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llvm-project/lld/ELF/Arch/PPC.cpp
Fangrui Song 3809f4ebab [ELF] Support R_PPC_ADDR24 (ba foo; bla foo)
2021-01-17 00:02:13 -08:00

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//===- PPC.cpp ------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "OutputSections.h"
#include "Symbols.h"
#include "SyntheticSections.h"
#include "Target.h"
#include "Thunks.h"
#include "lld/Common/ErrorHandler.h"
#include "llvm/Support/Endian.h"
using namespace llvm;
using namespace llvm::support::endian;
using namespace llvm::ELF;
using namespace lld;
using namespace lld::elf;
namespace {
class PPC final : public TargetInfo {
public:
PPC();
RelExpr getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const override;
RelType getDynRel(RelType type) const override;
void writeGotHeader(uint8_t *buf) const override;
void writePltHeader(uint8_t *buf) const override {
llvm_unreachable("should call writePPC32GlinkSection() instead");
}
void writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override {
llvm_unreachable("should call writePPC32GlinkSection() instead");
}
void writeIplt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
void writeGotPlt(uint8_t *buf, const Symbol &s) const override;
bool needsThunk(RelExpr expr, RelType relocType, const InputFile *file,
uint64_t branchAddr, const Symbol &s,
int64_t a) const override;
uint32_t getThunkSectionSpacing() const override;
bool inBranchRange(RelType type, uint64_t src, uint64_t dst) const override;
void relocate(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
RelExpr adjustTlsExpr(RelType type, RelExpr expr) const override;
int getTlsGdRelaxSkip(RelType type) const override;
void relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
void relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const override;
};
} // namespace
static uint16_t lo(uint32_t v) { return v; }
static uint16_t ha(uint32_t v) { return (v + 0x8000) >> 16; }
static uint32_t readFromHalf16(const uint8_t *loc) {
return read32(config->isLE ? loc : loc - 2);
}
static void writeFromHalf16(uint8_t *loc, uint32_t insn) {
write32(config->isLE ? loc : loc - 2, insn);
}
void elf::writePPC32GlinkSection(uint8_t *buf, size_t numEntries) {
// Create canonical PLT entries for non-PIE code. Compilers don't generate
// non-GOT-non-PLT relocations referencing external functions for -fpie/-fPIE.
uint32_t glink = in.plt->getVA(); // VA of .glink
if (!config->isPic) {
for (const Symbol *sym : cast<PPC32GlinkSection>(in.plt)->canonical_plts) {
writePPC32PltCallStub(buf, sym->getGotPltVA(), nullptr, 0);
buf += 16;
glink += 16;
}
}
// On PPC Secure PLT ABI, bl foo@plt jumps to a call stub, which loads an
// absolute address from a specific .plt slot (usually called .got.plt on
// other targets) and jumps there.
//
// a) With immediate binding (BIND_NOW), the .plt entry is resolved at load
// time. The .glink section is not used.
// b) With lazy binding, the .plt entry points to a `b PLTresolve`
// instruction in .glink, filled in by PPC::writeGotPlt().
// Write N `b PLTresolve` first.
for (size_t i = 0; i != numEntries; ++i)
write32(buf + 4 * i, 0x48000000 | 4 * (numEntries - i));
buf += 4 * numEntries;
// Then write PLTresolve(), which has two forms: PIC and non-PIC. PLTresolve()
// computes the PLT index (by computing the distance from the landing b to
// itself) and calls _dl_runtime_resolve() (in glibc).
