aboutsummaryrefslogtreecommitdiff
path: root/arch/avr32/mm/fault.c
blob: 678557260a356fd28fb86fb5046e84dadc9fd873 (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
/*
 * Copyright (C) 2004-2006 Atmel Corporation
 *
 * Based on linux/arch/sh/mm/fault.c:
 *   Copyright (C) 1999  Niibe Yutaka
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/mm.h>
#include <linux/module.h>
#include <linux/pagemap.h>

#include <asm/kdebug.h>
#include <asm/mmu_context.h>
#include <asm/sysreg.h>
#include <asm/uaccess.h>
#include <asm/tlb.h>

#ifdef DEBUG
static void dump_code(unsigned long pc)
{
	char *p = (char *)pc;
	char val;
	int i;


	printk(KERN_DEBUG "Code:");
	for (i = 0; i < 16; i++) {
		if (__get_user(val, p + i))
			break;
		printk(" %02x", val);
	}
	printk("\n");
}
#endif

#ifdef CONFIG_KPROBES
ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);

/* Hook to register for page fault notifications */
int register_page_fault_notifier(struct notifier_block *nb)
{
	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
}

int unregister_page_fault_notifier(struct notifier_block *nb)
{
	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
}

static inline int notify_page_fault(enum die_val val, struct pt_regs *regs,
				    int trap, int sig)
{
	struct die_args args = {
		.regs = regs,
		.trapnr = trap,
	};
	return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
}
#else
static inline int notify_page_fault(enum die_val val, struct pt_regs *regs,
				    int trap, int sig)
{
	return NOTIFY_DONE;
}
#endif

/*
 * This routine handles page faults. It determines the address and the
 * problem, and then passes it off to one of the appropriate routines.
 *
 * ecr is the Exception Cause Register. Possible values are:
 *   5:  Page not found (instruction access)
 *   6:  Protection fault (instruction access)
 *   12: Page not found (read access)
 *   13: Page not found (write access)
 *   14: Protection fault (read access)
 *   15: Protection fault (write access)
 */
asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
{
	struct task_struct *tsk;
	struct mm_struct *mm;
	struct vm_area_struct *vma;
	const struct exception_table_entry *fixup;
	unsigned long address;
	unsigned long page;
	int writeaccess = 0;

	if (notify_page_fault(DIE_PAGE_FAULT, regs,
			      ecr, SIGSEGV) == NOTIFY_STOP)
		return;

	address = sysreg_read(TLBEAR);

	tsk = current;
	mm = tsk->mm;

	/*
	 * If we're in an interrupt or have no user context, we must
	 * not take the fault...
	 */
	if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
		goto no_context;

	local_irq_enable();

	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 (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:
	//pr_debug("good area: vm_flags = 0x%lx\n", vma->vm_flags);
	switch (ecr) {
	case ECR_PROTECTION_X:
	case ECR_TLB_MISS_X:
		if (!(vma->vm_flags & VM_EXEC))
			goto bad_area;
		break;
	case ECR_PROTECTION_R:
	case ECR_TLB_MISS_R:
		if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
			goto bad_area;
		break;
	case ECR_PROTECTION_W:
	case ECR_TLB_MISS_W:
		if (!(vma->vm_flags & VM_WRITE))
			goto bad_area;
		writeaccess = 1;
		break;
	default:
		panic("Unhandled case %lu in do_page_fault!", ecr);
	}

	/*
	 * If for any reason at all we couldn't handle the fault, make
	 * sure we exit gracefully rather than endlessly redo the
	 * fault.
	 */
survive:
	switch (handle_mm_fault(mm, vma, address, writeaccess)) {
	case VM_FAULT_MINOR:
		tsk->min_flt++;
		break;
	case VM_FAULT_MAJOR:
		tsk->maj_flt++;
		break;
	case VM_FAULT_SIGBUS:
		goto do_sigbus;
	case VM_FAULT_OOM:
		goto out_of_memory;
	default:
		BUG();
	}

