1 // TODO VM_EXEC flag work-around, cache aliasing
2 /*
3 * arch/xtensa/mm/fault.c
4 *
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License. See the file "COPYING" in the main directory of this archive
7 * for more details.
8 *
9 * Copyright (C) 2001 - 2010 Tensilica Inc.
10 *
11 * Chris Zankel <chris@zankel.net>
12 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
13 */
14
15 #include <linux/mm.h>
16 #include <linux/extable.h>
17 #include <linux/hardirq.h>
18 #include <linux/perf_event.h>
19 #include <linux/uaccess.h>
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/hardirq.h>
23 #include <asm/traps.h>
24
25 void bad_page_fault(struct pt_regs*, unsigned long, int);
26
27 static void vmalloc_fault(struct pt_regs *regs, unsigned int address)
28 {
29 #ifdef CONFIG_MMU
30 /* Synchronize this task's top level page-table
31 * with the 'reference' page table.
32 */
33 struct mm_struct *act_mm = current->active_mm;
34 int index = pgd_index(address);
35 pgd_t *pgd, *pgd_k;
36 p4d_t *p4d, *p4d_k;
37 pud_t *pud, *pud_k;
38 pmd_t *pmd, *pmd_k;
39 pte_t *pte_k;
40
41 if (act_mm == NULL)
42 goto bad_page_fault;
43
44 pgd = act_mm->pgd + index;
45 pgd_k = init_mm.pgd + index;
46
47 if (!pgd_present(*pgd_k))
48 goto bad_page_fault;
49
50 pgd_val(*pgd) = pgd_val(*pgd_k);
51
52 p4d = p4d_offset(pgd, address);
53 p4d_k = p4d_offset(pgd_k, address);
54 if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
55 goto bad_page_fault;
56
57 pud = pud_offset(p4d, address);
58 pud_k = pud_offset(p4d_k, address);
59 if (!pud_present(*pud) || !pud_present(*pud_k))
60 goto bad_page_fault;
61
62 pmd = pmd_offset(pud, address);
63 pmd_k = pmd_offset(pud_k, address);
64 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
65 goto bad_page_fault;
66
67 pmd_val(*pmd) = pmd_val(*pmd_k);
68 pte_k = pte_offset_kernel(pmd_k, address);
69
70 if (!pte_present(*pte_k))
71 goto bad_page_fault;
72 return;
73
74 bad_page_fault:
75 bad_page_fault(regs, address, SIGKILL);
76 #else
77 WARN_ONCE(1, "%s in noMMU configuration\n", __func__);
78 #endif
79 }
80 /*
81 * This routine handles page faults. It determines the address,
82 * and the problem, and then passes it off to one of the appropriate
83 * routines.
84 *
85 * Note: does not handle Miss and MultiHit.
86 */
87
88 void do_page_fault(struct pt_regs *regs)
89 {
90 struct vm_area_struct * vma;
91 struct mm_struct *mm = current->mm;
92 unsigned int exccause = regs->exccause;
93 unsigned int address = regs->excvaddr;
94 int code;
95
96 int is_write, is_exec;
97 vm_fault_t fault;
98 unsigned int flags = FAULT_FLAG_DEFAULT;
99
100 code = SEGV_MAPERR;
101
102 /* We fault-in kernel-space virtual memory on-demand. The
103 * 'reference' page table is init_mm.pgd.
104 */
105 if (address >= TASK_SIZE && !user_mode(regs)) {
106 vmalloc_fault(regs, address);
107 return;
108 }
109
110 /* If we're in an interrupt or have no user
111 * context, we must not take the fault..
112 */
113 if (faulthandler_disabled() || !mm) {
114 bad_page_fault(regs, address, SIGSEGV);
115 return;
116 }
117
118 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
119 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
120 exccause == EXCCAUSE_ITLB_MISS ||
121 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
122
123 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
124 current->comm, current->pid,
125 address, exccause, regs->pc,
126 is_write ? "w" : "", is_exec ? "x" : "");
127
128 if (user_mode(regs))
129 flags |= FAULT_FLAG_USER;
130
131 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
132
133 retry:
134 vma = lock_mm_and_find_vma(mm, address, regs);
135 if (!vma)
136 goto bad_area_nosemaphore;
137
138 /* Ok, we have a good vm_area for this memory access, so
139 * we can handle it..
