Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
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
20static 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
51bad_area:
52 return 1;
53}
54
55void 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
92retry:
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 */
108good_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
124survive:
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 */
173bad_area:
174 up_read(&mm->mmap_sem);
175
176bad_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
189no_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
203out_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
215do_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}