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 #define CREATE_TRACE_POINTS
24 #include <trace/events/exceptions.h>
25
26 #include "../kernel/head.h"
27
show_pte(unsigned long addr)28 static void show_pte(unsigned long addr)
29 {
30 pgd_t *pgdp, pgd;
31 p4d_t *p4dp, p4d;
32 pud_t *pudp, pud;
33 pmd_t *pmdp, pmd;
34 pte_t *ptep, pte;
35 struct mm_struct *mm = current->mm;
36
37 if (!mm)
38 mm = &init_mm;
39
40 pr_alert("Current %s pgtable: %luK pagesize, %d-bit VAs, pgdp=0x%016llx\n",
41 current->comm, PAGE_SIZE / SZ_1K, VA_BITS,
42 mm == &init_mm ? (u64)__pa_symbol(mm->pgd) : virt_to_phys(mm->pgd));
43
44 pgdp = pgd_offset(mm, addr);
45 pgd = pgdp_get(pgdp);
46 pr_alert("[%016lx] pgd=%016lx", addr, pgd_val(pgd));
47 if (pgd_none(pgd) || pgd_bad(pgd) || pgd_leaf(pgd))
48 goto out;
49
50 p4dp = p4d_offset(pgdp, addr);
51 p4d = p4dp_get(p4dp);
52 pr_cont(", p4d=%016lx", p4d_val(p4d));
53 if (p4d_none(p4d) || p4d_bad(p4d) || p4d_leaf(p4d))
54 goto out;
55
56 pudp = pud_offset(p4dp, addr);
57 pud = pudp_get(pudp);
58 pr_cont(", pud=%016lx", pud_val(pud));
59 if (pud_none(pud) || pud_bad(pud) || pud_leaf(pud))
60 goto out;
61
62 pmdp = pmd_offset(pudp, addr);
63 pmd = pmdp_get(pmdp);
64 pr_cont(", pmd=%016lx", pmd_val(pmd));
65 if (pmd_none(pmd) || pmd_bad(pmd) || pmd_leaf(pmd))
66 goto out;
67
68 ptep = pte_offset_map(pmdp, addr);
69 if (!ptep)
70 goto out;
71
72 pte = ptep_get(ptep);
73 pr_cont(", pte=%016lx", pte_val(pte));
74 pte_unmap(ptep);
75 out:
76 pr_cont("\n");
77 }
78
die_kernel_fault(const char * msg,unsigned long addr,struct pt_regs * regs)79 static void die_kernel_fault(const char *msg, unsigned long addr,
80 struct pt_regs *regs)
81 {
82 bust_spinlocks(1);
83
84 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", msg,
85 addr);
86
87 bust_spinlocks(0);
88 show_pte(addr);
89 die(regs, "Oops");
90 make_task_dead(SIGKILL);
91 }
92
no_context(struct pt_regs * regs,unsigned long addr)93 static inline void no_context(struct pt_regs *regs, unsigned long addr)
94 {
95 const char *msg;
96
97 /* Are we prepared to handle this kernel fault? */
98 if (fixup_exception(regs))
99 return;
100
101 /*
102 * Oops. The kernel tried to access some bad page. We'll have to
103 * terminate things with extreme prejudice.
104 */
105 if (addr < PAGE_SIZE)
106 msg = "NULL pointer dereference";
107 else {
108 if (kfence_handle_page_fault(addr, regs->cause == EXC_STORE_PAGE_FAULT, regs))
109 return;
110
111 msg = "paging request";
112 }
113
114 die_kernel_fault(msg, addr, regs);
115 }
116
mm_fault_error(struct pt_regs * regs,unsigned long addr,vm_fault_t fault)117 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
118 {
119 if (!user_mode(regs)) {
120 no_context(regs, addr);
121 return;
122 }
123
124 if (fault & VM_FAULT_OOM) {
125 /*
126 * We ran out of memory, call the OOM killer, and return the userspace
127 * (which will retry the fault, or kill us if we got oom-killed).
128 */
129 pagefault_out_of_memory();
130 return;
131 } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
132 /* Kernel mode? Handle exceptions or die */
133 do_trap(regs, SIGBUS, BUS_ADRERR, addr);
134 return;
135 } else if (fault & VM_FAULT_SIGSEGV) {
136 do_trap(regs, SIGSEGV, SEGV_MAPERR, addr);
137 return;
138 }
139
140 BUG();
141 }
142
143 static inline void
bad_area_nosemaphore(struct pt_regs * regs,int code,unsigned long addr)144 bad_area_nosemaphore(struct pt_regs *regs, int code, unsigned long addr)
145 {
146 /*
147 * Something tried to access memory that isn't in our memory map.
148 * Fix it, but check if it's kernel or user first.