140 */
141
142 code = SEGV_ACCERR;
143
144 if (is_write) {
145 if (!(vma->vm_flags & VM_WRITE))
146 goto bad_area;
147 flags |= FAULT_FLAG_WRITE;
148 } else if (is_exec) {
149 if (!(vma->vm_flags & VM_EXEC))
150 goto bad_area;
151 } else /* Allow read even from write-only pages. */
152 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
153 goto bad_area;
154
155 /* If for any reason at all we couldn't handle the fault,
156 * make sure we exit gracefully rather than endlessly redo
157 * the fault.
158 */
159 fault = handle_mm_fault(vma, address, flags, regs);
160
161 if (fault_signal_pending(fault, regs)) {
162 if (!user_mode(regs))
163 bad_page_fault(regs, address, SIGKILL);
164 return;
165 }
166
167 /* The fault is fully completed (including releasing mmap lock) */
168 if (fault & VM_FAULT_COMPLETED)
169 return;
170
171 if (unlikely(fault & VM_FAULT_ERROR)) {
172 if (fault & VM_FAULT_OOM)
173 goto out_of_memory;
174 else if (fault & VM_FAULT_SIGSEGV)
175 goto bad_area;
176 else if (fault & VM_FAULT_SIGBUS)
177 goto do_sigbus;
178 BUG();
179 }
180
181 if (fault & VM_FAULT_RETRY) {
182 flags |= FAULT_FLAG_TRIED;
183
184 /* No need to mmap_read_unlock(mm) as we would
185 * have already released it in __lock_page_or_retry
186 * in mm/filemap.c.
187 */
188
189 goto retry;
190 }
191
192 mmap_read_unlock(mm);
193 return;
194
195 /* Something tried to access memory that isn't in our memory map..
196 * Fix it, but check if it's kernel or user first..
197 */
198 bad_area:
199 mmap_read_unlock(mm);
200 bad_area_nosemaphore:
201 if (user_mode(regs)) {
202 force_sig_fault(SIGSEGV, code, (void *) address);
203 return;
204 }
205 bad_page_fault(regs, address, SIGSEGV);
206 return;
207
208
209 /* We ran out of memory, or some other thing happened to us that made
210 * us unable to handle the page fault gracefully.
211 */
212 out_of_memory:
213 mmap_read_unlock(mm);
214 if (!user_mode(regs))
215 bad_page_fault(regs, address, SIGKILL);
216 else
217 pagefault_out_of_memory();
218 return;
219
220 do_sigbus:
221 mmap_read_unlock(mm);
222
223 /* Send a sigbus, regardless of whether we were in kernel
224 * or user mode.
225 */
226 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
227
228 /* Kernel mode? Handle exceptions or die */
229 if (!user_mode(regs))
230 bad_page_fault(regs, address, SIGBUS);
231 return;
232 }
233
234
235 void
236 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
237 {
238 extern void __noreturn die(const char*, struct pt_regs*, long);
239 const struct exception_table_entry *entry;
240
241 /* Are we prepared to handle this kernel fault? */
242 if ((entry = search_exception_tables(regs->pc)) != NULL) {
243 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
244 current->comm, regs->pc, entry->fixup);
245 regs->pc = entry->fixup;
246 return;
247 }
248
249 /* Oops. The kernel tried to access some bad page. We'll have to
250 * terminate things with extreme prejudice.
251 */
252 pr_alert("Unable to handle kernel paging request at virtual "
253 "address %08lx\n pc = %08lx, ra = %08lx\n",
254 address, regs->pc, regs->areg[0]);
255 die("Oops", regs, sig);
256 }
257
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