aboutsummaryrefslogtreecommitdiffstats
path: root/com32/lib/syslinux/load_linux.c
blob: df793625a9466fd28ea2eef607270ea26eabe7ba (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
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
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
/* ----------------------------------------------------------------------- *
 *
 *   Copyright 2007-2009 H. Peter Anvin - All Rights Reserved
 *   Copyright 2009 Intel Corporation; author: H. Peter Anvin
 *
 *   Permission is hereby granted, free of charge, to any person
 *   obtaining a copy of this software and associated documentation
 *   files (the "Software"), to deal in the Software without
 *   restriction, including without limitation the rights to use,
 *   copy, modify, merge, publish, distribute, sublicense, and/or
 *   sell copies of the Software, and to permit persons to whom
 *   the Software is furnished to do so, subject to the following
 *   conditions:
 *
 *   The above copyright notice and this permission notice shall
 *   be included in all copies or substantial portions of the Software.
 *
 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 *   OTHER DEALINGS IN THE SOFTWARE.
 *
 * ----------------------------------------------------------------------- */

/*
 * load_linux.c
 *
 * Load a Linux kernel (Image/zImage/bzImage).
 */

#include <ctype.h>
#include <stdbool.h>
#include <stdlib.h>
#include <inttypes.h>
#include <string.h>
#include <minmax.h>
#include <syslinux/align.h>
#include <syslinux/linux.h>
#include <syslinux/bootrm.h>
#include <syslinux/movebits.h>

#ifndef DEBUG
# define DEBUG 0
#endif
#if DEBUG
# include <stdio.h>
# define dprintf printf
#else
# define dprintf(f, ...) ((void)0)
#endif

struct linux_header {
    uint8_t boot_sector_1[0x0020];
    uint16_t old_cmd_line_magic;
    uint16_t old_cmd_line_offset;
    uint8_t boot_sector_2[0x01f1 - 0x0024];
    uint8_t setup_sects;
    uint16_t root_flags;
    uint32_t syssize;
    uint16_t ram_size;
    uint16_t vid_mode;
    uint16_t root_dev;
    uint16_t boot_flag;
    uint16_t jump;
    uint32_t header;
    uint16_t version;
    uint32_t realmode_swtch;
    uint16_t start_sys;
    uint16_t kernel_version;
    uint8_t type_of_loader;
    uint8_t loadflags;
    uint16_t setup_move_size;
    uint32_t code32_start;
    uint32_t ramdisk_image;
    uint32_t ramdisk_size;
    uint32_t bootsect_kludge;
    uint16_t heap_end_ptr;
    uint16_t pad1;
    uint32_t cmd_line_ptr;
    uint32_t initrd_addr_max;
    uint32_t kernel_alignment;
    uint8_t relocatable_kernel;
    uint8_t pad2[3];
    uint32_t cmdline_max_len;
} __packed;

#define BOOT_MAGIC 0xAA55
#define LINUX_MAGIC ('H' + ('d' << 8) + ('r' << 16) + ('S' << 24))
#define OLD_CMDLINE_MAGIC 0xA33F

/* loadflags */
#define LOAD_HIGH	0x01
#define CAN_USE_HEAP	0x80

/* Get a value with a potential suffix (k/m/g/t/p/e) */
static unsigned long long suffix_number(const char *str)
{
    char *ep;
    unsigned long long v;
    int shift;

    v = strtoull(str, &ep, 0);
    switch (*ep | 0x20) {
    case 'k':
	shift = 10;
	break;
    case 'm':
	shift = 20;
	break;
    case 'g':
	shift = 30;
	break;
    case 't':
	shift = 40;
	break;
    case 'p':
	shift = 50;
	break;
    case 'e':
	shift = 60;
	break;
    default:
	shift = 0;
	break;
    }
    v <<= shift;

    return v;
}

/* 
 * Find the last instance of a particular command line argument
 * (which should include the final =; do not use for boolean arguments)
 * Note: the resulting string is typically not null-terminated.
 */
static const char *find_argument(const char *cmdline, const char *argument)
{
    const char *found = NULL;
    const char *p = cmdline;
    bool was_space = true;
    size_t la = strlen(argument);

    while (*p) {
	if (isspace(*p)) {
	    was_space = true;
	} else if (was_space) {
	    if (!memcmp(p, argument, la))
		found = p + la;
	    was_space = false;
	}
	p++;
    }

    return found;
}

/* Truncate to 32 bits, with saturate */
static inline uint32_t saturate32(unsigned long long v)
{
    return (v > 0xffffffff) ? 0xffffffff : (uint32_t) v;
}