149 */
150 /* User mode accesses just cause a SIGSEGV */
151 if (user_mode(regs)) {
152 do_trap(regs, SIGSEGV, code, addr);
153 return;
154 }
155
156 no_context(regs, addr);
157 }
158
159 static inline void
bad_area(struct pt_regs * regs,struct mm_struct * mm,int code,unsigned long addr)160 bad_area(struct pt_regs *regs, struct mm_struct *mm, int code,
161 unsigned long addr)
162 {
163 mmap_read_unlock(mm);
164
165 bad_area_nosemaphore(regs, code, addr);
166 }
167
vmalloc_fault(struct pt_regs * regs,int code,unsigned long addr)168 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
169 {
170 pgd_t *pgd, *pgd_k;
171 pud_t *pud_k;
172 p4d_t *p4d_k;
173 pmd_t *pmd_k;
174 pte_t *pte_k;
175 int index;
176 unsigned long pfn;
177
178 /* User mode accesses just cause a SIGSEGV */
179 if (user_mode(regs))
180 return do_trap(regs, SIGSEGV, code, addr);
181
182 /*
183 * Synchronize this task's top level page-table
184 * with the 'reference' page table.
185 *
186 * Do _not_ use "tsk->active_mm->pgd" here.
187 * We might be inside an interrupt in the middle
188 * of a task switch.
189 */
190 index = pgd_index(addr);
191 pfn = csr_read(CSR_SATP) & SATP_PPN;
192 pgd = (pgd_t *)pfn_to_virt(pfn) + index;
193 pgd_k = init_mm.pgd + index;
194
195 if (!pgd_present(pgdp_get(pgd_k))) {
196 no_context(regs, addr);
197 return;
198 }
199 set_pgd(pgd, pgdp_get(pgd_k));
200
201 p4d_k = p4d_offset(pgd_k, addr);
202 if (!p4d_present(p4dp_get(p4d_k))) {
203 no_context(regs, addr);
204 return;
205 }
206
207 pud_k = pud_offset(p4d_k, addr);
208 if (!pud_present(pudp_get(pud_k))) {
209 no_context(regs, addr);
210 return;
211 }
212 if (pud_leaf(pudp_get(pud_k)))
213 goto flush_tlb;
214
215 /*
216 * Since the vmalloc area is global, it is unnecessary
217 * to copy individual PTEs
218 */
219 pmd_k = pmd_offset(pud_k, addr);
220 if (!pmd_present(pmdp_get(pmd_k))) {
221 no_context(regs, addr);
222 return;
223 }
224 if (pmd_leaf(pmdp_get(pmd_k)))
225 goto flush_tlb;
226
227 /*
228 * Make sure the actual PTE exists as well to
229 * catch kernel vmalloc-area accesses to non-mapped
230 * addresses. If we don't do this, this will just
231 * silently loop forever.
232 */
233 pte_k = pte_offset_kernel(pmd_k, addr);
234 if (!pte_present(ptep_get(pte_k))) {
235 no_context(regs, addr);
236 return;
237 }
238
239 /*
240 * The kernel assumes that TLBs don't cache invalid
241 * entries, but in RISC-V, SFENCE.VMA specifies an
242 * ordering constraint, not a cache flush; it is
243 * necessary even after writing invalid entries.
244 */
245 flush_tlb:
246 local_flush_tlb_page(addr);
247 }
248
access_error(unsigned long cause,struct vm_area_struct * vma)249 static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
250 {
251 switch (cause) {
252 case EXC_INST_PAGE_FAULT:
253 if (!(vma->vm_flags & VM_EXEC)) {
254 return true;
255 }
256 break;
257 case EXC_LOAD_PAGE_FAULT:
258 /* Write implies read */
259 if (!(vma->vm_flags & (VM_READ | VM_WRITE))) {
260 return true;
261 }
262 break;
263 case EXC_STORE_PAGE_FAULT:
264 if (!(vma->vm_flags & VM_WRITE)) {
265 return true;
266 }
267 break;
268 default:
269 panic("%s: unhandled cause %lu", __func__, cause);
270 }
271 return false;
272 }
273
274 /*
275 * This routine handles page faults. It determines the address and the
276 * problem, and then passes it off to one of the appropriate routines.
277 */
handle_page_fault(struct pt_regs * regs)278 void handle_page_fault(struct pt_regs *regs)
279 {
280 struct task_struct *tsk;
281 struct vm_area_struct *vma;
282 struct mm_struct *mm;
283 unsigned long addr, cause;
284 unsigned int flags = FAULT_FLAG_DEFAULT;
285 int code = SEGV_MAPERR;
286 vm_fault_t fault;
287
288 cause = regs->cause;
289 addr = regs->badaddr;
290
291 tsk = current;
292 mm = tsk->mm;
293
294 if (kprobe_page_fault(regs, cause))
295 return;
296
297 if (user_mode(regs))
298 trace_page_fault_user(addr, regs, cause);
299 else
300 trace_page_fault_kernel(addr, regs, cause);
301
302 /*
303 * Fault-in kernel-space virtual memory on-demand.
