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 #include <linux/kprobes.h> 17 #include <linux/kfence.h> 18 19 #include <asm/ptrace.h> 20 #include <asm/tlbflush.h> 21 22 #include "../kernel/head.h" 23 24 static void die_kernel_fault(const char *msg, unsigned long addr, 25 struct pt_regs *regs) 26 { 27 bust_spinlocks(1); 28 29 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg, 30 addr); 31 32 bust_spinlocks(0); 33 die(regs, "Oops"); 34 make_task_dead(SIGKILL); 35 } 36 37 static inline void no_context(struct pt_regs *regs, unsigned long addr) 38 { 39 const char *msg; 40 41 /* Are we prepared to handle this kernel fault? */ 42 if (fixup_exception(regs)) 43 return; 44 45 /* 46 * Oops. The kernel tried to access some bad page. We'll have to 47 * terminate things with extreme prejudice. 48 */ 49 if (addr < PAGE_SIZE) 50 msg = "NULL pointer dereference"; 51 else { 52 if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs)) 53 return; 54 55 msg = "paging request"; 56 } 57 58 die_kernel_fault(msg, addr, regs); 59 } 60 61 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) 62 { 63 if (fault & VM_FAULT_OOM) { 64 /* 65 * We ran out of memory, call the OOM killer, and return the userspace 66 * (which will retry the fault, or kill us if we got oom-killed). 67 */ 68 if (!user_mode(regs)) { 69 no_context(regs, addr); 70 return; 71 } 72 pagefault_out_of_memory(); 73 return; 74 } else if (fault & VM_FAULT_SIGBUS) { 75 /* Kernel mode? Handle exceptions or die */ 76 if (!user_mode(regs)) { 77 no_context(regs, addr); 78 return; 79 } 80 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 81 return; 82 } 83 BUG(); 84 } 85 86 static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr) 87 { 88 /* 89 * Something tried to access memory that isn't in our memory map. 90 * Fix it, but check if it's kernel or user first. 91 */ 92 mmap_read_unlock(mm); 93 /* User mode accesses just cause a SIGSEGV */ 94 if (user_mode(regs)) { 95 do_trap(regs, SIGSEGV, code, addr); 96 return; 97 } 98 99 no_context(regs, addr); 100 } 101 102 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr) 103 { 104 pgd_t *pgd, *pgd_k; 105 pud_t *pud_k; 106 p4d_t *p4d_k; 107 pmd_t *pmd_k; 108 pte_t *pte_k; 109 int index; 110 unsigned long pfn; 111 112 /* User mode accesses just cause a SIGSEGV */ 113 if (user_mode(regs)) 114 return do_trap(regs, SIGSEGV, code, addr); 115 116 /* 117 * Synchronize this task's top level page-table 118 * with the 'reference' page table. 119 * 120 * Do _not_ use "tsk->active_mm->pgd" here. 121 * We might be inside an interrupt in the middle 122 * of a task switch. 123 */ 124 index = pgd_index(addr); 125 pfn = csr_read(CSR_SATP) & SATP_PPN; 126 pgd = (pgd_t *)pfn_to_virt(pfn) + index; 127 pgd_k = init_mm.pgd + index; 128 129 if (!pgd_present(*pgd_k)) { 130 no_context(regs, addr); 131 return; 132 } 133 set_pgd(pgd, *pgd_k); 134 135 p4d_k = p4d_offset(pgd_k, addr); 136 if (!p4d_present(*p4d_k)) { 137 no_context(regs, addr); 138 return; 139 } 140 141 pud_k = pud_offset(p4d_k, addr); 142 if (!pud_present(*pud_k)) { 143 no_context(regs, addr); 144 return; 145 } 146 if (pud_leaf(*pud_k)) 147 goto flush_tlb; 148 149 /* 150 * Since the vmalloc area is global, it is unnecessary 151 * to copy individual PTEs 152 */ 153 pmd_k = pmd_offset(pud_k, addr); 154 if (!pmd_present(*pmd_k)) { 155 no_context(regs, addr); 156 return; 157 } 158 if (pmd_leaf(*pmd_k)) 159 goto flush_tlb; 160 161 /* 162 * Make sure the actual PTE exists as well to 163 * catch kernel vmalloc-area accesses to non-mapped 164 * addresses. If we don't do this, this will just 165 * silently loop forever. 166 */ 167 pte_k = pte_offset_kernel(pmd_k, addr); 168 if (!pte_present(*pte_k)) { 169 no_context(regs, addr); 170 return; 171 } 172 173 /* 174 * The kernel assumes that TLBs don't cache invalid 175 * entries, but in RISC-V, SFENCE.VMA specifies an 176 * ordering constraint, not a cache flush; it is 177 * necessary even after writing invalid entries. 178 */ 179 flush_tlb: 180 local_flush_tlb_page(addr); 181 } 182 183 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) 184 { 185 switch (cause) { 186 case EXC_INST_PAGE_FAULT: 187 if (!(vma->vm_flags & VM_EXEC)) { 188 return true; 189 } 190 break; 191 case EXC_LOAD_PAGE_FAULT: 192 /* Write implies read */ 193 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) { 194 return true; 195 } 196 break; 197 case EXC_STORE_PAGE_FAULT: 198 if (!