uint32_t got = in.got->getVA();
const uint8_t *end = buf + 64;
if (config->isPic) {
uint32_t afterBcl = 4 * in.plt->getNumEntries() + 12;
uint32_t gotBcl = got + 4 - (glink + afterBcl);
write32(buf + 0, 0x3d6b0000 | ha(afterBcl)); // addis r11,r11,1f-glink@ha
write32(buf + 4, 0x7c0802a6); // mflr r0
write32(buf + 8, 0x429f0005); // bcl 20,30,.+4
write32(buf + 12, 0x396b0000 | lo(afterBcl)); // 1: addi r11,r11,1b-glink@l
write32(buf + 16, 0x7d8802a6); // mflr r12
write32(buf + 20, 0x7c0803a6); // mtlr r0
write32(buf + 24, 0x7d6c5850); // sub r11,r11,r12
write32(buf + 28, 0x3d8c0000 | ha(gotBcl)); // addis 12,12,GOT+4-1b@ha
if (ha(gotBcl) == ha(gotBcl + 4)) {
write32(buf + 32, 0x800c0000 | lo(gotBcl)); // lwz r0,r12,GOT+4-1b@l(r12)
write32(buf + 36,
0x818c0000 | lo(gotBcl + 4)); // lwz r12,r12,GOT+8-1b@l(r12)
} else {
write32(buf + 32, 0x840c0000 | lo(gotBcl)); // lwzu r0,r12,GOT+4-1b@l(r12)
write32(buf + 36, 0x818c0000 | 4); // lwz r12,r12,4(r12)
}
write32(buf + 40, 0x7c0903a6); // mtctr 0
write32(buf + 44, 0x7c0b5a14); // add r0,11,11
write32(buf + 48, 0x7d605a14); // add r11,0,11
write32(buf + 52, 0x4e800420); // bctr
buf += 56;
} else {
write32(buf + 0, 0x3d800000 | ha(got + 4)); // lis r12,GOT+4@ha
write32(buf + 4, 0x3d6b0000 | ha(-glink)); // addis r11,r11,-glink@ha
if (ha(got + 4) == ha(got + 8))
write32(buf + 8, 0x800c0000 | lo(got + 4)); // lwz r0,GOT+4@l(r12)
else
write32(buf + 8, 0x840c0000 | lo(got + 4)); // lwzu r0,GOT+4@l(r12)
write32(buf + 12, 0x396b0000 | lo(-glink)); // addi r11,r11,-glink@l
write32(buf + 16, 0x7c0903a6); // mtctr r0
write32(buf + 20, 0x7c0b5a14); // add r0,r11,r11
if (ha(got + 4) == ha(got + 8))
write32(buf + 24, 0x818c0000 | lo(got + 8)); // lwz r12,GOT+8@l(r12)
else
write32(buf + 24, 0x818c0000 | 4); // lwz r12,4(r12)
write32(buf + 28, 0x7d605a14); // add r11,r0,r11
write32(buf + 32, 0x4e800420); // bctr
buf += 36;
}
// Pad with nop. They should not be executed.
for (; buf < end; buf += 4)
write32(buf, 0x60000000);
}
PPC::PPC() {
copyRel = R_PPC_COPY;
gotRel = R_PPC_GLOB_DAT;
noneRel = R_PPC_NONE;
pltRel = R_PPC_JMP_SLOT;
relativeRel = R_PPC_RELATIVE;
iRelativeRel = R_PPC_IRELATIVE;
symbolicRel = R_PPC_ADDR32;
gotBaseSymInGotPlt = false;
gotHeaderEntriesNum = 3;
gotPltHeaderEntriesNum = 0;
pltHeaderSize = 0;
pltEntrySize = 4;
ipltEntrySize = 16;
needsThunks = true;
tlsModuleIndexRel = R_PPC_DTPMOD32;
tlsOffsetRel = R_PPC_DTPREL32;
tlsGotRel = R_PPC_TPREL32;
defaultMaxPageSize = 65536;
defaultImageBase = 0x10000000;
write32(trapInstr.data(), 0x7fe00008);
}
void PPC::writeIplt(uint8_t *buf, const Symbol &sym,
uint64_t /*pltEntryAddr*/) const {
// In -pie or -shared mode, assume r30 points to .got2+0x8000, and use a
// .got2.plt_pic32. thunk.
writePPC32PltCallStub(buf, sym.getGotPltVA(), sym.file, 0x8000);
}
void PPC::writeGotHeader(uint8_t *buf) const {
// _GLOBAL_OFFSET_TABLE_[0] = _DYNAMIC
// glibc stores _dl_runtime_resolve in _GLOBAL_OFFSET_TABLE_[1],
// link_map in _GLOBAL_OFFSET_TABLE_[2].
write32(buf, mainPart->dynamic->getVA());
}
void PPC::writeGotPlt(uint8_t *buf, const Symbol &s) const {
// Address of the symbol resolver stub in .glink .
