pmd_k)) 242 goto no_context; 243 set_pmd(pmd, *pmd_k); 244 245 pte_k = pte_offset_kernel(pmd_k, address); 246 if (!pte_present(*pte_k)) 247 goto no_context; 248 return; 249 } 250 } 251