/* Get the combined size of the initramfs */
static addr_t initramfs_size(struct initramfs *initramfs)
{
    struct initramfs *ip;
    addr_t size = 0;

    if (!initramfs)
	return 0;

    for (ip = initramfs->next; ip->len; ip = ip->next) {
	size = (size + ip->align - 1) & ~(ip->align - 1);	/* Alignment */
	size += ip->len;
    }

    return size;
}

/* Create the appropriate mappings for the initramfs */
static int map_initramfs(struct syslinux_movelist **fraglist,
			 struct syslinux_memmap **mmap,
			 struct initramfs *initramfs, addr_t addr)
{
    struct initramfs *ip;
    addr_t next_addr, len, pad;

    for (ip = initramfs->next; ip->len; ip = ip->next) {
	len = ip->len;
	next_addr = addr + len;

	/* If this isn't the last entry, extend the zero-pad region
	   to enforce the alignment of the next chunk. */
	if (ip->next->len) {
	    pad = -next_addr & (ip->next->align - 1);
	    len += pad;
	    next_addr += pad;
	}

	if (ip->data_len) {
	    if (syslinux_add_movelist(fraglist, addr, (addr_t) ip->data, len))
		return -1;
	}
	if (len > ip->data_len) {
	    if (syslinux_add_memmap(mmap, addr + ip->data_len,
				    len - ip->data_len, SMT_ZERO))
		return -1;
	}
	addr = next_addr;
    }

    return 0;
}

int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
			struct initramfs *initramfs, char *cmdline)
{
    struct linux_header hdr, *whdr;
    size_t real_mode_size, prot_mode_size;
    addr_t real_mode_base, prot_mode_base;
    addr_t irf_size;
    size_t cmdline_size, cmdline_offset;
    struct syslinux_rm_regs regs;
    struct syslinux_movelist *fraglist = NULL;
    struct syslinux_memmap *mmap = NULL;
    struct syslinux_memmap *amap = NULL;
    bool ok;
    uint32_t memlimit = 0;
    uint16_t video_mode = 0;
    const char *arg;

    cmdline_size = strlen(cmdline) + 1;

    if (kernel_size < 2 * 512)
	goto bail;

    /* Look for specific command-line arguments we care about */
    if ((arg = find_argument(cmdline, "mem=")))
	memlimit = saturate32(suffix_number(arg));

    if ((arg = find_argument(cmdline, "vga="))) {
	switch (arg[0] | 0x20) {
	case 'a':		/* "ask" */
	    video_mode = 0xfffd;
	    break;
	case 'e':		/* "ext" */
	    video_mode = 0xfffe;
	    break;
	case 'n':		/* "normal" */
	    video_mode = 0xffff;
	    break;
	case 'c':		/* "current" */
	    video_mode = 0x0f04;
	    break;
	default:
	    video_mode = strtoul(arg, NULL, 0);
	    break;
	}
    }

    /* Copy the header into private storage */
    /* Use whdr to modify the actual kernel header */
    memcpy(&hdr, kernel_buf, sizeof hdr);
    whdr = (struct linux_header *)kernel_buf;

    if (hdr.boot_flag != BOOT_MAGIC)
	goto bail;

    if (hdr.header != LINUX_MAGIC) {
	hdr.version = 0x0100;	/* Very old kernel */
	hdr.loadflags = 0;
    }

    whdr->vid_mode = video_mode;

    if (!hdr.setup_sects)
	hdr.setup_sects = 4;

    if (hdr.version < 0x0203)
	hdr.initrd_addr_max = 0x37ffffff;

