summaryrefslogtreecommitdiffstats
path: root/utils/sbtools/elf.c
blob: 57f38b801632b5ecbc7eb9de4c4789add9b9f00d (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
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
#include "elf.h"

/**
 * Definitions
 *   taken from elf.h linux header
 *   based on ELF specification
 *   based on ARM ELF specification
 */
typedef uint16_t Elf32_Half;

typedef uint32_t Elf32_Word;
typedef int32_t  Elf32_Sword;
typedef uint32_t Elf32_Addr;
typedef uint32_t Elf32_Off;
typedef uint16_t Elf32_Section;

#define EI_NIDENT   16

typedef struct
{
    unsigned char   e_ident[EI_NIDENT]; /* Magic number and other info */
    Elf32_Half      e_type; /* Object file type */
    Elf32_Half      e_machine; /* Architecture */
    Elf32_Word      e_version; /* Object file version */
    Elf32_Addr      e_entry; /* Entry point virtual address */
    Elf32_Off       e_phoff; /* Program header table file offset */
    Elf32_Off       e_shoff; /* Section header table file offset */
    Elf32_Word      e_flags; /* Processor-specific flags */
    Elf32_Half      e_ehsize; /* ELF header size in bytes */
    Elf32_Half      e_phentsize; /* Program header table entry size */
    Elf32_Half      e_phnum; /* Program header table entry count */
    Elf32_Half      e_shentsize; /* Section header table entry size */
    Elf32_Half      e_shnum; /* Section header table entry count */
    Elf32_Half      e_shstrndx; /* Section header string table index */
}Elf32_Ehdr;

#define EI_MAG0     0 /* File identification byte 0 index */
#define ELFMAG0     0x7f /* Magic number byte 0 */

#define EI_MAG1     1 /* File identification byte 1 index */
#define ELFMAG1     'E' /* Magic number byte 1 */

#define EI_MAG2     2 /* File identification byte 2 index */
#define ELFMAG2     'L' /* Magic number byte 2 */

#define EI_MAG3     3 /* File identification byte 3 index */
#define ELFMAG3     'F' /* Magic number byte 3 */

#define EI_CLASS    4 /* File class byte index */
#define ELFCLASS32  1 /* 32-bit objects */

#define EI_DATA     5 /* Data encoding byte index */
#define ELFDATA2LSB 1 /* 2's complement, little endian */

#define EI_VERSION  6 /* File version byte index, Value must be EV_CURRENT */

#define EI_OSABI    7 /* OS ABI identification */
#define ELFOSABI_NONE       0 /* UNIX System V ABI */
#define ELFOSABI_ARM_AEABI  64 /* ARM EABI */
#define ELFOSABI_ARM        97 /* ARM */

#define EI_ABIVERSION   8 /* ABI version */

#define EI_PAD      9 /* Byte index of padding bytes */

#define ET_EXEC     2 /* Executable file */

#define EM_ARM      40 /* ARM */

#define EV_CURRENT  1 /* Current version */

#define EF_ARM_HASENTRY     0x00000002

#define SHN_UNDEF   0 /* Undefined section */

typedef struct
{
    Elf32_Word  sh_name; /* Section name (string tbl index) */
    Elf32_Word  sh_type; /* Section type */
    Elf32_Word  sh_flags; /* Section flags */
    Elf32_Addr  sh_addr; /* Section virtual addr at execution */
    Elf32_Off   sh_offset; /* Section file offset */
    Elf32_Word  sh_size; /* Section size in bytes */
    Elf32_Word  sh_link; /* Link to another section */
    Elf32_Word  sh_info; /* Additional section information */
    Elf32_Word  sh_addralign; /* Section alignment */
    Elf32_Word  sh_entsize; /* Entry size if section holds table */
}Elf32_Shdr;

