summaryrefslogtreecommitdiffstats
path: root/commands/linux16.c
blob: db8d08105fa578b39cf1e7161fc951786e23a935 (plain) (blame)
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
/*
 * Copyright (C) 2009 Juergen Beisert, Pengutronix
 *
 * In parts from the GRUB2 project:
 *
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999,2000,2001,2002,2003,2004,2005,2007,2008  Free Software Foundation, 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.
 *
 *
 */

#include <common.h>
#include <command.h>
#include <environment.h>
#include <fs.h>
#include <errno.h>
#include <libfile.h>
#include <getopt.h>
#include <malloc.h>
#include <boot.h>
#include <asm/syslib.h>

/** FIXME */
#define LINUX_MAGIC_SIGNATURE       0x53726448      /* "HdrS" */

/** FIXME */
#define LINUX_FLAG_BIG_KERNEL       0x1

/** FIXME */
#define LINUX_BOOT_LOADER_TYPE      0x72

/** FIXME */
#define LINUX_DEFAULT_SETUP_SECTS	4

/** FIXME */
#define LINUX_MAX_SETUP_SECTS		64

/** FIXME */
#define LINUX_OLD_REAL_MODE_SEGMT	0x9000

/** FIXME */
#define LINUX_OLD_REAL_MODE_ADDR	(LINUX_OLD_REAL_MODE_SEGMT << 4)

/** FIXME */
#define LINUX_HEAP_END_OFFSET		(LINUX_OLD_REAL_MODE_SEGMT - 0x200)

/** FIXME */
#define LINUX_FLAG_CAN_USE_HEAP		0x80

/** Define kernel command lines's start offset in the setup segment */
#define LINUX_CL_OFFSET			0x9000

/** Define kernel command lines's end offset */
#define LINUX_CL_END_OFFSET		0x90FF

/** FIXME */
#define LINUX_CL_MAGIC			0xA33F

/** FIXME */
#define LINUX_SETUP_MOVE_SIZE		0x9100

/** Sector size */
#define DISK_SECTOR_BITS		9
#define DISK_SECTOR_SIZE		0x200

/** Where to load a bzImage */
#define LINUX_BZIMAGE_ADDR		0x100000

struct linux_kernel_header {
	/* first sector of the image */
	uint8_t code1[0x0020];
	uint16_t cl_magic;		/**< Magic number 0xA33F */
	uint16_t cl_offset;		/**< The offset of command line */
	uint8_t code2[0x01F1 - 0x0020 - 2 - 2];
	uint8_t setup_sects;		/**< The size of the setup in sectors */
	uint16_t root_flags;		/**< If the root is mounted readonly */
	uint16_t syssize;		/**< obsolete */
	uint16_t swap_dev;		/**< obsolete */
	uint16_t ram_size;		/**< obsolete */
	uint16_t vid_mode;		/**< Video mode control */
	uint16_t root_dev;		/**< Default root device number */
	uint16_t boot_flag;		/**< 0xAA55 magic number */

	/* second sector of the image */
	uint16_t jump;			/**< Jump instruction (this is code!) */
	uint32_t header;		/**< Magic signature "HdrS" */
	uint16_t version;		/**< Boot protocol version supported */
	uint32_t realmode_swtch;	/**< Boot loader hook */
	uint16_t start_sys;		/**< The load-low segment (obsolete) */
	uint16_t kernel_version;	/**< Points to kernel version string */
	uint8_t type_of_loader;		/**< Boot loader identifier */
#define LINUX_LOADER_ID_LILO		0x0
#define LINUX_LOADER_ID_LOADLIN		0x1
#define LINUX_LOADER_ID_BOOTSECT	0x2
#define LINUX_LOADER_ID_SYSLINUX	0x3
#define LINUX_LOADER_ID_ETHERBOOT	0x4
#define LINUX_LOADER_ID_ELILO		0x5
#define LINUX_LOADER_ID_GRUB		0x7
#define LINUX_LOADER_ID_UBOOT		0x8
#define LINUX_LOADER_ID_XEN		0x9
#define LINUX_LOADER_ID_GUJIN		0xa
#define LINUX_LOADER_ID_QEMU		0xb
	uint8_t loadflags;		/**< Boot protocol option flags */
	uint16_t setup_move_size;	/**< Move to high memory size */
	uint32_t code32_start;		/**< Boot loader hook */
	uint32_t ramdisk_image;		/**< initrd load address */
	uint32_t ramdisk_size;		/**< initrd size */
	uint32_t bootsect_kludge;	/**< obsolete */
	uint16_t heap_end_ptr;		/**< Free memory after setup end */
	uint8_t ext_loader_ver;		/**< boot loader's extension of the version number */
	uint8_t ext_loader_type;	/**< boot loader's extension of its type */
	char *cmd_line_ptr;		/**< Points to the kernel command line */
	uint32_t initrd_addr_max;	/**< Highest address for initrd */
#if 0
	/* for the records only. These members are defined in
	 * more recent Linux kernels
	 */
	uint32_t kernel_alignment;	/**< Alignment unit required by the kernel */
	uint8_t relocatable_kernel;	/** */
	uint8_t min_alignment;		/** */
	uint32_t cmdline_size;		/** */
	uint32_t hardware_subarch;	/** */
	uint64_t hardware_subarch_data;	/** */
	uint32_t payload_offset;	/** */
	uint32_t payload_length;	/** */
	uint64_t setup_data;		/** */
	uint64_t pref_address;		/** */
	uint32_t init_size;		/** */
#endif
} __attribute__ ((packed));

