aboutsummaryrefslogtreecommitdiffstats
path: root/com32/lib/sys/module/x86_64/elf_module.c
blob: aa89d928e8b2ea19207567f917266dadb65b3222 (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
/*
 * elf_module.c
 *
 *  Created on: Aug 11, 2008
 *      Author: Stefan Bucur <stefanb@zytor.com>
 */

#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <elf.h>
#include <dprintf.h>
#include <core.h>

#include <linux/list.h>
#include <sys/module.h>
#include <sys/exec.h>

#include "elfutils.h"
#include "../common.h"

/*
 *
 * The implementation assumes that the loadable segments are present
 * in the PHT sorted by their offsets, so that only forward seeks would
 * be necessary.
 */
int load_segments(struct elf_module *module, Elf_Ehdr *elf_hdr) {
	int i;
	int res = 0;
	char *pht = NULL;
	char *sht = NULL;
	Elf64_Phdr *cr_pht;
	Elf64_Shdr *cr_sht;

	Elf64_Addr min_addr  = 0x0000000000000000; // Min. ELF vaddr
	Elf64_Addr max_addr  = 0x0000000000000000; // Max. ELF vaddr
	Elf64_Word max_align = sizeof(void*); // Min. align of posix_memalign()
	Elf64_Addr min_alloc, max_alloc;   // Min. and max. aligned allocables

	Elf64_Addr dyn_addr = 0x0000000000000000;

	// Get to the PHT
	image_seek(elf_hdr->e_phoff, module);

	// Load the PHT
	pht = malloc(elf_hdr->e_phnum * elf_hdr->e_phentsize);
	if (!pht)
		return -1;

	image_read(pht, elf_hdr->e_phnum * elf_hdr->e_phentsize, module);

	// Compute the memory needings of the module
	for (i=0; i < elf_hdr->e_phnum; i++) {
		cr_pht = (Elf64_Phdr*)(pht + i * elf_hdr->e_phentsize);

		switch (cr_pht->p_type) {
		case PT_LOAD:
			if (i == 0) {
				min_addr = cr_pht->p_vaddr;
			} else {
				min_addr = MIN(min_addr, cr_pht->p_vaddr);
			}

			max_addr = MAX(max_addr, cr_pht->p_vaddr + cr_pht->p_memsz);
			max_align = MAX(max_align, cr_pht->p_align);
			break;
		case PT_DYNAMIC:
			dyn_addr = cr_pht->p_vaddr;
			break;
		default:
			// Unsupported - ignore
			break;
		}
	}

	if (max_addr - min_addr == 0) {
		// No loadable segments
		DBG_PRINT("No loadable segments found\n");
		goto out;
	}

	if (dyn_addr == 0) {
		DBG_PRINT("No dynamic information segment found\n");
		goto out;
	}

	// The minimum address that should be allocated
	min_alloc = min_addr - (min_addr % max_align);

	// The maximum address that should be allocated
	max_alloc = max_addr - (max_addr % max_align);
	if (max_addr % max_align > 0)
		max_alloc += max_align;


	if (elf_malloc(&module->module_addr,
			max_align,
			max_alloc-min_alloc) != 0) {

		DBG_PRINT("Could not allocate segments\n");
		goto out;
	}

	module->base_addr = (Elf64_Addr)(module->module_addr) - min_alloc;
	module->module_size = max_alloc - min_alloc;

	// Zero-initialize the memory
	memset(module->module_addr, 0, module->module_size);

	for (i = 0; i < elf_hdr->e_phnum; i++) {
		cr_pht = (Elf64_Phdr*)(pht + i * elf_hdr->e_phentsize);

		if (cr_pht->p_type == PT_LOAD) {
			// Copy the segment at its destination
			if (cr_pht->p_offset < module->u.l._cr_offset) {
				// The segment contains data before the current offset
				// It can be discarded without worry - it would contain only
				// headers
				Elf64_Off aux_off = module->u.l._cr_offset - cr_pht->p_offset;

				if (image_read((char *)module_get_absolute(cr_pht->p_vaddr, module) + aux_off,
					       cr_pht->p_filesz - aux_off, module) < 0) {
					res = -1;
					goto out;
				}
			} else {
				if (image_seek(cr_pht->p_offset, module) < 0) {
					res = -1;
					goto out;
				}

				if (image_read(module_get_absolute(cr_pht->p_vaddr, module),
						cr_pht->p_filesz, module) < 0) {
					res = -1;
					goto out;
				}
			}