304 * The 'reference' page table is init_mm.pgd.
305 *
306 * NOTE! We MUST NOT take any locks for this case. We may
307 * be in an interrupt or a critical region, and should
308 * only copy the information from the master page table,
309 * nothing more.
310 */
311 if ((!IS_ENABLED(CONFIG_MMU) || !IS_ENABLED(CONFIG_64BIT)) &&
312 unlikely(addr >= VMALLOC_START && addr < VMALLOC_END)) {
313 vmalloc_fault(regs, code, addr);
314 return;
315 }
316
317 /* Enable interrupts if they were enabled in the parent context. */
318 if (!regs_irqs_disabled(regs))
319 local_irq_enable();
320
321 /*
322 * If we're in an interrupt, have no user context, or are running
323 * in an atomic region, then we must not take the fault.
324 */
325 if (unlikely(faulthandler_disabled() || !mm)) {
326 tsk->thread.bad_cause = cause;
327 no_context(regs, addr);
328 return;
329 }
330
331 if (user_mode(regs))
332 flags |= FAULT_FLAG_USER;
333
334 if (!user_mode(regs) && addr < TASK_SIZE && unlikely(!(regs->status & SR_SUM))) {
335 if (fixup_exception(regs))
336 return;
337
338 die_kernel_fault("access to user memory without uaccess routines", addr, regs);
339 }
340
341 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
342
343 if (cause == EXC_STORE_PAGE_FAULT)
344 flags |= FAULT_FLAG_WRITE;
345 else if (cause == EXC_INST_PAGE_FAULT)
346 flags |= FAULT_FLAG_INSTRUCTION;
347 if (!(flags & FAULT_FLAG_USER))
348 goto lock_mmap;
349
350 vma = lock_vma_under_rcu(mm, addr);
351 if (!vma)
352 goto lock_mmap;
353
354 if (unlikely(access_error(cause, vma))) {
355 vma_end_read(vma);
356 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
357 tsk->thread.bad_cause = cause;
358 bad_area_nosemaphore(regs, SEGV_ACCERR, addr);
359 return;
360 }
361
362 fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
363 if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
364 vma_end_read(vma);
365
366 if (!(fault & VM_FAULT_RETRY)) {
367 count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
368 goto done;
369 }
370 count_vm_vma_lock_event(VMA_LOCK_RETRY);
371 if (fault & VM_FAULT_MAJOR)
372 flags |= FAULT_FLAG_TRIED;
373
374 if (fault_signal_pending(fault, regs)) {
375 if (!user_mode(regs))
376 no_context(regs, addr);
377 return;
378 }
379 lock_mmap:
380
381 retry:
382 vma = lock_mm_and_find_vma(mm, addr, regs);
383 if (unlikely(!vma)) {
384 tsk->thread.bad_cause = cause;
385 bad_area_nosemaphore(regs, code, addr);
386 return;
387 }
388
389 /*
390 * Ok, we have a good vm_area for this memory access, so
391 * we can handle it.
392 */
393 code = SEGV_ACCERR;
394
395 if (unlikely(access_error(cause, vma))) {
396 tsk->thread.bad_cause = cause;
397 bad_area(regs, mm, code, addr);
398 return;
399 }
400
401 /*
402 * If for any reason at all we could not handle the fault,
403 * make sure we exit gracefully rather than endlessly redo
404 * the fault.
405 */
406 fault = handle_mm_fault(vma, addr, flags, regs);
407
408 /*
409 * If we need to retry but a fatal signal is pending, handle the
410 * signal first. We do not need to release the mmap_lock because it
411 * would already be released in __lock_page_or_retry in mm/filemap.c.
412 */
413 if (fault_signal_pending(fault, regs)) {
414 if (!user_mode(regs))
415 no_context(regs, addr);
416 return;
417 }
418
419 /* The fault is fully completed (including releasing mmap lock) */
420 if (fault & VM_FAULT_COMPLETED)
421 return;
422
423 if (unlikely(fault & VM_FAULT_RETRY)) {
424 flags |= FAULT_FLAG_TRIED;
425
426 /*
427 * No need to mmap_read_unlock(mm) as we would
428 * have already released it in __lock_page_or_retry
429 * in mm/filemap.c.
430 */
431 goto retry;
432 }
433
434 mmap_read_unlock(mm);
435
436 done:
437 if (unlikely(fault & VM_FAULT_ERROR)) {
438 tsk->thread.bad_cause = cause;
439 mm_fault_error(regs, addr, fault);
440 return;
441 }
442 return;
443 }
444