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862674d4 LFT |
1 | /* |
2 | * Copyright (C) 2009 Wind River Systems Inc | |
3 | * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com | |
4 | * | |
5 | * based on arch/mips/mm/fault.c which is: | |
6 | * | |
7 | * Copyright (C) 1995-2000 Ralf Baechle | |
8 | * | |
9 | * This file is subject to the terms and conditions of the GNU General Public | |
10 | * License. See the file "COPYING" in the main directory of this archive | |
11 | * for more details. | |
12 | */ | |
13 | ||
14 | #include <linux/signal.h> | |
15 | #include <linux/sched.h> | |
b17b0153 | 16 | #include <linux/sched/debug.h> |
862674d4 LFT |
17 | #include <linux/interrupt.h> |
18 | #include <linux/kernel.h> | |
19 | #include <linux/errno.h> | |
20 | #include <linux/string.h> | |
21 | #include <linux/types.h> | |
22 | #include <linux/ptrace.h> | |
23 | #include <linux/mman.h> | |
24 | #include <linux/mm.h> | |
7e227e88 | 25 | #include <linux/extable.h> |
862674d4 LFT |
26 | #include <linux/uaccess.h> |
27 | #include <linux/ptrace.h> | |
28 | ||
29 | #include <asm/mmu_context.h> | |
30 | #include <asm/traps.h> | |
31 | ||
32 | #define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */ | |
33 | #define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */ | |
34 | #define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */ | |
35 | #define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */ | |
36 | #define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */ | |
37 | ||
38 | /* | |
39 | * This routine handles page faults. It determines the address, | |
40 | * and the problem, and then passes it off to one of the appropriate | |
41 | * routines. | |
42 | */ | |
43 | asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, | |
44 | unsigned long address) | |
45 | { | |
46 | struct vm_area_struct *vma = NULL; | |
47 | struct task_struct *tsk = current; | |
48 | struct mm_struct *mm = tsk->mm; | |
49 | int code = SEGV_MAPERR; | |
50 | int fault; | |
96f3a5cc | 51 | unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; |
862674d4 LFT |
52 | |
53 | cause >>= 2; | |
54 | ||
55 | /* Restart the instruction */ | |
56 | regs->ea -= 4; | |
57 | ||
58 | /* | |
59 | * We fault-in kernel-space virtual memory on-demand. The | |
60 | * 'reference' page table is init_mm.pgd. | |
61 | * | |
62 | * NOTE! We MUST NOT take any locks for this case. We may | |
63 | * be in an interrupt or a critical region, and should | |
64 | * only copy the information from the master page table, | |
65 | * nothing more. | |
66 | */ | |
67 | if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) { | |
68 | if (user_mode(regs)) | |
69 | goto bad_area_nosemaphore; | |
70 | else | |
71 | goto vmalloc_fault; | |
72 | } | |
73 | ||
74 | if (unlikely(address >= TASK_SIZE)) | |
75 | goto bad_area_nosemaphore; | |
76 | ||
77 | /* | |
78 | * If we're in an interrupt or have no user | |
79 | * context, we must not take the fault.. | |
80 | */ | |
70ffdb93 | 81 | if (faulthandler_disabled() || !mm) |
862674d4 LFT |
82 | goto bad_area_nosemaphore; |
83 | ||
84 | if (user_mode(regs)) | |
85 | flags |= FAULT_FLAG_USER; | |
86 | ||
87 | if (!down_read_trylock(&mm->mmap_sem)) { | |
88 | if (!user_mode(regs) && !search_exception_tables(regs->ea)) | |
89 | goto bad_area_nosemaphore; | |
96f3a5cc | 90 | retry: |
862674d4 LFT |
91 | down_read(&mm->mmap_sem); |
92 | } | |
93 | ||
94 | vma = find_vma(mm, address); | |
95 | if (!vma) | |
96 | goto bad_area; | |
97 | if (vma->vm_start <= address) | |
98 | goto good_area; | |
99 | if (!(vma->vm_flags & VM_GROWSDOWN)) | |
100 | goto bad_area; | |
101 | if (expand_stack(vma, address)) | |
102 | goto bad_area; | |
103 | /* | |
104 | * Ok, we have a good vm_area for this memory access, so | |
105 | * we can handle it.. | |
106 | */ | |
107 | good_area: | |
108 | code = SEGV_ACCERR; | |
109 | ||
110 | switch (cause) { | |
111 | case EXC_SUPERV_INSN_ACCESS: | |
112 | goto bad_area; | |
113 | case EXC_SUPERV_DATA_ACCESS: | |
114 | goto bad_area; | |
115 | case EXC_X_PROTECTION_FAULT: | |
116 | if (!(vma->vm_flags & VM_EXEC)) | |
117 | goto bad_area; | |
118 | break; | |
119 | case EXC_R_PROTECTION_FAULT: | |
120 | if (!(vma->vm_flags & VM_READ)) | |
121 | goto bad_area; | |
122 | break; | |
123 | case EXC_W_PROTECTION_FAULT: | |
124 | if (!(vma->vm_flags & VM_WRITE)) | |
125 | goto bad_area; | |
126 | flags = FAULT_FLAG_WRITE; | |
127 | break; | |
128 | } | |
129 | ||
862674d4 LFT |
130 | /* |
131 | * If for any reason at all we couldn't handle the fault, | |
132 | * make sure we exit gracefully rather than endlessly redo | |
133 | * the fault. | |
