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1// SPDX-License-Identifier: GPL-2.0
2// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
3
4#include <linux/extable.h>
5#include <linux/kprobes.h>
6#include <linux/mmu_context.h>
7#include <linux/perf_event.h>
8
9int fixup_exception(struct pt_regs *regs)
10{
11 const struct exception_table_entry *fixup;
12
13 fixup = search_exception_tables(instruction_pointer(regs));
14 if (fixup) {
15 regs->pc = fixup->fixup;
16
17 return 1;
18 }
19
20 return 0;
21}
22
23static inline bool is_write(struct pt_regs *regs)
24{
25 switch (trap_no(regs)) {
26 case VEC_TLBINVALIDS:
27 return true;
28 case VEC_TLBMODIFIED:
29 return true;
30 }
31
32 return false;
33}
34
35#ifdef CONFIG_CPU_HAS_LDSTEX
36static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
37{
38 return;
39}
40#else
41extern unsigned long csky_cmpxchg_ldw;
42extern unsigned long csky_cmpxchg_stw;
43static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
44{
45 if (trap_no(regs) != VEC_TLBMODIFIED)
46 return;
47
48 if (instruction_pointer(regs) == csky_cmpxchg_stw)
49 instruction_pointer_set(regs, csky_cmpxchg_ldw);
50 return;
51}
52#endif
53
54static inline void no_context(struct pt_regs *regs, unsigned long addr)
55{
56 current->thread.trap_no = trap_no(regs);
57
58 /* Are we prepared to handle this kernel fault? */
59 if (fixup_exception(regs))
60 return;
61
62 /*
63 * Oops. The kernel tried to access some bad page. We'll have to
64 * terminate things with extreme prejudice.
65 */
66 bust_spinlocks(1);
67 pr_alert("Unable to handle kernel paging request at virtual "
68 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
69 die(regs, "Oops");
70 make_task_dead(SIGKILL);
71}
72
73static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
74{
75 current->thread.trap_no = trap_no(regs);
76
77 if (fault & VM_FAULT_OOM) {
78 /*
79 * We ran out of memory, call the OOM killer, and return the userspace
80 * (which will retry the fault, or kill us if we got oom-killed).
81 */
82 if (!user_mode(regs)) {
83 no_context(regs, addr);
84 return;
85 }
86 pagefault_out_of_memory();
87 return;
88 } else if (fault & VM_FAULT_SIGBUS) {
89 /* Kernel mode? Handle exceptions or die */
90 if (!user_mode(regs)) {
91 no_context(regs, addr);
92 return;
93 }
94 do_trap(regs, SIGBUS, BUS_ADRERR, addr);
95 return;
96 }
97 BUG();
98}
99
100static inline void bad_area_nosemaphore(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
101{
102 /*
103 * Something tried to access memory that isn't in our memory map.
104 * Fix it, but check if it's kernel or user first.
105 */
106 /* User mode accesses just cause a SIGSEGV */
107 if (user_mode(regs)) {
108 do_trap(regs, SIGSEGV, code, addr);
109 return;
110 }
111
112 no_context(regs, addr);
113}
114
115static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
116{
117 pgd_t *pgd, *pgd_k;
118 pud_t *pud, *pud_k;
119 pmd_t *pmd, *pmd_k;
120 pte_t *pte_k;
121 int offset;
122
123 /* User mode accesses just cause a SIGSEGV */
124 if (user_mode(regs)) {
125 do_trap(regs, SIGSEGV, code, addr);
126 return;
127 }
128
129 /*
130 * Synchronize this task's top level page-table
131 * with the 'reference' page table.
132 *
133 * Do _not_ use "tsk" here. We might be inside
134 * an interrupt in the middle of a task switch..
