1 //===- MIPS.cpp -----------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "InputFiles.h"
10 #include "Symbols.h"
11 #include "SyntheticSections.h"
12 #include "Target.h"
13 #include "llvm/BinaryFormat/ELF.h"
14
15 using namespace llvm;
16 using namespace llvm::object;
17 using namespace llvm::ELF;
18 using namespace lld;
19 using namespace lld::elf;
20
21 namespace {
22 template <class ELFT> class MIPS final : public TargetInfo {
23 public:
24 MIPS(Ctx &);
25 uint32_t calcEFlags() const override;
26 RelExpr getRelExpr(RelType type, const Symbol &s,
27 const uint8_t *loc) const override;
28 int64_t getImplicitAddend(const uint8_t *buf, RelType type) const override;
29 RelType getDynRel(RelType type) const override;
30 void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
31 void writePltHeader(uint8_t *buf) const override;
32 void writePlt(uint8_t *buf, const Symbol &sym,
33 uint64_t pltEntryAddr) const override;
34 bool needsThunk(RelExpr expr, RelType type, const InputFile *file,
35 uint64_t branchAddr, const Symbol &s,
36 int64_t a) const override;
37 void relocate(uint8_t *loc, const Relocation &rel,
38 uint64_t val) const override;
39 bool usesOnlyLowPageBits(RelType type) const override;
40 };
41 } // namespace
42
MIPS(Ctx & ctx)43 template <class ELFT> MIPS<ELFT>::MIPS(Ctx &ctx) : TargetInfo(ctx) {
44 gotPltHeaderEntriesNum = 2;
45 defaultMaxPageSize = 65536;
46 pltEntrySize = 16;
47 pltHeaderSize = 32;
48 copyRel = R_MIPS_COPY;
49 pltRel = R_MIPS_JUMP_SLOT;
50 needsThunks = true;
51
52 // Set `sigrie 1` as a trap instruction.
53 write32(ctx, trapInstr.data(), 0x04170001);
54
55 if (ELFT::Is64Bits) {
56 relativeRel = (R_MIPS_64 << 8) | R_MIPS_REL32;
57 symbolicRel = R_MIPS_64;
58 tlsGotRel = R_MIPS_TLS_TPREL64;
59 tlsModuleIndexRel = R_MIPS_TLS_DTPMOD64;
60 tlsOffsetRel = R_MIPS_TLS_DTPREL64;
61 } else {
62 relativeRel = R_MIPS_REL32;
63 symbolicRel = R_MIPS_32;
64 tlsGotRel = R_MIPS_TLS_TPREL32;
65 tlsModuleIndexRel = R_MIPS_TLS_DTPMOD32;
66 tlsOffsetRel = R_MIPS_TLS_DTPREL32;
67 }
68 }
69
calcEFlags() const70 template <class ELFT> uint32_t MIPS<ELFT>::calcEFlags() const {
71 return calcMipsEFlags<ELFT>(ctx);
72 }
73
74 template <class ELFT>
getRelExpr(RelType type,const Symbol & s,const uint8_t * loc) const75 RelExpr MIPS<ELFT>::getRelExpr(RelType type, const Symbol &s,
76 const uint8_t *loc) const {
77 // See comment in the calculateMipsRelChain.
78 if (ELFT::Is64Bits || ctx.arg.mipsN32Abi)
79 type.v &= 0xff;
80
81 switch (type) {
82 case R_MIPS_JALR:
83 // Older versions of clang would erroneously emit this relocation not only
84 // against functions (loaded from the GOT) but also against data symbols
85 // (e.g. a table of function pointers). When we encounter this, ignore the
86 // relocation and emit a warning instead.
87 if (!s.isFunc() && s.type != STT_NOTYPE) {
88 Warn(ctx) << getErrorLoc(ctx, loc)
89 << "found R_MIPS_JALR relocation against non-function symbol "
90 << &s << ". This is invalid and most likely a compiler bug.";
91 return R_NONE;
92 }
93
94 // If the target symbol is not preemptible and is not microMIPS,
95 // it might be possible to replace jalr/jr instruction by bal/b.
96 // It depends on the target symbol's offset.
97 if (!s.isPreemptible && !(s.getVA(ctx) & 0x1))
98 return R_PC;
99 return R_NONE;
100 case R_MICROMIPS_JALR:
101 return R_NONE;
102 case R_MIPS_GPREL16:
103 case R_MIPS_GPREL32:
104 case R_MICROMIPS_GPREL16:
105 case R_MICROMIPS_GPREL7_S2:
106 return RE_MIPS_GOTREL;
107 case R_MIPS_26:
108 case R_MICROMIPS_26_S1:
109 return R_PLT;
110 case R_MICROMIPS_PC26_S1:
111 return R_PLT_PC;
112 case R_MIPS_HI16:
113 case R_MIPS_LO16:
114 case R_MIPS_HIGHER:
115 case R_MIPS_HIGHEST:
116 case R_MICROMIPS_HI16:
117 case R_MICROMIPS_LO16:
118 // R_MIPS_HI16/R_MIPS_LO16 relocations against _gp_disp calculate
119 // offset between start of function and 'gp' value which by default
120 // equal to the start of .got section. In that case we consider these
121 // relocations as relative.
