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 29 /* 30 * This routine handles page faults. It determines the address, 31 * and the problem, and then passes it off to one of the appropriate 32 * routines. 33 */ 34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write, 35 unsigned long address) 36 { 37 struct vm_area_struct * vma = NULL; 38 struct task_struct *tsk = current; 39 struct mm_struct *mm = tsk->mm; 40 const int field = sizeof(unsigned long) * 2; 41 siginfo_t info; 42 43 #if 0 44 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", smp_processor_id(), 45 current->comm, current->pid, field, address, write, 46 field, regs->cp0_epc); 47 #endif 48 49 info.si_code = SEGV_MAPERR; 50 51 /* 52 * We fault-in kernel-space virtual memory on-demand. The 53 * 'reference' page table is init_mm.pgd. 54 * 55 * NOTE! We MUST NOT take any locks for this case. We may 56 * be in an interrupt or a critical region, and should 57 * only copy the information from the master page table, 58 * nothing more. 59 */ 60 if (unlikely(address >= VMALLOC_START)) 61 goto vmalloc_fault; 62 63 /* 64 * If we're in an interrupt or have no user 65 * context, we must not take the fault.. 66 */ 67 if (in_atomic() || !mm) 68 goto bad_area_nosemaphore; 69 70 down_read(&mm->mmap_sem); 71 vma = find_vma(mm, address); 72 if (!vma) 73 goto bad_area; 74 if (vma->vm_start <= address) 75 goto good_area; 76 if (!(vma->vm_flags & VM_GROWSDOWN)) 77 goto bad_area; 78 if (expand_stack(vma, address)) 79 goto bad_area; 80 /* 81 * Ok, we have a good vm_area for this memory access, so 82 * we can handle it.. 83 */ 84 good_area: 85 info.si_code = SEGV_ACCERR; 86 87 if (write) { 88 if (!(vma->vm_flags & VM_WRITE)) 89 goto bad_area; 90 } else { 91 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 92 goto bad_area; 93 } 94 95 survive: 96 /* 97 * If for any reason at all we couldn't handle the fault, 98 * make sure we exit gracefully rather than endlessly redo 99 * the fault. 100 */ 101 switch (handle_mm_fault(mm, vma, address, write)) { 102 case VM_FAULT_MINOR: 103 tsk->min_flt++; 104 break; 105 case VM_FAULT_MAJOR: 106 tsk->maj_flt++; 107 break; 108 case VM_FAULT_SIGBUS: 109 goto do_sigbus; 110 case VM_FAULT_OOM: 111 goto out_of_memory; 112 default: 113 BUG(); 114 } 115 116 up_read(&mm->mmap_sem); 117 return; 118 119 /* 120 * Something tried to access memory that isn't in our memory map.. 121 * Fix it, but check if it's kernel or user first.. 122 */ 123 bad_area: 124 up_read(&mm->mmap_sem); 125 126 bad_area_nosemaphore: 127 /* User mode accesses just cause a SIGSEGV */ 128 if (user_mode(regs)) { 129 tsk->thread.cp0_badvaddr = address; 130 tsk->thread.error_code = write; 131 #if 0 132 printk("do_page_fault() #2: sending SIGSEGV to %s for " 133 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 134 tsk->comm, 135 write ? "write access to" : "read access from", 136 field, address, 137 field, (unsigned long) regs->cp0_epc, 138 field, (unsigned long) regs->regs[31]); 139 #endif 140 info.si_signo = SIGSEGV; 141 info.si_errno = 0; 142 /* info.si_code has been set above */ 143 info.si_addr = (void *) address; 144 force_sig_info(SIGSEGV, &info, tsk); 145 return; 146 } 147 148 no_context: 149 /* Are we prepared to handle this kernel fault? */ 150 if (fixup_exception(regs)) { 151 current->thread.cp0_baduaddr = address; 152 return; 153 } 154 155 /* 156 * Oops. The kernel tried to access some bad page. We'll have to 157 * terminate things with extreme prejudice. 158 */ 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 (tsk->pid == 1) { 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; 190 191 /* 192 * Send a sigbus, regardless of whether we were in kernel 193 * or user mode. 194 */ 195 tsk->thread.cp0_badvaddr = address; 196 info.si_signo = SIGBUS; 197 info.si_errno = 0; 198 info.si_code = BUS_ADRERR; 199 info.si_addr = (void *) address; 200 force_sig_info(SIGBUS, &info, tsk); 201 202 return; 203 204 vmalloc_fault: 205 { 206 /* 207 * Synchronize this task's top level page-table 208 * with the 'reference' page table. 209 * 210 * Do _not_ use "tsk" here. We might be inside 211 * an interrupt in the middle of a task switch.. 212 */ 213 int offset = __pgd_offset(address); 214 pgd_t *pgd, *pgd_k; 215 pmd_t *pmd, *pmd_k; 216 pte_t *pte_k; 217 218 pgd = (pgd_t *) pgd_current[smp_processor_id()] + offset; 219 pgd_k = init_mm.pgd + offset; 220 221 if (!pgd_present(*pgd_k)) 222 goto no_context; 223 set_pgd(pgd, *pgd_k); 224 225 pmd = pmd_offset(pgd, address); 226 pmd_k = pmd_offset(pgd_k, address); 227 if (!pmd_present(*pmd_k)) 228 goto no_context; 229 set_pmd(pmd, *pmd_k); 230 231 pte_k = pte_offset_kernel(pmd_k, address); 232 if (!pte_present(*pte_k)) 233 goto no_context; 234 return; 235 } 236 } 237