1//===- PPC.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 "OutputSections.h"
10#include "Symbols.h"
11#include "SyntheticSections.h"
12#include "Target.h"
13#include "Thunks.h"
14#include "lld/Common/ErrorHandler.h"
15#include "llvm/Support/Endian.h"
16
17using namespace llvm;
18using namespace llvm::support::endian;
19using namespace llvm::ELF;
20using namespace lld;
21using namespace lld::elf;
22
23namespace {
24class PPC final : public TargetInfo {
25public:
26  PPC();
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");
33  }
34  void writePlt(uint8_t *buf, const Symbol &sym,
35                uint64_t pltEntryAddr) const override {
36    llvm_unreachable("should call writePPC32GlinkSection() instead");
37  }
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;
59};
60} // namespace
61
62static uint16_t lo(uint32_t v) { return v; }
63static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; }
64
65static uint32_t readFromHalf16(const uint8_t *loc) {
66  return read32(config->isLE ? loc : loc - 2);
67}
68
69static void writeFromHalf16(uint8_t *loc, uint32_t insn) {
70  write32(config->isLE ? loc : loc - 2, insn);
71}
72
73void 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
77  if (!config->isPic) {
78    for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) {
79      writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
80      buf += 16;
81      glink += 16;
82    }
83  }
84
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.
88  //
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().
93
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;
98
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;
104  if (config->isPic) {
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)
117      write32(buf + 36,
118              0x818c0000 | lo(gotBcl + 4));       // lwz r12,r12,GOT+8-1b@l(r12)
119    } else {
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)
122    }
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
127    buf += 56;
128  } else {
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)
133    else
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)
140    else
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
144    buf += 36;
145  }
146
147  // Pad with nop. They should not be executed.
148  for (; buf < end; buf += 4)
149    write32(buf, 0x60000000);
150}
151
152PPC::PPC() {
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;
163  pltHeaderSize = 0;
164  pltEntrySize = 4;
165  ipltEntrySize = 16;
166
167  needsThunks = true;
168
169  tlsModuleIndexRel = R_PPC_DTPMOD32;
170  tlsOffsetRel = R_PPC_DTPREL32;
171  tlsGotRel = R_PPC_TPREL32;
172
173  defaultMaxPageSize = 65536;
174  defaultImageBase = 0x10000000;
175
176  write32(trapInstr.data(), 0x7fe00008);
177}
178
179void 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);
184}
185
186void 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());
191}
192
193void 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);
196}
197
198bool 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)
201    return false;
202  if (s.isInPlt())
203    return true;
204  if (s.isUndefWeak())
205    return false;
206  return !PPC::inBranchRange(type, branchAddr, s.getVA(a));
207}
208
209uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; }
210
211bool 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");
216}
217
218RelExpr PPC::getRelExpr(RelType type, const Symbol &s,
219                        const uint8_t *loc) const {
220  switch (type) {
221  case R_PPC_NONE:
222    return R_NONE;
223  case R_PPC_ADDR16_HA:
224  case R_PPC_ADDR16_HI:
225  case R_PPC_ADDR16_LO:
226  case R_PPC_ADDR32:
227    return R_ABS;
228  case R_PPC_DTPREL16:
229  case R_PPC_DTPREL16_HA:
230  case R_PPC_DTPREL16_HI:
231  case R_PPC_DTPREL16_LO:
232  case R_PPC_DTPREL32:
233    return R_DTPREL;
234  case R_PPC_REL14:
235  case R_PPC_REL32:
236  case R_PPC_REL16_LO:
237  case R_PPC_REL16_HI:
238  case R_PPC_REL16_HA:
239    return R_PC;
240  case R_PPC_GOT16:
241    return R_GOT_OFF;
242  case R_PPC_LOCAL24PC:
243  case R_PPC_REL24:
244    return R_PLT_PC;
245  case R_PPC_PLTREL24:
246    return R_PPC32_PLTREL;
247  case R_PPC_GOT_TLSGD16:
248    return R_TLSGD_GOT;
249  case R_PPC_GOT_TLSLD16:
250    return R_TLSLD_GOT;
251  case R_PPC_GOT_TPREL16:
252    return R_GOT_OFF;
253  case R_PPC_TLS:
254    return R_TLSIE_HINT;
255  case R_PPC_TLSGD:
256    return R_TLSDESC_CALL;
257  case R_PPC_TLSLD:
258    return R_TLSLD_HINT;
259  case R_PPC_TPREL16:
260  case R_PPC_TPREL16_HA:
261  case R_PPC_TPREL16_LO:
262  case R_PPC_TPREL16_HI:
263    return R_TLS;
