1/* Copyright 2012 The Chromium OS Authors. All rights reserved.
2 * Use of this source code is governed by a BSD-style license that can be
3 * found in the LICENSE file.
4 *
5 * Exports the kernel commandline from a given partition/image.
6 */
7
8#include <stdio.h>
9#include <string.h>
10#include <sys/mman.h>
11#include <sys/fcntl.h>
12#include <sys/stat.h>
13#include <sys/types.h>
14#include <unistd.h>
15
16#include "host_common.h"
17#include "kernel_blob.h"
18#include "vboot_api.h"
19#include "vboot_host.h"
20
21#ifdef USE_MTD
22#include <linux/major.h>
23#include <mtd/mtd-user.h>
24#include <mtdutils.h>
25#endif
26
27typedef ssize_t (*ReadFullyFn)(void *ctx, void *buf, size_t count);
28
29static ssize_t ReadFullyWithRead(void *ctx, void *buf, size_t count)
30{
31	ssize_t nr_read = 0;
32	int fd = *((int*)ctx);
33	while (nr_read < count) {
34		ssize_t to_read = count - nr_read;
35		ssize_t chunk = read(fd, buf + nr_read, to_read);
36		if (chunk < 0) {
37			return -1;
38		} else if (chunk == 0) {
39			break;
40		}
41		nr_read += chunk;
42	}
43	return nr_read;
44}
45
46#ifdef USE_MTD
47static ssize_t ReadFullyWithMtdRead(void *ctx, void *buf, size_t count)
48{
49	MtdReadContext *mtd_ctx = (MtdReadContext*)ctx;
50	return mtd_read_data(mtd_ctx, buf, count);
51}
52#endif
53
54/* Skip the stream by calling |read_fn| many times. Return 0 on success. */
55static int SkipWithRead(void *ctx, ReadFullyFn read_fn, size_t count)
56{
57	char buf[1024];
58	ssize_t nr_skipped = 0;
59	while (nr_skipped < count) {
60		ssize_t to_read = count - nr_skipped;
61		if (to_read > sizeof(buf)) {
62			to_read = sizeof(buf);
63		}
64		if (read_fn(ctx, buf, to_read) != to_read) {
65			return -1;
66		}
67		nr_skipped += to_read;
68	}
69	return 0;
70}
71
72static char *FindKernelConfigFromStream(void *ctx, ReadFullyFn read_fn,
73					uint64_t kernel_body_load_address)
74{
75	VbKeyBlockHeader key_block;
76	VbKernelPreambleHeader preamble;
77	uint32_t now = 0;
78	uint32_t offset = 0;
79
80	/* Skip the key block */
81	if (read_fn(ctx, &key_block, sizeof(key_block)) != sizeof(key_block)) {
82		VbExError("not enough data to fill key block header\n");
83		return NULL;
84	}
85	ssize_t to_skip = key_block.key_block_size - sizeof(key_block);
86	if (to_skip < 0 || SkipWithRead(ctx, read_fn, to_skip)) {
87		VbExError("key_block_size advances past the end of the blob\n");
88		return NULL;
89	}
90	now += key_block.key_block_size;
91
92	/* Open up the preamble */
93	if (read_fn(ctx, &preamble, sizeof(preamble)) != sizeof(preamble)) {
94		VbExError("not enough data to fill preamble\n");
95		return NULL;
96	}
97	to_skip = preamble.preamble_size - sizeof(preamble);
98	if (to_skip < 0 || SkipWithRead(ctx, read_fn, to_skip)) {
99		VbExError("preamble_size advances past the end of the blob\n");
100		return NULL;
101	}
102	now += preamble.preamble_size;
103
104	/* Read body_load_address from preamble if no
105	 * kernel_body_load_address */
106	if (kernel_body_load_address == USE_PREAMBLE_LOAD_ADDR)
107		kernel_body_load_address = preamble.body_load_address;
108
109	/* The x86 kernels have a pointer to the kernel commandline in the
110	 * zeropage table, but that's irrelevant for ARM. Both types keep the
111	 * config blob in the same place, so just go find it. */
112	offset = preamble.bootloader_address -
113	    (kernel_body_load_address + CROS_PARAMS_SIZE +
114	     CROS_CONFIG_SIZE) + now;
115	to_skip = offset - now;
116	if (to_skip < 0 || SkipWithRead(ctx, read_fn, to_skip)) {
117		VbExError("params are outside of the memory blob: %x\n",
118			  offset);
119		return NULL;
120	}
121	char *ret = malloc(CROS_CONFIG_SIZE);
122	if (!ret) {
123		VbExError("No memory\n");
124		return NULL;
125	}
126	if (read_fn(ctx, ret, CROS_CONFIG_SIZE) != CROS_CONFIG_SIZE) {
127		VbExError("Cannot read kernel config\n");
128		free(ret);
129		ret = NULL;
130	}
131	return ret;
132}
133
134char *FindKernelConfig(const char *infile, uint64_t kernel_body_load_address)
135{
136	char *newstr = NULL;
137
138	int fd = open(infile, O_RDONLY | O_CLOEXEC | O_LARGEFILE);
139	if (fd < 0) {
140		VbExError("Cannot open %s\n", infile);
141		return NULL;
142	}
143
144	void *ctx = &fd;
145	ReadFullyFn read_fn = ReadFullyWithRead;
146
147#ifdef USE_MTD
148	struct stat stat_buf;
149	if (fstat(fd, &stat_buf)) {
150		VbExError("Cannot stat %s\n", infile);
151		return NULL;
152	}
153
154	int is_mtd = (major(stat_buf.st_rdev) == MTD_CHAR_MAJOR);
155	if (is_mtd) {
156		ctx = mtd_read_descriptor(fd, infile);
157		if (!ctx) {
158			VbExError("Cannot read from MTD device %s\n", infile);
159			return NULL;
160		}
161		read_fn = ReadFullyWithMtdRead;
162	}
163#endif
164
165	newstr = FindKernelConfigFromStream(ctx, read_fn,
166					    kernel_body_load_address);
167
168#ifdef USE_MTD
169	if (is_mtd) {
170		mtd_read_close(ctx);
171	}
172#endif
173	close(fd);
174
175	return newstr;
176}
177