forked from rui314/mold
-
Notifications
You must be signed in to change notification settings - Fork 0
/
arch_i386.cc
412 lines (375 loc) · 10.8 KB
/
arch_i386.cc
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
#include "mold.h"
template <>
void PltSection<I386>::copy_buf(Context<I386> &ctx) {
u8 *buf = ctx.buf + this->shdr.sh_offset;
// Write PLT header
if (ctx.arg.pic) {
static const u8 plt0[] = {
0xff, 0xb3, 0x04, 0, 0, 0, // pushl 4(%ebx)
0xff, 0xa3, 0x08, 0, 0, 0, // jmp *8(%ebx)
0x90, 0x90, 0x90, 0x90, // nop
};
memcpy(buf, plt0, sizeof(plt0));
} else {
static const u8 plt0[] = {
0xff, 0x35, 0, 0, 0, 0, // pushl (GOTPLT+4)
0xff, 0x25, 0, 0, 0, 0, // jmp *(GOTPLT+8)
0x90, 0x90, 0x90, 0x90, // nop
};
memcpy(buf, plt0, sizeof(plt0));
*(u32 *)(buf + 2) = ctx.gotplt->shdr.sh_addr + 4;
*(u32 *)(buf + 8) = ctx.gotplt->shdr.sh_addr + 8;
}
// Write PLT entries
i64 relplt_idx = 0;
for (Symbol<I386> *sym : symbols) {
u8 *ent = buf + sym->get_plt_idx(ctx) * I386::plt_size;
if (ctx.arg.pic) {
static const u8 data[] = {
0xff, 0xa3, 0, 0, 0, 0, // jmp *foo@GOT(%ebx)
0x68, 0, 0, 0, 0, // pushl $reloc_offset
0xe9, 0, 0, 0, 0, // jmp .PLT0@PC
};
memcpy(ent, data, sizeof(data));
*(u32 *)(ent + 2) = sym->get_gotplt_addr(ctx) - ctx.gotplt->shdr.sh_addr;
} else {
static const u8 data[] = {
0xff, 0x25, 0, 0, 0, 0, // jmp *foo@GOT
0x68, 0, 0, 0, 0, // pushl $reloc_offset
0xe9, 0, 0, 0, 0, // jmp .PLT0@PC
};
memcpy(ent, data, sizeof(data));
*(u32 *)(ent + 2) = sym->get_gotplt_addr(ctx);
}
*(u32 *)(ent + 7) = relplt_idx++ * sizeof(ElfRel<I386>);
*(u32 *)(ent + 12) = this->shdr.sh_addr - sym->get_plt_addr(ctx) - 16;
}
}
template <>
void PltGotSection<I386>::copy_buf(Context<I386> &ctx) {
u8 *buf = ctx.buf + this->shdr.sh_offset;
if (ctx.arg.pic) {
static const u8 data[] = {
0xff, 0xa3, 0, 0, 0, 0, // jmp *foo@GOT(%ebx)
0x66, 0x90, // nop
};
for (i64 i = 0; i < symbols.size(); i++) {
u8 *ent = buf + i * sizeof(data);
memcpy(ent, data, sizeof(data));
*(u32 *)(ent + 2) = symbols[i]->get_got_addr(ctx) - ctx.gotplt->shdr.sh_addr;
}
} else {
static const u8 data[] = {
0xff, 0x25, 0, 0, 0, 0, // jmp *foo@GOT
0x66, 0x90, // nop
};
for (i64 i = 0; i < symbols.size(); i++) {
u8 *ent = buf + i * sizeof(data);
memcpy(ent, data, sizeof(data));
*(u32 *)(ent + 2) = symbols[i]->get_got_addr(ctx);
}
}
}
template <>
void EhFrameSection<I386>::apply_reloc(Context<I386> &ctx,
ElfRel<I386> &rel,
u64 loc, u64 val) {
u8 *base = ctx.buf + this->shdr.sh_offset;
switch (rel.r_type) {
case R_386_NONE:
return;
case R_386_32:
*(u32 *)(base + loc) = val;
return;
case R_386_PC32:
*(u32 *)(base + loc) = val - this->shdr.sh_addr - loc;
return;
}
unreachable(ctx);
}
static void write_val(Context<I386> &ctx, u64 r_type, u8 *loc, u64 val) {
switch (r_type) {
case R_386_NONE:
return;
case R_386_8:
case R_386_PC8:
*loc += val;
return;
case R_386_16:
case R_386_PC16:
*(u16 *)loc += val;
return;
case R_386_32:
case R_386_PC32:
case R_386_GOT32:
case R_386_GOT32X:
case R_386_PLT32:
case R_386_GOTOFF:
case R_386_GOTPC:
case R_386_TLS_LDM:
case R_386_TLS_GOTIE:
case R_386_TLS_LE:
case R_386_TLS_IE:
case R_386_TLS_GD:
case R_386_TLS_LDO_32:
case R_386_SIZE32:
case R_386_TLS_GOTDESC:
*(u32 *)loc += val;
return;
}
unreachable(ctx);
}
template <>
void InputSection<I386>::apply_reloc_alloc(Context<I386> &ctx, u8 *base) {
ElfRel<I386> *dynrel = nullptr;
std::span<ElfRel<I386>> rels = get_rels(ctx);
i64 frag_idx = 0;
if (ctx.reldyn)
dynrel = (ElfRel<I386> *)(ctx.buf + ctx.reldyn->shdr.sh_offset +
file.reldyn_offset + this->reldyn_offset);
for (i64 i = 0; i < rels.size(); i++) {
const ElfRel<I386> &rel = rels[i];
if (rel.r_type == R_386_NONE)
continue;
Symbol<I386> &sym = *file.symbols[rel.r_sym];
u8 *loc = base + rel.r_offset;
const SectionFragmentRef<I386> *ref = nullptr;
if (rel_fragments && rel_fragments[frag_idx].idx == i)
ref = &rel_fragments[frag_idx++];
auto write = [&](u64 val) {
write_val(ctx, rel.r_type, loc, val);
};
#define S (ref ? ref->frag->get_addr(ctx) : sym.get_addr(ctx))
#define A (ref ? ref->addend : 0)
#define P (output_section->shdr.sh_addr + offset + rel.r_offset)
#define G (sym.get_got_addr(ctx) - ctx.got->shdr.sh_addr)
#define GOTPLT ctx.gotplt->shdr.sh_addr
switch (rel_exprs[i]) {
case R_BASEREL:
*dynrel++ = {P, R_386_RELATIVE, 0};
*(u32 *)loc += S + A;
continue;
case R_DYN:
*dynrel++ = {P, R_386_32, (u32)sym.get_dynsym_idx(ctx)};
*(u32 *)loc += A;
continue;
}
switch (rel.r_type) {
case R_386_8:
case R_386_16:
case R_386_32:
write(S + A);
continue;
case R_386_PC8:
case R_386_PC16:
case R_386_PC32:
case R_386_PLT32:
write(S + A - P);
continue;
case R_386_GOT32:
case R_386_GOT32X:
write(sym.get_got_addr(ctx) + A - GOTPLT);
continue;
case R_386_GOTOFF:
write(S + A - GOTPLT);
continue;
case R_386_GOTPC:
write(GOTPLT + A - P);
continue;
case R_386_TLS_GOTIE:
write(sym.get_gottp_addr(ctx) + A - GOTPLT);
continue;
case R_386_TLS_LE:
write(S + A - ctx.tls_end);
continue;
case R_386_TLS_IE:
write(sym.get_gottp_addr(ctx) + A);
continue;
case R_386_TLS_GD:
write(sym.get_tlsgd_addr(ctx) + A - GOTPLT);
continue;
case R_386_TLS_LDM:
write(ctx.got->get_tlsld_addr(ctx) + A - GOTPLT);
continue;
case R_386_TLS_LDO_32:
write(S + A - ctx.tls_begin);
continue;
case R_386_SIZE32:
write(sym.esym().st_size + A);
continue;
case R_386_TLS_GOTDESC:
if (sym.get_tlsdesc_idx(ctx) == -1) {
static const u8 insn[] = {
0x8d, 0x05, 0, 0, 0, 0, // lea 0, %eax
};
memcpy(loc - 2, insn, sizeof(insn));
write(S + A - ctx.tls_end);
} else {
write(sym.get_tlsdesc_addr(ctx) + A - GOTPLT);
}
continue;
case R_386_TLS_DESC_CALL:
if (ctx.arg.relax && !ctx.arg.shared) {
// call *(%rax) -> nop
loc[0] = 0x66;
loc[1] = 0x90;
}
continue;
default:
unreachable(ctx);
}
#undef S
#undef A
#undef P
#undef G
#undef GOTPLT
}
}
template <>
void InputSection<I386>::apply_reloc_nonalloc(Context<I386> &ctx, u8 *base) {
std::span<ElfRel<I386>> rels = get_rels(ctx);
i64 frag_idx = 0;
for (i64 i = 0; i < rels.size(); i++) {
const ElfRel<I386> &rel = rels[i];
if (rel.r_type == R_386_NONE)
continue;
Symbol<I386> &sym = *file.symbols[rel.r_sym];
u8 *loc = base + rel.r_offset;
if (!sym.file) {
report_undef(ctx, sym);
continue;