(vma->vm_flags & VM_WRITE)) { 199 return true; 200 } 201 break; 202 default: 203 panic("%s: unhandled cause %lu", __func__, cause); 204 } 205 return false; 206 } 207 208 /* 209 * This routine handles page faults. It determines the address and the 210 * problem, and then passes it off to one of the appropriate routines. 211 */ 212 asmlinkage void do_page_fault(struct pt_regs *regs) 213 { 214 struct task_struct *tsk; 215 struct vm_area_struct *vma; 216 struct mm_struct *mm; 217 unsigned long addr, cause; 218 unsigned int flags = FAULT_FLAG_DEFAULT; 219 int code = SEGV_MAPERR; 220 vm_fault_t fault; 221 222 cause = regs->cause; 223 addr = regs->badaddr; 224 225 tsk = current; 226 mm = tsk->mm; 227 228 if (kprobe_page_fault(regs, cause)) 229 return; 230 231 /* 232 * Fault-in kernel-space virtual memory on-demand. 233 * The 'reference' page table is init_mm.pgd. 234 * 235 * NOTE! We MUST NOT take any locks for this case. We may 236 * be in an interrupt or a critical region, and should 237 * only copy the information from the master page table, 238 * nothing more. 239 */ 240 if (unlikely((addr >= VMALLOC_START) && (addr < VMALLOC_END))) { 241 vmalloc_fault(regs, code, addr); 242 return; 243 } 244 245 #ifdef CONFIG_64BIT 246 /* 247 * Modules in 64bit kernels lie in their own virtual region which is not 248 * in the vmalloc region, but dealing with page faults in this region 249 * or the vmalloc region amounts to doing the same thing: checking that 250 * the mapping exists in init_mm.pgd and updating user page table, so 251 * just use vmalloc_fault. 252 */ 253 if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) { 254 vmalloc_fault(regs, code, addr); 255 return; 256 } 257 #endif 258 /* Enable interrupts if they were enabled in the parent context. */ 259 if (likely(regs->status & SR_PIE)) 260 local_irq_enable(); 261 262 /* 263 * If we're in an interrupt, have no user context, or are running 264 * in an atomic region, then we must not take the fault. 265 */ 266 if (unlikely(faulthandler_disabled() || !mm)) { 267 tsk->thread.bad_cause = cause; 268 no_context(regs, addr); 269 return; 270 } 271 272 if (user_mode(regs)) 273 flags |= FAULT_FLAG_USER; 274 275 if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) { 276 if (fixup_exception(regs)) 277 return; 278 279 die_kernel_fault("access to user memory without uaccess routines", addr, regs); 280 } 281 282 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 283 284 if (cause == EXC_STORE_PAGE_FAULT) 285 flags |= FAULT_FLAG_WRITE; 286 else if (cause == EXC_INST_PAGE_FAULT) 287 flags |= FAULT_FLAG_INSTRUCTION; 288 retry: 289 mmap_read_lock(mm); 290 vma = find_vma(mm, addr); 291 if (unlikely(!vma)) { 292 tsk->thread.bad_cause = cause; 293 bad_area(regs, mm, code, addr); 294 return; 295 } 296 if (likely(vma->vm_start <= addr)) 297 goto good_area; 298 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 299 tsk->thread.bad_cause = cause; 300 bad_area(regs, mm, code, addr); 301 return; 302 } 303 if (unlikely(expand_stack(vma, addr))) { 304 tsk->thread.bad_cause = cause; 305 bad_area(regs, mm, code, addr); 306 return; 307 } 308 309 /* 310 * Ok, we have a good vm_area for this memory access, so 311 * we can handle it. 312 */ 313 good_area: 314 code = SEGV_ACCERR; 315 316 if (unlikely(access_error(cause, vma))) { 317 tsk->thread.bad_cause = cause; 318 bad_area(regs, mm, code, addr); 319 return; 320 } 321 322 /* 323 * If for any reason at all we could not handle the fault, 324 * make sure we exit gracefully rather than endlessly redo 325 * the fault. 326 */ 327 fault = handle_mm_fault(vma, addr, flags, regs); 328 329 /* 330 * If we need to retry but a fatal signal is pending, handle the 331 * signal first. We do not need to release the mmap_lock because it 332 * would already be released in __lock_page_or_retry in mm/filemap.c. 333 */ 334 if (fault_signal_pending(fault, regs)) { 335 if (!user_mode(regs)) 336 no_context(regs, addr); 337 return; 338 } 339 340 /* The fault is fully completed (including releasing mmap lock) */ 341 if (fault & VM_FAULT_COMPLETED) 342 return; 343 344 if (unlikely(fault & VM_FAULT_RETRY)) { 345 flags |= FAULT_FLAG_TRIED; 346 347 /* 348 * No need to mmap_read_unlock(mm) as we would 349 * have already released it in __lock_page_or_retry 350 * in mm/filemap.c. 351 */ 352 goto retry; 353 } 354 355 mmap_read_unlock(mm); 356 357 if (unlikely(fault & VM_FAULT_ERROR)) { 358 tsk->thread.bad_cause = cause; 359 mm_fault_error(regs, addr, fault); 360 return; 361 } 362 return; 363 } 364 NOKPROBE_SYMBOL(do_page_fault); 365