aboutsummaryrefslogtreecommitdiffstats
path: root/payloads/libpayload/gdb/transport.c
blob: 22983e1bc095fe4e79f062b570dd696bb27e7d8e (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
/*
 * Copyright 2014 Google Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but without any warranty; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <endian.h>
#include <gdb.h>
#include <libpayload.h>

/* MMIO word size is not standardized, but *usually* 32 (even on ARM64) */
typedef u32 mmio_word_t;

static const int timeout_us = 100 * 1000;
static const char output_overrun[] = "GDB output buffer overrun (try "
				     "increasing reply.size)!\n";
static const char input_underrun[] = "GDB input message truncated (bug or "
				     "communication problem)?\n";

/* Serial-specific glue code... add more transport layers here when desired. */

static void gdb_raw_putchar(u8 c)
{
	serial_putchar(c);
}

static int gdb_raw_getchar(void)
{
	u64 start = timer_us(0);

	while (!serial_havechar())
		if (timer_us(start) > timeout_us)
			return -1;

	return serial_getchar();
}

void gdb_transport_init(void)
{
	console_remove_output_driver(serial_putchar);
}

void gdb_transport_teardown(void)
{
	serial_console_init();
}

/* Hex digit character <-> number conversion (illegal chars undefined!). */

static u8 from_hex(unsigned char c)
{
	static const s8 values[] = {
		-1, 10, 11, 12, 13, 14, 15, -1,
		-1, -1, -1, -1, -1, -1, -1, -1,
		 0,  1,  2,  3,  4,  5,  6,  7,
		 8,  9, -1, -1, -1, -1, -1, -1,
	};

	return values[c & 0x1f];
}

static char to_hex(u8 v)
{
	static const char digits[] = "0123456789abcdef";

	return digits[v & 0xf];
}

/* Message encode/decode functions (must access whole aligned words for MMIO) */

void gdb_message_encode_bytes(struct gdb_message *message, const void *data,
			      int length)
{
	die_if(message->used + length * 2 > message->size, output_overrun);
	const mmio_word_t *aligned =
		(mmio_word_t *)ALIGN_DOWN((uintptr_t)data, sizeof(*aligned));
	mmio_word_t word = be32toh(readl(aligned++));
	while (length--) {
		u8 byte = (word >> ((((void *)aligned - data) - 1) * 8));
		message->buf[message->used++] = to_hex(byte >> 4);
		message->buf[message->used++] = to_hex(byte & 0xf);
		if (length && ++data == (void *)aligned)
			word = be32toh(readl(aligned++));
	}
}

void gdb_message_decode_bytes(const struct gdb_message *message, int offset,
			      void *data, int length)
{
	die_if(offset + 2 * length > message->used, "Decode overrun in GDB "
		"message: %.*s", message->used, message->buf);
	mmio_word_t *aligned =
		(mmio_word_t *)ALIGN_DOWN((uintptr_t)data, sizeof(*aligned));
	int shift = ((void *)(aligned + 1) - data) * 8;
	mmio_word_t word = be32toh(readl(aligned)) >> shift;
	while (length--) {
		word <<= 8;
		word |= from_hex(message->buf[offset++]) << 4;
		word |= from_hex(message->buf[offset++]);
		if (++data - (void *)aligned == sizeof(*aligned))
			writel(htobe32(word), aligned++);
	}
	if (data != (void *)aligned) {
		shift = ((void *)(aligned + 1) - data) * 8;
		clrsetbits_be32(aligned, ~((1 << shift) - 1), word << shift);
	}
}

void gdb_message_encode_zero_bytes(struct gdb_message *message, int length)
{
	die_if(message->used + length * 2 > message->size, output_overrun);
	memset(message->buf + message->used, '0', length * 2);
	message->used += length * 2;
}

void gdb_message_add_string(struct gdb_message *message, const char *string)
{
	message->used += strlcpy((char *)message->buf + message->used,
			     string, message->size - message->used);

	/* Check >= instead of > to account for strlcpy's trailing '\0'. */
	die_if(message->used >= message->size, output_overrun);
}

void gdb_message_encode_int(struct gdb_message *message, uintptr_t val)
{
	int length = sizeof(uintptr_t) * 2 - __builtin_clz(val) / 4;
	die_if(message->used + length > message->size, output_overrun);
	while (length--)
		message->buf[message->used++] =
			to_hex((val >> length * 4) & 0xf);
}

uintptr_t gdb_message_decode_int(const struct gdb_message *message, int offset,
				 int length)
{
	uintptr_t val = 0;

	die_if(length > sizeof(uintptr_t) * 2, "GDB decoding invalid number: "
	       "%.*s", message->used, message->buf);

	while (length--) {
		val <<= 4;
		val |= from_hex(message->buf[offset++]);
	}

	return val;
}

/* Like strtok/strsep: writes back offset argument, returns original offset. */
int gdb_message_tokenize(const struct gdb_message *message, int *offset)
{
	int token = *offset;
	while (!strchr(",;:", message->buf[(*offset)++]))
		die_if(*offset >= message->used, "Undelimited token in GDB "
				"message at offset %d: %.*s",
				token, message->used, message->buf);
	return token;
}

/* High-level send/receive functions. */

void gdb_get_command(struct gdb_message *command)
{
	enum command_state {
		STATE_WAITING,
		STATE_COMMAND,
		STATE_CHECKSUM0,
		STATE_CHECKSUM1,
	};

	u8 checksum = 0;
	u8 running_checksum = 0;
	enum command_state state = STATE_WAITING;

	while (1) {
		int c = gdb_raw_getchar();
		if (c < 0) {
			/*
			 * Timeout waiting for a byte. Reset the
			 * state machine.
			 */
			state = STATE_WAITING;
			continue;
		}

		switch (state) {
		case STATE_WAITING:
			if (c == '$') {
				running_checksum = 0;
				command->used = 0;
				state = STATE_COMMAND;
			}
			break;
		case STATE_COMMAND:
			if (c == '#') {
				state = STATE_CHECKSUM0;
				break;
			}
			die_if(command->used >= command->size, "GDB input buf"
			       "fer overrun (try increasing command.size)!\n");
			command->buf[command->used++] = c;
			running_checksum += c;
			break;
		case STATE_CHECKSUM0:
			checksum = from_hex(c) << 4;
			state = STATE_CHECKSUM1;
			break;
		case STATE_CHECKSUM1:
			checksum += from_hex(c);
			if (running_checksum == checksum) {
				gdb_raw_putchar('+');
				return;
			} else {
				state = STATE_WAITING;
				gdb_raw_putchar('-');
			}
			break;
		}
	}
}

void gdb_send_reply(const struct gdb_message *reply)
{
	int i;
	int retries = 1 * 1000 * 1000 / timeout_us;
	u8 checksum = 0;

	for (i = 0; i < reply->used; i++)
		checksum += reply->buf[i];

	do {
		gdb_raw_putchar('$');
		for (i = 0; i < reply->used; i++)
			gdb_raw_putchar(reply->buf[i]);
		gdb_raw_putchar('#');
		gdb_raw_putchar(to_hex(checksum >> 4));
		gdb_raw_putchar(to_hex(checksum & 0xf));
	} while (gdb_raw_getchar() != '+' && retries--);
}