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fbd7053a VG |
1 | /* Page Fault Handling for ARC (TLB Miss / ProtV) |
2 | * | |
3 | * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU General Public License version 2 as | |
7 | * published by the Free Software Foundation. | |
8 | */ | |
9 | ||
10 | #include <linux/signal.h> | |
11 | #include <linux/interrupt.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/errno.h> | |
14 | #include <linux/ptrace.h> | |
15 | #include <linux/version.h> | |
16 | #include <linux/uaccess.h> | |
17 | #include <linux/kdebug.h> | |
18 | #include <asm/pgalloc.h> | |
19 | ||
20 | static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) | |
21 | { | |
22 | /* | |
23 | * Synchronize this task's top level page-table | |
24 | * with the 'reference' page table. | |
25 | */ | |
26 | pgd_t *pgd, *pgd_k; | |
27 | pud_t *pud, *pud_k; | |
28 | pmd_t *pmd, *pmd_k; | |
29 | ||
30 | pgd = pgd_offset_fast(mm, address); | |
31 | pgd_k = pgd_offset_k(address); | |
32 | ||
33 | if (!pgd_present(*pgd_k)) | |
34 | goto bad_area; | |
35 | ||
36 | pud = pud_offset(pgd, address); | |
37 | pud_k = pud_offset(pgd_k, address); | |
38 | if (!pud_present(*pud_k)) | |
39 | goto bad_area; | |
40 | ||
41 | pmd = pmd_offset(pud, address); | |
42 | pmd_k = pmd_offset(pud_k, address); | |
43 | if (!pmd_present(*pmd_k)) | |
44 | goto bad_area; | |
45 | ||
46 | set_pmd(pmd, *pmd_k); | |
47 | ||
48 | /* XXX: create the TLB entry here */ | |
49 | return 0; | |
50 | ||
51 | bad_area: | |
52 | return 1; | |
53 | } | |
54 | ||
55 | void do_page_fault(struct pt_regs *regs, int write, unsigned long address, | |
56 | unsigned long cause_code) | |
57 | { | |
58 | struct vm_area_struct *vma = NULL; | |
59 | struct task_struct *tsk = current; | |
60 | struct mm_struct *mm = tsk->mm; | |
61 | siginfo_t info; | |
62 | int fault, ret; | |
63 | unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | | |
64 | (write ? FAULT_FLAG_WRITE : 0); | |
65 | ||
66 | /* | |
67 | * We fault-in kernel-space virtual memory on-demand. The | |
68 | * 'reference' page table is init_mm.pgd. | |
69 | * | |
70 | * NOTE! We MUST NOT take any locks for this case. We may | |
71 | * be in an interrupt or a critical region, and should | |
72 | * only copy the information from the master page table, | |
73 | * nothing more. | |
74 | */ | |
75 | if (address >= VMALLOC_START && address <= VMALLOC_END) { | |
76 | ret = handle_vmalloc_fault(mm, address); | |
77 | if (unlikely(ret)) | |
78 | goto bad_area_nosemaphore; | |
79 | else | |
80 | return; | |
81 | } | |
82 | ||
83 | info.si_code = SEGV_MAPERR; | |
84 | ||
85 | /* | |
86 | * If we're in an interrupt or have no user | |
87 | * context, we must not take the fault.. | |
88 | */ | |
89 | if (in_atomic() || !mm) | |
90 | goto no_context; | |
91 | ||
92 | retry: | |
93 | down_read(&mm->mmap_sem); | |
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 | /* | |
105 | * Ok, we have a good vm_area for this memory access, so | |
106 | * we can handle it.. | |
107 | */ | |
108 | good_area: | |
109 | info.si_code = SEGV_ACCERR; | |
110 | ||
111 | /* Handle protection violation, execute on heap or stack */ | |
112 | ||
113 | if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH)) | |
114 | goto bad_area; | |
115 | ||
116 | if (write) { | |
117 | if (!(vma->vm_flags & VM_WRITE)) | |
118 | goto bad_area; | |
119 | } else { | |