264  default:
265    error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
266          ") against symbol " + toString(s));
267    return R_NONE;
268  }
269}
270
271RelType PPC::getDynRel(RelType type) const {
272  if (type == R_PPC_ADDR32)
273    return type;
274  return R_PPC_NONE;
275}
276
277static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) {
278  uint64_t dtpBiasedVal = val - 0x8000;
279  switch (type) {
280  case R_PPC_DTPREL16:
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};
288  case R_PPC_DTPREL32:
289    return {R_PPC_ADDR32, dtpBiasedVal};
290  default:
291    return {type, val};
292  }
293}
294
295void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
296  RelType newType;
297  std::tie(newType, val) = fromDTPREL(rel.type, val);
298  switch (newType) {
299  case R_PPC_ADDR16:
300    checkIntUInt(loc, val, 16, rel);
301    write16(loc, val);
302    break;
303  case R_PPC_GOT16:
304  case R_PPC_GOT_TLSGD16:
305  case R_PPC_GOT_TLSLD16:
306  case R_PPC_GOT_TPREL16:
307  case R_PPC_TPREL16:
308    checkInt(loc, val, 16, rel);
309    write16(loc, val);
310    break;
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:
316  case R_PPC_REL16_HA:
317  case R_PPC_TPREL16_HA:
318    write16(loc, ha(val));
319    break;
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:
325  case R_PPC_REL16_HI:
326  case R_PPC_TPREL16_HI:
327    write16(loc, val >> 16);
328    break;
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:
334  case R_PPC_REL16_LO:
335  case R_PPC_TPREL16_LO:
336    write16(loc, val);
337    break;
338  case R_PPC_ADDR32:
339  case R_PPC_REL32:
340    write32(loc, val);
341    break;
342  case R_PPC_REL14: {
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));
347    break;
348  }
349  case R_PPC_REL24:
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));
356    break;
357  }
358  default:
359    llvm_unreachable("unknown relocation");
360  }
361}
362
363RelExpr 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;
369  return expr;
370}
371
372int PPC::getTlsGdRelaxSkip(RelType type) const {
373  // A __tls_get_addr call instruction is marked with 2 relocations:
374  //
375  //   R_PPC_TLSGD / R_PPC_TLSLD: marker relocation
376  //   R_PPC_REL24: __tls_get_addr
377  //
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
380  // defined.
381  if (type == R_PPC_TLSGD || type == R_PPC_TLSLD)
382    return 2;
383  return 1;
384}
385
386void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
387                         uint64_t val) const {
388  switch (rel.type) {
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);
394    break;
395  }
396  case R_PPC_TLSGD:
397    // bl __tls_get_addr(x@tldgd) --> add r3, r3, r2
398    write32(loc, 0x7c631214);
399    break;
400  default:
401    llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
402  }
403}
404
405void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
406                         uint64_t val) const {
407  switch (rel.type) {
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));
411    break;
412  case R_PPC_TLSGD:
413    // bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l
414    write32(loc, 0x38630000 | lo(val));
415    break;
416  default:
417    llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
418  }
419}
420
421void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
422                         uint64_t val) const {
423  switch (rel.type) {
424  case R_PPC_GOT_TLSLD16:
425    // addi r3, rA, x@got@tlsgd --> addis r3, r2, 0
426    writeFromHalf16(loc, 0x3c620000);
427    break;
428  case R_PPC_TLSLD:
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);
433    break;
434  case R_PPC_DTPREL16:
435  case R_PPC_DTPREL16_HA:
436  case R_PPC_DTPREL16_HI:
437  case R_PPC_DTPREL16_LO:
438    relocate(loc, rel, val);
439    break;
440  default:
441    llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
442  }
443}
444
445void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
446                         uint64_t val) const {
447  switch (rel.type) {
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));
452    break;
453  }
454  case R_PPC_TLS: {
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);
460    if (dFormOp == 0)
461      error("unrecognized instruction for IE to LE R_PPC_TLS");
462    write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val));
463    break;
464  }
465  default:
466    llvm_unreachable("unsupported relocation for TLS IE to LE relaxation");
467  }
468}
469
470TargetInfo *elf::getPPCTargetInfo() {
471  static PPC target;
472  return &target;
473}
474