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 static inline void no_context(struct pt_regs *regs, unsigned long addr) 23 { 24 /* Are we prepared to handle this kernel fault? */ 25 if (fixup_exception(regs)) 26 return; 27 28 /* 29 * Oops. The kernel tried to access some bad page. We'll have to 30 * terminate things with extreme prejudice. 31 */ 32 bust_spinlocks(1); 33 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 34 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 35 "paging request", addr); 36 die(regs, "Oops"); 37 do_exit(SIGKILL); 38 } 39 40 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) 41 { 42 if (fault & VM_FAULT_OOM) { 43 /* 44 * We ran out of memory, call the OOM killer, and return the userspace 45 * (which will retry the fault, or kill us if we got oom-killed). 46 */ 47 if (!user_mode(regs)) { 48 no_context(regs, addr); 49 return; 50 } 51 pagefault_out_of_memory(); 52 return; 53 } else if (fault & VM_FAULT_SIGBUS) { 54 /* Kernel mode? Handle exceptions or die */ 55 if (!user_mode(regs)) { 56 no_context(regs, addr); 57 return; 58 } 59 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 60 return; 61 } 62 BUG(); 63 } 64 65 static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr) 66 { 67 /* 68 * Something tried to access memory that isn't in our memory map. 69 * Fix it, but check if it's kernel or user first. 70 */ 71 mmap_read_unlock(mm); 72 /* User mode accesses just cause a SIGSEGV */ 73 if (user_mode(regs)) { 74 do_trap(regs, SIGSEGV, code, addr); 75 return; 76 } 77 78 no_context(regs, addr); 79 } 80 81 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr) 82 { 83 pgd_t *pgd, *pgd_k; 84 pud_t *pud, *pud_k; 85 p4d_t *p4d, *p4d_k; 86 pmd_t *pmd, *pmd_k; 87 pte_t *pte_k; 88 int index; 89 unsigned long pfn; 90 91 /* User mode accesses just cause a SIGSEGV */ 92 if (user_mode(regs)) 93 return do_trap(regs, SIGSEGV, code, addr); 94 95 /* 96 * Synchronize this task's top level page-table 97 * with the 'reference' page table. 98 * 99 * Do _not_ use "tsk->active_mm->pgd" here. 100 * We might be inside an interrupt in the middle 101 * of a task switch. 102 */ 103 index = pgd_index(addr); 104 pfn = csr_read(CSR_SATP) & SATP_PPN; 105 pgd = (pgd_t *)pfn_to_virt(pfn) + index; 106 pgd_k = init_mm.pgd + index; 107 108 if (!pgd_present(*pgd_k)) { 109 no_context(regs, addr); 110 return; 111 } 112 set_pgd(pgd, *pgd_k); 113 114 p4d = p4d_offset(pgd, addr); 115 p4d_k = p4d_offset(pgd_k, addr); 116 if (!p4d_present(*p4d_k)) { 117 no_context(regs, addr); 118 return; 119 } 120 121 pud = pud_offset(p4d, addr); 122 pud_k = pud_offset(p4d_k, addr); 123 if (!pud_present(*pud_k)) { 124 no_context(regs, addr); 125 return; 126 } 127 128 /* 129 * Since the vmalloc area is global, it is unnecessary 130 * to copy individual PTEs 131 */ 132 pmd = pmd_offset(pud, addr); 133 pmd_k = pmd_offset(pud_k, addr); 134 if (!pmd_present(*pmd_k)) { 135 no_context(regs, addr); 136 return; 137 } 138 set_pmd(pmd, *pmd_k); 139 140 /* 141 * Make sure the actual PTE exists as well to 142 * catch kernel vmalloc-area accesses to non-mapped 143 * addresses. If we don't do this, this will just 144 * silently loop forever. 145 */ 146 pte_k = pte_offset_kernel(pmd_k, addr); 147 if (!pte_present(*pte_k)) { 148 no_context(regs, addr); 149 return; 150 } 151 152 /* 153 * The kernel assumes that TLBs don't cache invalid 154 * entries, but in RISC-V, SFENCE.VMA specifies an 155 * ordering constraint, not a cache flush; it is 156 * necessary even after writing invalid entries. 157 */ 158 local_flush_tlb_page(addr); 159 } 160 161 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) 162 { 163 switch (cause) { 164 case EXC_INST_PAGE_FAULT: 165 if (!