write32(buf, in.plt->getVA() + in.plt->headerSize + 4 * s.pltIndex);
}
bool PPC::needsThunk(RelExpr expr, RelType type, const InputFile *file,
uint64_t branchAddr, const Symbol &s, int64_t a) const {
if (type != R_PPC_LOCAL24PC && type != R_PPC_REL24 && type != R_PPC_PLTREL24)
return false;
if (s.isInPlt())
return true;
if (s.isUndefWeak())
return false;
return !PPC::inBranchRange(type, branchAddr, s.getVA(a));
}
uint32_t PPC::getThunkSectionSpacing() const { return 0x2000000; }
bool PPC::inBranchRange(RelType type, uint64_t src, uint64_t dst) const {
uint64_t offset = dst - src;
if (type == R_PPC_LOCAL24PC || type == R_PPC_REL24 || type == R_PPC_PLTREL24)
return isInt<26>(offset);
llvm_unreachable("unsupported relocation type used in branch");
}
RelExpr PPC::getRelExpr(RelType type, const Symbol &s,
const uint8_t *loc) const {
switch (type) {
case R_PPC_NONE:
return R_NONE;
case R_PPC_ADDR16_HA:
case R_PPC_ADDR16_HI:
case R_PPC_ADDR16_LO:
case R_PPC_ADDR24:
case R_PPC_ADDR32:
return R_ABS;
case R_PPC_DTPREL16:
case R_PPC_DTPREL16_HA:
case R_PPC_DTPREL16_HI:
case R_PPC_DTPREL16_LO:
case R_PPC_DTPREL32:
return R_DTPREL;
case R_PPC_REL14:
case R_PPC_REL32:
case R_PPC_REL16_LO:
case R_PPC_REL16_HI:
case R_PPC_REL16_HA:
return R_PC;
case R_PPC_GOT16:
return R_GOT_OFF;
case R_PPC_LOCAL24PC:
case R_PPC_REL24:
return R_PLT_PC;
case R_PPC_PLTREL24:
return R_PPC32_PLTREL;
case R_PPC_GOT_TLSGD16:
return R_TLSGD_GOT;
case R_PPC_GOT_TLSLD16:
return R_TLSLD_GOT;
case R_PPC_GOT_TPREL16:
return R_GOT_OFF;
case R_PPC_TLS:
return R_TLSIE_HINT;
case R_PPC_TLSGD:
return R_TLSDESC_CALL;
case R_PPC_TLSLD:
return R_TLSLD_HINT;
case R_PPC_TPREL16:
case R_PPC_TPREL16_HA:
case R_PPC_TPREL16_LO:
case R_PPC_TPREL16_HI:
return R_TPREL;
default:
error(getErrorLocation(loc) + "unknown relocation (" + Twine(type) +
") against symbol " + toString(s));
return R_NONE;
}
}
RelType PPC::getDynRel(RelType type) const {
if (type == R_PPC_ADDR32)
return type;
return R_PPC_NONE;
}
static std::pair<RelType, uint64_t> fromDTPREL(RelType type, uint64_t val) {
uint64_t dtpBiasedVal = val - 0x8000;
switch (type) {
case R_PPC_DTPREL16:
return {R_PPC64_ADDR16, dtpBiasedVal};
case R_PPC_DTPREL16_HA:
return {R_PPC_ADDR16_HA, dtpBiasedVal};
case R_PPC_DTPREL16_HI:
return {R_PPC_ADDR16_HI, dtpBiasedVal};
case R_PPC_DTPREL16_LO:
return {R_PPC_ADDR16_LO, dtpBiasedVal};
case R_PPC_DTPREL32:
return {R_PPC_ADDR32, dtpBiasedVal};
default:
return {type, val};
}
}
void PPC::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
RelType newType;
std::tie(newType, val) = fromDTPREL(rel.type, val);
switch (newType) {
case R_PPC_ADDR16:
checkIntUInt(loc, val, 16, rel);
write16(loc, val);
break;
case R_PPC_GOT16:
case R_PPC_GOT_TLSGD16:
case R_PPC_GOT_TLSLD16:
case R_PPC_GOT_TPREL16:
case R_PPC_TPREL16:
checkInt(loc, val, 16, rel);
write16(loc, val);
break;
case R_PPC_ADDR16_HA:
case R_PPC_DTPREL16_HA:
case R_PPC_GOT_TLSGD16_HA:
case R_PPC_GOT_TLSLD16_HA:
case R_PPC_GOT_TPREL16_HA:
case R_PPC_REL16_HA:
case R_PPC_TPREL16_HA:
write16(loc, ha(val));
break;
case R_PPC_ADDR16_HI:
case R_PPC_DTPREL16_HI:
case R_PPC_GOT_TLSGD16_HI:
case R_PPC_GOT_TLSLD16_HI:
case R_PPC_GOT_TPREL16_HI:
case R_PPC_REL16_HI:
case R_PPC_TPREL16_HI:
write16(loc, val >> 16);
break;
case R_PPC_ADDR16_LO:
case R_PPC_DTPREL16_LO:
case R_PPC_GOT_TLSGD16_LO:
case R_PPC_GOT_TLSLD16_LO:
case R_PPC_GOT_TPREL16_LO:
case R_PPC_REL16_LO:
case R_PPC_TPREL16_LO:
write16(loc, val);
break;
case R_PPC_ADDR32:
case R_PPC_REL32:
write32(loc, val);
break;
case R_PPC_REL14: {
uint32_t mask = 0x0000FFFC;
checkInt(loc, val, 16, rel);
checkAlignment(loc, val, 4, rel);
write32(loc, (read32(loc) & ~mask) | (val & mask));
break;
}
case R_PPC_ADDR24:
case R_PPC_REL24:
case R_PPC_LOCAL24PC:
case R_PPC_PLTREL24: {
uint32_t mask = 0x03FFFFFC;
checkInt(loc, val, 26, rel);
checkAlignment(loc, val, 4, rel);
write32(loc, (read32(loc) & ~mask) | (val & mask));
break;
}
default:
llvm_unreachable("unknown relocation");
}
}
RelExpr PPC::adjustTlsExpr(RelType type, RelExpr expr) const {
if (expr == R_RELAX_TLS_GD_TO_IE)
return R_RELAX_TLS_GD_TO_IE_GOT_OFF;
if (expr == R_RELAX_TLS_LD_TO_LE)
return R_RELAX_TLS_LD_TO_LE_ABS;
return expr;
}
int PPC::getTlsGdRelaxSkip(RelType type) const {
// A __tls_get_addr call instruction is marked with 2 relocations:
//
// R_PPC_TLSGD / R_PPC_TLSLD: marker relocation
// R_PPC_REL24: __tls_get_addr
//
// After the relaxation we no longer call __tls_get_addr and should skip both
// relocations to not create a false dependence on __tls_get_addr being
// defined.
