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/vt_kern.h> /* For unblank_screen() */ 20 #include <linux/module.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 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 */ do_page_fault(struct pt_regs * regs,unsigned long write,unsigned long address)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 int fault; 43 44 #if 0 45 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_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 /* 101 * If for any reason at all we couldn't handle the fault, 102 * make sure we exit gracefully rather than endlessly redo 103 * the fault. 104 */ 105 fault = handle_mm_fault(mm, vma, address, write); 106 if (unlikely(fault & VM_FAULT_ERROR)) { 107 if (fault & VM_FAULT_OOM) 108 goto out_of_memory; 109 else if (fault & VM_FAULT_SIGBUS) 110 goto do_sigbus; 111 BUG(); 112 } 113 if (fault & VM_FAULT_MAJOR) 114 tsk->maj_flt++; 115 else 116 tsk->min_flt++; 117 118 up_read(&mm->mmap_sem); 119 return; 120 121 /* 122 * Something tried to access memory that isn't in our memory map.. 123 * Fix it, but check if it's kernel or user first.. 124 */ 125 bad_area: 126 up_read(&mm->mmap_sem); 127 128 bad_area_nosemaphore: 129 /* User mode accesses just cause a SIGSEGV */ 130 if (user_mode(regs)) { 131 tsk->thread.cp0_badvaddr = address; 132 tsk->thread.error_code = write; 133 #if 0 134 printk("do_page_fault() #2: sending SIGSEGV to %s for " 135 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 136 tsk->comm, 137 write ? "write access to" : "read access from", 138 field, address, 139 field, (unsigned long) regs->cp0_epc, 140 field, (unsigned long) regs->regs[31]); 141 #endif 142 info.si_signo = SIGSEGV; 143 info.si_errno = 0; 144 /* info.si_code has been set above */ 145 info.si_addr = (void __user *) address; 146 force_sig_info(SIGSEGV, &info, tsk); 147 return; 148 } 149 150 no_context: 151 /* Are we prepared to handle this kernel fault? */ 152 if (fixup_exception(regs)) { 153 current->thread.cp0_baduaddr = address; 154 return; 155 } 156 157 /* 158 * Oops. The kernel tried to access some bad page. We'll have to 159 * terminate things with extreme prejudice. 160 */ 161 bust_spinlocks(1); 162 163 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 164 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 165 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 166 field, regs->regs[31]); 167 die("Oops", regs); 168 169 out_of_memory: 170 /* 171 * We ran out of memory, call the OOM killer, and return the userspace 172 * (which will retry the fault, or kill us if we got oom-killed). 173 */ 174 pagefault_out_of_memory(); 175 return; 176 177 do_sigbus: 178 up_read(&mm->mmap_sem); 179 180 /* Kernel mode? Handle exceptions or die */ 181 if (!user_mode(regs)) 182 goto no_context; 183 else 184 /* 185 * Send a sigbus, regardless of whether we were in kernel 186 * or user mode. 187 */ 188 #if 0 189 printk("do_page_fault() #3: sending SIGBUS to %s for " 190 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 191 tsk->comm, 192 write ? "write access to" : "read access from", 193 field, address, 194 field, (unsigned long) regs->cp0_epc, 195 field, (unsigned long) regs->regs[31]); 196 #endif 197 tsk->thread.cp0_badvaddr = address; 198 info.si_signo = SIGBUS; 199 info.si_errno = 0; 200 info.si_code = BUS_ADRERR; 201 info.si_addr = (void __user *) address; 202 force_sig_info(SIGBUS, &info, tsk); 203 204 return; 205 vmalloc_fault: 206 { 207 /* 208 * Synchronize this task's top level page-table 209 * with the 'reference' page table. 210 * 211 * Do _not_ use "tsk" here. We might be inside 212 * an interrupt in the middle of a task switch.. 213 */ 214 int offset = __pgd_offset(address); 215 pgd_t *pgd, *pgd_k; 216 pud_t *pud, *pud_k; 217 pmd_t *pmd, *pmd_k; 218 pte_t *pte_k; 219 220 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 221 pgd_k = init_mm.pgd + offset; 222 223 if (!pgd_present(*pgd_k)) 224 goto no_context; 225 set_pgd(pgd, *pgd_k); 226 227 pud = pud_offset(pgd, address); 228 pud_k = pud_offset(pgd_k, address); 229 if (!pud_present(*pud_k)) 230 goto no_context; 231 232 pmd = pmd_offset(pud, address); 233 pmd_k = pmd_offset(pud_k, address); 234 if (!pmd_present(*pmd_k)) 235 goto no_context; 236 set_pmd(pmd, *pmd_k); 237 238 pte_k = pte_offset_kernel(pmd_k, address); 239 if (!pte_present(*pte_k)) 240 goto no_context; 241 return; 242 } 243 } 244