(vma->vm_flags & VM_EXEC)) { 166 return true; 167 } 168 break; 169 case EXC_LOAD_PAGE_FAULT: 170 if (!(vma->vm_flags & VM_READ)) { 171 return true; 172 } 173 break; 174 case EXC_STORE_PAGE_FAULT: 175 if (!(vma->vm_flags & VM_WRITE)) { 176 return true; 177 } 178 break; 179 default: 180 panic("%s: unhandled cause %lu", __func__, cause); 181 } 182 return false; 183 } 184 185 /* 186 * This routine handles page faults. It determines the address and the 187 * problem, and then passes it off to one of the appropriate routines. 188 */ 189 asmlinkage void do_page_fault(struct pt_regs *regs) 190 { 191 struct task_struct *tsk; 192 struct vm_area_struct *vma; 193 struct mm_struct *mm; 194 unsigned long addr, cause; 195 unsigned int flags = FAULT_FLAG_DEFAULT; 196 int code = SEGV_MAPERR; 197 vm_fault_t fault; 198 199 cause = regs->cause; 200 addr = regs->badaddr; 201 202 tsk = current; 203 mm = tsk->mm; 204 205 /* 206 * Fault-in kernel-space virtual memory on-demand. 207 * The 'reference' page table is init_mm.pgd. 208 * 209 * NOTE! We MUST NOT take any locks for this case. We may 210 * be in an interrupt or a critical region, and should 211 * only copy the information from the master page table, 212 * nothing more. 213 */ 214 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) { 215 vmalloc_fault(regs, code, addr); 216 return; 217 } 218 219 /* Enable interrupts if they were enabled in the parent context. */ 220 if (likely(regs->status & SR_PIE)) 221 local_irq_enable(); 222 223 /* 224 * If we're in an interrupt, have no user context, or are running 225 * in an atomic region, then we must not take the fault. 226 */ 227 if (unlikely(faulthandler_disabled() || !mm)) { 228 no_context(regs, addr); 229 return; 230 } 231 232 if (user_mode(regs)) 233 flags |= FAULT_FLAG_USER; 234 235 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 236 237 if (cause == EXC_STORE_PAGE_FAULT) 238 flags |= FAULT_FLAG_WRITE; 239 else if (cause == EXC_INST_PAGE_FAULT) 240 flags |= FAULT_FLAG_INSTRUCTION; 241 retry: 242 mmap_read_lock(mm); 243 vma = find_vma(mm, addr); 244 if (unlikely(!vma)) { 245 bad_area(regs, mm, code, addr); 246 return; 247 } 248 if (likely(vma->vm_start <= addr)) 249 goto good_area; 250 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 251 bad_area(regs, mm, code, addr); 252 return; 253 } 254 if (unlikely(expand_stack(vma, addr))) { 255 bad_area(regs, mm, code, addr); 256 return; 257 } 258 259 /* 260 * Ok, we have a good vm_area for this memory access, so 261 * we can handle it. 262 */ 263 good_area: 264 code = SEGV_ACCERR; 265 266 if (unlikely(access_error(cause, vma))) { 267 bad_area(regs, mm, code, addr); 268 return; 269 } 270 271 /* 272 * If for any reason at all we could not handle the fault, 273 * make sure we exit gracefully rather than endlessly redo 274 * the fault. 275 */ 276 fault = handle_mm_fault(vma, addr, flags, regs); 277 278 /* 279 * If we need to retry but a fatal signal is pending, handle the 280 * signal first. We do not need to release the mmap_lock because it 281 * would already be released in __lock_page_or_retry in mm/filemap.c. 282 */ 283 if (fault_signal_pending(fault, regs)) 284 return; 285 286 if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) { 287 flags |= FAULT_FLAG_TRIED; 288 289 /* 290 * No need to mmap_read_unlock(mm) as we would 291 * have already released it in __lock_page_or_retry 292 * in mm/filemap.c. 293 */ 294 goto retry; 295 } 296 297 mmap_read_unlock(mm); 298 299 if (unlikely(fault & VM_FAULT_ERROR)) { 300 mm_fault_error(regs, addr, fault); 301 return; 302 } 303 return; 304 } 305