135 */
136 offset = pgd_index(addr);
137
138 pgd = get_pgd() + offset;
139 pgd_k = init_mm.pgd + offset;
140
141 if (!pgd_present(*pgd_k)) {
142 no_context(regs, addr);
143 return;
144 }
145 set_pgd(pgd, *pgd_k);
146
147 pud = (pud_t *)pgd;
148 pud_k = (pud_t *)pgd_k;
149 if (!pud_present(*pud_k)) {
150 no_context(regs, addr);
151 return;
152 }
153
154 pmd = pmd_offset(pud, addr);
155 pmd_k = pmd_offset(pud_k, addr);
156 if (!pmd_present(*pmd_k)) {
157 no_context(regs, addr);
158 return;
159 }
160 set_pmd(pmd, *pmd_k);
161
162 pte_k = pte_offset_kernel(pmd_k, addr);
163 if (!pte_present(*pte_k)) {
164 no_context(regs, addr);
165 return;
166 }
167
168 flush_tlb_one(addr);
169}
170
171static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
172{
173 if (is_write(regs)) {
174 if (!(vma->vm_flags & VM_WRITE))
175 return true;
176 } else {
177 if (unlikely(!vma_is_accessible(vma)))
178 return true;
179 }
180 return false;
181}
182
183/*
184 * This routine handles page faults. It determines the address and the
185 * problem, and then passes it off to one of the appropriate routines.
186 */
187asmlinkage void do_page_fault(struct pt_regs *regs)
188{
189 struct task_struct *tsk;
190 struct vm_area_struct *vma;
191 struct mm_struct *mm;
192 unsigned long addr = read_mmu_entryhi() & PAGE_MASK;
193 unsigned int flags = FAULT_FLAG_DEFAULT;
194 int code = SEGV_MAPERR;
195 vm_fault_t fault;
196
197 tsk = current;
198 mm = tsk->mm;
199
200 csky_cmpxchg_fixup(regs);
201
202 if (kprobe_page_fault(regs, tsk->thread.trap_no))
203 return;
204
205 /*
206 * Fault-in kernel-space virtual memory on-demand.
207 * The 'reference' page table is init_mm.pgd.
208 *
209 * NOTE! We MUST NOT take any locks for this case. We may
210 * be in an interrupt or a critical region, and should
211 * only copy the information from the master page table,
212 * nothing more.
213 */
214 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) {
215 vmalloc_fault(regs, code, addr);
216 return;
217 }
218
219 /* Enable interrupts if they were enabled in the parent context. */
220 if (likely(regs->sr & BIT(6)))
221 local_irq_enable();
222
223 /*
224 * If we're in an interrupt, have no user context, or are running
225 * in an atomic region, then we must not take the fault.
226 */
227 if (unlikely(faulthandler_disabled() || !mm)) {
228 no_context(regs, addr);
229 return;
230 }
231
232 if (user_mode(regs))
233 flags |= FAULT_FLAG_USER;
234
235 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
236
237 if (is_write(regs))
238 flags |= FAULT_FLAG_WRITE;
239retry:
240 vma = lock_mm_and_find_vma(mm, addr, regs);
241 if (unlikely(!vma)) {
242 bad_area_nosemaphore(regs, mm, code, addr);
243 return;
244 }
245
246 /*
247 * Ok, we have a good vm_area for this memory access, so
248 * we can handle it.
249 */
250 code = SEGV_ACCERR;
251
252 if (unlikely(access_error(regs, vma))) {
253 mmap_read_unlock(mm);
254 bad_area_nosemaphore(regs, mm, code, addr);
255 return;
256 }
257
258 /*
259 * If for any reason at all we could not handle the fault,
260 * make sure we exit gracefully rather than endlessly redo
261 * the fault.
262 */
263 fault = handle_mm_fault(vma, addr, flags, regs);
264
265 /*
266 * If we need to retry but a fatal signal is pending, handle the
267 * signal first. We do not need to release the mmap_lock because it
268 * would already be released in __lock_page_or_retry in mm/filemap.c.
269 */
270 if (fault_signal_pending(fault, regs)) {
271 if (!user_mode(regs))
272 no_context(regs, addr);
273 return;
274 }
275
276 /* The fault is fully completed (including releasing mmap lock) */
277 if (fault & VM_FAULT_COMPLETED)
278 return;
279
280 if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) {
281 flags |= FAULT_FLAG_TRIED;
282
283 /*
284 * No need to mmap_read_unlock(mm) as we would
285 * have already released it in __lock_page_or_retry
286 * in mm/filemap.c.