	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:
	pr_debug("Bad area [%s:%u]: addr %08lx, ecr %lu\n",
		 tsk->comm, tsk->pid, address, ecr);

	up_read(&mm->mmap_sem);

	if (user_mode(regs)) {
		/* Hmm...we have to pass address and ecr somehow... */
		/* tsk->thread.address = address;
		   tsk->thread.error_code = ecr; */
#ifdef DEBUG
		show_regs(regs);
		dump_code(regs->pc);

		page = sysreg_read(PTBR);
		printk("ptbr = %08lx", page);
		if (page) {
			page = ((unsigned long *)page)[address >> 22];
			printk(" pgd = %08lx", page);
			if (page & _PAGE_PRESENT) {
				page &= PAGE_MASK;
				address &= 0x003ff000;
				page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
				printk(" pte = %08lx\n", page);
			}
		}
#endif
		pr_debug("Sending SIGSEGV to PID %d...\n",
			tsk->pid);
		force_sig(SIGSEGV, tsk);
		return;
	}

no_context:
	pr_debug("No context\n");

	/* Are we prepared to handle this kernel fault? */
	fixup = search_exception_tables(regs->pc);
	if (fixup) {
		regs->pc = fixup->fixup;
		pr_debug("Found fixup at %08lx\n", fixup->fixup);
		return;
	}

	/*
	 * Oops. The kernel tried to access some bad page. We'll have
	 * to terminate things with extreme prejudice.
	 */
	if (address < PAGE_SIZE)
		printk(KERN_ALERT
		       "Unable to handle kernel NULL pointer dereference");
	else
		printk(KERN_ALERT
		       "Unable to handle kernel paging request");
	printk(" at virtual address %08lx\n", address);
	printk(KERN_ALERT "pc = %08lx\n", regs->pc);

	page = sysreg_read(PTBR);
	printk(KERN_ALERT "ptbr = %08lx", page);
	if (page) {
		page = ((unsigned long *)page)[address >> 22];
		printk(" pgd = %08lx", page);
		if (page & _PAGE_PRESENT) {
			page &= PAGE_MASK;
			address &= 0x003ff000;
			page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
			printk(" pte = %08lx\n", page);
		}
	}
	die("\nOops", regs, ecr);
	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:
	printk("Out of memory\n");
	up_read(&mm->mmap_sem);
	if (current->pid == 1) {
		yield();
		down_read(&mm->mmap_sem);
		goto survive;
	}
	printk("VM: Killing process %s\n", tsk->comm);
	if (user_mode(regs))
		do_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.
	 */
	/* address, error_code, trap_no, ... */
#ifdef DEBUG
	show_regs(regs);
	dump_code(regs->pc);
#endif
	pr_debug("Sending SIGBUS to PID %d...\n", tsk->pid);
	force_sig(SIGBUS, tsk);

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

asmlinkage void do_bus_error(unsigned long addr, int write_access,
			     struct pt_regs *regs)
{
	printk(KERN_ALERT
	       "Bus error at physical address 0x%08lx (%s access)\n",
	       addr, write_access ? "write" : "read");
	printk(KERN_INFO "DTLB dump:\n");
	dump_dtlb();
	die("Bus Error", regs, write_access);
	do_exit(SIGKILL);
}

/*
 * This functionality is currently not possible to implement because
 * we're using segmentation to ensure a fixed mapping of the kernel
 * virtual address space.
 *
 * It would be possible to implement this, but it would require us to
 * disable segmentation at startup and load the kernel mappings into
 * the TLB like any other pages. There will be lots of trickery to
 * avoid recursive invocation of the TLB miss handler, though...
 */
#ifdef CONFIG_DEBUG_PAGEALLOC
void kernel_map_pages(struct page *page, int numpages, int enable)
{

}
EXPORT_SYMBOL(kernel_map_pages);
#endif