134 | */ | |
dcddffd4 | 135 | fault = handle_mm_fault(vma, address, flags); |
96f3a5cc LFT |
136 | |
137 | if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) | |
138 | return; | |
139 | ||
862674d4 LFT |
140 | if (unlikely(fault & VM_FAULT_ERROR)) { |
141 | if (fault & VM_FAULT_OOM) | |
142 | goto out_of_memory; | |
33692f27 LT |
143 | else if (fault & VM_FAULT_SIGSEGV) |
144 | goto bad_area; | |
862674d4 LFT |
145 | else if (fault & VM_FAULT_SIGBUS) |
146 | goto do_sigbus; | |
147 | BUG(); | |
148 | } | |
96f3a5cc LFT |
149 | |
150 | /* | |
151 | * Major/minor page fault accounting is only done on the | |
152 | * initial attempt. If we go through a retry, it is extremely | |
153 | * likely that the page will be found in page cache at that point. | |
154 | */ | |
155 | if (flags & FAULT_FLAG_ALLOW_RETRY) { | |
156 | if (fault & VM_FAULT_MAJOR) | |
157 | current->maj_flt++; | |
158 | else | |
159 | current->min_flt++; | |
160 | if (fault & VM_FAULT_RETRY) { | |
161 | /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk | |
162 | * of starvation. */ | |
163 | flags &= ~FAULT_FLAG_ALLOW_RETRY; | |
164 | flags |= FAULT_FLAG_TRIED; | |
165 | ||
166 | /* | |
167 | * No need to up_read(&mm->mmap_sem) as we would | |
168 | * have already released it in __lock_page_or_retry | |
169 | * in mm/filemap.c. | |
170 | */ | |
171 | ||
172 | goto retry; | |
173 | } | |
174 | } | |
862674d4 LFT |
175 | |
176 | up_read(&mm->mmap_sem); | |
177 | return; | |
178 | ||
179 | /* | |
180 | * Something tried to access memory that isn't in our memory map.. | |
181 | * Fix it, but check if it's kernel or user first.. | |
182 | */ | |
183 | bad_area: | |
184 | up_read(&mm->mmap_sem); | |
185 | ||
186 | bad_area_nosemaphore: | |
187 | /* User mode accesses just cause a SIGSEGV */ | |
188 | if (user_mode(regs)) { | |
a3248d60 CLT |
189 | if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) { |
190 | pr_info("%s: unhandled page fault (%d) at 0x%08lx, " | |
191 | "cause %ld\n", current->comm, SIGSEGV, address, cause); | |
192 | show_regs(regs); | |
193 | } | |
862674d4 LFT |
194 | _exception(SIGSEGV, regs, code, address); |
195 | return; | |
196 | } | |
197 | ||
198 | no_context: | |
199 | /* Are we prepared to handle this kernel fault? */ | |
200 | if (fixup_exception(regs)) | |
201 | return; | |
202 | ||
203 | /* | |
204 | * Oops. The kernel tried to access some bad page. We'll have to | |
205 | * terminate things with extreme prejudice. | |
206 | */ | |
207 | bust_spinlocks(1); | |
208 | ||
209 | pr_alert("Unable to handle kernel %s at virtual address %08lx", | |
210 | address < PAGE_SIZE ? "NULL pointer dereference" : | |
211 | "paging request", address); | |
212 | pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra, | |
213 | cause); | |
214 | panic("Oops"); | |
215 | return; | |
216 | ||
217 | /* | |
218 | * We ran out of memory, or some other thing happened to us that made | |
219 | * us unable to handle the page fault gracefully. | |
220 | */ | |
221 | out_of_memory: | |
222 | up_read(&mm->mmap_sem); | |
862674d4 LFT |
223 | if (!user_mode(regs)) |
224 | goto no_context; | |
225 | pagefault_out_of_memory(); | |
226 | return; | |
227 | ||
228 | do_sigbus: | |
229 | up_read(&mm->mmap_sem); | |
230 | ||
231 | /* Kernel mode? Handle exceptions or die */ | |
232 | if (!user_mode(regs)) | |
233 | goto no_context; | |
234 | ||
235 | _exception(SIGBUS, regs, BUS_ADRERR, address); | |
236 | return; | |
237 | ||
238 | vmalloc_fault: | |
239 | { | |
240 | /* | |
241 | * Synchronize this task's top level page-table | |
242 | * with the 'reference' page table. | |
243 | * | |
244 | * Do _not_ use "tsk" here. We might be inside | |
245 | * an interrupt in the middle of a task switch.. | |
246 | */ | |
247 | int offset = pgd_index(address); | |
248 | pgd_t *pgd, *pgd_k; | |
249 | pud_t *pud, *pud_k; | |
250 | pmd_t *pmd, *pmd_k; | |
251 | pte_t *pte_k; | |
252 | ||
253 | pgd = pgd_current + offset; | |
254 | pgd_k = init_mm.pgd + offset; | |
255 | ||
256 | if (!pgd_present(*pgd_k)) | |
257 | goto no_context; | |
258 | set_pgd(pgd, *pgd_k); | |
259 | ||
260 | pud = pud_offset(pgd, address); | |
261 | pud_k = pud_offset(pgd_k, address); | |
262 | if (!pud_present(*pud_k)) | |
263 | goto no_context; | |
264 | pmd = pmd_offset(pud, address); | |
265 | pmd_k = pmd_offset(pud_k, address); | |
266 | if (!pmd_present(*pmd_k)) | |
267 | goto no_context; | |
268 | set_pmd(pmd, *pmd_k); | |
269 | ||
270 | pte_k = pte_offset_kernel(pmd_k, address); | |
271 | if (!pte_present(*pte_k)) | |
272 | goto no_context; | |
273 | ||
274 | flush_tlb_one(address); | |
275 | return; | |
276 | } | |
277 | } |