287 */
288 goto retry;
289 }
290
291 mmap_read_unlock(mm);
292
293 if (unlikely(fault & VM_FAULT_ERROR)) {
294 mm_fault_error(regs, addr, fault);
295 return;
296 }
297 return;
298}
1// SPDX-License-Identifier: GPL-2.0
2// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
3
4#include <linux/extable.h>
5#include <linux/kprobes.h>
6#include <linux/mmu_context.h>
7#include <linux/perf_event.h>
8
9int fixup_exception(struct pt_regs *regs)
10{
11 const struct exception_table_entry *fixup;
12
13 fixup = search_exception_tables(instruction_pointer(regs));
14 if (fixup) {
15 regs->pc = fixup->fixup;
16
17 return 1;
18 }
19
20 return 0;
21}
22
23static inline bool is_write(struct pt_regs *regs)
24{
25 switch (trap_no(regs)) {
26 case VEC_TLBINVALIDS:
27 return true;
28 case VEC_TLBMODIFIED:
29 return true;
30 }
31
32 return false;
33}
34
35#ifdef CONFIG_CPU_HAS_LDSTEX
36static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
37{
38 return;
39}
40#else
41extern unsigned long csky_cmpxchg_ldw;
42extern unsigned long csky_cmpxchg_stw;
43static inline void csky_cmpxchg_fixup(struct pt_regs *regs)
44{
45 if (trap_no(regs) != VEC_TLBMODIFIED)
46 return;
47
48 if (instruction_pointer(regs) == csky_cmpxchg_stw)
49 instruction_pointer_set(regs, csky_cmpxchg_ldw);
50 return;
51}
52#endif
53
54static inline void no_context(struct pt_regs *regs, unsigned long addr)
55{
56 current->thread.trap_no = trap_no(regs);
57
58 /* Are we prepared to handle this kernel fault? */
59 if (fixup_exception(regs))
60 return;
61
62 /*
63 * Oops. The kernel tried to access some bad page. We'll have to
64 * terminate things with extreme prejudice.
65 */
66 bust_spinlocks(1);
67 pr_alert("Unable to handle kernel paging request at virtual "
68 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc);
69 die(regs, "Oops");
70 make_task_dead(SIGKILL);
71}
72
73static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
74{
75 current->thread.trap_no = trap_no(regs);
76
77 if (fault & VM_FAULT_OOM) {
78 /*
79 * We ran out of memory, call the OOM killer, and return the userspace
80 * (which will retry the fault, or kill us if we got oom-killed).
81 */
82 if (!user_mode(regs)) {
83 no_context(regs, addr);
84 return;
85 }
86 pagefault_out_of_memory();
87 return;
88 } else if (fault & VM_FAULT_SIGBUS) {
89 /* Kernel mode? Handle exceptions or die */
90 if (!user_mode(regs)) {
91 no_context(regs, addr);
92 return;
93 }
94 do_trap(regs, SIGBUS, BUS_ADRERR, addr);
95 return;
96 }
97 BUG();
98}
99
100static inline void bad_area(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr)
101{
102 /*
103 * Something tried to access memory that isn't in our memory map.
104 * Fix it, but check if it's kernel or user first.
105 */
106 mmap_read_unlock(mm);
107 /* User mode accesses just cause a SIGSEGV */
108 if (user_mode(regs)) {
109 do_trap(regs, SIGSEGV, code, addr);
110 return;
111 }
112
113 no_context(regs, addr);
114}
115
116static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr)
117{
118 pgd_t *pgd, *pgd_k;
119 pud_t *pud, *pud_k;
120 pmd_t *pmd, *pmd_k;
121 pte_t *pte_k;
122 int offset;
123
124 /* User mode accesses just cause a SIGSEGV */
125 if (user_mode(regs)) {
126 do_trap(regs, SIGSEGV, code, addr);
127 return;
128 }
129
130 /*
131 * Synchronize this task's top level page-table
132 * with the 'reference' page table.
133 *
134 * Do _not_ use "tsk" here. We might be inside
135 * an interrupt in the middle of a task switch..