#define SHT_NULL            0 /* Section header table entry unused */
#define SHT_PROGBITS        1 /* Program data */
#define SHT_SYMTAB          2 /* Symbol table */
#define SHT_STRTAB          3 /* String table */
#define SHT_RELA            4 /* Relocation entries with addends */
#define SHT_HASH            5 /* Symbol hash table */
#define SHT_DYNAMIC         6 /* Dynamic linking information */
#define SHT_NOTE            7 /* Notes */
#define SHT_NOBITS          8 /* Program space with no data (bss) */
#define SHT_REL             9 /* Relocation entries, no addends */
#define SHT_SHLIB           10 /* Reserved */
#define SHT_DYNSYM          11 /* Dynamic linker symbol table */
#define SHT_INIT_ARRAY      14 /* Array of constructors */
#define SHT_FINI_ARRAY      15 /* Array of destructors */
#define SHT_PREINIT_ARRAY   16 /* Array of pre-constructors */
#define SHT_GROUP           17 /* Section group */
#define SHT_SYMTAB_SHNDX    18 /* Extended section indeces */
#define	SHT_NUM             19 /* Number of defined types.  */

#define SHF_WRITE       (1 << 0) /* Writable */
#define SHF_ALLOC       (1 << 1) /* Occupies memory during execution */
#define SHF_EXECINSTR   (1 << 2) /* Executable */
#define SHF_MERGE       (1 << 4) /* Might be merged */
#define SHF_STRINGS     (1 << 5) /* Contains nul-terminated strings */

typedef struct
{
    Elf32_Word  p_type; /* Segment type */
    Elf32_Off   p_offset; /* Segment file offset */
    Elf32_Addr  p_vaddr; /* Segment virtual address */
    Elf32_Addr  p_paddr; /* Segment physical address */
    Elf32_Word  p_filesz; /* Segment size in file */
    Elf32_Word  p_memsz; /* Segment size in memory */
    Elf32_Word  p_flags; /* Segment flags */
    Elf32_Word  p_align; /* Segment alignment */
}Elf32_Phdr;

#define PT_LOAD     1 /* Loadable program segment */

#define PF_X    (1 << 0) /* Segment is executable */
#define PF_W    (1 << 1) /* Segment is writable */
#define PF_R    (1 << 2) /* Segment is readable */

void elf_init(struct elf_params_t *params)
{
    params->has_start_addr = false;
    params->start_addr = 0;
    params->first_section = NULL;
    params->last_section = NULL;
}

extern void *xmalloc(size_t s);

static struct elf_section_t *elf_add_section(struct elf_params_t *params)
{
    struct elf_section_t *sec = xmalloc(sizeof(struct elf_section_t));
    if(params->first_section == NULL)
        params->first_section = params->last_section = sec;
    else
    {
        params->last_section->next = sec;
        params->last_section = sec;
    }
    sec->next = NULL;

    return sec;
}

static struct elf_segment_t *elf_add_segment(struct elf_params_t *params)
{
    struct elf_segment_t *seg = xmalloc(sizeof(struct elf_section_t));
    if(params->first_segment == NULL)
        params->first_segment = params->last_segment = seg;
    else
    {
        params->last_segment->next = seg;
        params->last_segment = seg;
    }
    seg->next = NULL;

    return seg;
}

void elf_add_load_section(struct elf_params_t *params,
    uint32_t load_addr, uint32_t size, const void *section)
{
    struct elf_section_t *sec = elf_add_section(params);

    sec->type = EST_LOAD;
    sec->addr = load_addr;
    sec->size = size;
    sec->section = xmalloc(size);
    memcpy(sec->section, section, size);
}

void elf_add_fill_section(struct elf_params_t *params,
    uint32_t fill_addr, uint32_t size, uint32_t pattern)
{
    if(pattern != 0x00)
    {
        printf("oops, non-zero filling, ignore fill section\n");
        return;
    }
    
    struct elf_section_t *sec = elf_add_section(params);
    
    sec->type = EST_FILL;
    sec->addr = fill_addr;
    sec->size = size;
    sec->pattern = pattern;
}

void elf_write_file(struct elf_params_t *params, elf_write_fn_t write, void *user)
{
    Elf32_Ehdr ehdr;
    uint32_t phnum = 0;
    struct elf_section_t *sec = params->first_section;
    uint32_t offset = 0;
    Elf32_Phdr phdr;
    Elf32_Shdr shdr;
    memset(&ehdr, 0, EI_NIDENT);