122 if (&s == ctx.sym.mipsGpDisp)
123 return RE_MIPS_GOT_GP_PC;
124 if (&s == ctx.sym.mipsLocalGp)
125 return RE_MIPS_GOT_GP;
126 [[fallthrough]];
127 case R_MIPS_32:
128 case R_MIPS_64:
129 case R_MIPS_GOT_OFST:
130 case R_MIPS_SUB:
131 return R_ABS;
132 case R_MIPS_TLS_DTPREL_HI16:
133 case R_MIPS_TLS_DTPREL_LO16:
134 case R_MIPS_TLS_DTPREL32:
135 case R_MIPS_TLS_DTPREL64:
136 case R_MICROMIPS_TLS_DTPREL_HI16:
137 case R_MICROMIPS_TLS_DTPREL_LO16:
138 return R_DTPREL;
139 case R_MIPS_TLS_TPREL_HI16:
140 case R_MIPS_TLS_TPREL_LO16:
141 case R_MIPS_TLS_TPREL32:
142 case R_MIPS_TLS_TPREL64:
143 case R_MICROMIPS_TLS_TPREL_HI16:
144 case R_MICROMIPS_TLS_TPREL_LO16:
145 return R_TPREL;
146 case R_MIPS_PC32:
147 case R_MIPS_PC16:
148 case R_MIPS_PC19_S2:
149 case R_MIPS_PC21_S2:
150 case R_MIPS_PC26_S2:
151 case R_MIPS_PCHI16:
152 case R_MIPS_PCLO16:
153 case R_MICROMIPS_PC7_S1:
154 case R_MICROMIPS_PC10_S1:
155 case R_MICROMIPS_PC16_S1:
156 case R_MICROMIPS_PC18_S3:
157 case R_MICROMIPS_PC19_S2:
158 case R_MICROMIPS_PC23_S2:
159 case R_MICROMIPS_PC21_S1:
160 return R_PC;
161 case R_MIPS_GOT16:
162 case R_MICROMIPS_GOT16:
163 if (s.isLocal())
164 return RE_MIPS_GOT_LOCAL_PAGE;
165 [[fallthrough]];
166 case R_MIPS_CALL16:
167 case R_MIPS_GOT_DISP:
168 case R_MIPS_TLS_GOTTPREL:
169 case R_MICROMIPS_CALL16:
170 case R_MICROMIPS_TLS_GOTTPREL:
171 return RE_MIPS_GOT_OFF;
172 case R_MIPS_CALL_HI16:
173 case R_MIPS_CALL_LO16:
174 case R_MIPS_GOT_HI16:
175 case R_MIPS_GOT_LO16:
176 case R_MICROMIPS_CALL_HI16:
177 case R_MICROMIPS_CALL_LO16:
178 case R_MICROMIPS_GOT_HI16:
179 case R_MICROMIPS_GOT_LO16:
180 return RE_MIPS_GOT_OFF32;
181 case R_MIPS_GOT_PAGE:
182 return RE_MIPS_GOT_LOCAL_PAGE;
183 case R_MIPS_TLS_GD:
184 case R_MICROMIPS_TLS_GD:
185 return RE_MIPS_TLSGD;
186 case R_MIPS_TLS_LDM:
187 case R_MICROMIPS_TLS_LDM:
188 return RE_MIPS_TLSLD;
189 case R_MIPS_NONE:
190 return R_NONE;
191 default:
192 Err(ctx) << getErrorLoc(ctx, loc) << "unknown relocation (" << type.v
193 << ") against symbol " << &s;
194 return R_NONE;
195 }
196 }
197
getDynRel(RelType type) const198 template <class ELFT> RelType MIPS<ELFT>::getDynRel(RelType type) const {
199 if (type == symbolicRel)
200 return type;
201 return R_MIPS_NONE;
202 }
203
204 template <class ELFT>
writeGotPlt(uint8_t * buf,const Symbol &) const205 void MIPS<ELFT>::writeGotPlt(uint8_t *buf, const Symbol &) const {
206 uint64_t va = ctx.in.plt->getVA();
207 if (isMicroMips(ctx))
208 va |= 1;
209 write32(ctx, buf, va);
210 }
211
212 template <endianness E>
readShuffle(Ctx & ctx,const uint8_t * loc)213 static uint32_t readShuffle(Ctx &ctx, const uint8_t *loc) {
214 // The major opcode of a microMIPS instruction needs to appear
215 // in the first 16-bit word (lowest address) for efficient hardware
216 // decode so that it knows if the instruction is 16-bit or 32-bit
217 // as early as possible. To do so, little-endian binaries keep 16-bit
218 // words in a big-endian order. That is why we have to swap these
219 // words to get a correct value.
