1 /*
2 * arch/cris/mm/fault.c
3 *
4 * Copyright (C) 2000-2010 Axis Communications AB
5 */
6
7 #include <linux/mm.h>
8 #include <linux/interrupt.h>
9 #include <linux/module.h>
10 #include <linux/wait.h>
11 #include <linux/uaccess.h>
12 #include <arch/system.h>
13
14 extern int find_fixup_code(struct pt_regs *);
15 extern void die_if_kernel(const char *, struct pt_regs *, long);
16 extern void show_registers(struct pt_regs *regs);
17
18 /* debug of low-level TLB reload */
19 #undef DEBUG
20
21 #ifdef DEBUG
22 #define D(x) x
23 #else
24 #define D(x)
25 #endif
26
27 /* debug of higher-level faults */
28 #define DPG(x)
29
30 /* current active page directory */
31
32 DEFINE_PER_CPU(pgd_t *, current_pgd);
33 unsigned long cris_signal_return_page;
34
35 /*
36 * This routine handles page faults. It determines the address,
37 * and the problem, and then passes it off to one of the appropriate
38 * routines.
39 *
40 * Notice that the address we're given is aligned to the page the fault
41 * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
42 * address.
43 *
44 * error_code:
45 * bit 0 == 0 means no page found, 1 means protection fault
46 * bit 1 == 0 means read, 1 means write
47 *
48 * If this routine detects a bad access, it returns 1, otherwise it
49 * returns 0.
50 */
51
52 asmlinkage void
do_page_fault(unsigned long address,struct pt_regs * regs,int protection,int writeaccess)53 do_page_fault(unsigned long address, struct pt_regs *regs,
54 int protection, int writeaccess)
55 {
56 struct task_struct *tsk;
57 struct mm_struct *mm;
58 struct vm_area_struct * vma;
59 siginfo_t info;
60 int fault;
61 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
62
63 D(printk(KERN_DEBUG
64 "Page fault for %lX on %X at %lX, prot %d write %d\n",
65 address, smp_processor_id(), instruction_pointer(regs),
66 protection, writeaccess));
67
68 tsk = current;
69
70 /*
71 * We fault-in kernel-space virtual memory on-demand. The
72 * 'reference' page table is init_mm.pgd.
73 *
74 * NOTE! We MUST NOT take any locks for this case. We may
75 * be in an interrupt or a critical region, and should
76 * only copy the information from the master page table,
77 * nothing more.
78 *
79 * NOTE2: This is done so that, when updating the vmalloc
80 * mappings we don't have to walk all processes pgdirs and
81 * add the high mappings all at once. Instead we do it as they
82 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
83 * bit set so sometimes the TLB can use a lingering entry.
84 *
85 * This verifies that the fault happens in kernel space
86 * and that the fault was not a protection error (error_code & 1).
87 */
88
89 if (address >= VMALLOC_START &&
90 !protection &&
91 !user_mode(regs))
92 goto vmalloc_fault;
93
94 /* When stack execution is not allowed we store the signal
95 * trampolines in the reserved cris_signal_return_page.
96 * Handle this in the exact same way as vmalloc (we know
97 * that the mapping is there and is valid so no need to
98 * call handle_mm_fault).
99 */
100 if (cris_signal_return_page &&
101 address == cris_signal_return_page &&
102 !protection && user_mode(regs))
103 goto vmalloc_fault;
104
105 /* we can and should enable interrupts at this point */
106 local_irq_enable();
107
108 mm = tsk->mm;
109 info.si_code = SEGV_MAPERR;
110
111 /*
112 * If we're in an interrupt, have pagefaults disabled or have no
113 * user context, we must not take the fault.
114 */
115
116 if (faulthandler_disabled() || !mm)
117 goto no_context;
118
119 if (user_mode(regs))
120 flags |= FAULT_FLAG_USER;
121 retry:
122 down_read(&mm->mmap_sem);
123 vma = find_vma(mm, address);
124 if (!vma)
125 goto bad_area;
126 if (vma->vm_start <= address)
127 goto good_area;
128 if (!(vma->vm_flags & VM_GROWSDOWN))
129 goto bad_area;
130 if (user_mode(regs)) {
131 /*
132 * accessing the stack below usp is always a bug.