/* This is -1. Keep this value in sync with the kernel */
#define NORMAL_VGA	0xffff		/* 80x25 mode */
#define ASK_VGA		0xfffd		/* ask for it at bootup */

/**
 * Load an x86 Linux kernel bzImage and start it
 * @param argc parameter count
 * @param argv list of parameter
 *
 * Loads an x86 bzImage, checks for its integrity, stores the two parts
 * (setup = 'real mode code' and kernel = 'protected mode code') to their
 * default locations, switches back to real mode and runs the setup code.
 */
static int do_linux16(int argc, char *argv[])
{
	struct linux_kernel_header *lh = NULL;
	int rc, opt;
	unsigned setup_sects;
	unsigned real_mode_size;
	int vid_mode = NORMAL_VGA;
	size_t image_size;
	const char *cmdline = linux_bootargs_get();
	const char *kernel_file;

	while((opt = getopt(argc, argv, "v:")) > 0) {
		switch(opt) {
		case 'v':
			vid_mode = simple_strtoul(optarg, NULL, 0);
			if (vid_mode == 0) {
				if (!strcmp(optarg, "ask"))
					vid_mode = ASK_VGA;
				else {
					printf("Unknown video mode: %s\n", optarg);
					return 1;
				}
			}
			break;
		default:
			return COMMAND_ERROR_USAGE;
		}
	}

	if (optind == argc) {
		printf("No kernel filename given\n");
		return 1;
	}
	kernel_file = argv[optind];

	lh = read_file(kernel_file, &image_size);
	if (lh == NULL) {
		printf("Cannot read file '%s'\n", argv[1]);
		return 1;
	}

	if (lh->boot_flag != 0xaa55) {
		printf("File '%s' has invalid magic number\n", argv[1]);
		rc = 1;
		goto on_error;
	}

	if (lh->setup_sects > LINUX_MAX_SETUP_SECTS) {
		printf("File '%s' contains too many setup sectors\n", argv[1]);
		rc = 1;
		goto on_error;
	}

	setup_sects = lh->setup_sects;

	printf("Found a %d.%d image header\n", lh->version >> 8, lh->version & 0xFF);

	if (lh->header == LINUX_MAGIC_SIGNATURE && lh->version >= 0x0200) {
		/* kernel is recent enough */
		;
		if (!(lh->loadflags & LINUX_FLAG_BIG_KERNEL)) {
			printf("Cannot load a classic zImage. Use a bzImage instead\n");
			goto on_error;
		}
		lh->type_of_loader = LINUX_BOOT_LOADER_TYPE;	/* TODO */

		if (lh->version >= 0x0201) {
			lh->heap_end_ptr = LINUX_HEAP_END_OFFSET;
			lh->loadflags |= LINUX_FLAG_CAN_USE_HEAP;
		}

		if (lh->version >= 0x0202)
			lh->cmd_line_ptr = (void*)(LINUX_OLD_REAL_MODE_ADDR + LINUX_CL_OFFSET);	/* FIXME */
		else {
			lh->cl_magic = LINUX_CL_MAGIC;
			lh->cl_offset = LINUX_CL_OFFSET;
			lh->setup_move_size = LINUX_SETUP_MOVE_SIZE;
		}
	} else {
		printf("Kernel too old to handle\n");
		rc = 1;
		goto on_error;
	}

	if (strlen(cmdline) >= (LINUX_CL_END_OFFSET -  LINUX_CL_OFFSET)) {
		printf("Kernel command line exceeds the available space\n");
		rc = 1;
		goto on_error;
	}