220 uint32_t v = read32(ctx, loc);
221 if (E == llvm::endianness::little)
222 return (v << 16) | (v >> 16);
223 return v;
224 }
225
writeValue(Ctx & ctx,uint8_t * loc,uint64_t v,uint8_t bitsSize,uint8_t shift)226 static void writeValue(Ctx &ctx, uint8_t *loc, uint64_t v, uint8_t bitsSize,
227 uint8_t shift) {
228 uint32_t instr = read32(ctx, loc);
229 uint32_t mask = 0xffffffff >> (32 - bitsSize);
230 uint32_t data = (instr & ~mask) | ((v >> shift) & mask);
231 write32(ctx, loc, data);
232 }
233
234 template <endianness E>
writeShuffle(Ctx & ctx,uint8_t * loc,uint64_t v,uint8_t bitsSize,uint8_t shift)235 static void writeShuffle(Ctx &ctx, uint8_t *loc, uint64_t v, uint8_t bitsSize,
236 uint8_t shift) {
237 // See comments in readShuffle for purpose of this code.
238 uint16_t *words = (uint16_t *)loc;
239 if (E == llvm::endianness::little)
240 std::swap(words[0], words[1]);
241
242 writeValue(ctx, loc, v, bitsSize, shift);
243
244 if (E == llvm::endianness::little)
245 std::swap(words[0], words[1]);
246 }
247
248 template <endianness E>
writeMicroRelocation16(Ctx & ctx,uint8_t * loc,uint64_t v,uint8_t bitsSize,uint8_t shift)249 static void writeMicroRelocation16(Ctx &ctx, uint8_t *loc, uint64_t v,
250 uint8_t bitsSize, uint8_t shift) {
251 uint16_t instr = read16(ctx, loc);
252 uint16_t mask = 0xffff >> (16 - bitsSize);
253 uint16_t data = (instr & ~mask) | ((v >> shift) & mask);
254 write16(ctx, loc, data);
255 }
256
writePltHeader(uint8_t * buf) const257 template <class ELFT> void MIPS<ELFT>::writePltHeader(uint8_t *buf) const {
258 if (isMicroMips(ctx)) {
259 uint64_t gotPlt = ctx.in.gotPlt->getVA();
260 uint64_t plt = ctx.in.plt->getVA();
261 // Overwrite trap instructions written by Writer::writeTrapInstr.
262 memset(buf, 0, pltHeaderSize);
263
264 write16(ctx, buf,
265 isMipsR6(ctx) ? 0x7860 : 0x7980); // addiupc v1, (GOTPLT) - .
266 write16(ctx, buf + 4, 0xff23); // lw $25, 0($3)
267 write16(ctx, buf + 8, 0x0535); // subu16 $2, $2, $3
268 write16(ctx, buf + 10, 0x2525); // srl16 $2, $2, 2
269 write16(ctx, buf + 12, 0x3302); // addiu $24, $2, -2
270 write16(ctx, buf + 14, 0xfffe);
271 write16(ctx, buf + 16, 0x0dff); // move $15, $31
272 if (isMipsR6(ctx)) {
273 write16(ctx, buf + 18, 0x0f83); // move $28, $3
274 write16(ctx, buf + 20, 0x472b); // jalrc $25
275 write16(ctx, buf + 22, 0x0c00); // nop
276 relocateNoSym(buf, R_MICROMIPS_PC19_S2, gotPlt - plt);
277 } else {
278 write16(ctx, buf + 18, 0x45f9); // jalrc $25
279 write16(ctx, buf + 20, 0x0f83); // move $28, $3
280 write16(ctx, buf + 22, 0x0c00); // nop
281 relocateNoSym(buf, R_MICROMIPS_PC23_S2, gotPlt - plt);
282 }
283 return;
284 }
285
286 if (ctx.arg.mipsN32Abi) {
287 write32(ctx, buf, 0x3c0e0000); // lui $14, %hi(&GOTPLT[0])
288 write32(ctx, buf + 4, 0x8dd90000); // lw $25, %lo(&GOTPLT[0])($14)
289 write32(ctx, buf + 8, 0x25ce0000); // addiu $14, $14, %lo(&GOTPLT[0])
290 write32(ctx, buf + 12, 0x030ec023); // subu $24, $24, $14
291 write32(ctx, buf + 16, 0x03e07825); // move $15, $31
292 write32(ctx, buf + 20, 0x0018c082); // srl $24, $24, 2
293 } else if (ELFT::Is64Bits) {
294 write32(ctx, buf, 0x3c0e0000); // lui $14, %hi(&GOTPLT[0])
295 write32(ctx, buf + 4, 0xddd90000); // ld $25, %lo(&GOTPLT[0])($14)
296 write32(ctx, buf + 8, 0x25ce0000); // addiu $14, $14, %lo(&GOTPLT[0])
297 write32(ctx, buf + 12, 0x030ec023); // subu $24, $24, $14
298 write32(ctx, buf + 16, 0x03e07825); // move $15, $31
299 write32(ctx, buf + 20, 0x0018c0c2); // srl $24, $24, 3
300 } else {
301 write32(ctx, buf, 0x3c1c0000); // lui $28, %hi(&GOTPLT[0])
302 write32(ctx, buf + 4, 0x8f990000); // lw $25, %lo(&GOTPLT[0])($28)
303 write32(ctx, buf + 8, 0x279c0000); // addiu $28, $28, %lo(&GOTPLT[0])
304 write32(ctx, buf + 12, 0x031cc023); // subu $24, $24, $28
305 write32(ctx, buf + 16, 0x03e07825); // move $15, $31
306 write32(ctx, buf + 20, 0x0018c082); // srl $24, $24, 2
307 }
308
309 uint32_t jalrInst = ctx.arg.zHazardplt ? 0x0320fc09 : 0x0320f809;
310 write32(ctx, buf + 24, jalrInst); // jalr.hb $25 or jalr $25
311 write32(ctx, buf + 28, 0x2718fffe); // subu $24, $24, 2
312
313 uint64_t gotPlt = ctx.in.gotPlt->getVA();
314 writeValue(ctx, buf, gotPlt + 0x8000, 16, 16);
315 writeValue(ctx, buf + 4, gotPlt, 16, 0);
316 writeValue(ctx, buf + 8, gotPlt, 16, 0);
317 }
318
319 template <class ELFT>
writePlt(uint8_t * buf,const Symbol & sym,uint64_t pltEntryAddr) const320 void MIPS<ELFT>::writePlt(uint8_t *buf, const Symbol &sym,
321 uint64_t pltEntryAddr) const {
322 uint64_t gotPltEntryAddr = sym.getGotPltVA(ctx);
323 if (isMicroMips(ctx)) {
324 // Overwrite trap instructions written by Writer::writeTrapInstr.
