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