    while(sec)
    {
        if(sec->type == EST_LOAD)
        {
            sec->offset = offset;
            offset += sec->size;
        }
        
        phnum++;
        sec = sec->next;
    }

    uint32_t strtbl_offset = offset;

    ehdr.e_ident[EI_MAG0] = ELFMAG0;
    ehdr.e_ident[EI_MAG1] = ELFMAG1;
    ehdr.e_ident[EI_MAG2] = ELFMAG2;
    ehdr.e_ident[EI_MAG3] = ELFMAG3;
    ehdr.e_ident[EI_CLASS] = ELFCLASS32;
    ehdr.e_ident[EI_DATA] = ELFDATA2LSB;
    ehdr.e_ident[EI_VERSION] = EV_CURRENT;
    ehdr.e_ident[EI_OSABI] = ELFOSABI_NONE;
    ehdr.e_ident[EI_ABIVERSION] = 0;
    ehdr.e_type = ET_EXEC;
    ehdr.e_machine = EM_ARM;
    ehdr.e_version = EV_CURRENT;
    ehdr.e_entry = params->start_addr;
    ehdr.e_flags = 0;
    if(params->has_start_addr)
        ehdr.e_flags |= EF_ARM_HASENTRY;
    ehdr.e_ehsize = sizeof ehdr;
    ehdr.e_phentsize = sizeof phdr;
    ehdr.e_phnum = phnum;
    ehdr.e_shentsize = sizeof shdr;
    ehdr.e_shnum = phnum + 2; /* one for section 0 and one for string table */
    ehdr.e_shstrndx = ehdr.e_shnum - 1;
    ehdr.e_phoff = ehdr.e_ehsize;
    ehdr.e_shoff = ehdr.e_ehsize + ehdr.e_phnum * ehdr.e_phentsize;

    write(user, 0, &ehdr, sizeof ehdr);

    /* allocate enough size to hold any combinaison of .text/.bss in the string table:
     * - one empty name ("\0")
     * - at most N names of the form ".textXX\0" or ".bssXX\0"
     * - one name ".shstrtab\0" */
    char *strtbl_content = malloc(1 + strlen(".shstrtab") + 1 +
        phnum * (strlen(".textXX") + 1));
    
    strtbl_content[0] = '\0';
    strcpy(&strtbl_content[1], ".shstrtab");
    uint32_t strtbl_index = 1 + strlen(".shstrtab") + 1;

    uint32_t data_offset = ehdr.e_ehsize + ehdr.e_phnum * ehdr.e_phentsize +
        ehdr.e_shnum * ehdr.e_shentsize;

    sec = params->first_section;
    offset = ehdr.e_phoff;
    while(sec)
    {
        sec->offset += data_offset;
        
        phdr.p_type = PT_LOAD;
        if(sec->type == EST_LOAD)
            phdr.p_offset = sec->offset;
        else
            phdr.p_offset = 0;
        phdr.p_paddr = sec->addr;
        phdr.p_vaddr = phdr.p_paddr; /* assume identity map ? */
        phdr.p_memsz = sec->size;
        if(sec->type == EST_LOAD)
            phdr.p_filesz = phdr.p_memsz;
        else
            phdr.p_filesz = 0;
        phdr.p_flags = PF_X | PF_W | PF_R;
        phdr.p_align = 0;

        write(user, offset, &phdr, sizeof phdr);

        offset += sizeof(Elf32_Phdr);
        sec = sec->next;
    }

    sec = params->first_section;
    offset = ehdr.e_shoff;

    {
        shdr.sh_name = 0;
        shdr.sh_type = SHT_NULL;
        shdr.sh_flags = 0;
        shdr.sh_addr = 0;
        shdr.sh_offset = 0;
        shdr.sh_size = 0;
        shdr.sh_link = SHN_UNDEF;
        shdr.sh_info = 0;
        shdr.sh_addralign = 0;
        shdr.sh_entsize = 0;

        write(user, offset, &shdr, sizeof shdr);

