summaryrefslogtreecommitdiffstats
path: root/arch/cris/mm/fault.c
blob: 3034f3ff950c6014f807ad03a898b1619ac9669c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
/*
 *  linux/arch/cris/mm/fault.c
 *
 *  Copyright (C) 2000, 2001  Axis Communications AB
 *
 *  Authors:  Bjorn Wesen 
 * 
 *  $Log: fault.c,v $
 *  Revision 1.20  2005/03/04 08:16:18  starvik
 *  Merge of Linux 2.6.11.
 *
 *  Revision 1.19  2005/01/14 10:07:59  starvik
 *  Fixed warning.
 *
 *  Revision 1.18  2005/01/12 08:10:14  starvik
 *  Re-added the change of frametype when handling kernel page fault fixup
 *  for v10. This is necessary to avoid that the CPU remakes the faulting
 *  access.
 *
 *  Revision 1.17  2005/01/11 13:53:05  starvik
 *  Use raw_printk.
 *
 *  Revision 1.16  2004/12/17 11:39:41  starvik
 *  SMP support.
 *
 *  Revision 1.15  2004/11/23 18:36:18  starvik
 *  Stack is now non-executable.
 *  Signal handler trampolines are placed in a reserved page mapped into all
 *  processes.
 *
 *  Revision 1.14  2004/11/23 07:10:21  starvik
 *  Moved find_fixup_code to generic code.
 *
 *  Revision 1.13  2004/11/23 07:00:54  starvik
 *  Actually use the execute permission bit in the MMU. This makes it possible
 *  to prevent e.g. attacks where executable code is put on the stack.
 *
 *  Revision 1.12  2004/09/29 06:16:04  starvik
 *  Use instruction_pointer
 *
 *  Revision 1.11  2004/05/14 07:58:05  starvik
 *  Merge of changes from 2.4
 *
 *  Revision 1.10  2003/10/27 14:51:24  starvik
 *  Removed debugcode
 *
 *  Revision 1.9  2003/10/27 14:50:42  starvik
 *  Changed do_page_fault signature
 *
 *  Revision 1.8  2003/07/04 13:02:48  tobiasa
 *  Moved code snippet from arch/cris/mm/fault.c that searches for fixup code
 *  to separate function in arch-specific files.
 *
 *  Revision 1.7  2003/01/22 06:48:38  starvik
 *  Fixed warnings issued by GCC 3.2.1
 *
 *  Revision 1.6  2003/01/09 14:42:52  starvik
 *  Merge of Linux 2.5.55
 *
 *  Revision 1.5  2002/12/11 14:44:48  starvik
 *  Extracted v10 (ETRAX 100LX) specific stuff to arch/cris/arch-v10/mm
 *
 *  Revision 1.4  2002/11/13 15:10:28  starvik
 *  pte_offset has been renamed to pte_offset_kernel
 *
 *  Revision 1.3  2002/11/05 06:45:13  starvik
 *  Merge of Linux 2.5.45
 *
 *  Revision 1.2  2001/12/18 13:35:22  bjornw
 *  Applied the 2.4.13->2.4.16 CRIS patch to 2.5.1 (is a copy of 2.4.15).
 *
 *  Revision 1.20  2001/11/22 13:34:06  bjornw
 *  * Bug workaround (LX TR89): force a rerun of the whole of an interrupted
 *    unaligned write, because the second half of the write will be corrupted
 *    otherwise. Affected unaligned writes spanning not-yet mapped pages.
 *  * Optimization: use the wr_rd bit in R_MMU_CAUSE to know whether a miss
 *    was due to a read or a write (before we didn't know this until the next
 *    restart of the interrupted instruction, thus wasting one fault-irq)
 *
 *  Revision 1.19  2001/11/12 19:02:10  pkj
 *  Fixed compiler warnings.
 *
 *  Revision 1.18  2001/07/18 22:14:32  bjornw
 *  Enable interrupts in the bulk of do_page_fault
 *
 *  Revision 1.17  2001/07/18 13:07:23  bjornw
 *  * Detect non-existant PTE's in vmalloc pmd synchronization
 *  * Remove comment about fast-paths for VMALLOC_START etc, because all that
 *    was totally bogus anyway it turned out :)
 *  * Fix detection of vmalloc-area synchronization
 *  * Add some comments
 *
 *  Revision 1.16  2001/06/13 00:06:08  bjornw
 *  current_pgd should be volatile
 *
 *  Revision 1.15  2001/06/13 00:02:23  bjornw
 *  Use a separate variable to store the current pgd to avoid races in schedule
 *
 *  Revision 1.14  2001/05/16 17:41:07  hp
 *  Last comment tweak further tweaked.
 *
 *  Revision 1.13  2001/05/15 00:58:44  hp
 *  Expand a bit on the comment why we compare address >= TASK_SIZE rather
 *  than >= VMALLOC_START.
 *
 *  Revision 1.12  2001/04/04 10:51:14  bjornw
 *  mmap_sem is grabbed for reading
 *
 *  Revision 1.11  2001/03/23 07:36:07  starvik
 *  Corrected according to review remarks
 *
 *  Revision 1.10  2001/03/21 16:10:11  bjornw
 *  CRIS_FRAME_FIXUP not needed anymore, use FRAME_NORMAL
 *
 *  Revision 1.9  2001/03/05 13:22:20  bjornw
 *  Spell-fix and fix in vmalloc_fault handling
 *
 *  Revision 1.8  2000/11/22 14:45:31  bjornw
 *  * 2.4.0-test10 removed the set_pgdir instantaneous kernel global mapping
 *    into all processes. Instead we fill in the missing PTE entries on demand.
 *
 *  Revision 1.7  2000/11/21 16:39:09  bjornw
 *  fixup switches frametype
 *
 *  Revision 1.6  2000/11/17 16:54:08  bjornw
 *  More detailed siginfo reporting
 *
 *
 */

