1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. 3 4 #include <linux/signal.h> 5 #include <linux/module.h> 6 #include <linux/sched.h> 7 #include <linux/interrupt.h> 8 #include <linux/kernel.h> 9 #include <linux/errno.h> 10 #include <linux/string.h> 11 #include <linux/types.h> 12 #include <linux/ptrace.h> 13 #include <linux/mman.h> 14 #include <linux/mm.h> 15 #include <linux/smp.h> 16 #include <linux/version.h> 17 #include <linux/vt_kern.h> 18 #include <linux/extable.h> 19 #include <linux/uaccess.h> 20 #include <linux/perf_event.h> 21 22 #include <asm/hardirq.h> 23 #include <asm/mmu_context.h> 24 #include <asm/traps.h> 25 #include <asm/page.h> 26 27 int fixup_exception(struct pt_regs *regs) 28 { 29 const struct exception_table_entry *fixup; 30 31 fixup = search_exception_tables(instruction_pointer(regs)); 32 if (fixup) { 33 regs->pc = fixup->nextinsn; 34 35 return 1; 36 } 37 38 return 0; 39 } 40 41 /* 42 * This routine handles page faults. It determines the address, 43 * and the problem, and then passes it off to one of the appropriate 44 * routines. 45 */ 46 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write, 47 unsigned long mmu_meh) 48 { 49 struct vm_area_struct *vma = NULL; 50 struct task_struct *tsk = current; 51 struct mm_struct *mm = tsk->mm; 52 int si_code; 53 int fault; 54 unsigned long address = mmu_meh & PAGE_MASK; 55 56 si_code = SEGV_MAPERR; 57 58 #ifndef CONFIG_CPU_HAS_TLBI 59 /* 60 * We fault-in kernel-space virtual memory on-demand. The 61 * 'reference' page table is init_mm.pgd. 62 * 63 * NOTE! We MUST NOT take any locks for this case. We may 64 * be in an interrupt or a critical region, and should 65 * only copy the information from the master page table, 66 * nothing more. 67 */ 68 if (unlikely(address >= VMALLOC_START) && 69 unlikely(address <= VMALLOC_END)) { 70 /* 71 * Synchronize this task's top level page-table 72 * with the 'reference' page table. 73 * 74 * Do _not_ use "tsk" here. We might be inside 75 * an interrupt in the middle of a task switch.. 76 */ 77 int offset = __pgd_offset(address); 78 pgd_t *pgd, *pgd_k; 79 pud_t *pud, *pud_k; 80 pmd_t *pmd, *pmd_k; 81 pte_t *pte_k; 82 83 unsigned long pgd_base; 84 85 pgd_base = (unsigned long)__va(get_pgd()); 86 pgd = (pgd_t *)pgd_base + offset; 87 pgd_k = init_mm.pgd + offset; 88 89 if (!pgd_present(*pgd_k)) 90 goto no_context; 91 set_pgd(pgd, *pgd_k); 92 93 pud = (pud_t *)pgd; 94 pud_k = (pud_t *)pgd_k; 95 if (!pud_present(*pud_k)) 96 goto no_context; 97 98 pmd = pmd_offset(pud, address); 99 pmd_k = pmd_offset(pud_k, address); 100 if (!pmd_present(*pmd_k)) 101 goto no_context; 102 set_pmd(pmd, *pmd_k); 103 104 pte_k = pte_offset_kernel(pmd_k, address); 105 if (!pte_present(*pte_k)) 106 goto no_context; 107 return; 108 } 109 #endif 110 111 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 112 /* 113 * If we're in an interrupt or have no user 114 * context, we must not take the fault.. 115 */ 116 if (in_atomic() || !mm) 117 goto bad_area_nosemaphore; 118 119 down_read(&mm->mmap_sem); 120 vma = find_vma(mm, address); 121 if (!vma) 122 goto bad_area; 123 if (vma->vm_start <= address) 124 goto good_area; 125 if (!(vma->vm_flags & VM_GROWSDOWN)) 126 goto bad_area; 127 if (expand_stack(vma, address)) 128 goto bad_area; 129 /* 130 * Ok, we have a good vm_area for this memory access, so 131 * we can handle it.. 132 */ 133 good_area: 134 si_code = SEGV_ACCERR; 135 136 if (write) { 137 if (!(vma->vm_flags & VM_WRITE)) 138 goto bad_area; 139 } else { 140 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 141 goto bad_area; 142 } 143 144 /* 145 * If for any reason at all we couldn't handle the fault, 146 * make sure we exit gracefully rather than endlessly redo 147 * the fault. 148 */ 149 fault = handle_mm_fault(vma, address, write ? FAULT_FLAG_WRITE : 0); 150 if (unlikely(fault & VM_FAULT_ERROR)) { 151 if (fault & VM_FAULT_OOM) 152 goto out_of_memory; 153 else if (fault & VM_FAULT_SIGBUS) 154 goto do_sigbus; 155 else if (fault & VM_FAULT_SIGSEGV) 156 goto bad_area; 157 BUG(); 158 } 159 if (fault & VM_FAULT_MAJOR) { 160 tsk->maj_flt++; 161 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, 162 address); 163 } else { 164 tsk->min_flt++; 165 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, 166 address); 167 } 168 169 up_read(&mm->mmap_sem); 170 return; 171 172 /* 173 * Something tried to access memory that isn't in our memory map.. 174 * Fix it, but check if it's kernel or user first.. 175 */ 176 bad_area: 177 up_read(&mm->mmap_sem); 178 179 bad_area_nosemaphore: 180 /* User mode accesses just cause a SIGSEGV */ 181 if (user_mode(regs)) { 182 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 183 return; 184 } 185 186 no_context: 187 /* Are we prepared to handle this kernel fault? */ 188 if (fixup_exception(regs)) 189 return; 190 191 /* 192 * Oops. The kernel tried to access some bad page. We'll have to 193 * terminate things with extreme prejudice. 194 */ 195 bust_spinlocks(1); 196 pr_alert("Unable to handle kernel paging request at virtual " 197 "address 0x%08lx, pc: 0x%08lx\n", address, regs->pc); 198 die_if_kernel("Oops", regs, write); 199 200 out_of_memory: 201 /* 202 * We ran out of memory, call the OOM killer, and return the userspace 203 * (which will retry the fault, or kill us if we got oom-killed). 204 */ 205 pagefault_out_of_memory(); 206 return; 207 208 do_sigbus: 209 up_read(&mm->mmap_sem); 210 211 /* Kernel mode? Handle exceptions or die */ 212 if (!user_mode(regs)) 213 goto no_context; 214 215 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 216 } 217