    if (!memlimit && memlimit - 1 > hdr.initrd_addr_max)
	memlimit = hdr.initrd_addr_max + 1;	/* Zero for no limit */

    if (hdr.version < 0x0205 || !(hdr.loadflags & LOAD_HIGH))
	hdr.relocatable_kernel = 0;

    if (hdr.version < 0x0206)
	hdr.cmdline_max_len = 256;

    if (cmdline_size > hdr.cmdline_max_len) {
	cmdline_size = hdr.cmdline_max_len;
	cmdline[cmdline_size - 1] = '\0';
    }

    if (hdr.version < 0x0202 || !(hdr.loadflags & 0x01))
	cmdline_offset = (0x9ff0 - cmdline_size) & ~15;
    else
	cmdline_offset = 0x10000;

    real_mode_size = (hdr.setup_sects + 1) << 9;
    real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
    prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
    prot_mode_size = kernel_size - real_mode_size;

    if (!(hdr.loadflags & LOAD_HIGH) && prot_mode_size > 512 * 1024)
	goto bail;		/* Kernel cannot be loaded low */

    if (initramfs && hdr.version < 0x0200)
	goto bail;		/* initrd/initramfs not supported */

    if (hdr.version >= 0x0200) {
	whdr->type_of_loader = 0x30;	/* SYSLINUX unknown module */
	if (hdr.version >= 0x0201) {
	    whdr->heap_end_ptr = cmdline_offset - 0x0200;
	    whdr->loadflags |= CAN_USE_HEAP;
	}
	if (hdr.version >= 0x0202) {
	    whdr->cmd_line_ptr = real_mode_base + cmdline_offset;
	} else {
	    whdr->old_cmd_line_magic = OLD_CMDLINE_MAGIC;
	    whdr->old_cmd_line_offset = cmdline_offset;
	    /* Be paranoid and round up to a multiple of 16 */
	    whdr->setup_move_size = (cmdline_offset + cmdline_size + 15) & ~15;
	}
    }

    /* Get the memory map */
    mmap = syslinux_memory_map();	/* Memory map for shuffle_boot */
    amap = syslinux_dup_memmap(mmap);	/* Keep track of available memory */
    if (!mmap || !amap)
	goto bail;

#if DEBUG
    dprintf("Initial memory map:\n");
    syslinux_dump_memmap(stdout, mmap);
#endif

    /* If the user has specified a memory limit, mark that as unavailable.
       Question: should we mark this off-limit in the mmap as well (meaning
       it's unavailable to the boot loader, which probably has already touched
       some of it), or just in the amap? */
    if (memlimit)
	if (syslinux_add_memmap(&amap, memlimit, -memlimit, SMT_RESERVED))
	    goto bail;

    /* Place the kernel in memory */

    /* First, find a suitable place for the protected-mode code */
    if (syslinux_memmap_type(amap, prot_mode_base, prot_mode_size)
	!= SMT_FREE) {
	const struct syslinux_memmap *mp;
	if (!hdr.relocatable_kernel)
	    goto bail;		/* Can't relocate - no hope */

	ok = false;
	for (mp = amap; mp; mp = mp->next) {
	    addr_t start, end;
	    start = mp->start;
	    end = mp->next->start;

	    if (mp->type != SMT_FREE)
		continue;

	    if (end <= prot_mode_base)
		continue;	/* Only relocate upwards */

	    if (start <= prot_mode_base)
		start = prot_mode_base;

	    start = ALIGN_UP(start, hdr.kernel_alignment);
	    if (start >= end)
		continue;