325 memset(buf, 0, pltEntrySize);
326
327 if (isMipsR6(ctx)) {
328 write16(ctx, buf, 0x7840); // addiupc $2, (GOTPLT) - .
329 write16(ctx, buf + 4, 0xff22); // lw $25, 0($2)
330 write16(ctx, buf + 8, 0x0f02); // move $24, $2
331 write16(ctx, buf + 10, 0x4723); // jrc $25 / jr16 $25
332 relocateNoSym(buf, R_MICROMIPS_PC19_S2, gotPltEntryAddr - pltEntryAddr);
333 } else {
334 write16(ctx, buf, 0x7900); // addiupc $2, (GOTPLT) - .
335 write16(ctx, buf + 4, 0xff22); // lw $25, 0($2)
336 write16(ctx, buf + 8, 0x4599); // jrc $25 / jr16 $25
337 write16(ctx, buf + 10, 0x0f02); // move $24, $2
338 relocateNoSym(buf, R_MICROMIPS_PC23_S2, gotPltEntryAddr - pltEntryAddr);
339 }
340 return;
341 }
342
343 uint32_t loadInst = ELFT::Is64Bits ? 0xddf90000 : 0x8df90000;
344 uint32_t jrInst = isMipsR6(ctx)
345 ? (ctx.arg.zHazardplt ? 0x03200409 : 0x03200009)
346 : (ctx.arg.zHazardplt ? 0x03200408 : 0x03200008);
347 uint32_t addInst = ELFT::Is64Bits ? 0x65f80000 : 0x25f80000;
348
349 write32(ctx, buf, 0x3c0f0000); // lui $15, %hi(.got.plt entry)
350 write32(ctx, buf + 4, loadInst); // l[wd] $25, %lo(.got.plt entry)($15)
351 write32(ctx, buf + 8, jrInst); // jr $25 / jr.hb $25
352 write32(ctx, buf + 12, addInst); // [d]addiu $24, $15, %lo(.got.plt entry)
353 writeValue(ctx, buf, gotPltEntryAddr + 0x8000, 16, 16);
354 writeValue(ctx, buf + 4, gotPltEntryAddr, 16, 0);
355 writeValue(ctx, buf + 12, gotPltEntryAddr, 16, 0);
356 }
357
358 template <class ELFT>
needsThunk(RelExpr expr,RelType type,const InputFile * file,uint64_t branchAddr,const Symbol & s,int64_t) const359 bool MIPS<ELFT>::needsThunk(RelExpr expr, RelType type, const InputFile *file,
360 uint64_t branchAddr, const Symbol &s,
361 int64_t /*a*/) const {
362 // Any MIPS PIC code function is invoked with its address in register $t9.
363 // So if we have a branch instruction from non-PIC code to the PIC one
364 // we cannot make the jump directly and need to create a small stubs
365 // to save the target function address.
366 // See page 3-38 ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
367 if (type != R_MIPS_26 && type != R_MIPS_PC26_S2 &&
368 type != R_MICROMIPS_26_S1 && type != R_MICROMIPS_PC26_S1)
369 return false;
370 auto *f = dyn_cast<ObjFile<ELFT>>(file);
371 if (!f)
372 return false;
373 // If current file has PIC code, LA25 stub is not required.
374 if (f->getObj().getHeader().e_flags & EF_MIPS_PIC)
375 return false;
376 auto *d = dyn_cast<Defined>(&s);
377 // LA25 is required if target file has PIC code
378 // or target symbol is a PIC symbol.