#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <asm/uaccess.h>

extern int find_fixup_code(struct pt_regs *);
extern void die_if_kernel(const char *, struct pt_regs *, long);
extern int raw_printk(const char *fmt, ...);

/* debug of low-level TLB reload */
#undef DEBUG

#ifdef DEBUG
#define D(x) x
#else
#define D(x)
#endif

/* debug of higher-level faults */
#define DPG(x)

/* current active page directory */

volatile DEFINE_PER_CPU(pgd_t *,current_pgd);
unsigned long cris_signal_return_page;

/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * Notice that the address we're given is aligned to the page the fault
 * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
 * address.
 *
 * error_code:
 *	bit 0 == 0 means no page found, 1 means protection fault
 *	bit 1 == 0 means read, 1 means write
 *
 * If this routine detects a bad access, it returns 1, otherwise it
 * returns 0.
 */

asmlinkage void
do_page_fault(unsigned long address, struct pt_regs *regs,
	      int protection, int writeaccess)
{
	struct task_struct *tsk;
	struct mm_struct *mm;
	struct vm_area_struct * vma;
	siginfo_t info;
	int fault;

        D(printk("Page fault for %lX on %X at %lX, prot %d write %d\n",
                 address, smp_processor_id(), instruction_pointer(regs),
                 protection, writeaccess));

	tsk = current;

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * NOTE2: This is done so that, when updating the vmalloc
	 * mappings we don't have to walk all processes pgdirs and
	 * add the high mappings all at once. Instead we do it as they
	 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
	 * bit set so sometimes the TLB can use a lingering entry.
	 *
	 * This verifies that the fault happens in kernel space
	 * and that the fault was not a protection error (error_code & 1).
	 */

	if (address >= VMALLOC_START &&
	    !protection &&
	    !user_mode(regs))
		goto vmalloc_fault;

	/* When stack execution is not allowed we store the signal
	 * trampolines in the reserved cris_signal_return_page.
	 * Handle this in the exact same way as vmalloc (we know
	 * that the mapping is there and is valid so no need to
	 * call handle_mm_fault).
	 */
	if (cris_signal_return_page &&
	    address == cris_signal_return_page &&
	    !protection && user_mode(regs))
		goto vmalloc_fault;

	/* we can and should enable interrupts at this point */
	local_irq_enable();

	mm = tsk->mm;
	info.si_code = SEGV_MAPERR;

	/*
	 * If we're in an interrupt or have no user
	 * context, we must not take the fault..
	 */

	if (in_atomic() || !mm)
		goto no_context;

	down_read(&mm->mmap_sem);
	vma = find_vma(mm, address);
	if (!vma)
		goto bad_area;
	if (vma->vm_start <= address)
		goto good_area;
	if (!(vma->vm_flags & VM_GROWSDOWN))
		goto bad_area;
	if (user_mode(regs)) {
		/*
		 * accessing the stack below usp is always a bug.
		 * we get page-aligned addresses so we can only check
		 * if we're within a page from usp, but that might be
		 * enough to catch brutal errors at least.
		 */
		if (address + PAGE_SIZE < rdusp())
			goto bad_area;
	}
	if (expand_stack(vma, address))
		goto bad_area;

	/*
	 * Ok, we have a good vm_area for this memory access, so
	 * we can handle it..
	 */

 good_area:
	info.si_code = SEGV_ACCERR;

	/* first do some preliminary protection checks */

	if (writeaccess == 2){
		if (!(vma->vm_flags & VM_EXEC))
			goto bad_area;
	} else if (writeaccess == 1) {
		if (!(vma->vm_flags & VM_WRITE))
			goto bad_area;
	} else {
		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
			goto bad_area;
	}