133 * we get page-aligned addresses so we can only check
134 * if we're within a page from usp, but that might be
135 * enough to catch brutal errors at least.
136 */
137 if (address + PAGE_SIZE < rdusp())
138 goto bad_area;
139 }
140 if (expand_stack(vma, address))
141 goto bad_area;
142
143 /*
144 * Ok, we have a good vm_area for this memory access, so
145 * we can handle it..
146 */
147
148 good_area:
149 info.si_code = SEGV_ACCERR;
150
151 /* first do some preliminary protection checks */
152
153 if (writeaccess == 2){
154 if (!(vma->vm_flags & VM_EXEC))
155 goto bad_area;
156 } else if (writeaccess == 1) {
157 if (!(vma->vm_flags & VM_WRITE))
158 goto bad_area;
159 flags |= FAULT_FLAG_WRITE;
160 } else {
161 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
162 goto bad_area;
163 }
164
165 /*
166 * If for any reason at all we couldn't handle the fault,
167 * make sure we exit gracefully rather than endlessly redo
168 * the fault.
169 */
170
171 fault = handle_mm_fault(mm, vma, address, flags);
172
173 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
174 return;
175
176 if (unlikely(fault & VM_FAULT_ERROR)) {
177 if (fault & VM_FAULT_OOM)
178 goto out_of_memory;
179 else if (fault & VM_FAULT_SIGSEGV)
180 goto bad_area;
181 else if (fault & VM_FAULT_SIGBUS)
182 goto do_sigbus;
183 BUG();
184 }
185
186 if (flags & FAULT_FLAG_ALLOW_RETRY) {
187 if (fault & VM_FAULT_MAJOR)
188 tsk->maj_flt++;
189 else
190 tsk->min_flt++;
191 if (fault & VM_FAULT_RETRY) {
192 flags &= ~FAULT_FLAG_ALLOW_RETRY;
193 flags |= FAULT_FLAG_TRIED;
194
195 /*
196 * No need to up_read(&mm->mmap_sem) as we would
197 * have already released it in __lock_page_or_retry
198 * in mm/filemap.c.
199 */
200
201 goto retry;
202 }
203 }
204
205 up_read(&mm->mmap_sem);
206 return;
207
208 /*
209 * Something tried to access memory that isn't in our memory map..
210 * Fix it, but check if it's kernel or user first..
211 */
212
213 bad_area:
214 up_read(&mm->mmap_sem);
215
216 bad_area_nosemaphore:
217 DPG(show_registers(regs));
218
219 /* User mode accesses just cause a SIGSEGV */
220
221 if (user_mode(regs)) {
222 #ifdef CONFIG_NO_SEGFAULT_TERMINATION
223 DECLARE_WAIT_QUEUE_HEAD(wq);
224 #endif
225 printk(KERN_NOTICE "%s (pid %d) segfaults for page "
226 "address %08lx at pc %08lx\n",
227 tsk->comm, tsk->pid,
228 address, instruction_pointer(regs));
229
230 /* With DPG on, we've already dumped registers above. */
231 DPG(if (0))
232 show_registers(regs);
233
234 #ifdef CONFIG_NO_SEGFAULT_TERMINATION
235 wait_event_interruptible(wq, 0 == 1);
236 #else
237 info.si_signo = SIGSEGV;
238 info.si_errno = 0;
239 /* info.si_code has been set above */
240 info.si_addr = (void *)address;
241 force_sig_info(SIGSEGV, &info, tsk);
242 #endif
243 return;
244 }
245
246 no_context:
247
248 /* Are we prepared to handle this kernel fault?
249 *
250 * (The kernel has valid exception-points in the source
251 * when it accesses user-memory. When it fails in one
252 * of those points, we find it in a table and do a jump
253 * to some fixup code that loads an appropriate error
254 * code)
255 */
256
257 if (find_fixup_code(regs))
258 return;
259
260 /*
261 * Oops. The kernel tried to access some bad page. We'll have to
262 * terminate things with extreme prejudice.