379 return d && isMipsPIC<ELFT>(d);
380 }
381
382 template <class ELFT>
getImplicitAddend(const uint8_t * buf,RelType type) const383 int64_t MIPS<ELFT>::getImplicitAddend(const uint8_t *buf, RelType type) const {
384 const endianness e = ELFT::Endianness;
385 switch (type) {
386 case R_MIPS_32:
387 case R_MIPS_REL32:
388 case R_MIPS_GPREL32:
389 case R_MIPS_TLS_DTPREL32:
390 case R_MIPS_TLS_DTPMOD32:
391 case R_MIPS_TLS_TPREL32:
392 return SignExtend64<32>(read32(ctx, buf));
393 case R_MIPS_26:
394 // FIXME (simon): If the relocation target symbol is not a PLT entry
395 // we should use another expression for calculation:
396 // ((A << 2) | (P & 0xf0000000)) >> 2
397 return SignExtend64<28>(read32(ctx, buf) << 2);
398 case R_MIPS_CALL_HI16:
399 case R_MIPS_GOT16:
400 case R_MIPS_GOT_HI16:
401 case R_MIPS_HI16:
402 case R_MIPS_PCHI16:
403 return SignExtend64<16>(read32(ctx, buf)) << 16;
404 case R_MIPS_CALL16:
405 case R_MIPS_CALL_LO16:
406 case R_MIPS_GOT_LO16:
407 case R_MIPS_GPREL16:
408 case R_MIPS_LO16:
409 case R_MIPS_PCLO16:
410 case R_MIPS_TLS_DTPREL_HI16:
411 case R_MIPS_TLS_DTPREL_LO16:
412 case R_MIPS_TLS_GD:
413 case R_MIPS_TLS_GOTTPREL:
414 case R_MIPS_TLS_LDM:
415 case R_MIPS_TLS_TPREL_HI16:
416 case R_MIPS_TLS_TPREL_LO16:
417 return SignExtend64<16>(read32(ctx, buf));
418 case R_MICROMIPS_GOT16:
419 case R_MICROMIPS_HI16:
420 return SignExtend64<16>(readShuffle<e>(ctx, buf)) << 16;
421 case R_MICROMIPS_CALL16:
422 case R_MICROMIPS_GPREL16:
423 case R_MICROMIPS_LO16:
424 case R_MICROMIPS_TLS_DTPREL_HI16:
425 case R_MICROMIPS_TLS_DTPREL_LO16:
426 case R_MICROMIPS_TLS_GD:
427 case R_MICROMIPS_TLS_GOTTPREL:
428 case R_MICROMIPS_TLS_LDM:
429 case R_MICROMIPS_TLS_TPREL_HI16:
430 case R_MICROMIPS_TLS_TPREL_LO16:
431 return SignExtend64<16>(readShuffle<e>(ctx, buf));
432 case R_MICROMIPS_GPREL7_S2:
433 return SignExtend64<9>(readShuffle<e>(ctx, buf) << 2);
434 case R_MIPS_PC16:
435 return SignExtend64<18>(read32(ctx, buf) << 2);
436 case R_MIPS_PC19_S2:
437 return SignExtend64<21>(read32(ctx, buf) << 2);
438 case R_MIPS_PC21_S2:
439 return SignExtend64<23>(read32(ctx, buf) << 2);
440 case R_MIPS_PC26_S2:
441 return SignExtend64<28>(read32(ctx, buf) << 2);
442 case R_MIPS_PC32:
443 return SignExtend64<32>(read32(ctx, buf));
444 case R_MICROMIPS_26_S1:
445 return SignExtend64<27>(readShuffle<e>(ctx, buf) << 1);
446 case R_MICROMIPS_PC7_S1:
447 return SignExtend64<8>(read16(ctx, buf) << 1);
448 case R_MICROMIPS_PC10_S1:
449 return SignExtend64<11>(read16(ctx, buf) << 1);
450 case R_MICROMIPS_PC16_S1:
451 return SignExtend64<17>(readShuffle<e>(ctx, buf) << 1);
452 case R_MICROMIPS_PC18_S3:
453 return SignExtend64<21>(readShuffle<e>(ctx, buf) << 3);
454 case R_MICROMIPS_PC19_S2:
455 return SignExtend64<21>(readShuffle<e>(ctx, buf) << 2);
456 case R_MICROMIPS_PC21_S1:
457 return SignExtend64<22>(readShuffle<e>(ctx, buf) << 1);
458 case R_MICROMIPS_PC23_S2:
459 return SignExtend64<25>(readShuffle<e>(ctx, buf) << 2);
460 case R_MICROMIPS_PC26_S1:
461 return SignExtend64<27>(readShuffle<e>(ctx, buf) << 1);
462 case R_MIPS_64:
463 case R_MIPS_TLS_DTPMOD64:
464 case R_MIPS_TLS_DTPREL64:
465 case R_MIPS_TLS_TPREL64:
466 case (R_MIPS_64 << 8) | R_MIPS_REL32:
467 return read64(ctx, buf);
468 case R_MIPS_COPY:
469 return ctx.arg.is64 ? read64(ctx, buf) : read32(ctx, buf);
470 case R_MIPS_NONE:
471 case R_MIPS_JUMP_SLOT:
472 case R_MIPS_JALR:
473 // These relocations are defined as not having an implicit addend.
