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
24 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
25 void bad_page_fault(struct pt_regs*, unsigned long, int);
26
27 /*
28 * This routine handles page faults. It determines the address,
29 * and the problem, and then passes it off to one of the appropriate
30 * routines.
31 *
32 * Note: does not handle Miss and MultiHit.
33 */
34
do_page_fault(struct pt_regs * regs)35 void do_page_fault(struct pt_regs *regs)
36 {
37 struct vm_area_struct * vma;
38 struct mm_struct *mm = current->mm;
39 unsigned int exccause = regs->exccause;
40 unsigned int address = regs->excvaddr;
41 int code;
42
43 int is_write, is_exec;
44 vm_fault_t fault;
45 unsigned int flags = FAULT_FLAG_DEFAULT;
46
47 code = SEGV_MAPERR;
48
49 /* We fault-in kernel-space virtual memory on-demand. The
50 * 'reference' page table is init_mm.pgd.
51 */
52 if (address >= TASK_SIZE && !user_mode(regs))
53 goto vmalloc_fault;
54
55 /* If we're in an interrupt or have no user
56 * context, we must not take the fault..
57 */
58 if (faulthandler_disabled() || !mm) {
59 bad_page_fault(regs, address, SIGSEGV);
60 return;
61 }
62
63 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
64 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
65 exccause == EXCCAUSE_ITLB_MISS ||
66 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
67
68 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
69 current->comm, current->pid,
70 address, exccause, regs->pc,
71 is_write ? "w" : "", is_exec ? "x" : "");
72
73 if (user_mode(regs))
74 flags |= FAULT_FLAG_USER;
75
76 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
77
78 retry:
79 mmap_read_lock(mm);
80 vma = find_vma(mm, address);
81
82 if (!vma)
83 goto bad_area;
84 if (vma->vm_start <= address)
85 goto good_area;
86 if (!(vma->vm_flags & VM_GROWSDOWN))
87 goto bad_area;
88 if (expand_stack(vma, address))
89 goto bad_area;
90
91 /* Ok, we have a good vm_area for this memory access, so
92 * we can handle it..
93 */
94
95 good_area:
96 code = SEGV_ACCERR;
97
98 if (is_write) {
99 if (!(vma->vm_flags & VM_WRITE))
100 goto bad_area;
101 flags |= FAULT_FLAG_WRITE;
102 } else if (is_exec) {
103 if (!(vma->vm_flags & VM_EXEC))
104 goto bad_area;
105 } else /* Allow read even from write-only pages. */
106 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
107 goto bad_area;
108
109 /* If for any reason at all we couldn't handle the fault,
110 * make sure we exit gracefully rather than endlessly redo
111 * the fault.
112 */
113 fault = handle_mm_fault(vma, address, flags, regs);
114
115 if (fault_signal_pending(fault, regs))
116 return;
117
118 if (unlikely(fault & VM_FAULT_ERROR)) {
119 if (fault & VM_FAULT_OOM)
120 goto out_of_memory;
121 else if (fault & VM_FAULT_SIGSEGV)
122 goto bad_area;
123 else if (fault & VM_FAULT_SIGBUS)
124 goto do_sigbus;
125 BUG();
126 }
127 if (flags & FAULT_FLAG_ALLOW_RETRY) {
128 if (fault & VM_FAULT_RETRY) {
129 flags |= FAULT_FLAG_TRIED;
130
131 /* No need to mmap_read_unlock(mm) as we would
132 * have already released it in __lock_page_or_retry
133 * in mm/filemap.c.
134 */
135
136 goto retry;
137 }
138 }
139
140 mmap_read_unlock(mm);
141 return;
142
143 /* Something tried to access memory that isn't in our memory map..
144 * Fix it, but check if it's kernel or user first..
145 */
146 bad_area:
147 mmap_read_unlock(mm);
148 if (user_mode(regs)) {
149 current->thread.bad_vaddr = address;
150 current->thread.error_code = is_write;
151 force_sig_fault(SIGSEGV, code, (void *) address);
152 return;
153 }
154 bad_page_fault(regs, address, SIGSEGV);
155 return;
156
157
158 /* We ran out of memory, or some other thing happened to us that made
159 * us unable to handle the page fault gracefully.
160 */
161 out_of_memory:
162 mmap_read_unlock(mm);
163 if (!user_mode(regs))
164 bad_page_fault(regs, address, SIGKILL);
165 else
166 pagefault_out_of_memory();
167 return;
168
169 do_sigbus:
170 mmap_read_unlock(mm);
171
172 /* Send a sigbus, regardless of whether we were in kernel
173 * or user mode.
174 */
175 current->thread.bad_vaddr = address;
176 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
177
178 /* Kernel mode? Handle exceptions or die */
179 if (!user_mode(regs))
180 bad_page_fault(regs, address, SIGBUS);
181 return;
182
183 vmalloc_fault:
184 {
185 /* Synchronize this task's top level page-table
186 * with the 'reference' page table.
187 */
188 struct mm_struct *act_mm = current->active_mm;
189 int index = pgd_index(address);
190 pgd_t *pgd, *pgd_k;
191 p4d_t *p4d, *p4d_k;
192 pud_t *pud, *pud_k;
193 pmd_t *pmd, *pmd_k;
194 pte_t *pte_k;
195
196 if (act_mm == NULL)
197 goto bad_page_fault;
198
199 pgd = act_mm->pgd + index;
200 pgd_k = init_mm.pgd + index;
201
202 if (!pgd_present(*pgd_k))
203 goto bad_page_fault;
204
205 pgd_val(*pgd) = pgd_val(*pgd_k);
206
207 p4d = p4d_offset(pgd, address);
208 p4d_k = p4d_offset(pgd_k, address);
209 if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
210 goto bad_page_fault;
211
212 pud = pud_offset(p4d, address);
213 pud_k = pud_offset(p4d_k, address);
214 if (!pud_present(*pud) || !pud_present(*pud_k))
215 goto bad_page_fault;
216
217 pmd = pmd_offset(pud, address);
218 pmd_k = pmd_offset(pud_k, address);
219 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
220 goto bad_page_fault;
221
222 pmd_val(*pmd) = pmd_val(*pmd_k);
223 pte_k = pte_offset_kernel(pmd_k, address);
224
225 if (!pte_present(*pte_k))
226 goto bad_page_fault;
227 return;
228 }
229 bad_page_fault:
230 bad_page_fault(regs, address, SIGKILL);
231 return;
232 }
233
234
235 void
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)236 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
237 {
238 extern void 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 current->thread.bad_uaddr = address;
246 regs->pc = entry->fixup;
247 return;
248 }
249
250 /* Oops. The kernel tried to access some bad page. We'll have to
251 * terminate things with extreme prejudice.
252 */
253 pr_alert("Unable to handle kernel paging request at virtual "
254 "address %08lx\n pc = %08lx, ra = %08lx\n",
255 address, regs->pc, regs->areg[0]);
256 die("Oops", regs, sig);
257 do_exit(sig);
258 }
259