	    /* The 3* here is a total fudge factor... it's supposed to
	       account for the fact that the kernel needs to be decompressed,
	       and then followed by the BSS and BRK regions.  This doesn't,
	       however, account for the fact that the kernel is decompressed
	       into a whole other place, either. */
	    if (end - start >= 3 * prot_mode_size) {
		whdr->code32_start += start - prot_mode_base;
		prot_mode_base = start;
		ok = true;
		break;
	    }
	}

	if (!ok)
	    goto bail;
    }

    /* Real mode code */
    if (syslinux_memmap_type(amap, real_mode_base,
			     cmdline_offset + cmdline_size) != SMT_FREE) {
	const struct syslinux_memmap *mp;

	ok = false;
	for (mp = amap; mp; mp = mp->next) {
	    addr_t start, end;
	    start = mp->start;
	    end = mp->next->start;

	    if (mp->type != SMT_FREE)
		continue;

	    if (start < real_mode_base)
		start = real_mode_base;	/* Lowest address we'll use */
	    if (end > 640 * 1024)
		end = 640 * 1024;

	    start = ALIGN_UP(start, 16);
	    if (start > 0x90000 || start >= end)
		continue;

	    if (end - start >= cmdline_offset + cmdline_size) {
		real_mode_base = start;
		ok = true;
		break;
	    }
	}
    }

    if (syslinux_add_movelist(&fraglist, real_mode_base, (addr_t) kernel_buf,
			      real_mode_size))
	goto bail;
    if (syslinux_add_memmap
	(&amap, real_mode_base, cmdline_offset + cmdline_size, SMT_ALLOC))
	goto bail;

    /* Zero region between real mode code and cmdline */
    if (syslinux_add_memmap(&mmap, real_mode_base + real_mode_size,
			    cmdline_offset - real_mode_size, SMT_ZERO))
	goto bail;

    /* Command line */
    if (syslinux_add_movelist(&fraglist, real_mode_base + cmdline_offset,
			      (addr_t) cmdline, cmdline_size))
	goto bail;

    /* Protected-mode code */
    if (syslinux_add_movelist(&fraglist, prot_mode_base,
			      (addr_t) kernel_buf + real_mode_size,
			      prot_mode_size))
	goto bail;
    if (syslinux_add_memmap(&amap, prot_mode_base, prot_mode_size, SMT_ALLOC))
	goto bail;

    /* Figure out the size of the initramfs, and where to put it.
       We should put it at the highest possible address which is
       <= hdr.initrd_addr_max, which fits the entire initramfs. */

    irf_size = initramfs_size(initramfs);	/* Handles initramfs == NULL */

    if (irf_size) {
	addr_t best_addr = 0;
	struct syslinux_memmap *ml;
	const addr_t align_mask = INITRAMFS_MAX_ALIGN - 1;

	if (irf_size) {
	    for (ml = amap; ml->type != SMT_END; ml = ml->next) {
		addr_t adj_start = (ml->start + align_mask) & ~align_mask;
		addr_t adj_end = ml->next->start & ~align_mask;
		if (ml->type == SMT_FREE && adj_end - adj_start >= irf_size)
		    best_addr = (adj_end - irf_size) & ~align_mask;
	    }

	    if (!best_addr)
		goto bail;	/* Insufficient memory for initramfs */

	    whdr->ramdisk_image = best_addr;
	    whdr->ramdisk_size = irf_size;

	    if (syslinux_add_memmap(&amap, best_addr, irf_size, SMT_ALLOC))
		goto bail;

	    if (map_initramfs(&fraglist, &mmap, initramfs, best_addr))
		goto bail;
	}
    }

    /* Set up the registers on entry */
    memset(&regs, 0, sizeof regs);
    regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
    regs.cs = (real_mode_base >> 4) + 0x20;
    /* regs.ip = 0; */
    /* Linux is OK with sp = 0 = 64K, but perhaps other things aren't... */
    regs.esp.w[0] = min(cmdline_offset, (size_t) 0xfff0);

#if DEBUG
    dprintf("Final memory map:\n");
    syslinux_dump_memmap(stdout, mmap);

    dprintf("Final available map:\n");
    syslinux_dump_memmap(stdout, amap);

    dprintf("Initial movelist:\n");
    syslinux_dump_movelist(stdout, fraglist);
#endif

    syslinux_shuffle_boot_rm(fraglist, mmap, 0, &regs);

bail:
    syslinux_free_movelist(fraglist);
    syslinux_free_memmap(mmap);
    syslinux_free_memmap(amap);
    return -1;
}