474 return 0;
475 default:
476 InternalErr(ctx, buf) << "cannot read addend for relocation " << type;
477 return 0;
478 }
479 }
480
481 static std::pair<uint32_t, uint64_t>
calculateMipsRelChain(Ctx & ctx,uint8_t * loc,uint32_t type,uint64_t val)482 calculateMipsRelChain(Ctx &ctx, uint8_t *loc, uint32_t type, uint64_t val) {
483 // MIPS N64 ABI packs multiple relocations into the single relocation
484 // record. In general, all up to three relocations can have arbitrary
485 // types. In fact, Clang and GCC uses only a few combinations. For now,
486 // we support two of them. That is allow to pass at least all LLVM
487 // test suite cases.
488 // <any relocation> / R_MIPS_SUB / R_MIPS_HI16 | R_MIPS_LO16
489 // <any relocation> / R_MIPS_64 / R_MIPS_NONE
490 // The first relocation is a 'real' relocation which is calculated
491 // using the corresponding symbol's value. The second and the third
492 // relocations used to modify result of the first one: extend it to
493 // 64-bit, extract high or low part etc. For details, see part 2.9 Relocation
494 // at the https://dmz-portal.mips.com/mw/images/8/82/007-4658-001.pdf
495 uint32_t type2 = (type >> 8) & 0xff;
496 uint32_t type3 = (type >> 16) & 0xff;
497 if (type2 == R_MIPS_NONE && type3 == R_MIPS_NONE)
498 return std::make_pair(type, val);
499 if (type2 == R_MIPS_64 && type3 == R_MIPS_NONE)
500 return std::make_pair(type2, val);
501 if (type2 == R_MIPS_SUB && (type3 == R_MIPS_HI16 || type3 == R_MIPS_LO16))
502 return std::make_pair(type3, -val);
503 Err(ctx) << getErrorLoc(ctx, loc) << "unsupported relocations combination "
504 << type;
505 return std::make_pair(type & 0xff, val);
506 }
507
isBranchReloc(RelType type)508 static bool isBranchReloc(RelType type) {
509 return type == R_MIPS_26 || type == R_MIPS_PC26_S2 ||
510 type == R_MIPS_PC21_S2 || type == R_MIPS_PC16;
511 }
512
isMicroBranchReloc(RelType type)513 static bool isMicroBranchReloc(RelType type) {
514 return type == R_MICROMIPS_26_S1 || type == R_MICROMIPS_PC16_S1 ||
515 type == R_MICROMIPS_PC10_S1 || type == R_MICROMIPS_PC7_S1;
516 }
517
518 template <class ELFT>
fixupCrossModeJump(Ctx & ctx,uint8_t * loc,RelType type,uint64_t val)519 static uint64_t fixupCrossModeJump(Ctx &ctx, uint8_t *loc, RelType type,
520 uint64_t val) {
521 // Here we need to detect jump/branch from regular MIPS code
522 // to a microMIPS target and vice versa. In that cases jump
523 // instructions need to be replaced by their "cross-mode"
524 // equivalents.
525 const endianness e = ELFT::Endianness;
526 bool isMicroTgt = val & 0x1;
527 bool isCrossJump = (isMicroTgt && isBranchReloc(type)) ||
528 (!isMicroTgt && isMicroBranchReloc(type));
529 if (!isCrossJump)
530 return val;
531
532 switch (type) {
533 case R_MIPS_26: {
534 uint32_t inst = read32(ctx, loc) >> 26;
535 if (inst == 0x3 || inst == 0x1d) { // JAL or JALX
536 writeValue(ctx, loc, 0x1d << 26, 32, 0);
537 return val;
538 }
539 break;
540 }
541 case R_MICROMIPS_26_S1: {
542 uint32_t inst = readShuffle<e>(ctx, loc) >> 26;
543 if (inst == 0x3d || inst == 0x3c) { // JAL32 or JALX32
544 val >>= 1;
545 writeShuffle<e>(ctx, loc, 0x3c << 26, 32, 0);
546 return val;
547 }
548 break;
549 }
550 case R_MIPS_PC26_S2:
551 case R_MIPS_PC21_S2:
552 case R_MIPS_PC16:
553 case R_MICROMIPS_PC16_S1:
554 case R_MICROMIPS_PC10_S1:
555 case R_MICROMIPS_PC7_S1:
556 // FIXME (simon): Support valid branch relocations.
557 break;
558 default:
559 llvm_unreachable("unexpected jump/branch relocation");
560 }
561
562 ErrAlways(ctx)
563 << getErrorLoc(ctx, loc)
564 << "unsupported jump/branch instruction between ISA modes referenced by "
565 << type << " relocation";
566 return val;
567 }
568
569 template <class ELFT>
relocate(uint8_t * loc,const Relocation & rel,uint64_t val) const570 void MIPS<ELFT>::relocate(uint8_t *loc, const Relocation &rel,
571 uint64_t val) const {
572 const endianness e = ELFT::Endianness;
573 RelType type = rel.type;
574
575 if (ELFT::Is64Bits || ctx.arg.mipsN32Abi)
576 std::tie(type, val) = calculateMipsRelChain(ctx, loc, type, val);
577
578 // Detect cross-mode jump/branch and fix instruction.
