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 <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 clear_siginfo(&info); 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 info.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 info.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 Pagefault was interrupted by SIGKILL, exit page fault "early" */ 145 if (unlikely(fatal_signal_pending(current))) { 146 if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) 147 up_read(&mm->mmap_sem); 148 if (user_mode(regs)) 149 return; 150 } 151 152 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 153 154 if (likely(!(fault & VM_FAULT_ERROR))) { 155 if (flags & FAULT_FLAG_ALLOW_RETRY) { 156 /* To avoid updating stats twice for retry case */ 157 if (fault & VM_FAULT_MAJOR) { 158 tsk->maj_flt++; 159 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 160 regs, address); 161 } else { 162 tsk->min_flt++; 163 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 164 regs, address); 165 } 166 167 if (fault & VM_FAULT_RETRY) { 168 flags &= ~FAULT_FLAG_ALLOW_RETRY; 169 flags |= FAULT_FLAG_TRIED; 170 goto retry; 171 } 172 } 173 174 /* Fault Handled Gracefully */ 175 up_read(&mm->mmap_sem); 176 return; 177 } 178 179 if (fault & VM_FAULT_OOM) 180 goto out_of_memory; 181 else if (fault & VM_FAULT_SIGSEGV) 182 goto bad_area; 183 else if (fault & VM_FAULT_SIGBUS) 184 goto do_sigbus; 185 186 /* no man's land */ 187 BUG(); 188 189 /* 190 * Something tried to access memory that isn't in our memory map.. 191 * Fix it, but check if it's kernel or user first.. 192 */ 193 bad_area: 194 up_read(&mm->mmap_sem); 195 196 bad_area_nosemaphore: 197 /* User mode accesses just cause a SIGSEGV */ 198 if (user_mode(regs)) { 199 tsk->thread.fault_address = address; 200 info.si_signo = SIGSEGV; 201 info.si_errno = 0; 202 /* info.si_code has been set above */ 203 info.si_addr = (void __user *)address; 204 force_sig_info(SIGSEGV, &info, tsk); 205 return; 206 } 207 208 no_context: 209 /* Are we prepared to handle this kernel fault? 210 * 211 * (The kernel has valid exception-points in the source 212 * when it accesses user-memory. When it fails in one 213 * of those points, we find it in a table and do a jump 214 * to some fixup code that loads an appropriate error 215 * code) 216 */ 217 if (fixup_exception(regs)) 218 return; 219 220 die("Oops", regs, address); 221 222 out_of_memory: 223 up_read(&mm->mmap_sem); 224 225 if (user_mode(regs)) { 226 pagefault_out_of_memory(); 227 return; 228 } 229 230 goto no_context; 231 232 do_sigbus: 233 up_read(&mm->mmap_sem); 234 235 if (!user_mode(regs)) 236 goto no_context; 237 238 tsk->thread.fault_address = address; 239 info.si_signo = SIGBUS; 240 info.si_errno = 0; 241 info.si_code = BUS_ADRERR; 242 info.si_addr = (void __user *)address; 243 force_sig_info(SIGBUS, &info, tsk); 244 } 245