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/uaccess.h> 16 #include <linux/kdebug.h> 17 #include <asm/pgalloc.h> 18 #include <asm/mmu.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, unsigned long address) 56 { 57 struct vm_area_struct *vma = NULL; 58 struct task_struct *tsk = current; 59 struct mm_struct *mm = tsk->mm; 60 siginfo_t info; 61 int fault, ret; 62 int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */ 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 ((regs->ecr_vec == ECR_V_PROTV) && 114 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 115 goto bad_area; 116 117 if (write) { 118 if (!(vma->vm_flags & VM_WRITE)) 119 goto bad_area; 120 } else { 121 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 122 goto bad_area; 123 } 124 125 survive: 126 /* 127 * If for any reason at all we couldn't handle the fault, 128 * make sure we exit gracefully rather than endlessly redo 129 * the fault. 130 */ 131 fault = handle_mm_fault(mm, vma, address, flags); 132 133 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ 134 if (unlikely(fatal_signal_pending(current))) { 135 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 136 up_read(&mm->mmap_sem); 137 if (user_mode(regs)) 138 return; 139 } 140 141 if (likely(!(fault & VM_FAULT_ERROR))) { 142 if (flags & FAULT_FLAG_ALLOW_RETRY) { 143 /* To avoid updating stats twice for retry case */ 144 if (fault & VM_FAULT_MAJOR) 145 tsk->maj_flt++; 146 else 147 tsk->min_flt++; 148 149 if (fault & VM_FAULT_RETRY) { 150 flags &= ~FAULT_FLAG_ALLOW_RETRY; 151 flags |= FAULT_FLAG_TRIED; 152 goto retry; 153 } 154 } 155 156 /* Fault Handled Gracefully */ 157 up_read(&mm->mmap_sem); 158 return; 159 } 160 161 /* TBD: switch to pagefault_out_of_memory() */ 162 if (fault & VM_FAULT_OOM) 163 goto out_of_memory; 164 else if (fault & VM_FAULT_SIGBUS) 165 goto do_sigbus; 166 167 /* no man's land */ 168 BUG(); 169 170 /* 171 * Something tried to access memory that isn't in our memory map.. 172 * Fix it, but check if it's kernel or user first.. 173 */ 174 bad_area: 175 up_read(&mm->mmap_sem); 176 177 bad_area_nosemaphore: 178 /* User mode accesses just cause a SIGSEGV */ 179 if (user_mode(regs)) { 180 tsk->thread.fault_address = address; 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); 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 pagefault_out_of_memory(); 212 return; 213 } 214 215 goto no_context; 216 217 do_sigbus: 218 up_read(&mm->mmap_sem); 219 220 if (!user_mode(regs)) 221 goto no_context; 222 223 tsk->thread.fault_address = address; 224 info.si_signo = SIGBUS; 225 info.si_errno = 0; 226 info.si_code = BUS_ADRERR; 227 info.si_addr = (void __user *)address; 228 force_sig_info(SIGBUS, &info, tsk); 229 } 230