579 val = fixupCrossModeJump<ELFT>(ctx, loc, type, val);
580
581 // Thread pointer and DRP offsets from the start of TLS data area.
582 // https://www.linux-mips.org/wiki/NPTL
583 if (type == R_MIPS_TLS_DTPREL_HI16 || type == R_MIPS_TLS_DTPREL_LO16 ||
584 type == R_MIPS_TLS_DTPREL32 || type == R_MIPS_TLS_DTPREL64 ||
585 type == R_MICROMIPS_TLS_DTPREL_HI16 ||
586 type == R_MICROMIPS_TLS_DTPREL_LO16) {
587 val -= 0x8000;
588 }
589
590 switch (type) {
591 case R_MIPS_32:
592 case R_MIPS_GPREL32:
593 case R_MIPS_TLS_DTPREL32:
594 case R_MIPS_TLS_TPREL32:
595 write32(ctx, loc, val);
596 break;
597 case R_MIPS_64:
598 case R_MIPS_TLS_DTPREL64:
599 case R_MIPS_TLS_TPREL64:
600 write64(ctx, loc, val);
601 break;
602 case R_MIPS_26:
603 writeValue(ctx, loc, val, 26, 2);
604 break;
605 case R_MIPS_GOT16:
606 // The R_MIPS_GOT16 relocation's value in "relocatable" linking mode
607 // is updated addend (not a GOT index). In that case write high 16 bits
608 // to store a correct addend value.
609 if (ctx.arg.relocatable) {
610 writeValue(ctx, loc, val + 0x8000, 16, 16);
611 } else {
612 checkInt(ctx, loc, val, 16, rel);
613 writeValue(ctx, loc, val, 16, 0);
614 }
615 break;
616 case R_MICROMIPS_GOT16:
617 if (ctx.arg.relocatable) {
618 writeShuffle<e>(ctx, loc, val + 0x8000, 16, 16);
619 } else {
620 checkInt(ctx, loc, val, 16, rel);
621 writeShuffle<e>(ctx, loc, val, 16, 0);
622 }
623 break;
624 case R_MIPS_CALL16:
625 case R_MIPS_GOT_DISP:
626 case R_MIPS_GOT_PAGE:
627 case R_MIPS_GPREL16:
628 case R_MIPS_TLS_GD:
629 case R_MIPS_TLS_GOTTPREL:
630 case R_MIPS_TLS_LDM:
631 checkInt(ctx, loc, val, 16, rel);
632 [[fallthrough]];
633 case R_MIPS_CALL_LO16:
634 case R_MIPS_GOT_LO16:
635 case R_MIPS_GOT_OFST:
636 case R_MIPS_LO16:
637 case R_MIPS_PCLO16:
638 case R_MIPS_TLS_DTPREL_LO16:
639 case R_MIPS_TLS_TPREL_LO16:
640 writeValue(ctx, loc, val, 16, 0);
641 break;
642 case R_MICROMIPS_GPREL16:
643 case R_MICROMIPS_TLS_GD:
644 case R_MICROMIPS_TLS_LDM:
645 checkInt(ctx, loc, val, 16, rel);
646 writeShuffle<e>(ctx, loc, val, 16, 0);
647 break;
648 case R_MICROMIPS_CALL16:
649 case R_MICROMIPS_CALL_LO16:
650 case R_MICROMIPS_LO16:
651 case R_MICROMIPS_TLS_DTPREL_LO16:
652 case R_MICROMIPS_TLS_GOTTPREL:
653 case R_MICROMIPS_TLS_TPREL_LO16:
654 writeShuffle<e>(ctx, loc, val, 16, 0);
655 break;
656 case R_MICROMIPS_GPREL7_S2:
657 checkInt(ctx, loc, val, 7, rel);
658 writeShuffle<e>(ctx, loc, val, 7, 2);
659 break;
660 case R_MIPS_CALL_HI16:
661 case R_MIPS_GOT_HI16:
662 case R_MIPS_HI16:
663 case R_MIPS_PCHI16:
664 case R_MIPS_TLS_DTPREL_HI16:
665 case R_MIPS_TLS_TPREL_HI16:
666 writeValue(ctx, loc, val + 0x8000, 16, 16);
667 break;
668 case R_MICROMIPS_CALL_HI16:
669 case R_MICROMIPS_GOT_HI16:
670 case R_MICROMIPS_HI16:
671 case R_MICROMIPS_TLS_DTPREL_HI16:
672 case R_MICROMIPS_TLS_TPREL_HI16:
673 writeShuffle<e>(ctx, loc, val + 0x8000, 16, 16);
674 break;
675 case R_MIPS_HIGHER:
676 writeValue(ctx, loc, val + 0x80008000, 16, 32);
677 break;
678 case R_MIPS_HIGHEST:
679 writeValue(ctx, loc, val + 0x800080008000, 16, 48);
680 break;
681 case R_MIPS_JALR:
682 val -= 4;
683 // Replace jalr/jr instructions by bal/b if the target
684 // offset fits into the 18-bit range.
