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 siginfo_t info; 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 clear_siginfo(&info); 76 77 /* 78 * We fault-in kernel-space virtual memory on-demand. The 79 * 'reference' page table is init_mm.pgd. 80 * 81 * NOTE! We MUST NOT take any locks for this case. We may 82 * be in an interrupt or a critical region, and should 83 * only copy the information from the master page table, 84 * nothing more. 85 */ 86 if (address >= VMALLOC_START) { 87 ret = handle_kernel_vaddr_fault(address); 88 if (unlikely(ret)) 89 goto bad_area_nosemaphore; 90 else 91 return; 92 } 93 94 info.si_code = SEGV_MAPERR; 95 96 /* 97 * If we're in an interrupt or have no user 98 * context, we must not take the fault.. 99 */ 100 if (faulthandler_disabled() || !mm) 101 goto no_context; 102 103 if (user_mode(regs)) 104 flags |= FAULT_FLAG_USER; 105 retry: 106 down_read(&mm->mmap_sem); 107 vma = find_vma(mm, address); 108 if (!vma) 109 goto bad_area; 110 if (vma->vm_start <= address) 111 goto good_area; 112 if (!(vma->vm_flags & VM_GROWSDOWN)) 113 goto bad_area; 114 if (expand_stack(vma, address)) 115 goto bad_area; 116 117 /* 118 * Ok, we have a good vm_area for this memory access, so 119 * we can handle it.. 120 */ 121 good_area: 122 info.si_code = SEGV_ACCERR; 123 124 /* Handle protection violation, execute on heap or stack */ 125 126 if ((regs->ecr_vec == ECR_V_PROTV) && 127 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 128 goto bad_area; 129 130 if (write) { 131 if (!(vma->vm_flags & VM_WRITE)) 132 goto bad_area; 133 flags |= FAULT_FLAG_WRITE; 134 } else { 135 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 136 goto bad_area; 137 } 138 139 /* 140 * If for any reason at all we couldn't handle the fault, 141 * make sure we exit gracefully rather than endlessly redo 142 * the fault. 143 */ 144 fault = handle_mm_fault(vma, address, flags); 145 146 /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ 147 if (unlikely(fatal_signal_pending(current))) { 148 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 149 up_read(&mm->mmap_sem); 150 if (user_mode(regs)) 151 return; 152 } 153 154 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 155 156 if (likely(!(fault & VM_FAULT_ERROR))) { 157 if (flags & FAULT_FLAG_ALLOW_RETRY) { 158 /* To avoid updating stats twice for retry case */ 159 if (fault & VM_FAULT_MAJOR) { 160 tsk->maj_flt++; 161 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 162 regs, address); 163 } else { 164 tsk->min_flt++; 165 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 166 regs, address); 167 } 168 169 if (fault & VM_FAULT_RETRY) { 170 flags &= ~FAULT_FLAG_ALLOW_RETRY; 171 flags |= FAULT_FLAG_TRIED; 172 goto retry; 173 } 174 } 175 176 /* Fault Handled Gracefully */ 177 up_read(&mm->mmap_sem); 178 return; 179 } 180 181 if (fault & VM_FAULT_OOM) 182 goto out_of_memory; 183 else if (fault & VM_FAULT_SIGSEGV) 184 goto bad_area; 185 else if (fault & VM_FAULT_SIGBUS) 186 goto do_sigbus; 187 188 /* no man's land */ 189 BUG(); 190 191 /* 192 * Something tried to access memory that isn't in our memory map.. 193 * Fix it, but check if it's kernel or user first.. 194 */ 195 bad_area: 196 up_read(&mm->mmap_sem); 197 198 bad_area_nosemaphore: 199 /* User mode accesses just cause a SIGSEGV */ 200 if (user_mode(regs)) { 201 tsk->thread.fault_address = address; 202 info.si_signo = SIGSEGV; 203 info.si_errno = 0; 204 /* info.si_code has been set above */ 205 info.si_addr = (void __user *)address; 206 force_sig_info(SIGSEGV, &info, tsk); 207 return; 208 } 209 210 no_context: 211 /* Are we prepared to handle this kernel fault? 212 * 213 * (The kernel has valid exception-points in the source 214 * when it accesses user-memory. When it fails in one 215 * of those points, we find it in a table and do a jump 216 * to some fixup code that loads an appropriate error 217 * code) 218 */ 219 if (fixup_exception(regs)) 220 return; 221 222 die("Oops", regs, address); 223 224 out_of_memory: 225 up_read(&mm->mmap_sem); 226 227 if (user_mode(regs)) { 228 pagefault_out_of_memory(); 229 return; 230 } 231 232 goto no_context; 233 234 do_sigbus: 235 up_read(&mm->mmap_sem); 236 237 if (!user_mode(regs)) 238 goto no_context; 239 240 tsk->thread.fault_address = address; 241 info.si_signo = SIGBUS; 242 info.si_errno = 0; 243 info.si_code = BUS_ADRERR; 244 info.si_addr = (void __user *)address; 245 force_sig_info(SIGBUS, &info, tsk); 246 } 247