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(current->active_mm, address); 37 pgd_k = pgd_offset_k(address); 38 39 if (pgd_none (*pgd_k)) 40 goto bad_area; 41 if (!pgd_present(*pgd)) 42 set_pgd(pgd, *pgd_k); 43 44 p4d = p4d_offset(pgd, address); 45 p4d_k = p4d_offset(pgd_k, address); 46 if (p4d_none(*p4d_k)) 47 goto bad_area; 48 if (!p4d_present(*p4d)) 49 set_p4d(p4d, *p4d_k); 50 51 pud = pud_offset(p4d, address); 52 pud_k = pud_offset(p4d_k, address); 53 if (pud_none(*pud_k)) 54 goto bad_area; 55 if (!pud_present(*pud)) 56 set_pud(pud, *pud_k); 57 58 pmd = pmd_offset(pud, address); 59 pmd_k = pmd_offset(pud_k, address); 60 if (pmd_none(*pmd_k)) 61 goto bad_area; 62 if (!pmd_present(*pmd)) 63 set_pmd(pmd, *pmd_k); 64 65 /* XXX: create the TLB entry here */ 66 return 0; 67 68 bad_area: 69 return 1; 70 } 71 72 void do_page_fault(unsigned long address, struct pt_regs *regs) 73 { 74 struct vm_area_struct *vma = NULL; 75 struct task_struct *tsk = current; 76 struct mm_struct *mm = tsk->mm; 77 int sig, si_code = SEGV_MAPERR; 78 unsigned int write = 0, exec = 0, mask; 79 vm_fault_t fault = VM_FAULT_SIGSEGV; /* handle_mm_fault() output */ 80 unsigned int flags; /* handle_mm_fault() input */ 81 82 /* 83 * NOTE! We MUST NOT take any locks for this case. We may 84 * be in an interrupt or a critical region, and should 85 * only copy the information from the master page table, 86 * nothing more. 87 */ 88 if (address >= VMALLOC_START && !user_mode(regs)) { 89 if (unlikely(handle_kernel_vaddr_fault(address))) 90 goto no_context; 91 else 92 return; 93 } 94 95 /* 96 * If we're in an interrupt or have no user 97 * context, we must not take the fault.. 98 */ 99 if (faulthandler_disabled() || !mm) 100 goto no_context; 101 102 if (regs->ecr_cause & ECR_C_PROTV_STORE) /* ST/EX */ 103 write = 1; 104 else if ((regs->ecr_vec == ECR_V_PROTV) && 105 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH)) 106 exec = 1; 107 108 flags = FAULT_FLAG_DEFAULT; 109 if (user_mode(regs)) 110 flags |= FAULT_FLAG_USER; 111 if (write) 112 flags |= FAULT_FLAG_WRITE; 113 114 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 115 retry: 116 mmap_read_lock(mm); 117 118 vma = find_vma(mm, address); 119 if (!vma) 120 goto bad_area; 121 if (unlikely(address < vma->vm_start)) { 122 if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address)) 123 goto bad_area; 124 } 125 126 /* 127 * vm_area is good, now check permissions for this memory access 128 */ 129 mask = VM_READ; 130 if (write) 131 mask = VM_WRITE; 132 if (exec) 133 mask = VM_EXEC; 134 135 if (!(vma->vm_flags & mask)) { 136 si_code = SEGV_ACCERR; 137 goto bad_area; 138 } 139 140 fault = handle_mm_fault(vma, address, flags, regs); 141 142 /* Quick path to respond to signals */ 143 if (fault_signal_pending(fault, regs)) { 144 if (!user_mode(regs)) 145 goto no_context; 146 return; 147 } 148 149 /* The fault is fully completed (including releasing mmap lock) */ 150 if (fault & VM_FAULT_COMPLETED) 151 return; 152 153 /* 154 * Fault retry nuances, mmap_lock already relinquished by core mm 155 */ 156 if (unlikely(fault & VM_FAULT_RETRY)) { 157 flags |= FAULT_FLAG_TRIED; 158 goto retry; 159 } 160 161 bad_area: 162 mmap_read_unlock(mm); 163 164 /* 165 * Major/minor page fault accounting 166 * (in case of retry we only land here once) 167 */ 168 if (likely(!(fault & VM_FAULT_ERROR))) 169 /* Normal return path: fault Handled Gracefully */ 170 return; 171 172 if (!user_mode(regs)) 173 goto no_context; 174 175 if (fault & VM_FAULT_OOM) { 176 pagefault_out_of_memory(); 177 return; 178 } 179 180 if (fault & VM_FAULT_SIGBUS) { 181 sig = SIGBUS; 182 si_code = BUS_ADRERR; 183 } 184 else { 185 sig = SIGSEGV; 186 } 187 188 tsk->thread.fault_address = address; 189 force_sig_fault(sig, si_code, (void __user *)address); 190 return; 191 192 no_context: 193 if (fixup_exception(regs)) 194 return; 195 196 die("Oops", regs, address); 197 } 198