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/mmu.h> 17 18 /* 19 * kernel virtual address is required to implement vmalloc/pkmap/fixmap 20 * Refer to asm/processor.h for System Memory Map 21 * 22 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage) 23 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared 24 */ 25 noinline static int handle_kernel_vaddr_fault(unsigned long address) 26 { 27 /* 28 * Synchronize this task's top level page-table 29 * with the 'reference' page table. 30 */ 31 pgd_t *pgd, *pgd_k; 32 p4d_t *p4d, *p4d_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 p4d = p4d_offset(pgd, address); 43 p4d_k = p4d_offset(pgd_k, address); 44 if (!p4d_present(*p4d_k)) 45 goto bad_area; 46 47 pud = pud_offset(p4d, address); 48 pud_k = pud_offset(p4d_k, address); 49 if (!pud_present(*pud_k)) 50 goto bad_area; 51 52 pmd = pmd_offset(pud, address); 53 pmd_k = pmd_offset(pud_k, address); 54 if (!pmd_present(*pmd_k)) 55 goto bad_area; 56 57 set_pmd(pmd, *pmd_k); 58 59 /* XXX: create the TLB entry here */ 60 return 0; 61 62 bad_area: 63 return 1; 64 } 65 66 void do_page_fault(unsigned long address, struct pt_regs *regs) 67 { 68 struct vm_area_struct *vma = NULL; 69 struct task_struct *tsk = current; 70 struct mm_struct *mm = tsk->mm; 71 int sig, si_code = SEGV_MAPERR; 72 unsigned int write = 0, exec = 0, mask; 73 vm_fault_t fault = VM_FAULT_SIGSEGV; /* handle_mm_fault() output */ 74 unsigned int flags; /* handle_mm_fault() input */ 75 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 && !user_mode(regs)) { 83 if (unlikely(handle_kernel_vaddr_fault(address))) 84 goto no_context; 85 else 86 return; 87 } 88 89 /* 90 * If we're in an interrupt or have no user 91 * context, we must not take the fault.. 92 */ 93 if (faulthandler_disabled() || !mm) 94 goto no_context; 95 96 if (regs->ecr_cause & ECR_C_PROTV_STORE) /* ST/EX */ 97 write = 1; 98 else if ((regs->ecr_vec == ECR_V_PROTV) && 99 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 100 exec = 1; 101 102 flags = FAULT_FLAG_DEFAULT; 103 if (user_mode(regs)) 104 flags |= FAULT_FLAG_USER; 105 if (write) 106 flags |= FAULT_FLAG_WRITE; 107 108 retry: 109 mmap_read_lock(mm); 110 111 vma = find_vma(mm, address); 112 if (!vma) 113 goto bad_area; 114 if (unlikely(address < vma->vm_start)) { 115 if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address)) 116 goto bad_area; 117 } 118 119 /* 120 * vm_area is good, now check permissions for this memory access 121 */ 122 mask = VM_READ; 123 if (write) 124 mask = VM_WRITE; 125 if (exec) 126 mask = VM_EXEC; 127 128 if (!(vma->vm_flags & mask)) { 129 si_code = SEGV_ACCERR; 130 goto bad_area; 131 } 132 133 fault = handle_mm_fault(vma, address, flags); 134 135 /* Quick path to respond to signals */ 136 if (fault_signal_pending(fault, regs)) { 137 if (!user_mode(regs)) 138 goto no_context; 139 return; 140 } 141 142 /* 143 * Fault retry nuances, mmap_lock already relinquished by core mm 144 */ 145 if (unlikely((fault & VM_FAULT_RETRY) && 146 (flags & FAULT_FLAG_ALLOW_RETRY))) { 147 flags |= FAULT_FLAG_TRIED; 148 goto retry; 149 } 150 151 bad_area: 152 mmap_read_unlock(mm); 153 154 /* 155 * Major/minor page fault accounting 156 * (in case of retry we only land here once) 157 */ 158 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 159 160 if (likely(!(fault & VM_FAULT_ERROR))) { 161 if (fault & VM_FAULT_MAJOR) { 162 tsk->maj_flt++; 163 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 164 regs, address); 165 } else { 166 tsk->min_flt++; 167 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 168 regs, address); 169 } 170 171 /* Normal return path: fault Handled Gracefully */ 172 return; 173 } 174 175 if (!user_mode(regs)) 176 goto no_context; 177 178 if (fault & VM_FAULT_OOM) { 179 pagefault_out_of_memory(); 180 return; 181 } 182 183 if (fault & VM_FAULT_SIGBUS) { 184 sig = SIGBUS; 185 si_code = BUS_ADRERR; 186 } 187 else { 188 sig = SIGSEGV; 189 } 190 191 tsk->thread.fault_address = address; 192 force_sig_fault(sig, si_code, (void __user *)address); 193 return; 194 195 no_context: 196 if (fixup_exception(regs)) 197 return; 198 199 die("Oops", regs, address); 200 } 201