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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
25static 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
38static 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
62static 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 | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
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
87static inline void
88bad_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
103static inline void
104bad_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
112static 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(pgdp_get(pgd_k))) {
140 no_context(regs, addr);
141 return;
142 }
143 set_pgd(pgd, pgdp_get(pgd_k));
144
145 p4d_k = p4d_offset(pgd_k, addr);
146 if (!p4d_present(p4dp_get(p4d_k))) {
147 no_context(regs, addr);
148 return;
149 }
150
151 pud_k = pud_offset(p4d_k, addr);
152 if (!pud_present(pudp_get(pud_k))) {
153 no_context(regs, addr);
154 return;
155 }
156 if (pud_leaf(pudp_get(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(pmdp_get(pmd_k))) {
165 no_context(regs, addr);
166 return;
167 }
168 if (pmd_leaf(pmdp_get(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(ptep_get(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 */
189flush_tlb:
190 local_flush_tlb_page(addr);
191}
192
193static 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 */
222void 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 if (fault & VM_FAULT_MAJOR)
308 flags |= FAULT_FLAG_TRIED;
309
310 if (fault_signal_pending(fault, regs)) {
311 if (!user_mode(regs))
312 no_context(regs, addr);
313 return;
314 }
315lock_mmap:
316
317retry:
318 vma = lock_mm_and_find_vma(mm, addr, regs);
319 if (unlikely(!vma)) {
320 tsk->thread.bad_cause = cause;
321 bad_area_nosemaphore(regs, code, addr);
322 return;
323 }
324
325 /*
326 * Ok, we have a good vm_area for this memory access, so
327 * we can handle it.
328 */
329 code = SEGV_ACCERR;
330
331 if (unlikely(access_error(cause, vma))) {
332 tsk->thread.bad_cause = cause;
333 bad_area(regs, mm, code, addr);
334 return;
335 }
336
337 /*
338 * If for any reason at all we could not handle the fault,
339 * make sure we exit gracefully rather than endlessly redo
340 * the fault.
341 */
342 fault = handle_mm_fault(vma, addr, flags, regs);
343
344 /*
345 * If we need to retry but a fatal signal is pending, handle the
346 * signal first. We do not need to release the mmap_lock because it
347 * would already be released in __lock_page_or_retry in mm/filemap.c.
348 */
349 if (fault_signal_pending(fault, regs)) {
350 if (!user_mode(regs))
351 no_context(regs, addr);
352 return;
353 }
354
355 /* The fault is fully completed (including releasing mmap lock) */
356 if (fault & VM_FAULT_COMPLETED)
357 return;
358
359 if (unlikely(fault & VM_FAULT_RETRY)) {
360 flags |= FAULT_FLAG_TRIED;
361
362 /*
363 * No need to mmap_read_unlock(mm) as we would
364 * have already released it in __lock_page_or_retry
365 * in mm/filemap.c.
366 */
367 goto retry;
368 }
369
370 mmap_read_unlock(mm);
371
372done:
373 if (unlikely(fault & VM_FAULT_ERROR)) {
374 tsk->thread.bad_cause = cause;
375 mm_fault_error(regs, addr, fault);
376 return;
377 }
378 return;
379}
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
24static 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
37static 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
61static 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
86static 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
102static 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
182static 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 */
210asmlinkage 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;
284retry:
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 */
309good_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}
353NOKPROBE_SYMBOL(do_page_fault);