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 #include <linux/entry-common.h> 19 20 #include <asm/ptrace.h> 21 #include <asm/tlbflush.h> 22 23 #include "../kernel/head.h" 24 25 static void die_kernel_fault(const char *msg, unsigned long addr, 26 struct pt_regs *regs) 27 { 28 bust_spinlocks(1); 29 30 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg, 31 addr); 32 33 bust_spinlocks(0); 34 die(regs, "Oops"); 35 make_task_dead(SIGKILL); 36 } 37 38 static inline void no_context(struct pt_regs *regs, unsigned long addr) 39 { 40 const char *msg; 41 42 /* Are we prepared to handle this kernel fault? */ 43 if (fixup_exception(regs)) 44 return; 45 46 /* 47 * Oops. The kernel tried to access some bad page. We'll have to 48 * terminate things with extreme prejudice. 49 */ 50 if (addr < PAGE_SIZE) 51 msg = "NULL pointer dereference"; 52 else { 53 if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs)) 54 return; 55 56 msg = "paging request"; 57 } 58 59 die_kernel_fault(msg, addr, regs); 60 } 61 62 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) 63 { 64 if (fault & VM_FAULT_OOM) { 65 /* 66 * We ran out of memory, call the OOM killer, and return the userspace 67 * (which will retry the fault, or kill us if we got oom-killed). 68 */ 69 if (!user_mode(regs)) { 70 no_context(regs, addr); 71 return; 72 } 73 pagefault_out_of_memory(); 74 return; 75 } else if (fault & VM_FAULT_SIGBUS) { 76 /* Kernel mode? Handle exceptions or die */ 77 if (!user_mode(regs)) { 78 no_context(regs, addr); 79 return; 80 } 81 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 82 return; 83 } 84 BUG(); 85 } 86 87 static inline void 88 bad_area_nosemaphore(struct pt_regs *regs, int code, unsigned long addr) 89 { 90 /* 91 * Something tried to access memory that isn't in our memory map. 92 * Fix it, but check if it's kernel or user first. 93 */ 94 /* User mode accesses just cause a SIGSEGV */ 95 if (user_mode(regs)) { 96 do_trap(regs, SIGSEGV, code, addr); 97 return; 98 } 99 100 no_context(regs, addr); 101 } 102 103 static inline void 104 bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, 105 unsigned long addr) 106 { 107 mmap_read_unlock(mm); 108 109 bad_area_nosemaphore(regs, code, addr); 110 } 111 112 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr) 113 { 114 pgd_t *pgd, *pgd_k; 115 pud_t *pud_k; 116 p4d_t *p4d_k; 117 pmd_t *pmd_k; 118 pte_t *pte_k; 119 int index; 120 unsigned long pfn; 121 122 /* User mode accesses just cause a SIGSEGV */ 123 if (user_mode(regs)) 124 return do_trap(regs, SIGSEGV, code, addr); 125 126 /* 127 * Synchronize this task's top level page-table 128 * with the 'reference' page table. 129 * 130 * Do _not_ use "tsk->active_mm->pgd" here. 131 * We might be inside an interrupt in the middle 132 * of a task switch. 133 */ 134 index = pgd_index(addr); 135 pfn = csr_read(CSR_SATP) & SATP_PPN; 136 pgd = (pgd_t *)pfn_to_virt(pfn) + index; 137 pgd_k = init_mm.pgd + index; 138 139 if (!pgd_present(*pgd_k)) { 140 no_context(regs, addr); 141 return; 142 } 143 set_pgd(pgd, *pgd_k); 144 145 p4d_k = p4d_offset(pgd_k, addr); 146 if (!p4d_present(*p4d_k)) { 147 no_context(regs, addr); 148 return; 149 } 150 151 pud_k = pud_offset(p4d_k, addr); 152 if (!pud_present(*pud_k)) { 153 no_context(regs, addr); 154 return; 155 } 156 if (pud_leaf(*pud_k)) 157 goto flush_tlb; 158 159 /* 160 * Since the vmalloc area is global, it is unnecessary 161 * to copy individual PTEs 162 */ 163 pmd_k = pmd_offset(pud_k, addr); 164 if (!pmd_present(*pmd_k)) { 165 no_context(regs, addr); 166 return; 167 } 168 if (pmd_leaf(*pmd_k)) 169 goto flush_tlb; 170 171 /* 172 * Make sure the actual PTE exists as well to 173 * catch kernel vmalloc-area accesses to non-mapped 174 * addresses. If we don't do this, this will just 175 * silently loop forever. 176 */ 177 pte_k = pte_offset_kernel(pmd_k, addr); 178 if (!pte_present(*pte_k)) { 179 no_context(regs, addr); 180 return; 181 } 182 183 /* 184 * The kernel assumes that TLBs don't cache invalid 185 * entries, but in RISC-V, SFENCE.VMA specifies an 186 * ordering constraint, not a cache flush; it is 187 * necessary even after writing invalid entries. 188 */ 189 flush_tlb: 190 local_flush_tlb_page(addr); 191 } 192 193 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) 194 { 195 switch (cause) { 196 case EXC_INST_PAGE_FAULT: 197 if (!(vma->vm_flags & VM_EXEC)) { 198 return true; 199 } 200 break; 201 case EXC_LOAD_PAGE_FAULT: 202 /* Write implies read */ 203 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) { 204 return true; 205 } 206 break; 207 case EXC_STORE_PAGE_FAULT: 208 if (!