1 /* Page Fault Handling for ARC (TLB Miss / ProtV) 2 * 3 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License version 2 as 7 * published by the Free Software Foundation. 8 */ 9 10 #include <linux/signal.h> 11 #include <linux/interrupt.h> 12 #include <linux/sched.h> 13 #include <linux/errno.h> 14 #include <linux/ptrace.h> 15 #include <linux/version.h> 16 #include <linux/uaccess.h> 17 #include <linux/kdebug.h> 18 #include <asm/pgalloc.h> 19 20 static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) 21 { 22 /* 23 * Synchronize this task's top level page-table 24 * with the 'reference' page table. 25 */ 26 pgd_t *pgd, *pgd_k; 27 pud_t *pud, *pud_k; 28 pmd_t *pmd, *pmd_k; 29 30 pgd = pgd_offset_fast(mm, address); 31 pgd_k = pgd_offset_k(address); 32 33 if (!pgd_present(*pgd_k)) 34 goto bad_area; 35 36 pud = pud_offset(pgd, address); 37 pud_k = pud_offset(pgd_k, address); 38 if (!pud_present(*pud_k)) 39 goto bad_area; 40 41 pmd = pmd_offset(pud, address); 42 pmd_k = pmd_offset(pud_k, address); 43 if (!pmd_present(*pmd_k)) 44 goto bad_area; 45 46 set_pmd(pmd, *pmd_k); 47 48 /* XXX: create the TLB entry here */ 49 return 0; 50 51 bad_area: 52 return 1; 53 } 54 55 void do_page_fault(struct pt_regs *regs, int write, unsigned long address, 56 unsigned long cause_code) 57 { 58 struct vm_area_struct *vma = NULL; 59 struct task_struct *tsk = current; 60 struct mm_struct *mm = tsk->mm; 61 siginfo_t info; 62 int fault, ret; 63 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 64 (write ? FAULT_FLAG_WRITE : 0); 65 66 /* 67 * We fault-in kernel-space virtual memory on-demand. The 68 * 'reference' page table is init_mm.pgd. 69 * 70 * NOTE! We MUST NOT take any locks for this case. We may 71 * be in an interrupt or a critical region, and should 72 * only copy the information from the master page table, 73 * nothing more. 74 */ 75 if (address >= VMALLOC_START && address <= VMALLOC_END) { 76 ret = handle_vmalloc_fault(mm, address); 77 if (unlikely(ret)) 78 goto bad_area_nosemaphore; 79 else 80 return; 81 } 82 83 info.si_code = SEGV_MAPERR; 84 85 /* 86 * If we're in an interrupt or have no user 87 * context, we must not take the fault.. 88 */ 89 if (in_atomic() || !mm) 90 goto no_context; 91 92 retry: 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 /* 105 * Ok, we have a good vm_area for this memory access, so 106 * we can handle it.. 107 */ 108 good_area: 109 info.si_code = SEGV_ACCERR; 110 111 /* Handle protection violation, execute on heap or stack */ 112 113 if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH)) 114 goto bad_area; 115 116 if (write) { 117 if (!(vma->vm_flags & VM_WRITE)) 118 goto bad_area; 119 } else { 120 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 121 goto bad_area; 122 } 123 124 survive: 125 /* 126 * If for any reason at all we couldn't handle the fault, 127 * make sure we exit gracefully rather than endlessly redo 128 * the fault. 129 */ 130 fault = handle_mm_fault(mm, vma, address, flags); 131 132 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ 133 if (unlikely(fatal_signal_pending(current))) { 134 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 135 up_read(&mm->mmap_sem); 136 if (user_mode(regs)) 137 return; 138 } 139 140 if (likely(!(fault & VM_FAULT_ERROR))) { 141 if (flags & FAULT_FLAG_ALLOW_RETRY) { 142 /* To avoid updating stats twice for retry case */ 143 if (fault & VM_FAULT_MAJOR) 144 tsk->maj_flt++; 145 else 146 tsk->min_flt++; 147 148 if (fault & VM_FAULT_RETRY) { 149 flags &= ~FAULT_FLAG_ALLOW_RETRY; 150 flags |= FAULT_FLAG_TRIED; 151 goto retry; 152 } 153 } 154 155 /* Fault Handled Gracefully */ 156 up_read(&mm->mmap_sem); 157 return; 158 } 159 160 /* TBD: switch to pagefault_out_of_memory() */ 161 if (fault & VM_FAULT_OOM) 162 goto out_of_memory; 163 else if (fault & VM_FAULT_SIGBUS) 164 goto do_sigbus; 165 166 /* no man's land */ 167 BUG(); 168 169 /* 170 * Something tried to access memory that isn't in our memory map.. 171 * Fix it, but check if it's kernel or user first.. 172 */ 173 bad_area: 174 up_read(&mm->mmap_sem); 175 176 bad_area_nosemaphore: 177 /* User mode accesses just cause a SIGSEGV */ 178 if (user_mode(regs)) { 179 tsk->thread.fault_address = address; 180 tsk->thread.cause_code = cause_code; 181 info.si_signo = SIGSEGV; 182 info.si_errno = 0; 183 /* info.si_code has been set above */ 184 info.si_addr = (void __user *)address; 185 force_sig_info(SIGSEGV, &info, tsk); 186 return; 187 } 188 189 no_context: 190 /* Are we prepared to handle this kernel fault? 191 * 192 * (The kernel has valid exception-points in the source 193 * when it acesses user-memory. When it fails in one 194 * of those points, we find it in a table and do a jump 195 * to some fixup code that loads an appropriate error 196 * code) 197 */ 198 if (fixup_exception(regs)) 199 return; 200 201 die("Oops", regs, address, cause_code); 202 203 out_of_memory: 204 if (is_global_init(tsk)) { 205 yield(); 206 goto survive; 207 } 208 up_read(&mm->mmap_sem); 209 210 if (user_mode(regs)) 211 do_group_exit(SIGKILL); /* This will never return */ 212 213 goto no_context; 214 215 do_sigbus: 216 up_read(&mm->mmap_sem); 217 218 if (!user_mode(regs)) 219 goto no_context; 220 221 tsk->thread.fault_address = address; 222 tsk->thread.cause_code = cause_code; 223 info.si_signo = SIGBUS; 224 info.si_errno = 0; 225 info.si_code = BUS_ADRERR; 226 info.si_addr = (void __user *)address; 227 force_sig_info(SIGBUS, &info, tsk); 228 } 229