1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd. 4 * Lennox Wu <lennox.wu@sunplusct.com> 5 * Chen Liqin <liqin.chen@sunplusct.com> 6 * Copyright (C) 2012 Regents of the University of California 7 */ 8 9 10 #include <linux/mm.h> 11 #include <linux/kernel.h> 12 #include <linux/interrupt.h> 13 #include <linux/perf_event.h> 14 #include <linux/signal.h> 15 #include <linux/uaccess.h> 16 17 #include <asm/ptrace.h> 18 #include <asm/tlbflush.h> 19 20 #include "../kernel/head.h" 21 22 /* 23 * This routine handles page faults. It determines the address and the 24 * problem, and then passes it off to one of the appropriate routines. 25 */ 26 asmlinkage void do_page_fault(struct pt_regs *regs) 27 { 28 struct task_struct *tsk; 29 struct vm_area_struct *vma; 30 struct mm_struct *mm; 31 unsigned long addr, cause; 32 unsigned int flags = FAULT_FLAG_DEFAULT; 33 int code = SEGV_MAPERR; 34 vm_fault_t fault; 35 36 cause = regs->cause; 37 addr = regs->badaddr; 38 39 tsk = current; 40 mm = tsk->mm; 41 42 /* 43 * Fault-in kernel-space virtual memory on-demand. 44 * The 'reference' page table is init_mm.pgd. 45 * 46 * NOTE! We MUST NOT take any locks for this case. We may 47 * be in an interrupt or a critical region, and should 48 * only copy the information from the master page table, 49 * nothing more. 50 */ 51 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 52 goto vmalloc_fault; 53 54 /* Enable interrupts if they were enabled in the parent context. */ 55 if (likely(regs->status & SR_PIE)) 56 local_irq_enable(); 57 58 /* 59 * If we're in an interrupt, have no user context, or are running 60 * in an atomic region, then we must not take the fault. 61 */ 62 if (unlikely(faulthandler_disabled() || !mm)) 63 goto no_context; 64 65 if (user_mode(regs)) 66 flags |= FAULT_FLAG_USER; 67 68 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 69 70 retry: 71 mmap_read_lock(mm); 72 vma = find_vma(mm, addr); 73 if (unlikely(!vma)) 74 goto bad_area; 75 if (likely(vma->vm_start <= addr)) 76 goto good_area; 77 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 78 goto bad_area; 79 if (unlikely(expand_stack(vma, addr))) 80 goto bad_area; 81 82 /* 83 * Ok, we have a good vm_area for this memory access, so 84 * we can handle it. 85 */ 86 good_area: 87 code = SEGV_ACCERR; 88 89 switch (cause) { 90 case EXC_INST_PAGE_FAULT: 91 if (!(vma->vm_flags & VM_EXEC)) 92 goto bad_area; 93 break; 94 case EXC_LOAD_PAGE_FAULT: 95 if (!(vma->vm_flags & VM_READ)) 96 goto bad_area; 97 break; 98 case EXC_STORE_PAGE_FAULT: 99 if (!(vma->vm_flags & VM_WRITE)) 100 goto bad_area; 101 flags |= FAULT_FLAG_WRITE; 102 break; 103 default: 104 panic("%s: unhandled cause %lu", __func__, cause); 105 } 106 107 /* 108 * If for any reason at all we could not handle the fault, 109 * make sure we exit gracefully rather than endlessly redo 110 * the fault. 111 */ 112 fault = handle_mm_fault(vma, addr, flags); 113 114 /* 115 * If we need to retry but a fatal signal is pending, handle the 116 * signal first. We do not need to release the mmap_lock because it 117 * would already be released in __lock_page_or_retry in mm/filemap.c. 118 */ 119 if (fault_signal_pending(fault, regs)) 120 return; 121 122 if (unlikely(fault & VM_FAULT_ERROR)) { 123 if (fault & VM_FAULT_OOM) 124 goto out_of_memory; 125 else if (fault & VM_FAULT_SIGBUS) 126 goto do_sigbus; 127 BUG(); 128 } 129 130 /* 131 * Major/minor page fault accounting is only done on the 132 * initial attempt. If we go through a retry, it is extremely 133 * likely that the page will be found in page cache at that point. 