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 do_exit(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, *pud_k; 106 p4d_t *p4d, *p4d_k; 107 pmd_t *pmd, *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 = p4d_offset(pgd, addr); 136 p4d_k = p4d_offset(pgd_k, addr); 137 if (!p4d_present(*p4d_k)) { 138 no_context(regs, addr); 139 return; 140 } 141 142 pud = pud_offset(p4d, addr); 143 pud_k = pud_offset(p4d_k, addr); 144 if (!pud_present(*pud_k)) { 145 no_context(regs, addr); 146 return; 147 } 148 149 /* 150 * Since the vmalloc area is global, it is unnecessary 151 * to copy individual PTEs 152 */ 153 pmd = pmd_offset(pud, addr); 154 pmd_k = pmd_offset(pud_k, addr); 155 if (!pmd_present(*pmd_k)) { 156 no_context(regs, addr); 157 return; 158 } 159 set_pmd(pmd, *pmd_k); 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 local_flush_tlb_page(addr); 180 } 181 182 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) 183 { 184 switch (cause) { 185 case EXC_INST_PAGE_FAULT: 186 if (!(vma->vm_flags & VM_EXEC)) { 187 return true; 188 } 189 break; 190 case EXC_LOAD_PAGE_FAULT: 191 if (!(vma->vm_flags & VM_READ)) { 192 return true; 193 } 194 break; 195 case EXC_STORE_PAGE_FAULT: 196 if (!(vma->vm_flags & VM_WRITE)) { 197 return true; 198 } 199 break; 200 default: 201 panic("%s: unhandled cause %lu", __func__, cause); 202 } 203 return false; 204 } 205 206 /* 207 * This routine handles page faults. It determines the address and the 208 * problem, and then passes it off to one of the appropriate routines. 209 */ 210 asmlinkage void do_page_fault(struct pt_regs *regs) 211 { 212 struct task_struct *tsk; 213 struct vm_area_struct *vma; 214 struct mm_struct *mm; 215 unsigned long addr, cause; 216 unsigned int flags = FAULT_FLAG_DEFAULT; 217 int code = SEGV_MAPERR; 218 vm_fault_t fault; 219 220 cause = regs->cause; 221 addr = regs->badaddr; 222 223 tsk = current; 224 mm = tsk->mm; 225 226 if (kprobe_page_fault(regs, cause)) 227 return; 228 229 /* 230 * Fault-in kernel-space virtual memory on-demand. 231 * The 'reference' page table is init_mm.pgd. 232 * 233 * NOTE! We MUST NOT take any locks for this case. We may 234 * be in an interrupt or a critical region, and should 235 * only copy the information from the master page table, 236 * nothing more. 237 */ 238 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) { 239 vmalloc_fault(regs, code, addr); 240 return; 241 } 242 243 #ifdef CONFIG_64BIT 244 /* 245 * Modules in 64bit kernels lie in their own virtual region which is not 246 * in the vmalloc region, but dealing with page faults in this region 247 * or the vmalloc region amounts to doing the same thing: checking that 248 * the mapping exists in init_mm.pgd and updating user page table, so 249 * just use vmalloc_fault. 250 */ 251 if (unlikely(addr >= MODULES_VADDR && addr < MODULES_END)) { 252 vmalloc_fault(regs, code, addr); 253 return; 254 } 255 #endif 256 /* Enable interrupts if they were enabled in the parent context. */ 257 if (likely(regs->status & SR_PIE)) 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 && 274 unlikely(!(regs->status & SR_SUM))) 275 die_kernel_fault("access to user memory without uaccess routines", 276 addr, regs); 277 278 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 279 280 if (cause == EXC_STORE_PAGE_FAULT) 281 flags |= FAULT_FLAG_WRITE; 282 else if (cause == EXC_INST_PAGE_FAULT) 283 flags |= FAULT_FLAG_INSTRUCTION; 284 retry: 285 mmap_read_lock(mm); 286 vma = find_vma(mm, addr); 287 if (unlikely(!vma)) { 288 tsk->thread.bad_cause = cause; 289 bad_area(regs, mm, code, addr); 290 return; 291 } 292 if (likely(vma->vm_start <= addr)) 293 goto good_area; 294 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) { 295 tsk->thread.bad_cause = cause; 296 bad_area(regs, mm, code, addr); 297 return; 298 } 299 if (unlikely(expand_stack(vma, addr))) { 300 tsk->thread.bad_cause = cause; 301 bad_area(regs, mm, code, addr); 302 return; 303 } 304 305 /* 306 * Ok, we have a good vm_area for this memory access, so 307 * we can handle it. 308 */ 309 good_area: 310 code = SEGV_ACCERR; 311 312 if (unlikely(access_error(cause, vma))) { 313 tsk->thread.bad_cause = cause; 314 bad_area(regs, mm, code, addr); 315 return; 316 } 317 318 /* 319 * If for any reason at all we could not handle the fault, 320 * make sure we exit gracefully rather than endlessly redo 321 * the fault. 322 */ 323 fault = handle_mm_fault(vma, addr, flags, regs); 324 325 /* 326 * If we need to retry but a fatal signal is pending, handle the 327 * signal first. We do not need to release the mmap_lock because it 328 * would already be released in __lock_page_or_retry in mm/filemap.c. 329 */ 330 if (fault_signal_pending(fault, regs)) 331 return; 332 333 if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) { 334 flags |= FAULT_FLAG_TRIED; 335 336 /* 337 * No need to mmap_read_unlock(mm) as we would 338 * have already released it in __lock_page_or_retry 339 * in mm/filemap.c. 340 */ 341 goto retry; 342 } 343 344 mmap_read_unlock(mm); 345 346 if (unlikely(fault & VM_FAULT_ERROR)) { 347 tsk->thread.bad_cause = cause; 348 mm_fault_error(regs, addr, fault); 349 return; 350 } 351 return; 352 } 353 NOKPROBE_SYMBOL(do_page_fault); 354