1 //===- PPC.cpp ------------------------------------------------------------===//
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
7 //===----------------------------------------------------------------------===//
9 #include "OutputSections.h"
11 #include "SyntheticSections.h"
14 #include "lld/Common/ErrorHandler.h"
15 #include "llvm/Support/Endian.h"
18 using namespace llvm::support::endian;
19 using namespace llvm::ELF;
21 using namespace lld::elf;
24 class PPC final : public TargetInfo {
27 RelExpr getRelExpr(RelType type, const Symbol &s,
28 const uint8_t *loc) const override;
29 RelType getDynRel(RelType type) const override;
30 void writeGotHeader(uint8_t *buf) const override;
31 void writePltHeader(uint8_t *buf) const override {
32 llvm_unreachable("should call writePPC32GlinkSection() instead");
34 void writePlt(uint8_t *buf, const Symbol &sym,
35 uint64_t pltEntryAddr) const override {
36 llvm_unreachable("should call writePPC32GlinkSection() instead");
38 void writeIplt(uint8_t *buf, const Symbol &sym,
39 uint64_t pltEntryAddr) const override;
40 void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
41 bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file,
42 uint64_t branchAddr, const Symbol &s,
43 int64_t a) const override;
44 uint32_t getThunkSectionSpacing() const override;
45 bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
46 void relocate(uint8_t *loc, const Relocation &rel,
47 uint64_t val) const override;
48 RelExpr adjustRelaxExpr(RelType type, const uint8_t *data,
49 RelExpr expr) const override;
50 int getTlsGdRelaxSkip(RelType type) const override;
51 void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
52 uint64_t val) const override;
53 void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
54 uint64_t val) const override;
55 void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
56 uint64_t val) const override;
57 void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
58 uint64_t val) const override;
62 static uint16_t lo(uint32_t v) { return v; }
63 static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; }
65 static uint32_t readFromHalf16(const uint8_t *loc) {
66 return read32(config->isLE ? loc : loc - 2);
69 static void writeFromHalf16(uint8_t *loc, uint32_t insn) {
70 write32(config->isLE ? loc : loc - 2, insn);
73 void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) {
74 // Create canonical PLT entries for non-PIE code. Compilers don't generate
75 // non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE.
76 uint32_t glink = in.plt->getVA(); // VA of .glink
78 for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) {
79 writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
85 // On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an
86 // absolute address from a specific .plt slot (usually called .got.plt on
87 // other targets) and jumps there.
89 // a) With immediate binding (BIND_NOW), the .plt entry is resolved at load
90 // time. The .glink section is not used.
91 // b) With lazy binding, the .plt entry points to a `b PLTresolve`
92 // instruction in .glink, filled in by PPC::writeGotPlt().
94 // Write N `b PLTresolve` first.
95 for (size_t i = 0; i != numEntries; ++i)
96 write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i));
97 buf += 4 * numEntries;
99 // Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve()
100 // computes the PLT index (by computing the distance from the landing b to
101 // itself) and calls _dl_runtime_resolve() (in glibc).
102 uint32_t got = in.got->getVA();
103 const uint8_t *end = buf + 64;
105 uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12;
106 uint32_t gotBcl = got + 4 - (glink + afterBcl);
107 write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha
108 write32(buf + 4, 0x7c0802a6); // mflr r0
109 write32(buf + 8, 0x429f0005); // bcl 20,30,.+4
110 write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l
111 write32(buf + 16, 0x7d8802a6); // mflr r12
112 write32(buf + 20, 0x7c0803a6); // mtlr r0
113 write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12
114 write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha
115 if (ha(gotBcl) == ha(gotBcl + 4)) {
116 write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12)
118 0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12)
120 write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12)
121 write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12)
123 write32(buf + 40, 0x7c0903a6); // mtctr 0
124 write32(buf + 44, 0x7c0b5a14); // add r0,11,11
125 write32(buf + 48, 0x7d605a14); // add r11,0,11
126 write32(buf + 52, 0x4e800420); // bctr
129 write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha
130 write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha
131 if (ha(got + 4) == ha(got + 8))
132 write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12)
134 write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12)
135 write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l
136 write32(buf + 16, 0x7c0903a6); // mtctr r0
137 write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11
138 if (ha(got + 4) == ha(got + 8))
139 write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12)
141 write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12)
142 write32(buf + 28, 0x7d605a14); // add r11,r0,r11
143 write32(buf + 32, 0x4e800420); // bctr
147 // Pad with nop. They should not be executed.
