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 } 146 147 /* 148 * Since the vmalloc area is global, it is unnecessary 149 * to copy individual PTEs 150 */ 151 pmd_k = pmd_offset(pud_k, addr); 152 if (!pmd_present(*pmd_k)) { 153 no_context(regs, addr); 154 return; 155 } 156 157 /* 158 * Make sure the actual PTE exists as well to 159 * catch kernel vmalloc-area accesses to non-mapped 160 * addresses. If we don't do this, this will just 161 * silently loop forever. 162 */ 163 pte_k = pte_offset_kernel(pmd_k, addr); 164 if (!pte_present(*pte_k)) { 165 no_context(regs, addr); 166 return; 167 } 168 169 /* 170 * The kernel assumes that TLBs don't cache invalid 171 * entries, but in RISC-V, SFENCE.VMA specifies an 172 * ordering constraint, not a cache flush; it is 173 * necessary even after writing invalid entries. 174 */ 175 local_flush_tlb_page(addr); 176 } 177 178 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) 179 { 180 switch (cause) { 181 case EXC_INST_PAGE_FAULT: 182 if (!(vma->vm_flags & VM_EXEC)) { 183 return true; 184 } 185 break; 186 case EXC_LOAD_PAGE_FAULT: 187 /* Write implies read */ 188 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) { 189 return true; 190 } 191 break; 192 case EXC_STORE_PAGE_FAULT: 193 if (!(vma->vm_flags & VM_WRITE)) { 194 return true; 195 } 196 break; 197 default: 198 panic("%s: unhandled cause %lu", __func__, cause); 199 } 200 return false; 201 } 202 203 /* 204 * This routine handles page faults. It determines the address and the 205 * problem, and then passes it off to one of the appropriate routines. 206 */ 207 asmlinkage void do_page_fault(struct pt_regs *regs) 208 { 209 struct task_struct *tsk; 210 struct vm_area_struct *vma; 211 struct mm_struct *mm; 212 unsigned long addr, cause; 213 unsigned int flags = FAULT_FLAG_DEFAULT; 214 int code = SEGV_MAPERR; 215 vm_fault_t fault; 216 217 cause = regs->cause; 218 addr = regs->badaddr; 219 220 tsk = current; 221 mm = tsk->mm; 222 223 if (kprobe_page_fault(regs, cause)) 224 return; 225 226 /* 227 * Fault-in kernel-space virtual memory on-demand. 228 * The 'reference' page table is init_mm.pgd. 229 * 230 * NOTE! We MUST NOT take any locks for this case. We may 231 * be in an interrupt or a critical region, and should 232 * only copy the information from the master page table, 233 * nothing more. 234 */ 235 if (unlikely((addr >= VMALLOC_START) && (addr < VMALLOC_END))) { 236 vmalloc_fault(regs, code, addr); 237 return; 238 } 239 240 #ifdef CONFIG_64BIT 241 /* 242 * Modules in 64bit kernels lie in their own virtual region which is not 243 * in the vmalloc region, but dealing with page faults in this region 244 * or the vmalloc region amounts to doing the same thing: checking that 245 * the mapping exists in init_mm.pgd and updating user page table, so 246 * just use vmalloc_fault. 247 */ 248 if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) { 249 vmalloc_fault(regs, code, addr); 250 return; 251 } 252 #endif 253 /* Enable interrupts if they were enabled in the parent context. */ 254 if (likely(regs->status & SR_PIE)) 255 local_irq_enable(); 256 257 /* 258 * If we're in an interrupt, have no user context, or are running 259 * in an atomic region, then we must not take the fault. 260 */ 261 if (unlikely(faulthandler_disabled() || !mm)) { 262 tsk->thread.bad_cause = cause; 263 no_context(regs, addr); 264 return; 265 } 266 267 if (user_mode(regs)) 268 flags |= FAULT_FLAG_USER; 269 270 if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) { 271 if (fixup_exception(regs)) 272 return; 273 274 die_kernel_fault("access to user memory without uaccess routines", addr, regs); 275 } 276 277 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 278 279 if (cause == EXC_STORE_PAGE_FAULT) 280 flags |= FAULT_FLAG_WRITE; 281 else if (cause == EXC_INST_PAGE_FAULT) 282 flags |= FAULT_FLAG_INSTRUCTION; 283 retry: 284 mmap_read_lock(mm); 285 vma = find_vma(mm, addr); 286 if (unlikely(!vma)) { 287 tsk->thread.bad_cause = cause; 288 bad_area(regs, mm, code, addr); 289 return; 290 } 291 if (likely(vma->vm_start <= addr)) 292 goto good_area; 293 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 294 tsk->thread.bad_cause = cause; 295 bad_area(regs, mm, code, addr); 296 return; 297 } 298 if (unlikely(expand_stack(vma, addr))) { 299 tsk->thread.bad_cause = cause; 300 bad_area(regs, mm, code, addr); 301 return; 302 } 303 304 /* 305 * Ok, we have a good vm_area for this memory access, so 306 * we can handle it. 307 */ 308 good_area: 309 code = SEGV_ACCERR; 310 311 if (unlikely(access_error(cause, vma))) { 312 tsk->thread.bad_cause = cause; 313 bad_area(regs, mm, code, addr); 314 return; 315 } 316 317 /* 318 * If for any reason at all we could not handle the fault, 319 * make sure we exit gracefully rather than endlessly redo 320 * the fault. 321 */ 322 fault = handle_mm_fault(vma, addr, flags, regs); 323 324 /* 325 * If we need to retry but a fatal signal is pending, handle the 326 * signal first. We do not need to release the mmap_lock because it 327 * would already be released in __lock_page_or_retry in mm/filemap.c. 328 */ 329 if (fault_signal_pending(fault, regs)) { 330 if (!user_mode(regs)) 331 no_context(regs, addr); 332 return; 333 } 334 335 /* The fault is fully completed (including releasing mmap lock) */ 336 if (fault & VM_FAULT_COMPLETED) 337 return; 338 339 if (unlikely(fault & VM_FAULT_RETRY)) { 340 flags |= FAULT_FLAG_TRIED; 341 342 /* 343 * No need to mmap_read_unlock(mm) as we would 344 * have already released it in __lock_page_or_retry 345 * in mm/filemap.c. 346 */ 347 goto retry; 348 } 349 350 mmap_read_unlock(mm); 351 352 if (unlikely(fault & VM_FAULT_ERROR)) { 353 tsk->thread.bad_cause = cause; 354 mm_fault_error(regs, addr, fault); 355 return; 356 } 357 return; 358 } 359 NOKPROBE_SYMBOL(do_page_fault); 360