	/*
	 * If for any reason at all we couldn't handle the fault,
	 * make sure we exit gracefully rather than endlessly redo
	 * the fault.
	 */

	fault = handle_mm_fault(mm, vma, address, writeaccess & 1);
	if (unlikely(fault & VM_FAULT_ERROR)) {
		if (fault & VM_FAULT_OOM)
			goto out_of_memory;
		else if (fault & VM_FAULT_SIGBUS)
			goto do_sigbus;
		BUG();
	}
	if (fault & VM_FAULT_MAJOR)
		tsk->maj_flt++;
	else
		tsk->min_flt++;

	up_read(&mm->mmap_sem);
	return;

	/*
	 * Something tried to access memory that isn't in our memory map..
	 * Fix it, but check if it's kernel or user first..
	 */

 bad_area:
	up_read(&mm->mmap_sem);

 bad_area_nosemaphore:
	DPG(show_registers(regs));

	/* User mode accesses just cause a SIGSEGV */

	if (user_mode(regs)) {
		info.si_signo = SIGSEGV;
		info.si_errno = 0;
		/* info.si_code has been set above */
		info.si_addr = (void *)address;
		force_sig_info(SIGSEGV, &info, tsk);
		return;
	}

 no_context:

	/* Are we prepared to handle this kernel fault?
	 *
	 * (The kernel has valid exception-points in the source 
	 *  when it acesses user-memory. When it fails in one
	 *  of those points, we find it in a table and do a jump
	 *  to some fixup code that loads an appropriate error
	 *  code)
	 */

	if (find_fixup_code(regs))
		return;

	/*
	 * Oops. The kernel tried to access some bad page. We'll have to
	 * terminate things with extreme prejudice.
	 */

	if ((unsigned long) (address) < PAGE_SIZE)
		raw_printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
	else
		raw_printk(KERN_ALERT "Unable to handle kernel access");
	raw_printk(" at virtual address %08lx\n",address);

	die_if_kernel("Oops", regs, (writeaccess << 1) | protection);

	do_exit(SIGKILL);

	/*
	 * We ran out of memory, or some other thing happened to us that made
	 * us unable to handle the page fault gracefully.
	 */

 out_of_memory:
	up_read(&mm->mmap_sem);
	printk("VM: killing process %s\n", tsk->comm);
	if (user_mode(regs))
		do_group_exit(SIGKILL);
	goto no_context;

 do_sigbus:
	up_read(&mm->mmap_sem);

	/*
	 * Send a sigbus, regardless of whether we were in kernel
	 * or user mode.
	 */
	info.si_signo = SIGBUS;
	info.si_errno = 0;
	info.si_code = BUS_ADRERR;
	info.si_addr = (void *)address;
	force_sig_info(SIGBUS, &info, tsk);

	/* Kernel mode? Handle exceptions or die */
	if (!user_mode(regs))
		goto no_context;
	return;

vmalloc_fault:
	{
		/*
		 * Synchronize this task's top level page-table
		 * with the 'reference' page table.
		 *
		 * Use current_pgd instead of tsk->active_mm->pgd
		 * since the latter might be unavailable if this
		 * code is executed in a misfortunately run irq
		 * (like inside schedule() between switch_mm and
		 *  switch_to...).
		 */

		int offset = pgd_index(address);
		pgd_t *pgd, *pgd_k;
		pud_t *pud, *pud_k;
		pmd_t *pmd, *pmd_k;
		pte_t *pte_k;

		pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
		pgd_k = init_mm.pgd + offset;

		/* Since we're two-level, we don't need to do both
		 * set_pgd and set_pmd (they do the same thing). If
		 * we go three-level at some point, do the right thing
		 * with pgd_present and set_pgd here. 
		 * 
		 * Also, since the vmalloc area is global, we don't
		 * need to copy individual PTE's, it is enough to
		 * copy the pgd pointer into the pte page of the
		 * root task. If that is there, we'll find our pte if
		 * it exists.
		 */

		pud = pud_offset(pgd, address);
		pud_k = pud_offset(pgd_k, address);
		if (!pud_present(*pud_k))
			goto no_context;

		pmd = pmd_offset(pud, address);
		pmd_k = pmd_offset(pud_k, address);

		if (!pmd_present(*pmd_k))
			goto bad_area_nosemaphore;

		set_pmd(pmd, *pmd_k);

		/* Make sure the actual PTE exists as well to
		 * catch kernel vmalloc-area accesses to non-mapped
		 * addresses. If we don't do this, this will just
		 * silently loop forever.
		 */

		pte_k = pte_offset_kernel(pmd_k, address);
		if (!pte_present(*pte_k))
			goto no_context;

		return;
	}
}

/* Find fixup code. */
int
find_fixup_code(struct pt_regs *regs)
{
	const struct exception_table_entry *fixup;

	if ((fixup = search_exception_tables(instruction_pointer(regs))) != 0) {
		/* Adjust the instruction pointer in the stackframe. */
		instruction_pointer(regs) = fixup->fixup;
		arch_fixup(regs);
		return 1;
	}

	return 0;
}