			/*
			DBG_PRINT("Loadable segment of size 0x%08x copied from vaddr 0x%08x at 0x%08x\n",
					cr_pht->p_filesz,
					cr_pht->p_vaddr,
					(Elf64_Addr)module_get_absolute(cr_pht->p_vaddr, module));
			*/
		}
	}

	// Get to the SHT
	image_seek(elf_hdr->e_shoff, module);

	// Load the SHT
	sht = malloc(elf_hdr->e_shnum * elf_hdr->e_shentsize);
	if (!sht) {
		res = -1;
		goto out;
	}

	image_read(sht, elf_hdr->e_shnum * elf_hdr->e_shentsize, module);

	// Setup the symtable size
	for (i = 0; i < elf_hdr->e_shnum; i++) {
		cr_sht = (Elf64_Shdr*)(sht + i * elf_hdr->e_shentsize);

		if (cr_sht->sh_type == SHT_DYNSYM) {
			module->symtable_size = cr_sht->sh_size;
			break;
		}
	}

	free(sht);

	// Setup dynamic segment location
	module->dyn_table = module_get_absolute(dyn_addr, module);

	/*
	DBG_PRINT("Base address: 0x%08x, aligned at 0x%08x\n", module->base_addr,
			max_align);
	DBG_PRINT("Module size: 0x%08x\n", module->module_size);
	*/

out:
	// Free up allocated memory
	if (pht != NULL)
		free(pht);

	return res;
}

int perform_relocation(struct elf_module *module, Elf_Rel *rel) {
	Elf64_Xword *dest = module_get_absolute(rel->r_offset, module);

	// The symbol reference index
	Elf64_Word sym = ELF64_R_SYM(rel->r_info);
	unsigned char type = ELF64_R_TYPE(rel->r_info);

	// The symbol definition (if applicable)
	Elf64_Sym *sym_def = NULL;
	struct elf_module *sym_module = NULL;
	Elf64_Addr sym_addr = 0x0;

	if (sym > 0) {
		// Find out details about the symbol

		// The symbol reference
		Elf64_Sym *sym_ref = symbol_get_entry(module, sym);

		// The symbol definition
		sym_def =
			global_find_symbol(module->str_table + sym_ref->st_name,
					&sym_module);

		if (sym_def == NULL) {
			DBG_PRINT("Cannot perform relocation for symbol %s\n",
					module->str_table + sym_ref->st_name);

			if (ELF64_ST_BIND(sym_ref->st_info) != STB_WEAK)
				return -1;

			// This must be a derivative-specific
			// function. We're OK as long as we never
			// execute the function.
			sym_def = global_find_symbol("undefined_symbol", &sym_module);
		}

		// Compute the absolute symbol virtual address
		sym_addr = (Elf64_Addr)module_get_absolute(sym_def->st_value, sym_module);

		if (sym_module != module) {
			// Create a dependency
			enforce_dependency(sym_module, module);
		}
	}

	switch (type) {
	case R_X86_64_NONE:
		// Do nothing
		break;
	case R_X86_64_64:
		*dest += sym_addr;
		break;
	case R_X86_64_PC32:
	        *(uint32_t *)dest += sym_addr - (Elf64_Addr)dest;
		break;
	case R_X86_64_COPY:
		if (sym_addr > 0) {
			memcpy((void*)dest, (void*)sym_addr, sym_def->st_size);
		}
		break;
	case R_X86_64_GLOB_DAT:
	case R_X86_64_JUMP_SLOT:
		 //Maybe TODO: Keep track of the GOT entries allocations
		*dest = sym_addr;
		break;
	case R_X86_64_RELATIVE:
		*dest += module->base_addr;
		break;
	default:
		DBG_PRINT("Relocation type %d not supported\n", type);
		return -1;
	}

	return 0;
}

int resolve_symbols(struct elf_module *module) {
	Elf64_Dyn  *dyn_entry = module->dyn_table;
	unsigned int i;
	int res;