136 */
137 offset = pgd_index(addr);
138
139 pgd = get_pgd() + offset;
140 pgd_k = init_mm.pgd + offset;
141
142 if (!pgd_present(*pgd_k)) {
143 no_context(regs, addr);
144 return;
145 }
146 set_pgd(pgd, *pgd_k);
147
148 pud = (pud_t *)pgd;
149 pud_k = (pud_t *)pgd_k;
150 if (!pud_present(*pud_k)) {
151 no_context(regs, addr);
152 return;
153 }
154
155 pmd = pmd_offset(pud, addr);
156 pmd_k = pmd_offset(pud_k, addr);
157 if (!pmd_present(*pmd_k)) {
158 no_context(regs, addr);
159 return;
160 }
161 set_pmd(pmd, *pmd_k);
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 flush_tlb_one(addr);
170}
171
172static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma)
173{
174 if (is_write(regs)) {
175 if (!(vma->vm_flags & VM_WRITE))
176 return true;
177 } else {
178 if (unlikely(!vma_is_accessible(vma)))
179 return true;
180 }
181 return false;
182}
183
184/*
185 * This routine handles page faults. It determines the address and the
186 * problem, and then passes it off to one of the appropriate routines.
187 */
188asmlinkage void do_page_fault(struct pt_regs *regs)
189{
190 struct task_struct *tsk;
191 struct vm_area_struct *vma;
192 struct mm_struct *mm;
193 unsigned long addr = read_mmu_entryhi() & PAGE_MASK;
194 unsigned int flags = FAULT_FLAG_DEFAULT;
195 int code = SEGV_MAPERR;
196 vm_fault_t fault;
197
198 tsk = current;
199 mm = tsk->mm;
200
201 csky_cmpxchg_fixup(regs);
202
203 if (kprobe_page_fault(regs, tsk->thread.trap_no))
204 return;
205
206 /*
207 * Fault-in kernel-space virtual memory on-demand.
208 * The 'reference' page table is init_mm.pgd.
209 *
210 * NOTE! We MUST NOT take any locks for this case. We may
211 * be in an interrupt or a critical region, and should
212 * only copy the information from the master page table,
213 * nothing more.
214 */
215 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) {
216 vmalloc_fault(regs, code, addr);
217 return;
218 }
219
220 /* Enable interrupts if they were enabled in the parent context. */
221 if (likely(regs->sr & BIT(6)))
222 local_irq_enable();
223
224 /*
225 * If we're in an interrupt, have no user context, or are running
226 * in an atomic region, then we must not take the fault.
227 */
228 if (unlikely(faulthandler_disabled() || !mm)) {
229 no_context(regs, addr);
230 return;
231 }
232
233 if (user_mode(regs))
234 flags |= FAULT_FLAG_USER;
235
236 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
237
238 if (is_write(regs))
239 flags |= FAULT_FLAG_WRITE;
240retry:
241 mmap_read_lock(mm);
242 vma = find_vma(mm, addr);
243 if (unlikely(!vma)) {
244 bad_area(regs, mm, code, addr);
245 return;
246 }
247 if (likely(vma->vm_start <= addr))
248 goto good_area;
249 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
250 bad_area(regs, mm, code, addr);
251 return;
252 }
253 if (unlikely(expand_stack(vma, addr))) {
254 bad_area(regs, mm, code, addr);
255 return;
256 }
257
258 /*
259 * Ok, we have a good vm_area for this memory access, so
260 * we can handle it.
261 */
262good_area:
263 code = SEGV_ACCERR;
264
265 if (unlikely(access_error(regs, vma))) {
266 bad_area(regs, mm, code, addr);
267 return;
268 }
269
270 /*
271 * If for any reason at all we could not handle the fault,
272 * make sure we exit gracefully rather than endlessly redo
273 * the fault.
274 */
275 fault = handle_mm_fault(vma, addr, flags, regs);
276
277 /*
278 * If we need to retry but a fatal signal is pending, handle the
279 * signal first. We do not need to release the mmap_lock because it
280 * would already be released in __lock_page_or_retry in mm/filemap.c.
281 */
282 if (fault_signal_pending(fault, regs)) {
283 if (!user_mode(regs))
284 no_context(regs, addr);
285 return;
286 }
287
288 /* The fault is fully completed (including releasing mmap lock) */
289 if (fault & VM_FAULT_COMPLETED)
290 return;
291
292 if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) {
293 flags |= FAULT_FLAG_TRIED;
294
295 /*
296 * No need to mmap_read_unlock(mm) as we would
297 * have already released it in __lock_page_or_retry
298 * in mm/filemap.c.
299 */
300 goto retry;
301 }
302
303 mmap_read_unlock(mm);
304
305 if (unlikely(fault & VM_FAULT_ERROR)) {
306 mm_fault_error(regs, addr, fault);
307 return;
308 }
309 return;
310}