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 65 /* 66 * We fault-in kernel-space virtual memory on-demand. The 67 * 'reference' page table is init_mm.pgd. 68 * 69 * NOTE! We MUST NOT take any locks for this case. We may 70 * be in an interrupt or a critical region, and should 71 * only copy the information from the master page table, 72 * nothing more. 73 */ 74 if (address >= VMALLOC_START && address <= VMALLOC_END) { 75 ret = handle_vmalloc_fault(mm, address); 76 if (unlikely(ret)) 77 goto bad_area_nosemaphore; 78 else 79 return; 80 } 81 82 info.si_code = SEGV_MAPERR; 83 84 /* 85 * If we're in an interrupt or have no user 86 * context, we must not take the fault.. 87 */ 88 if (in_atomic() || !mm) 89 goto no_context; 90 91 if (user_mode(regs)) 92 flags |= FAULT_FLAG_USER; 93 retry: 94 down_read(&mm->mmap_sem); 95 vma = find_vma(mm, address); 96 if (!vma) 97 goto bad_area; 98 if (vma->vm_start <= address) 99 goto good_area; 100 if (!(vma->vm_flags & VM_GROWSDOWN)) 101 goto bad_area; 102 if (expand_stack(vma, address)) 103 goto bad_area; 104 105 /* 106 * Ok, we have a good vm_area for this memory access, so 107 * we can handle it.. 108 */ 109 good_area: 110 info.si_code = SEGV_ACCERR; 111 112 /* Handle protection violation, execute on heap or stack */ 113 114 if ((regs->ecr_vec == ECR_V_PROTV) && 115 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 116 goto bad_area; 117 118 if (write) { 119 if (!(vma->vm_flags & VM_WRITE)) 120 goto bad_area; 121 flags |= FAULT_FLAG_WRITE; 122 } else { 123 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 124 goto bad_area; 125 } 126 127 /* 128 * If for any reason at all we couldn't handle the fault, 129 * make sure we exit gracefully rather than endlessly redo 130 * the fault. 131 */ 132 fault = handle_mm_fault(mm, vma, address, flags); 133 134 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ 135 if (unlikely(fatal_signal_pending(current))) { 136 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 137 up_read(&mm->mmap_sem); 138 if (user_mode(regs)) 139 return; 140 } 141 142 if (likely(!(fault & VM_FAULT_ERROR))) { 143 if (flags & FAULT_FLAG_ALLOW_RETRY) { 144 /* To avoid updating stats twice for retry case */ 145 if (fault & VM_FAULT_MAJOR) 146 tsk->maj_flt++; 147 else 148 tsk->min_flt++; 149 150 if (fault & VM_FAULT_RETRY) { 151 flags &= ~FAULT_FLAG_ALLOW_RETRY; 152 flags |= FAULT_FLAG_TRIED; 153 goto retry; 154 } 155 } 156 157 /* Fault Handled Gracefully */ 158 up_read(&mm->mmap_sem); 159 return; 160 } 161 162 /* TBD: switch to pagefault_out_of_memory() */ 163 if (fault & VM_FAULT_OOM) 164 goto out_of_memory; 165 else if (fault & VM_FAULT_SIGBUS) 166 goto do_sigbus; 167 168 /* no man's land */ 169 BUG(); 170 171 /* 172 * Something tried to access memory that isn't in our memory map.. 173 * Fix it, but check if it's kernel or user first.. 174 */ 175 bad_area: 176 up_read(&mm->mmap_sem); 177 178 bad_area_nosemaphore: 179 /* User mode accesses just cause a SIGSEGV */ 180 if (user_mode(regs)) { 181 tsk->thread.fault_address = address; 182 info.si_signo = SIGSEGV; 183 info.si_errno = 0; 184 /* info.si_code has been set above */ 185 info.si_addr = (void __user *)address; 186 force_sig_info(SIGSEGV, &info, tsk); 187 return; 188 } 189 190 no_context: 191 /* Are we prepared to handle this kernel fault? 192 * 193 * (The kernel has valid exception-points in the source 194 * when it acesses user-memory. When it fails in one 195 * of those points, we find it in a table and do a jump 196 * to some fixup code that loads an appropriate error 197 * code) 198 */ 199 if (fixup_exception(regs)) 200 return; 201 202 die("Oops", regs, address); 203 204 out_of_memory: 205 up_read(&mm->mmap_sem); 206 207 if (user_mode(regs)) { 208 pagefault_out_of_memory(); 209 return; 210 } 211 212 goto no_context; 213 214 do_sigbus: 215 up_read(&mm->mmap_sem); 216 217 if (!user_mode(regs)) 218 goto no_context; 219 220 tsk->thread.fault_address = address; 221 info.si_signo = SIGBUS; 222 info.si_errno = 0; 223 info.si_code = BUS_ADRERR; 224 info.si_addr = (void __user *)address; 225 force_sig_info(SIGBUS, &info, tsk); 226 } 227