}
const SectionFragmentRef<I386> *ref = nullptr;
if (rel_fragments && rel_fragments[frag_idx].idx == i)
ref = &rel_fragments[frag_idx++];
auto write = [&](u64 val) {
write_val(ctx, rel.r_type, loc, val);
};
switch (rel.r_type) {
case R_386_8:
case R_386_16:
case R_386_32:
case R_386_PC8:
case R_386_PC16:
case R_386_PC32:
case R_386_GOTPC:
if (ref)
write(ref->frag->get_addr(ctx) + ref->addend);
else
write(sym.get_addr(ctx));
break;
case R_386_GOTOFF:
write(sym.get_addr(ctx) - ctx.got->shdr.sh_addr);
break;
case R_386_TLS_LDO_32:
write(sym.get_addr(ctx) - ctx.tls_begin);
break;
case R_386_SIZE32:
write(sym.esym().st_size);
break;
default:
Fatal(ctx) << *this << ": invalid relocation for non-allocated sections: "
<< rel_to_string<I386>(rel.r_type);
break;
}
}
}
template <>
void InputSection<I386>::scan_relocations(Context<I386> &ctx) {
ASSERT(shdr.sh_flags & SHF_ALLOC);
this->reldyn_offset = file.num_dynrel * sizeof(ElfRel<I386>);
std::span<ElfRel<I386>> rels = get_rels(ctx);
bool is_writable = (shdr.sh_flags & SHF_WRITE);
// Scan relocations
for (i64 i = 0; i < rels.size(); i++) {
const ElfRel<I386> &rel = rels[i];
if (rel.r_type == R_386_NONE)
continue;
Symbol<I386> &sym = *file.symbols[rel.r_sym];
u8 *loc = (u8 *)(contents.data() + rel.r_offset);
if (!sym.file) {
report_undef(ctx, sym);
continue;
}
if (sym.get_type() == STT_GNU_IFUNC) {
sym.flags |= NEEDS_GOT;
sym.flags |= NEEDS_PLT;
}
switch (rel.r_type) {
case R_386_8:
case R_386_16: {
Action table[][4] = {
// Absolute Local Imported data Imported code
{ NONE, ERROR, ERROR, ERROR }, // DSO
{ NONE, ERROR, ERROR, ERROR }, // PIE
{ NONE, NONE, COPYREL, PLT }, // PDE
};
dispatch(ctx, table, i);
break;
}
case R_386_32: {
Action table[][4] = {
// Absolute Local Imported data Imported code
{ NONE, BASEREL, DYNREL, DYNREL }, // DSO
{ NONE, BASEREL, DYNREL, DYNREL }, // PIE
{ NONE, NONE, DYNREL, DYNREL }, // PDE
};
dispatch(ctx, table, i);
break;
}
case R_386_PC8:
case R_386_PC16: {
Action table[][4] = {
// Absolute Local Imported data Imported code
{ ERROR, NONE, ERROR, ERROR }, // DSO
{ ERROR, NONE, COPYREL, PLT }, // PIE
{ NONE, NONE, COPYREL, PLT }, // PDE
};
dispatch(ctx, table, i);
break;
}
case R_386_PC32: {
Action table[][4] = {
// Absolute Local Imported data Imported code
{ BASEREL, NONE, ERROR, ERROR }, // DSO
{ BASEREL, NONE, COPYREL, PLT }, // PIE
{ NONE, NONE, COPYREL, PLT }, // PDE
};
dispatch(ctx, table, i);
break;
}
case R_386_GOT32:
case R_386_GOT32X:
case R_386_GOTPC:
sym.flags |= NEEDS_GOT;
break;
case R_386_PLT32:
if (sym.is_imported)
sym.flags |= NEEDS_PLT;
break;
case R_386_TLS_GOTIE:
case R_386_TLS_LE:
case R_386_TLS_IE:
sym.flags |= NEEDS_GOTTP;
break;
case R_386_TLS_GD:
sym.flags |= NEEDS_TLSGD;
break;
case R_386_TLS_LDM:
sym.flags |= NEEDS_TLSLD;
break;
case R_386_TLS_GOTDESC:
if (!ctx.arg.relax || ctx.arg.shared)
sym.flags |= NEEDS_TLSDESC;
break;
case R_386_GOTOFF:
case R_386_TLS_LDO_32:
case R_386_SIZE32:
case R_386_TLS_DESC_CALL:
break;
default:
Error(ctx) << *this << ": unknown relocation: "
<< rel_to_string<I386>(rel.r_type);
}
}
}