263 */
264
265 if (!oops_in_progress) {
266 oops_in_progress = 1;
267 if ((unsigned long) (address) < PAGE_SIZE)
268 printk(KERN_ALERT "Unable to handle kernel NULL "
269 "pointer dereference");
270 else
271 printk(KERN_ALERT "Unable to handle kernel access"
272 " at virtual address %08lx\n", address);
273
274 die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
275 oops_in_progress = 0;
276 }
277
278 do_exit(SIGKILL);
279
280 /*
281 * We ran out of memory, or some other thing happened to us that made
282 * us unable to handle the page fault gracefully.
283 */
284
285 out_of_memory:
286 up_read(&mm->mmap_sem);
287 if (!user_mode(regs))
288 goto no_context;
289 pagefault_out_of_memory();
290 return;
291
292 do_sigbus:
293 up_read(&mm->mmap_sem);
294
295 /*
296 * Send a sigbus, regardless of whether we were in kernel
297 * or user mode.
298 */
299 info.si_signo = SIGBUS;
300 info.si_errno = 0;
301 info.si_code = BUS_ADRERR;
302 info.si_addr = (void *)address;
303 force_sig_info(SIGBUS, &info, tsk);
304
305 /* Kernel mode? Handle exceptions or die */
306 if (!user_mode(regs))
307 goto no_context;
308 return;
309
310 vmalloc_fault:
311 {
312 /*
313 * Synchronize this task's top level page-table
314 * with the 'reference' page table.
315 *
316 * Use current_pgd instead of tsk->active_mm->pgd
317 * since the latter might be unavailable if this
318 * code is executed in a misfortunately run irq
319 * (like inside schedule() between switch_mm and
320 * switch_to...).
321 */
322
323 int offset = pgd_index(address);
324 pgd_t *pgd, *pgd_k;
325 pud_t *pud, *pud_k;
326 pmd_t *pmd, *pmd_k;
327 pte_t *pte_k;
328
329 pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
330 pgd_k = init_mm.pgd + offset;
331
332 /* Since we're two-level, we don't need to do both
333 * set_pgd and set_pmd (they do the same thing). If
334 * we go three-level at some point, do the right thing
335 * with pgd_present and set_pgd here.
336 *
337 * Also, since the vmalloc area is global, we don't
338 * need to copy individual PTE's, it is enough to
339 * copy the pgd pointer into the pte page of the
340 * root task. If that is there, we'll find our pte if
341 * it exists.
342 */
343
344 pud = pud_offset(pgd, address);
345 pud_k = pud_offset(pgd_k, address);
346 if (!pud_present(*pud_k))
347 goto no_context;
348
349 pmd = pmd_offset(pud, address);
350 pmd_k = pmd_offset(pud_k, address);
351
352 if (!pmd_present(*pmd_k))
353 goto bad_area_nosemaphore;
354
355 set_pmd(pmd, *pmd_k);
356
357 /* Make sure the actual PTE exists as well to
358 * catch kernel vmalloc-area accesses to non-mapped
359 * addresses. If we don't do this, this will just
360 * silently loop forever.
361 */
362
363 pte_k = pte_offset_kernel(pmd_k, address);
364 if (!pte_present(*pte_k))
365 goto no_context;
366
367 return;
368 }
369 }
370
371 /* Find fixup code. */
372 int
find_fixup_code(struct pt_regs * regs)373 find_fixup_code(struct pt_regs *regs)
374 {
375 const struct exception_table_entry *fixup;
376 /* in case of delay slot fault (v32) */
377 unsigned long ip = (instruction_pointer(regs) & ~0x1);
378
379 fixup = search_exception_tables(ip);
380 if (fixup != 0) {
381 /* Adjust the instruction pointer in the stackframe. */
382 instruction_pointer(regs) = fixup->fixup;
383 arch_fixup(regs);
384 return 1;
385 }
386
387 return 0;
388 }
389