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 <linux/perf_event.h> 18 #include <asm/pgalloc.h> 19 #include <asm/mmu.h> 20 21 /* 22 * kernel virtual address is required to implement vmalloc/pkmap/fixmap 23 * Refer to asm/processor.h for System Memory Map 24 * 25 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage) 26 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared 27 */ 28 noinline static int handle_kernel_vaddr_fault(unsigned long address) 29 { 30 /* 31 * Synchronize this task's top level page-table 32 * with the 'reference' page table. 33 */ 34 pgd_t *pgd, *pgd_k; 35 pud_t *pud, *pud_k; 36 pmd_t *pmd, *pmd_k; 37 38 pgd = pgd_offset_fast(current->active_mm, address); 39 pgd_k = pgd_offset_k(address); 40 41 if (!pgd_present(*pgd_k)) 42 goto bad_area; 43 44 pud = pud_offset(pgd, address); 45 pud_k = pud_offset(pgd_k, address); 46 if (!pud_present(*pud_k)) 47 goto bad_area; 48 49 pmd = pmd_offset(pud, address); 50 pmd_k = pmd_offset(pud_k, address); 51 if (!pmd_present(*pmd_k)) 52 goto bad_area; 53 54 set_pmd(pmd, *pmd_k); 55 56 /* XXX: create the TLB entry here */ 57 return 0; 58 59 bad_area: 60 return 1; 61 } 62 63 void do_page_fault(unsigned long address, struct pt_regs *regs) 64 { 65 struct vm_area_struct *vma = NULL; 66 struct task_struct *tsk = current; 67 struct mm_struct *mm = tsk->mm; 68 siginfo_t info; 69 int fault, ret; 70 int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */ 71 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 72 73 /* 74 * We fault-in kernel-space virtual memory on-demand. The 75 * 'reference' page table is init_mm.pgd. 76 * 77 * NOTE! We MUST NOT take any locks for this case. We may 78 * be in an interrupt or a critical region, and should 79 * only copy the information from the master page table, 80 * nothing more. 81 */ 82 if (address >= VMALLOC_START) { 83 ret = handle_kernel_vaddr_fault(address); 84 if (unlikely(ret)) 85 goto bad_area_nosemaphore; 86 else 87 return; 88 } 89 90 info.si_code = SEGV_MAPERR; 91 92 /* 93 * If we're in an interrupt or have no user 94 * context, we must not take the fault.. 95 */ 96 if (faulthandler_disabled() || !mm) 97 goto no_context; 98 99 if (user_mode(regs)) 100 flags |= FAULT_FLAG_USER; 101 retry: 102 down_read(&mm->mmap_sem); 103 vma = find_vma(mm, address); 104 if (!vma) 105 goto bad_area; 106 if (vma->vm_start <= address) 107 goto good_area; 108 if (!(vma->vm_flags & VM_GROWSDOWN)) 109 goto bad_area; 110 if (expand_stack(vma, address)) 111 goto bad_area; 112 113 /* 114 * Ok, we have a good vm_area for this memory access, so 115 * we can handle it.. 116 */ 117 good_area: 118 info.si_code = SEGV_ACCERR; 119 120 /* Handle protection violation, execute on heap or stack */ 121 122 if ((regs->ecr_vec == ECR_V_PROTV) && 123 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 124 goto bad_area; 125 126 if (write) { 127 if (!(vma->vm_flags & VM_WRITE)) 128 goto bad_area; 129 flags |= FAULT_FLAG_WRITE; 130 } else { 131 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 132 goto bad_area; 133 } 134 135 /* 136 * If for any reason at all we couldn't handle the fault, 137 * make sure we exit gracefully rather than endlessly redo 138 * the fault. 139 */ 140 fault = handle_mm_fault(mm, vma, address, flags); 141 142 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ 143 if (unlikely(fatal_signal_pending(current))) { 144 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 145 up_read(&mm->mmap_sem); 146 if (user_mode(regs)) 147 return; 148 } 149 150 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 151 152 if (likely(!(fault & VM_FAULT_ERROR))) { 153 if (flags & FAULT_FLAG_ALLOW_RETRY) { 154 /* To avoid updating stats twice for retry case */ 155 if (fault & VM_FAULT_MAJOR) { 156 tsk->maj_flt++; 157 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 158 regs, address); 159 } else { 160 tsk->min_flt++; 161 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 162 regs, address); 163 } 164 165 if (fault & VM_FAULT_RETRY) { 166 flags &= ~FAULT_FLAG_ALLOW_RETRY; 167 flags |= FAULT_FLAG_TRIED; 168 goto retry; 169 } 170 } 171 172 /* Fault Handled Gracefully */ 173 up_read(&mm->mmap_sem); 174 return; 175 } 176 177 if (fault & VM_FAULT_OOM) 178 goto out_of_memory; 179 else if (fault & VM_FAULT_SIGSEGV) 180 goto bad_area; 181 else if (fault & VM_FAULT_SIGBUS) 182 goto do_sigbus; 183 184 /* no man's land */ 185 BUG(); 186 187 /* 188 * Something tried to access memory that isn't in our memory map.. 189 * Fix it, but check if it's kernel or user first.. 190 */ 191 bad_area: 192 up_read(&mm->mmap_sem); 193 194 bad_area_nosemaphore: 195 /* User mode accesses just cause a SIGSEGV */ 196 if (user_mode(regs)) { 197 tsk->thread.fault_address = address; 198 info.si_signo = SIGSEGV; 199 info.si_errno = 0; 200 /* info.si_code has been set above */ 201 info.si_addr = (void __user *)address; 202 force_sig_info(SIGSEGV, &info, tsk); 203 return; 204 } 205 206 no_context: 207 /* Are we prepared to handle this kernel fault? 208 * 209 * (The kernel has valid exception-points in the source 210 * when it acesses user-memory. When it fails in one 211 * of those points, we find it in a table and do a jump 212 * to some fixup code that loads an appropriate error 213 * code) 214 */ 215 if (fixup_exception(regs)) 216 return; 217 218 die("Oops", regs, address); 219 220 out_of_memory: 221 up_read(&mm->mmap_sem); 222 223 if (user_mode(regs)) { 224 pagefault_out_of_memory(); 225 return; 226 } 227 228 goto no_context; 229 230 do_sigbus: 231 up_read(&mm->mmap_sem); 232 233 if (!user_mode(regs)) 234 goto no_context; 235 236 tsk->thread.fault_address = address; 237 info.si_signo = SIGBUS; 238 info.si_errno = 0; 239 info.si_code = BUS_ADRERR; 240 info.si_addr = (void __user *)address; 241 force_sig_info(SIGBUS, &info, tsk); 242 } 243