	/*
	 * The kernel does not check for the "vga=<val>" kernel command line
	 * parameter anymore. It expects this kind of information in the
	 * boot parameters instead.
	 */
	if (vid_mode != NORMAL_VGA)
		lh->vid_mode = vid_mode;

	/* If SETUP_SECTS is not set, set it to the default.  */
	if (setup_sects == 0) {
		printf("Fixing setup sector count\n");
		setup_sects = LINUX_DEFAULT_SETUP_SECTS;
	}

	if (setup_sects >= 15) {
		void *src = lh;
		if (lh->kernel_version != 0)
			printf("Kernel version: '%s'\n",
			       (char *)src + lh->kernel_version + DISK_SECTOR_SIZE);
	}

	/*
	 * Size of the real mode part to handle in a separate way
	 */
	real_mode_size = (setup_sects << DISK_SECTOR_BITS) + DISK_SECTOR_SIZE;

	/*
	 *                real mode space                     hole            extended memory
	 * |---------------------------------------------->|----------->|------------------------------>
	 * 0                                            0xa0000     0x100000
	 *  <-1-|----------2-----------><-3-   |
	 *    0x7e00                        0x90000
	 *                                <-4--|-5-->                   |---------6------------->
	 *
	 * 1) real mode stack
	 * 2) barebox code
	 * 3) flat mode stack
	 * 4) realmode stack when starting a Linux kernel
	 * 5) Kernel's real mode setup code
	 * 6) compressed kernel image
	 */
	/*
	 * Parts of the image we know:
	 * - real mode part
	 * - kernel payload
	 */
	/*
	 * NOTE: This part is dangerous, as it copies some image content to
	 * various locations in the main memory. This could overwrite important
	 * data of the running barebox (hopefully not)
	 */
	/* copy the real mode part of the image to the 9th segment */
	memcpy((void*)LINUX_OLD_REAL_MODE_ADDR, lh, LINUX_SETUP_MOVE_SIZE);

	/* TODO add 'BOOT_IMAGE=<file>' and 'auto' if no user intervention was done (in front of all other params) */
	/* copy also the command line into this area */
	memcpy((void*)(LINUX_OLD_REAL_MODE_ADDR + LINUX_CL_OFFSET), cmdline, strlen(cmdline) + 1);
	printf("Using kernel command line: '%s'\n", cmdline);

	/* copy the compressed image part to its final address the setup code expects it
	 * Note: The protected mode part starts at offset (setup_sects + 1) * 512
	 */
	memcpy((void*)LINUX_BZIMAGE_ADDR, ((void*)lh) + real_mode_size, image_size - real_mode_size);

	/*
	 * switch back to real mode now and start the real mode part of the
	 * image at address "(LINUX_OLD_REAL_MODE_ADDR >> 4) + 0x20:0x0000"
	 * which means "0x9020:0x000" -> 0x90200
	 */
	bios_start_linux(LINUX_OLD_REAL_MODE_SEGMT);	/* does not return */

on_error:
	if (lh != NULL)
		free(lh);

	return rc;
}

BAREBOX_CMD_HELP_START(linux16)
BAREBOX_CMD_HELP_TEXT("Load kernel from FILE and boot on x86 in real-mode.")
BAREBOX_CMD_HELP_TEXT("")
BAREBOX_CMD_HELP_TEXT("Only kernel images in bzImage format are supported by now.")
BAREBOX_CMD_HELP_TEXT("")
BAREBOX_CMD_HELP_TEXT("For the video mode refer the Linux kernel documentation")
BAREBOX_CMD_HELP_TEXT("'Documentation/fb/vesafb.txt' for correct VESA mode numbers. Use 'ask'")
BAREBOX_CMD_HELP_TEXT("instead of a number to make Linux for options..")
BAREBOX_CMD_HELP_TEXT("")
BAREBOX_CMD_HELP_TEXT("Options:")
BAREBOX_CMD_HELP_OPT ("-v VESAMODE",   "set VESAMODE")
BAREBOX_CMD_HELP_END

BAREBOX_CMD_START(linux16)
	.cmd		= do_linux16,
	BAREBOX_CMD_DESC("boot a linux kernel on x86 via real-mode code")
	BAREBOX_CMD_OPTS("[-v VESAMODE] FILE")
	BAREBOX_CMD_GROUP(CMD_GRP_BOOT)
	BAREBOX_CMD_HELP(cmd_linux16_help)
BAREBOX_CMD_END