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 if (!user_mode(regs))
117 goto bad_page_fault;
118 return;
119 }
120
121 if (unlikely(fault & VM_FAULT_ERROR)) {
122 if (fault & VM_FAULT_OOM)
123 goto out_of_memory;
124 else if (fault & VM_FAULT_SIGSEGV)
125 goto bad_area;
126 else if (fault & VM_FAULT_SIGBUS)
127 goto do_sigbus;
128 BUG();
129 }
130 if (flags & FAULT_FLAG_ALLOW_RETRY) {
131 if (fault & VM_FAULT_RETRY) {
132 flags |= FAULT_FLAG_TRIED;
133
134 /* No need to mmap_read_unlock(mm) as we would
135 * have already released it in __lock_page_or_retry
136 * in mm/filemap.c.
137 */
138
139 goto retry;
140 }
141 }
142
143 mmap_read_unlock(mm);
144 return;
145
146 /* Something tried to access memory that isn't in our memory map..
147 * Fix it, but check if it's kernel or user first..
148 */
149 bad_area:
150 mmap_read_unlock(mm);
151 if (user_mode(regs)) {
152 current->thread.bad_vaddr = address;
153 current->thread.error_code = is_write;
154 force_sig_fault(SIGSEGV, code, (void *) address);
155 return;
156 }
157 bad_page_fault(regs, address, SIGSEGV);
158 return;
159
160
161 /* We ran out of memory, or some other thing happened to us that made
162 * us unable to handle the page fault gracefully.
163 */
164 out_of_memory:
165 mmap_read_unlock(mm);
166 if (!user_mode(regs))
167 bad_page_fault(regs, address, SIGKILL);
168 else
169 pagefault_out_of_memory();
170 return;
171
172 do_sigbus:
173 mmap_read_unlock(mm);
174
175 /* Send a sigbus, regardless of whether we were in kernel
176 * or user mode.
177 */
178 current->thread.bad_vaddr = address;
179 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
180
181 /* Kernel mode? Handle exceptions or die */
182 if (!user_mode(regs))
183 bad_page_fault(regs, address, SIGBUS);
184 return;
185
186 vmalloc_fault:
187 {
188 /* Synchronize this task's top level page-table
189 * with the 'reference' page table.
190 */
191 struct mm_struct *act_mm = current->active_mm;
192 int index = pgd_index(address);
193 pgd_t *pgd, *pgd_k;
194 p4d_t *p4d, *p4d_k;
195 pud_t *pud, *pud_k;
196 pmd_t *pmd, *pmd_k;
197 pte_t *pte_k;
198
199 if (act_mm == NULL)
200 goto bad_page_fault;
201
202 pgd = act_mm->pgd + index;
203 pgd_k = init_mm.pgd + index;
204
205 if (!pgd_present(*pgd_k))
206 goto bad_page_fault;
207
208 pgd_val(*pgd) = pgd_val(*pgd_k);
209
210 p4d = p4d_offset(pgd, address);
211 p4d_k = p4d_offset(pgd_k, address);
212 if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
213 goto bad_page_fault;
214
215 pud = pud_offset(p4d, address);
216 pud_k = pud_offset(p4d_k, address);
217 if (!pud_present(*pud) || !pud_present(*pud_k))
218 goto bad_page_fault;
219
220 pmd = pmd_offset(pud, address);
221 pmd_k = pmd_offset(pud_k, address);
222 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
223 goto bad_page_fault;
224
225 pmd_val(*pmd) = pmd_val(*pmd_k);
226 pte_k = pte_offset_kernel(pmd_k, address);
227
228 if (!pte_present(*pte_k))
229 goto bad_page_fault;
230 return;
231 }
232 bad_page_fault:
233 bad_page_fault(regs, address, SIGKILL);
234 return;
235 }
236
237
238 void
bad_page_fault(struct pt_regs * regs,unsigned long address,int sig)239 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
240 {
241 extern void die(const char*, struct pt_regs*, long);
242 const struct exception_table_entry *entry;
243
244 /* Are we prepared to handle this kernel fault? */
245 if ((entry = search_exception_tables(regs->pc)) != NULL) {
246 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
247 current->comm, regs->pc, entry->fixup);
248 current->thread.bad_uaddr = address;
249 regs->pc = entry->fixup;
250 return;
251 }
252
253 /* Oops. The kernel tried to access some bad page. We'll have to
254 * terminate things with extreme prejudice.
255 */
256 pr_alert("Unable to handle kernel paging request at virtual "
257 "address %08lx\n pc = %08lx, ra = %08lx\n",
258 address, regs->pc, regs->areg[0]);
259 die("Oops", regs, sig);
260 do_exit(sig);
261 }
262