	Elf64_Word plt_rel_size = 0;
	void *plt_rel = NULL;

	void *rel = NULL;
	Elf64_Word rel_size = 0;
	Elf64_Word rel_entry = 0;
	Elf64_Xword rela_size = 0;
	Elf64_Xword rela_entry = 0;
	Elf64_Xword sym_ent = 0;

	// The current relocation
	Elf64_Rel *crt_rel;

	while (dyn_entry->d_tag != DT_NULL) {
		switch(dyn_entry->d_tag) {

		// PLT relocation information
		case DT_PLTRELSZ:
			plt_rel_size = dyn_entry->d_un.d_val;
			break;
		case DT_PLTREL:
			if (dyn_entry->d_un.d_val != DT_REL && dyn_entry->d_un.d_val != DT_RELA) {
				DBG_PRINT("Unsupported PLT relocation\n");
				return -1;
			}
			//break;
		case DT_JMPREL:
			plt_rel = module_get_absolute(dyn_entry->d_un.d_ptr, module);
			break;

		// Standard relocation information
		case DT_REL:
			rel = module_get_absolute(dyn_entry->d_un.d_ptr, module);
			break;
		case DT_RELA:
			rel = module_get_absolute(dyn_entry->d_un.d_ptr, module);
			break;
		case DT_RELSZ:
			rel_size = dyn_entry->d_un.d_val;
			break;
		case DT_RELASZ:
			rela_size = dyn_entry->d_un.d_val;
			break;
		case DT_RELENT:
			rel_entry = dyn_entry->d_un.d_val;
			break;
		case DT_RELAENT:
			rela_entry = dyn_entry->d_un.d_val;
			break;
		/* FIXME: We may need to rely upon SYMENT if DT_RELAENT is missing in the object file */
		case DT_SYMENT:
			sym_ent = dyn_entry->d_un.d_val;
			break;

		// Module initialization and termination
		case DT_INIT:
			// TODO Implement initialization functions
			break;
		case DT_FINI:
			// TODO Implement finalization functions
			break;
		}

		dyn_entry++;
	}

	if (rel_size > 0) {
		// Process standard relocations
		for (i = 0; i < rel_size/rel_entry; i++) {
		    crt_rel = (Elf64_Rel*)((char *)rel + i*rel_entry);

			res = perform_relocation(module, crt_rel);

			if (res < 0)
				return res;
		}

	}

	if (rela_size > 0) {
		// Process standard relocations
		for (i = 0; i < rela_size/rela_entry; i++) {
		    crt_rel = (Elf64_Rel*)((char *)rel + i*rela_entry);

			res = perform_relocation(module, crt_rel);

			if (res < 0)
				return res;
		}
	}
	if (plt_rel_size > 0) {
		// TODO: Permit this lazily
		// Process PLT relocations
		/* some modules do not have DT_SYMENT, set it sym_ent in such cases */
		if (!rela_entry) rela_entry = sym_ent; 
		//for (i = 0; i < plt_rel_size/sizeof(Elf64_Rel); i++) {
		for (i = 0; i < plt_rel_size/rela_entry; i++) {
			//crt_rel = (Elf64_Rel*)(plt_rel + i*sizeof(Elf64_Rel));
		        crt_rel = (Elf64_Rel*)((char *)plt_rel + i*rela_entry);

			res = perform_relocation(module, crt_rel);

			if (res < 0)
				return res;
		}
	}

	return 0;
}