148 for (; buf < end; buf += 4)
149 write32(buf, 0x60000000);
153 copyRel = R_PPC_COPY;
154 gotRel = R_PPC_GLOB_DAT;
155 noneRel = R_PPC_NONE;
156 pltRel = R_PPC_JMP_SLOT;
157 relativeRel = R_PPC_RELATIVE;
158 iRelativeRel = R_PPC_IRELATIVE;
159 symbolicRel = R_PPC_ADDR32;
160 gotBaseSymInGotPlt = false;
161 gotHeaderEntriesNum = 3;
162 gotPltHeaderEntriesNum = 0;
169 tlsModuleIndexRel = R_PPC_DTPMOD32;
170 tlsOffsetRel = R_PPC_DTPREL32;
171 tlsGotRel = R_PPC_TPREL32;
173 defaultMaxPageSize = 65536;
174 defaultImageBase = 0x10000000;
176 write32(trapInstr.data(), 0x7fe00008);
179 void PPC::writeIplt(uint8_t *buf, const Symbol &sym,
180 uint64_t /*pltEntryAddr*/) const {
181 // In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a
182 // .got2.plt_pic32. thunk.
183 writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000);
186 void PPC::writeGotHeader(uint8_t *buf) const {
187 // _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC
188 // glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1],
189 // link_map in _GLOBAL_OFFSET_TABLE_[2].
190 write32(buf, mainPart->dynamic->getVA());
193 void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const {
194 // Address of the symbol resolver stub in .glink .
195 write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.pltIndex);
198 bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file,
199 uint64_t branchAddr, const Symbol &s, int64_t a) const {
200 if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24)
206 return !PPC::inBranchRange(type, branchAddr, s.getVA(a));
209 uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; }
211 bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
212 uint64_t offset = dst - src;
213 if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24)
214 return isInt<26>(offset);
215 llvm_unreachable("unsupported relocation type used in branch");
218 RelExpr PPC::getRelExpr(RelType type, const Symbol &s,
219 const uint8_t *loc) const {
223 case R_PPC_ADDR16_HA:
224 case R_PPC_ADDR16_HI:
225 case R_PPC_ADDR16_LO:
229 case R_PPC_DTPREL16_HA:
230 case R_PPC_DTPREL16_HI:
231 case R_PPC_DTPREL16_LO:
242 case R_PPC_LOCAL24PC:
246 return R_PPC32_PLTREL;
247 case R_PPC_GOT_TLSGD16:
249 case R_PPC_GOT_TLSLD16:
251 case R_PPC_GOT_TPREL16:
256 return R_TLSDESC_CALL;
260 case R_PPC_TPREL16_HA:
261 case R_PPC_TPREL16_LO:
262 case R_PPC_TPREL16_HI:
265 error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
266 ") against symbol " + toString(s));
271 RelType PPC::getDynRel(RelType type) const {
272 if (type == R_PPC_ADDR32)
277 static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) {
278 uint64_t dtpBiasedVal = val - 0x8000;
281 return {R_PPC64_ADDR16, dtpBiasedVal};
282 case R_PPC_DTPREL16_HA:
283 return {R_PPC_ADDR16_HA, dtpBiasedVal};
284 case R_PPC_DTPREL16_HI:
285 return {R_PPC_ADDR16_HI, dtpBiasedVal};
286 case R_PPC_DTPREL16_LO:
287 return {R_PPC_ADDR16_LO, dtpBiasedVal};
289 return {R_PPC_ADDR32, dtpBiasedVal};
295 void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
297 std::tie(newType, val) = fromDTPREL(rel.type, val);
300 checkIntUInt(loc, val, 16, rel);
304 case R_PPC_GOT_TLSGD16:
305 case R_PPC_GOT_TLSLD16:
306 case R_PPC_GOT_TPREL16:
308 checkInt(loc, val, 16, rel);
311 case R_PPC_ADDR16_HA:
312 case R_PPC_DTPREL16_HA:
313 case R_PPC_GOT_TLSGD16_HA:
314 case R_PPC_GOT_TLSLD16_HA:
315 case R_PPC_GOT_TPREL16_HA:
317 case R_PPC_TPREL16_HA:
318 write16(loc, ha(val));
320 case R_PPC_ADDR16_HI:
321 case R_PPC_DTPREL16_HI:
322 case R_PPC_GOT_TLSGD16_HI:
323 case R_PPC_GOT_TLSLD16_HI:
324 case R_PPC_GOT_TPREL16_HI:
326 case R_PPC_TPREL16_HI:
327 write16(loc, val >> 16);
329 case R_PPC_ADDR16_LO:
330 case R_PPC_DTPREL16_LO:
331 case R_PPC_GOT_TLSGD16_LO:
332 case R_PPC_GOT_TLSLD16_LO:
333 case R_PPC_GOT_TPREL16_LO:
335 case R_PPC_TPREL16_LO:
343 uint32_t mask = 0x0000FFFC;
344 checkInt(loc, val, 16, rel);
345 checkAlignment(loc, val, 4, rel);
346 write32(loc, (read32(loc) & ~mask) | (val & mask));
350 case R_PPC_LOCAL24PC:
351 case R_PPC_PLTREL24: {
352 uint32_t mask = 0x03FFFFFC;
353 checkInt(loc, val, 26, rel);
354 checkAlignment(loc, val, 4, rel);
355 write32(loc, (read32(loc) & ~mask) | (val & mask));
359 llvm_unreachable("unknown relocation");
363 RelExpr PPC::adjustRelaxExpr(RelType type, const uint8_t *data,
364 RelExpr expr) const {
365 if (expr == R_RELAX_TLS_GD_TO_IE)
366 return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
367 if (expr == R_RELAX_TLS_LD_TO_LE)
368 return R_RELAX_TLS_LD_TO_LE_ABS;
372 int PPC::getTlsGdRelaxSkip(RelType type) const {
373 // A __tls_get_addr call instruction is marked with 2 relocations:
375 // R_PPC_TLSGD / R_PPC_TLSLD: marker relocation
376 // R_PPC_REL24: __tls_get_addr
378 // After the relaxation we no longer call __tls_get_addr and should skip both
379 // relocations to not create a false dependence on __tls_get_addr being
381 if (type == R_PPC_TLSGD || type == R_PPC_TLSLD)
386 void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
387 uint64_t val) const {
389 case R_PPC_GOT_TLSGD16: {
390 // addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA)
391 uint32_t insn = readFromHalf16(loc);
392 writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000));
393 relocateNoSym(loc, R_PPC_GOT_TPREL16, val);
397 // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2
398 write32(loc, 0x7c631214);
401 llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
405 void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
406 uint64_t val) const {
408 case R_PPC_GOT_TLSGD16:
409 // addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha
410 writeFromHalf16(loc, 0x3c620000 | ha(val));
413 // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l
414 write32(loc, 0x38630000 | lo(val));
417 llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
421 void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
422 uint64_t val) const {
424 case R_PPC_GOT_TLSLD16:
425 // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0
426 writeFromHalf16(loc, 0x3c620000);
429 // r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel
430 // = r3+x-0x7000, so add 4096 to r3.
431 // bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096
432 write32(loc, 0x38631000);
435 case R_PPC_DTPREL16_HA:
436 case R_PPC_DTPREL16_HI:
437 case R_PPC_DTPREL16_LO:
438 relocate(loc, rel, val);
441 llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
445 void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
446 uint64_t val) const {
448 case R_PPC_GOT_TPREL16: {
449 // lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha
450 uint32_t rt = readFromHalf16(loc) & 0x03e00000;
451 writeFromHalf16(loc, 0x3c020000 | rt | ha(val));
455 uint32_t insn = read32(loc);
456 if (insn >> 26 != 31)
457 error("unrecognized instruction for IE to LE R_PPC_TLS");
458 // addi rT, rT, x@tls --> addi rT, rT, x@tprel@l
459 uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1);
461 error("unrecognized instruction for IE to LE R_PPC_TLS");
462 write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val));
466 llvm_unreachable("unsupported relocation for TLS IE to LE relaxation");
470 TargetInfo *elf::getPPCTargetInfo() {