685 if (isInt<18>(val)) {
686 switch (read32(ctx, loc)) {
687 case 0x0320f809: // jalr $25 => bal sym
688 write32(ctx, loc, 0x04110000 | ((val >> 2) & 0xffff));
689 break;
690 case 0x03200008: // jr $25 => b sym
691 write32(ctx, loc, 0x10000000 | ((val >> 2) & 0xffff));
692 break;
693 }
694 }
695 break;
696 case R_MICROMIPS_JALR:
697 // Ignore this optimization relocation for now
698 break;
699 case R_MIPS_PC16:
700 checkAlignment(ctx, loc, val, 4, rel);
701 checkInt(ctx, loc, val, 18, rel);
702 writeValue(ctx, loc, val, 16, 2);
703 break;
704 case R_MIPS_PC19_S2:
705 checkAlignment(ctx, loc, val, 4, rel);
706 checkInt(ctx, loc, val, 21, rel);
707 writeValue(ctx, loc, val, 19, 2);
708 break;
709 case R_MIPS_PC21_S2:
710 checkAlignment(ctx, loc, val, 4, rel);
711 checkInt(ctx, loc, val, 23, rel);
712 writeValue(ctx, loc, val, 21, 2);
713 break;
714 case R_MIPS_PC26_S2:
715 checkAlignment(ctx, loc, val, 4, rel);
716 checkInt(ctx, loc, val, 28, rel);
717 writeValue(ctx, loc, val, 26, 2);
718 break;
719 case R_MIPS_PC32:
720 writeValue(ctx, loc, val, 32, 0);
721 break;
722 case R_MICROMIPS_26_S1:
723 case R_MICROMIPS_PC26_S1:
724 checkInt(ctx, loc, val, 27, rel);
725 writeShuffle<e>(ctx, loc, val, 26, 1);
726 break;
727 case R_MICROMIPS_PC7_S1:
728 checkInt(ctx, loc, val, 8, rel);
729 writeMicroRelocation16<e>(ctx, loc, val, 7, 1);
730 break;
731 case R_MICROMIPS_PC10_S1:
732 checkInt(ctx, loc, val, 11, rel);
733 writeMicroRelocation16<e>(ctx, loc, val, 10, 1);
734 break;
735 case R_MICROMIPS_PC16_S1:
736 checkInt(ctx, loc, val, 17, rel);
737 writeShuffle<e>(ctx, loc, val, 16, 1);
738 break;
739 case R_MICROMIPS_PC18_S3:
740 checkInt(ctx, loc, val, 21, rel);
741 writeShuffle<e>(ctx, loc, val, 18, 3);
742 break;
743 case R_MICROMIPS_PC19_S2:
744 checkInt(ctx, loc, val, 21, rel);
745 writeShuffle<e>(ctx, loc, val, 19, 2);
746 break;
747 case R_MICROMIPS_PC21_S1:
748 checkInt(ctx, loc, val, 22, rel);
749 writeShuffle<e>(ctx, loc, val, 21, 1);
750 break;
751 case R_MICROMIPS_PC23_S2:
752 checkInt(ctx, loc, val, 25, rel);
753 writeShuffle<e>(ctx, loc, val, 23, 2);
754 break;
755 default:
756 llvm_unreachable("unknown relocation");
757 }
758 }
759
usesOnlyLowPageBits(RelType type) const760 template <class ELFT> bool MIPS<ELFT>::usesOnlyLowPageBits(RelType type) const {
761 return type == R_MIPS_LO16 || type == R_MIPS_GOT_OFST ||
762 type == R_MICROMIPS_LO16;
763 }
764
765 // Return true if the symbol is a PIC function.
isMipsPIC(const Defined * sym)766 template <class ELFT> bool elf::isMipsPIC(const Defined *sym) {
767 if (!sym->isFunc())
768 return false;
769
770 if (sym->stOther & STO_MIPS_PIC)
771 return true;
772
773 if (!sym->section)
774 return false;
775
776 InputFile *file = cast<InputSectionBase>(sym->section)->file;
777 if (!file || file->isInternal())
778 return false;
779
780 return cast<ObjFile<ELFT>>(file)->getObj().getHeader().e_flags & EF_MIPS_PIC;
781 }
782
setMipsTargetInfo(Ctx & ctx)783 void elf::setMipsTargetInfo(Ctx &ctx) {
784 switch (ctx.arg.ekind) {
785 case ELF32LEKind: {
786 ctx.target.reset(new MIPS<ELF32LE>(ctx));
787 return;
788 }
789 case ELF32BEKind: {
790 ctx.target.reset(new MIPS<ELF32BE>(ctx));
791 return;
792 }
793 case ELF64LEKind: {
794 ctx.target.reset(new MIPS<ELF64LE>(ctx));
795 return;
796 }
797 case ELF64BEKind: {
798 ctx.target.reset(new MIPS<ELF64BE>(ctx));
799 return;
800 }
801 default:
802 llvm_unreachable("unsupported target");
803 }
804 }
805
806 template bool elf::isMipsPIC<ELF32LE>(const Defined *);
807 template bool elf::isMipsPIC<ELF32BE>(const Defined *);
808 template bool elf::isMipsPIC<ELF64LE>(const Defined *);
809 template bool elf::isMipsPIC<ELF64BE>(const Defined *);
810