        offset += sizeof(Elf32_Shdr);
    }

    uint32_t text_idx = 0;
    uint32_t bss_idx = 0;
    while(sec)
    {
        shdr.sh_name = strtbl_index;
        if(sec->type == EST_LOAD)
        {
            strtbl_index += 1 + sprintf(&strtbl_content[strtbl_index], ".text%d", text_idx++);
            shdr.sh_type = SHT_PROGBITS;
        }
        else
        {
            strtbl_index += 1 + sprintf(&strtbl_content[strtbl_index], ".bss%d", bss_idx++);
            shdr.sh_type = SHT_NOBITS;
        }
        shdr.sh_flags = SHF_ALLOC | SHF_EXECINSTR;
        shdr.sh_addr = sec->addr;
        shdr.sh_offset = sec->offset;
        shdr.sh_size = sec->size;
        shdr.sh_link = SHN_UNDEF;
        shdr.sh_info = 0;
        shdr.sh_addralign = 1;
        shdr.sh_entsize = 0;

        write(user, offset, &shdr, sizeof shdr);

        offset += sizeof(Elf32_Shdr);
        sec = sec->next;
    }

    {
        shdr.sh_name = 1;
        shdr.sh_type = SHT_STRTAB;
        shdr.sh_flags = 0;
        shdr.sh_addr = 0;
        shdr.sh_offset = strtbl_offset + data_offset;
        shdr.sh_size = strtbl_index;
        shdr.sh_link = SHN_UNDEF;
        shdr.sh_info = 0;
        shdr.sh_addralign = 1;
        shdr.sh_entsize = 0;

        write(user, offset, &shdr, sizeof shdr);

        offset += sizeof(Elf32_Shdr);
    }

    sec = params->first_section;
    while(sec)
    {
        if(sec->type == EST_LOAD)
            write(user, sec->offset, sec->section, sec->size);
        sec = sec->next;
    }

    write(user, strtbl_offset + data_offset, strtbl_content, strtbl_index);
    free(strtbl_content);
}

bool elf_read_file(struct elf_params_t *params, elf_read_fn_t read,
    elf_printf_fn_t printf, void *user)
{
    #define error_printf(...) ({printf(user, true, __VA_ARGS__); return false;})
    
    /* read header */
    Elf32_Ehdr ehdr;
    if(!read(user, 0, &ehdr, sizeof(ehdr)))
    {
        printf(user, true, "error reading elf header\n");
        return false;
    }
    /* basic checks */
    if(ehdr.e_ident[EI_MAG0] != ELFMAG0 || ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
            ehdr.e_ident[EI_MAG2] != ELFMAG2 || ehdr.e_ident[EI_MAG3] != ELFMAG3)
        error_printf("invalid elf header\n");
    if(ehdr.e_ident[EI_CLASS] != ELFCLASS32)
        error_printf("invalid elf class: must be a 32-bit object\n");
    if(ehdr.e_ident[EI_DATA] != ELFDATA2LSB)
        error_printf("invalid elf data encoding: must be 32-bit lsb\n");
    if(ehdr.e_ident[EI_VERSION] != EV_CURRENT)
        error_printf("invalid elf version\n");
    if(ehdr.e_type != ET_EXEC)
        error_printf("invalid elf file: must be an executable file\n");
    if(ehdr.e_machine != EM_ARM)
        error_printf("invalid elf file: must target an arm machine\n");
    if(ehdr.e_ehsize != sizeof(ehdr))
        error_printf("invalid elf file: size header mismatch\n");
    if(ehdr.e_phnum > 0 && ehdr.e_phentsize != sizeof(Elf32_Phdr))
        error_printf("invalid elf file: program header size mismatch\n");
    if(ehdr.e_shnum > 0 && ehdr.e_shentsize != sizeof(Elf32_Shdr))
        error_printf("invalid elf file: section header size mismatch\n");
    elf_set_start_addr(params, ehdr.e_entry);

