aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/mm/kmemcheck/error.c
blob: af3b6c8a436f7b7ec49a2366738a28faa58cdfc5 (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
#include <linux/interrupt.h>
#include <linux/kdebug.h>
#include <linux/kmemcheck.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/stacktrace.h>
#include <linux/string.h>

#include "error.h"
#include "shadow.h"

enum kmemcheck_error_type {
	KMEMCHECK_ERROR_INVALID_ACCESS,
	KMEMCHECK_ERROR_BUG,
};

#define SHADOW_COPY_SIZE (1 << CONFIG_KMEMCHECK_SHADOW_COPY_SHIFT)

struct kmemcheck_error {
	enum kmemcheck_error_type type;

	union {
		/* KMEMCHECK_ERROR_INVALID_ACCESS */
		struct {
			/* Kind of access that caused the error */
			enum kmemcheck_shadow state;
			/* Address and size of the erroneous read */
			unsigned long	address;
			unsigned int	size;
		};
	};

	struct pt_regs		regs;
	struct stack_trace	trace;
	unsigned long		trace_entries[32];

	/* We compress it to a char. */
	unsigned char		shadow_copy[SHADOW_COPY_SIZE];
	unsigned char		memory_copy[SHADOW_COPY_SIZE];
};

/*
 * Create a ring queue of errors to output. We can't call printk() directly
 * from the kmemcheck traps, since this may call the console drivers and
 * result in a recursive fault.
 */
static struct kmemcheck_error error_fifo[CONFIG_KMEMCHECK_QUEUE_SIZE];
static unsigned int error_count;
static unsigned int error_rd;
static unsigned int error_wr;
static unsigned int error_missed_count;

static struct kmemcheck_error *error_next_wr(void)
{
	struct kmemcheck_error *e;

	if (error_count == ARRAY_SIZE(error_fifo)) {
		++error_missed_count;
		return NULL;
	}

	e = &error_fifo[error_wr];
	if (++error_wr == ARRAY_SIZE(error_fifo))
		error_wr = 0;
	++error_count;
	return e;
}

static struct kmemcheck_error *error_next_rd(void)
{
	struct kmemcheck_error *e;

	if (error_count == 0)
		return NULL;

	e = &error_fifo[error_rd];
	if (++error_rd == ARRAY_SIZE(error_fifo))
		error_rd = 0;
	--error_count;
	return e;
}

void kmemcheck_error_recall(void)
{
	static const char *desc[] = {
		[KMEMCHECK_SHADOW_UNALLOCATED]		= "unallocated",
		[KMEMCHECK_SHADOW_UNINITIALIZED]	= "uninitialized",
		[KMEMCHECK_SHADOW_INITIALIZED]		= "initialized",
		[KMEMCHECK_SHADOW_FREED]		= "freed",
	};

	static const char short_desc[] = {
		[KMEMCHECK_SHADOW_UNALLOCATED]		= 'a',
		[KMEMCHECK_SHADOW_UNINITIALIZED]	= 'u',
		[KMEMCHECK_SHADOW_INITIALIZED]		= 'i',
		[KMEMCHECK_SHADOW_FREED]		= 'f',
	};

	struct kmemcheck_error *e;
	unsigned int i;

	e = error_next_rd();
	if (!e)
		return;

	switch (e->type) {
	case KMEMCHECK_ERROR_INVALID_ACCESS:
		printk(KERN_WARNING "WARNING: kmemcheck: Caught %d-bit read from %s memory (%p)\n",
			8 * e->size, e->state < ARRAY_SIZE(desc) ?
				desc[e->state] : "(invalid shadow state)",
			(void *) e->address);

		printk(KERN_WARNING);
		for (i = 0; i < SHADOW_COPY_SIZE; ++i)
			printk(KERN_CONT "%02x", e->memory_copy[i]);
		printk(KERN_CONT "\n");

		printk(KERN_WARNING);
		for (i = 0; i < SHADOW_COPY_SIZE; ++i) {
			if (e->shadow_copy[i] < ARRAY_SIZE(short_desc))
				printk(KERN_CONT " %c", short_desc[e->shadow_copy[i]]);
			else
				printk(KERN_CONT " ?");
		}
		printk(KERN_CONT "\n");
		printk(KERN_WARNING "%*c\n", 2 + 2
			* (int) (e->address & (SHADOW_COPY_SIZE - 1)), '^');
		break;
	case KMEMCHECK_ERROR_BUG:
		printk(KERN_EMERG "ERROR: kmemcheck: Fatal error\n");
		break;
	}

	__show_regs(&e->regs, 1);
	print_stack_trace(&e->trace, 0);
}

static void do_wakeup(unsigned long data)
{
	while (error_count > 0)
		kmemcheck_error_recall();

	if (error_missed_count > 0) {
		printk(KERN_WARNING "kmemcheck: Lost %d error reports because "
			"the queue was too small\n", error_missed_count);
		error_missed_count = 0;
	}
}

static DECLARE_TASKLET(kmemcheck_tasklet, &do_wakeup, 0);

/*
 * Save the context of an error report.
 */
void kmemcheck_error_save(enum kmemcheck_shadow state,
	unsigned long address, unsigned int size, struct pt_regs *regs)
{
	static unsigned long prev_ip;

	struct kmemcheck_error *e;
	void *shadow_copy;
	void *memory_copy;

	/* Don't report several adjacent errors from the same EIP. */
	if (regs->ip == prev_ip)
		return;
	prev_ip = regs->ip;

	e = error_next_wr();
	if (!e)
		return;

	e->type = KMEMCHECK_ERROR_INVALID_ACCESS;

	e->state = state;
	e->address = address;
	e->size = size;

	/* Save regs */
	memcpy(&e->regs, regs, sizeof(*regs));

	/* Save stack trace */
	e->trace.nr_entries = 0;
	e->trace.entries = e->trace_entries;
	e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
	e->trace.skip = 0;
	save_stack_trace_bp(&e->trace, regs->bp);

	/* Round address down to nearest 16 bytes */
	shadow_copy = kmemcheck_shadow_lookup(address
		& ~(SHADOW_COPY_SIZE - 1));
	BUG_ON(!shadow_copy);

	memcpy(e->shadow_copy, shadow_copy, SHADOW_COPY_SIZE);

	kmemcheck_show_addr(address);
	memory_copy = (void *) (address & ~(SHADOW_COPY_SIZE - 1));
	memcpy(e->memory_copy, memory_copy, SHADOW_COPY_SIZE);
	kmemcheck_hide_addr(address);

	tasklet_hi_schedule_first(&kmemcheck_tasklet);
}

/*
 * Save the context of a kmemcheck bug.
 */
void kmemcheck_error_save_bug(struct pt_regs *regs)
{
	struct kmemcheck_error *e;

	e = error_next_wr();
	if (!e)
		return;

	e->type = KMEMCHECK_ERROR_BUG;

	memcpy(&e->regs, regs, sizeof(*regs));

	e->trace.nr_entries = 0;
	e->trace.entries = e->trace_entries;
	e->trace.max_entries = ARRAY_SIZE(e->trace_entries);
	e->trace.skip = 1;
	save_stack_trace(&e->trace);

	tasklet_hi_schedule_first(&kmemcheck_tasklet);
}