if (type == R_PPC_TLSGD || type == R_PPC_TLSLD)
return 2;
return 1;
}
void PPC::relaxTlsGdToIe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.type) {
case R_PPC_GOT_TLSGD16: {
// addi rT, rA, x@got@tlsgd --> lwz rT, x@got@tprel(rA)
uint32_t insn = readFromHalf16(loc);
writeFromHalf16(loc, 0x80000000 | (insn & 0x03ff0000));
relocateNoSym(loc, R_PPC_GOT_TPREL16, val);
break;
}
case R_PPC_TLSGD:
// bl __tls_get_addr(x@tldgd) --> add r3, r3, r2
write32(loc, 0x7c631214);
break;
default:
llvm_unreachable("unsupported relocation for TLS GD to IE relaxation");
}
}
void PPC::relaxTlsGdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.type) {
case R_PPC_GOT_TLSGD16:
// addi r3, r31, x@got@tlsgd --> addis r3, r2, x@tprel@ha
writeFromHalf16(loc, 0x3c620000 | ha(val));
break;
case R_PPC_TLSGD:
// bl __tls_get_addr(x@tldgd) --> add r3, r3, x@tprel@l
write32(loc, 0x38630000 | lo(val));
break;
default:
llvm_unreachable("unsupported relocation for TLS GD to LE relaxation");
}
}
void PPC::relaxTlsLdToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.type) {
case R_PPC_GOT_TLSLD16:
// addi r3, rA, x@got@tlsgd --> addis r3, r2, 0
writeFromHalf16(loc, 0x3c620000);
break;
case R_PPC_TLSLD:
// r3+x@dtprel computes r3+x-0x8000, while we want it to compute r3+x@tprel
// = r3+x-0x7000, so add 4096 to r3.
// bl __tls_get_addr(x@tlsld) --> addi r3, r3, 4096
write32(loc, 0x38631000);
break;
case R_PPC_DTPREL16:
case R_PPC_DTPREL16_HA:
case R_PPC_DTPREL16_HI:
case R_PPC_DTPREL16_LO:
relocate(loc, rel, val);
break;
default:
llvm_unreachable("unsupported relocation for TLS LD to LE relaxation");
}
}
void PPC::relaxTlsIeToLe(uint8_t *loc, const Relocation &rel,
uint64_t val) const {
switch (rel.type) {
case R_PPC_GOT_TPREL16: {
// lwz rT, x@got@tprel(rA) --> addis rT, r2, x@tprel@ha
uint32_t rt = readFromHalf16(loc) & 0x03e00000;
writeFromHalf16(loc, 0x3c020000 | rt | ha(val));
break;
}
case R_PPC_TLS: {
uint32_t insn = read32(loc);
if (insn >> 26 != 31)
error("unrecognized instruction for IE to LE R_PPC_TLS");
// addi rT, rT, x@tls --> addi rT, rT, x@tprel@l
uint32_t dFormOp = getPPCDFormOp((read32(loc) & 0x000007fe) >> 1);
if (dFormOp == 0)
error("unrecognized instruction for IE to LE R_PPC_TLS");
write32(loc, (dFormOp << 26) | (insn & 0x03ff0000) | lo(val));
break;
}
default:
llvm_unreachable("unsupported relocation for TLS IE to LE relaxation");
}
}
TargetInfo *elf::getPPCTargetInfo() {
static PPC target;
return &target;
}
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