120 | if (!(vma->vm_flags & (VM_READ | VM_EXEC))) | |
121 | goto bad_area; | |
122 | } | |
123 | ||
124 | survive: | |
125 | /* | |
126 | * If for any reason at all we couldn't handle the fault, | |
127 | * make sure we exit gracefully rather than endlessly redo | |
128 | * the fault. | |
129 | */ | |
130 | fault = handle_mm_fault(mm, vma, address, flags); | |
131 | ||
132 | /* If Pagefault was interrupted by SIGKILL, exit page fault "early" */ | |
133 | if (unlikely(fatal_signal_pending(current))) { | |
134 | if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY)) | |
135 | up_read(&mm->mmap_sem); | |
136 | if (user_mode(regs)) | |
137 | return; | |
138 | } | |
139 | ||
140 | if (likely(!(fault & VM_FAULT_ERROR))) { | |
141 | if (flags & FAULT_FLAG_ALLOW_RETRY) { | |
142 | /* To avoid updating stats twice for retry case */ | |
143 | if (fault & VM_FAULT_MAJOR) | |
144 | tsk->maj_flt++; | |
145 | else | |
146 | tsk->min_flt++; | |
147 | ||
148 | if (fault & VM_FAULT_RETRY) { | |
149 | flags &= ~FAULT_FLAG_ALLOW_RETRY; | |
150 | flags |= FAULT_FLAG_TRIED; | |
151 | goto retry; | |
152 | } | |
153 | } | |
154 | ||
155 | /* Fault Handled Gracefully */ | |
156 | up_read(&mm->mmap_sem); | |
157 | return; | |
158 | } | |
159 | ||
160 | /* TBD: switch to pagefault_out_of_memory() */ | |
161 | if (fault & VM_FAULT_OOM) | |
162 | goto out_of_memory; | |
163 | else if (fault & VM_FAULT_SIGBUS) | |
164 | goto do_sigbus; | |
165 | ||
166 | /* no man's land */ | |
167 | BUG(); | |
168 | ||
169 | /* | |
170 | * Something tried to access memory that isn't in our memory map.. | |
171 | * Fix it, but check if it's kernel or user first.. | |
172 | */ | |
173 | bad_area: | |
174 | up_read(&mm->mmap_sem); | |
175 | ||
176 | bad_area_nosemaphore: | |
177 | /* User mode accesses just cause a SIGSEGV */ | |
178 | if (user_mode(regs)) { | |
179 | tsk->thread.fault_address = address; | |
180 | tsk->thread.cause_code = cause_code; | |
181 | info.si_signo = SIGSEGV; | |
182 | info.si_errno = 0; | |
183 | /* info.si_code has been set above */ | |
184 | info.si_addr = (void __user *)address; | |
185 | force_sig_info(SIGSEGV, &info, tsk); | |
186 | return; | |
187 | } | |
188 | ||
189 | no_context: | |
190 | /* Are we prepared to handle this kernel fault? | |
191 | * | |
192 | * (The kernel has valid exception-points in the source | |
193 | * when it acesses user-memory. When it fails in one | |
194 | * of those points, we find it in a table and do a jump | |
195 | * to some fixup code that loads an appropriate error | |
196 | * code) | |
197 | */ | |
198 | if (fixup_exception(regs)) | |
199 | return; | |
200 | ||
201 | die("Oops", regs, address, cause_code); | |
202 | ||
203 | out_of_memory: | |
204 | if (is_global_init(tsk)) { | |
205 | yield(); | |
206 | goto survive; | |
207 | } | |
208 | up_read(&mm->mmap_sem); | |
209 | ||
210 | if (user_mode(regs)) | |
211 | do_group_exit(SIGKILL); /* This will never return */ | |
212 | ||
213 | goto no_context; | |
214 | ||
215 | do_sigbus: | |
216 | up_read(&mm->mmap_sem); | |
217 | ||
218 | if (!user_mode(regs)) | |
219 | goto no_context; | |
220 | ||
221 | tsk->thread.fault_address = address; | |
222 | tsk->thread.cause_code = cause_code; | |
223 | info.si_signo = SIGBUS; | |
224 | info.si_errno = 0; | |
225 | info.si_code = BUS_ADRERR; | |
226 | info.si_addr = (void __user *)address; | |
227 | force_sig_info(SIGBUS, &info, tsk); | |
228 | } |