134 */ 135 if (flags & FAULT_FLAG_ALLOW_RETRY) { 136 if (fault & VM_FAULT_MAJOR) { 137 tsk->maj_flt++; 138 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 139 1, regs, addr); 140 } else { 141 tsk->min_flt++; 142 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 143 1, regs, addr); 144 } 145 if (fault & VM_FAULT_RETRY) { 146 flags |= FAULT_FLAG_TRIED; 147 148 /* 149 * No need to mmap_read_unlock(mm) as we would 150 * have already released it in __lock_page_or_retry 151 * in mm/filemap.c. 152 */ 153 goto retry; 154 } 155 } 156 157 mmap_read_unlock(mm); 158 return; 159 160 /* 161 * Something tried to access memory that isn't in our memory map. 162 * Fix it, but check if it's kernel or user first. 163 */ 164 bad_area: 165 mmap_read_unlock(mm); 166 /* User mode accesses just cause a SIGSEGV */ 167 if (user_mode(regs)) { 168 do_trap(regs, SIGSEGV, code, addr); 169 return; 170 } 171 172 no_context: 173 /* Are we prepared to handle this kernel fault? */ 174 if (fixup_exception(regs)) 175 return; 176 177 /* 178 * Oops. The kernel tried to access some bad page. We'll have to 179 * terminate things with extreme prejudice. 180 */ 181 bust_spinlocks(1); 182 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 183 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 184 "paging request", addr); 185 die(regs, "Oops"); 186 do_exit(SIGKILL); 187 188 /* 189 * We ran out of memory, call the OOM killer, and return the userspace 190 * (which will retry the fault, or kill us if we got oom-killed). 191 */ 192 out_of_memory: 193 mmap_read_unlock(mm); 194 if (!user_mode(regs)) 195 goto no_context; 196 pagefault_out_of_memory(); 197 return; 198 199 do_sigbus: 200 mmap_read_unlock(mm); 201 /* Kernel mode? Handle exceptions or die */ 202 if (!user_mode(regs)) 203 goto no_context; 204 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 205 return; 206 207 vmalloc_fault: 208 { 209 pgd_t *pgd, *pgd_k; 210 pud_t *pud, *pud_k; 211 p4d_t *p4d, *p4d_k; 212 pmd_t *pmd, *pmd_k; 213 pte_t *pte_k; 214 int index; 215 216 /* User mode accesses just cause a SIGSEGV */ 217 if (user_mode(regs)) 218 return do_trap(regs, SIGSEGV, code, addr); 219 220 /* 221 * Synchronize this task's top level page-table 222 * with the 'reference' page table. 223 * 224 * Do _not_ use "tsk->active_mm->pgd" here. 225 * We might be inside an interrupt in the middle 226 * of a task switch. 227 */ 228 index = pgd_index(addr); 229 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index; 230 pgd_k = init_mm.pgd + index; 231 232 if (!pgd_present(*pgd_k)) 233 goto no_context; 234 set_pgd(pgd, *pgd_k); 235 236 p4d = p4d_offset(pgd, addr); 237 p4d_k = p4d_offset(pgd_k, addr); 238 if (!p4d_present(*p4d_k)) 239 goto no_context; 240 241 pud = pud_offset(p4d, addr); 242 pud_k = pud_offset(p4d_k, addr); 243 if (!pud_present(*pud_k)) 244 goto no_context; 245 246 /* 247 * Since the vmalloc area is global, it is unnecessary 248 * to copy individual PTEs 249 */ 250 pmd = pmd_offset(pud, addr); 251 pmd_k = pmd_offset(pud_k, addr); 252 if (!pmd_present(*pmd_k)) 253 goto no_context; 254 set_pmd(pmd, *pmd_k); 255 256 /* 257 * Make sure the actual PTE exists as well to 258 * catch kernel vmalloc-area accesses to non-mapped 259 * addresses. If we don't do this, this will just 260 * silently loop forever. 261 */ 262 pte_k = pte_offset_kernel(pmd_k, addr); 263 if (!pte_present(*pte_k)) 264 goto no_context; 265 266 /* 267 * The kernel assumes that TLBs don't cache invalid 268 * entries, but in RISC-V, SFENCE.VMA specifies an 269 * ordering constraint, not a cache flush; it is 270 * necessary even after writing invalid entries. 271 */ 272 local_flush_tlb_page(addr); 273 274 return; 275 } 276 } 277