1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Page Fault Handling for ARC (TLB Miss / ProtV) 3 * 4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) 5 */ 6 7 #include <linux/signal.h> 8 #include <linux/interrupt.h> 9 #include <linux/sched/signal.h> 10 #include <linux/errno.h> 11 #include <linux/ptrace.h> 12 #include <linux/uaccess.h> 13 #include <linux/kdebug.h> 14 #include <linux/perf_event.h> 15 #include <linux/mm_types.h> 16 #include <asm/pgalloc.h> 17 #include <asm/mmu.h> 18 19 /* 20 * kernel virtual address is required to implement vmalloc/pkmap/fixmap 21 * Refer to asm/processor.h for System Memory Map 22 * 23 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage) 24 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared 25 */ 26 noinline static int handle_kernel_vaddr_fault(unsigned long address) 27 { 28 /* 29 * Synchronize this task's top level page-table 30 * with the 'reference' page table. 31 */ 32 pgd_t *pgd, *pgd_k; 33 pud_t *pud, *pud_k; 34 pmd_t *pmd, *pmd_k; 35 36 pgd = pgd_offset_fast(current->active_mm, address); 37 pgd_k = pgd_offset_k(address); 38 39 if (!pgd_present(*pgd_k)) 40 goto bad_area; 41 42 pud = pud_offset(pgd, address); 43 pud_k = pud_offset(pgd_k, address); 44 if (!pud_present(*pud_k)) 45 goto bad_area; 46 47 pmd = pmd_offset(pud, address); 48 pmd_k = pmd_offset(pud_k, address); 49 if (!pmd_present(*pmd_k)) 50 goto bad_area; 51 52 set_pmd(pmd, *pmd_k); 53 54 /* XXX: create the TLB entry here */ 55 return 0; 56 57 bad_area: 58 return 1; 59 } 60 61 void do_page_fault(unsigned long address, struct pt_regs *regs) 62 { 63 struct vm_area_struct *vma = NULL; 64 struct task_struct *tsk = current; 65 struct mm_struct *mm = tsk->mm; 66 int si_code = SEGV_MAPERR; 67 unsigned int write = 0, exec = 0, mask; 68 vm_fault_t fault; /* handle_mm_fault() output */ 69 unsigned int flags; /* handle_mm_fault() input */ 70 71 /* 72 * NOTE! We MUST NOT take any locks for this case. We may 73 * be in an interrupt or a critical region, and should 74 * only copy the information from the master page table, 75 * nothing more. 76 */ 77 if (address >= VMALLOC_START && !user_mode(regs)) { 78 if (unlikely(handle_kernel_vaddr_fault(address))) 79 goto no_context; 80 else 81 return; 82 } 83 84 /* 85 * If we're in an interrupt or have no user 86 * context, we must not take the fault.. 87 */ 88 if (faulthandler_disabled() || !mm) 89 goto no_context; 90 91 if (regs->ecr_cause & ECR_C_PROTV_STORE) /* ST/EX */ 92 write = 1; 93 else if ((regs->ecr_vec == ECR_V_PROTV) && 94 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 95 exec = 1; 96 97 flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 98 if (user_mode(regs)) 99 flags |= FAULT_FLAG_USER; 100 if (write) 101 flags |= FAULT_FLAG_WRITE; 102 103 retry: 104 down_read(&mm->mmap_sem); 105 106 vma = find_vma(mm, address); 107 if (!vma) 108 goto bad_area; 109 if (unlikely(address < vma->vm_start)) { 110 if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address)) 111 goto bad_area; 112 } 113 114 /* 115 * vm_area is good, now check permissions for this memory access 116 */ 117 mask = VM_READ; 118 if (write) 119 mask = VM_WRITE; 120 if (exec) 121 mask = VM_EXEC; 122 123 if (!(vma->vm_flags & mask)) { 124 si_code = SEGV_ACCERR; 125 goto bad_area; 126 } 127 128 fault = handle_mm_fault(vma, address, flags); 129 130 /* 131 * Fault retry nuances 132 */ 133 if (unlikely(fault & VM_FAULT_RETRY)) { 134 135 /* 136 * If fault needs to be retried, handle any pending signals 137 * first (by returning to user mode). 138 * mmap_sem already relinquished by core mm for RETRY case 139 */ 140 if (fatal_signal_pending(current)) { 141 if (!user_mode(regs)) 142 goto no_context; 143 return; 144 } 145 /* 146 * retry state machine 147 */ 148 if (flags & FAULT_FLAG_ALLOW_RETRY) { 149 flags &= ~FAULT_FLAG_ALLOW_RETRY; 150 flags |= FAULT_FLAG_TRIED; 151 goto retry; 152 } 153 } 154 155 /* 156 * Major/minor page fault accounting 157 * (in case of retry we only land here once) 158 */ 159 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 160 161 if (likely(!(fault & VM_FAULT_ERROR))) { 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 /* Normal return path: 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 /* User mode accesses just cause a SIGSEGV */ 195 if (user_mode(regs)) { 196 tsk->thread.fault_address = address; 197 force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk); 198 return; 199 } 200 201 out_of_memory: 202 up_read(&mm->mmap_sem); 203 204 if (user_mode(regs)) { 205 pagefault_out_of_memory(); 206 return; 207 } 208 209 goto no_context; 210 211 do_sigbus: 212 up_read(&mm->mmap_sem); 213 214 if (!user_mode(regs)) 215 goto no_context; 216 217 tsk->thread.fault_address = address; 218 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk); 219 return; 220 221 no_context: 222 if (fixup_exception(regs)) 223 return; 224 225 die("Oops", regs, address); 226 } 227