    char *strtab = NULL;
    if(ehdr.e_shstrndx != SHN_UNDEF)
    {
        Elf32_Shdr shstrtab;
        if(read(user, ehdr.e_shoff + ehdr.e_shstrndx * ehdr.e_shentsize,
                &shstrtab, sizeof(shstrtab)))
        {
            strtab = xmalloc(shstrtab.sh_size);
            if(!read(user, shstrtab.sh_offset, strtab, shstrtab.sh_size))
            {
                free(strtab);
                strtab = NULL;
            }
        }
    }
    /* run through sections */
    printf(user, false, "ELF file:\n");
    for(int i = 1; i < ehdr.e_shnum; i++)
    {
        uint32_t off = ehdr.e_shoff + i * ehdr.e_shentsize;
        Elf32_Shdr shdr;
        memset(&shdr, 0, sizeof(shdr));
        if(!read(user, off, &shdr, sizeof(shdr)))
            error_printf("error reading elf section header");

        if(shdr.sh_type == SHT_PROGBITS && shdr.sh_flags & SHF_ALLOC)
        {
            void *data = xmalloc(shdr.sh_size);
            if(!read(user, shdr.sh_offset, data, shdr.sh_size))
                error_printf("error read self section data\n");
            elf_add_load_section(params, shdr.sh_addr, shdr.sh_size, data);

            if(strtab)
                printf(user, false, "create load segment for %s\n", &strtab[shdr.sh_name]);
        }
        else if(shdr.sh_type == SHT_NOBITS && shdr.sh_flags & SHF_ALLOC)
        {
            elf_add_fill_section(params, shdr.sh_addr, shdr.sh_size, 0);
            if(strtab)
                printf(user, false, "create fill segment for %s\n", &strtab[shdr.sh_name]);
        }
        else
        {
            if(strtab)
                printf(user, false, "filter out %s\n", &strtab[shdr.sh_name], shdr.sh_type);
        }
        
    }
    /* run through segments */
    for(int i = 1; i < ehdr.e_phnum; i++)
    {
        uint32_t off = ehdr.e_phoff + i * ehdr.e_phentsize;
        Elf32_Phdr phdr;
        memset(&phdr, 0, sizeof(phdr));
        if(!read(user, off, &phdr, sizeof(phdr)))
            error_printf("error reading elf segment header");
        if(phdr.p_type != PT_LOAD)
            continue;
        struct elf_segment_t *seg = elf_add_segment(params);
        seg->vaddr = phdr.p_vaddr;
        seg->paddr = phdr.p_paddr;
        seg->vsize = phdr.p_memsz;
        seg->psize = phdr.p_filesz;
        printf(user, false, "create segment [%#x,+%#x[ -> [%#x,+%#x[\n",
            seg->vaddr, seg->vsize, seg->paddr, seg->psize);
    }
    
    return true;
}

uint32_t elf_translate_virtual_address(struct elf_params_t *params, uint32_t addr)
{
    struct elf_segment_t *seg = params->first_segment;
    while(seg)
    {
        if(seg->vaddr <= addr && addr < seg->vaddr + seg->vsize)
            return addr - seg->vaddr + seg->paddr;
        seg = seg->next;
    }
    return addr;
}

void elf_translate_addresses(struct elf_params_t *params)
{
    struct elf_section_t *sec = params->first_section;
    while(sec)
    {
        sec->addr = elf_translate_virtual_address(params, sec->addr);
        sec = sec->next;
    }
    params->start_addr = elf_translate_virtual_address(params, params->start_addr);
}

bool elf_is_empty(struct elf_params_t *params)
{
    return params->first_section == NULL;
}

void elf_set_start_addr(struct elf_params_t *params, uint32_t addr)
{
    params->has_start_addr = true;
    params->start_addr = addr;
}

bool elf_get_start_addr(struct elf_params_t *params, uint32_t *addr)
{
    if(params->has_start_addr && addr != NULL)
        *addr = params->start_addr;
    return params->has_start_addr;
}

int elf_get_nr_sections(struct elf_params_t *params)
{
    int nr = 0;
    struct elf_section_t *sec = params->first_section;
    while(sec)
    {
        nr++;
        sec = sec->next;
    }
    return nr;
}

void elf_release(struct elf_params_t *params)
{
    struct elf_section_t *sec, *next_sec;
    sec = params->first_section;
    while(sec)
    {
        next_sec = sec->next;
        if(sec->type == EST_LOAD)
            free(sec->section);
        free(sec);
        sec = next_sec;
    }
    params->first_section = NULL;
    params->last_section = NULL;
}