(vma->vm_flags & VM_WRITE)) { 209 return true; 210 } 211 break; 212 default: 213 panic("%s: unhandled cause %lu", __func__, cause); 214 } 215 return false; 216 } 217 218 /* 219 * This routine handles page faults. It determines the address and the 220 * problem, and then passes it off to one of the appropriate routines. 221 */ 222 void handle_page_fault(struct pt_regs *regs) 223 { 224 struct task_struct *tsk; 225 struct vm_area_struct *vma; 226 struct mm_struct *mm; 227 unsigned long addr, cause; 228 unsigned int flags = FAULT_FLAG_DEFAULT; 229 int code = SEGV_MAPERR; 230 vm_fault_t fault; 231 232 cause = regs->cause; 233 addr = regs->badaddr; 234 235 tsk = current; 236 mm = tsk->mm; 237 238 if (kprobe_page_fault(regs, cause)) 239 return; 240 241 /* 242 * Fault-in kernel-space virtual memory on-demand. 243 * The 'reference' page table is init_mm.pgd. 244 * 245 * NOTE! We MUST NOT take any locks for this case. We may 246 * be in an interrupt or a critical region, and should 247 * only copy the information from the master page table, 248 * nothing more. 249 */ 250 if ((!IS_ENABLED(CONFIG_MMU) || !IS_ENABLED(CONFIG_64BIT)) && 251 unlikely(addr >= VMALLOC_START && addr < VMALLOC_END)) { 252 vmalloc_fault(regs, code, addr); 253 return; 254 } 255 256 /* Enable interrupts if they were enabled in the parent context. */ 257 if (!regs_irqs_disabled(regs)) 258 local_irq_enable(); 259 260 /* 261 * If we're in an interrupt, have no user context, or are running 262 * in an atomic region, then we must not take the fault. 263 */ 264 if (unlikely(faulthandler_disabled() || !mm)) { 265 tsk->thread.bad_cause = cause; 266 no_context(regs, addr); 267 return; 268 } 269 270 if (user_mode(regs)) 271 flags |= FAULT_FLAG_USER; 272 273 if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) { 274 if (fixup_exception(regs)) 275 return; 276 277 die_kernel_fault("access to user memory without uaccess routines", addr, regs); 278 } 279 280 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 281 282 if (cause == EXC_STORE_PAGE_FAULT) 283 flags |= FAULT_FLAG_WRITE; 284 else if (cause == EXC_INST_PAGE_FAULT) 285 flags |= FAULT_FLAG_INSTRUCTION; 286 if (!(flags & FAULT_FLAG_USER)) 287 goto lock_mmap; 288 289 vma = lock_vma_under_rcu(mm, addr); 290 if (!vma) 291 goto lock_mmap; 292 293 if (unlikely(access_error(cause, vma))) { 294 vma_end_read(vma); 295 goto lock_mmap; 296 } 297 298 fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs); 299 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED))) 300 vma_end_read(vma); 301 302 if (!(fault & VM_FAULT_RETRY)) { 303 count_vm_vma_lock_event(VMA_LOCK_SUCCESS); 304 goto done; 305 } 306 count_vm_vma_lock_event(VMA_LOCK_RETRY); 307 308 if (fault_signal_pending(fault, regs)) { 309 if (!user_mode(regs)) 310 no_context(regs, addr); 311 return; 312 } 313 lock_mmap: 314 315 retry: 316 vma = lock_mm_and_find_vma(mm, addr, regs); 317 if (unlikely(!vma)) { 318 tsk->thread.bad_cause = cause; 319 bad_area_nosemaphore(regs, code, addr); 320 return; 321 } 322 323 /* 324 * Ok, we have a good vm_area for this memory access, so 325 * we can handle it. 326 */ 327 code = SEGV_ACCERR; 328 329 if (unlikely(access_error(cause, vma))) { 330 tsk->thread.bad_cause = cause; 331 bad_area(regs, mm, code, addr); 332 return; 333 } 334 335 /* 336 * If for any reason at all we could not handle the fault, 337 * make sure we exit gracefully rather than endlessly redo 338 * the fault. 339 */ 340 fault = handle_mm_fault(vma, addr, flags, regs); 341 342 /* 343 * If we need to retry but a fatal signal is pending, handle the 344 * signal first. We do not need to release the mmap_lock because it 345 * would already be released in __lock_page_or_retry in mm/filemap.c. 346 */ 347 if (fault_signal_pending(fault, regs)) { 348 if (!user_mode(regs)) 349 no_context(regs, addr); 350 return; 351 } 352 353 /* The fault is fully completed (including releasing mmap lock) */ 354 if (fault & VM_FAULT_COMPLETED) 355 return; 356 357 if (unlikely(fault & VM_FAULT_RETRY)) { 358 flags |= FAULT_FLAG_TRIED; 359 360 /* 361 * No need to mmap_read_unlock(mm) as we would 362 * have already released it in __lock_page_or_retry 363 * in mm/filemap.c. 364 */ 365 goto retry; 366 } 367 368 mmap_read_unlock(mm); 369 370 done: 371 if (unlikely(fault & VM_FAULT_ERROR)) { 372 tsk->thread.bad_cause = cause; 373 mm_fault_error(regs, addr, fault); 374 return; 375 } 376 return; 377 } 378