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[ELF] Simplify DynamicSection content computation. NFC 

The new code computes the content twice, but avoides the tricky
std::function<uint64_t()>. Removed 13KiB code in a Release build.
This commit is contained in:
Fangrui Song 2021-11-25 14:12:34 -08:00
parent 536b9eb31e
commit 55c14d6dbf
2 changed files with 44 additions and 85 deletions
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117
lld/ELF/SyntheticSections.cpp
View File

@ -1258,43 +1258,6 @@ DynamicSection<ELFT>::DynamicSection()
this->flags = SHF_ALLOC;
}
template <class ELFT>
void DynamicSection<ELFT>::add(int32_t tag, std::function<uint64_t()> fn) {
entries.push_back({tag, fn});
}
template <class ELFT>
void DynamicSection<ELFT>::addInt(int32_t tag, uint64_t val) {
entries.push_back({tag, [=] { return val; }});
}
template <class ELFT>
void DynamicSection<ELFT>::addInSec(int32_t tag, InputSection *sec) {
entries.push_back({tag, [=] { return sec->getVA(0); }});
}
template <class ELFT>
void DynamicSection<ELFT>::addInSecRelative(int32_t tag, InputSection *sec) {
size_t tagOffset = entries.size() * entsize;
entries.push_back(
{tag, [=] { return sec->getVA(0) - (getVA() + tagOffset); }});
}
template <class ELFT>
void DynamicSection<ELFT>::addOutSec(int32_t tag, OutputSection *sec) {
entries.push_back({tag, [=] { return sec->addr; }});
}
template <class ELFT>
void DynamicSection<ELFT>::addSize(int32_t tag, OutputSection *sec) {
entries.push_back({tag, [=] { return sec->size; }});
}
template <class ELFT>
void DynamicSection<ELFT>::addSym(int32_t tag, Symbol *sym) {
entries.push_back({tag, [=] { return sym->getVA(); }});
}
// The output section .rela.dyn may include these synthetic sections:
//
// - part.relaDyn
@ -1303,15 +1266,13 @@ void DynamicSection<ELFT>::addSym(int32_t tag, Symbol *sym) {
// .rela.dyn
//
// DT_RELASZ is the total size of the included sections.
static std::function<uint64_t()> addRelaSz(RelocationBaseSection *relaDyn) {
return [=]() {
size_t size = relaDyn->getSize();
if (in.relaIplt->getParent() == relaDyn->getParent())
size += in.relaIplt->getSize();
if (in.relaPlt->getParent() == relaDyn->getParent())
size += in.relaPlt->getSize();
return size;
};
static uint64_t addRelaSz(RelocationBaseSection *relaDyn) {
size_t size = relaDyn->getSize();
if (in.relaIplt->getParent() == relaDyn->getParent())
size += in.relaIplt->getSize();
if (in.relaPlt->getParent() == relaDyn->getParent())
size += in.relaPlt->getSize();
return size;
}
// A Linker script may assign the RELA relocation sections to the same
@ -1327,9 +1288,19 @@ static uint64_t addPltRelSz() {
}
// Add remaining entries to complete .dynamic contents.
template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
template <class ELFT>
std::vector<std::pair<int32_t, uint64_t>>
DynamicSection<ELFT>::computeContents() {
elf::Partition &part = getPartition();
bool isMain = part.name.empty();
std::vector<std::pair<int32_t, uint64_t>> entries;
auto addInt = [&](int32_t tag, uint64_t val) {
entries.emplace_back(tag, val);
};
auto addInSec = [&](int32_t tag, const InputSection *sec) {
entries.emplace_back(tag, sec->getVA());
};
for (StringRef s : config->filterList)
addInt(DT_FILTER, part.dynStrTab->addString(s));
@ -1401,14 +1372,11 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
if (!config->shared && !config->relocatable && !config->zRodynamic)
addInt(DT_DEBUG, 0);
if (OutputSection *sec = part.dynStrTab->getParent())
this->link = sec->sectionIndex;
if (part.relaDyn->isNeeded() ||
(in.relaIplt->isNeeded() &&
part.relaDyn->getParent() == in.relaIplt->getParent())) {
addInSec(part.relaDyn->dynamicTag, part.relaDyn);
entries.push_back({part.relaDyn->sizeDynamicTag, addRelaSz(part.relaDyn)});
entries.emplace_back(part.relaDyn->sizeDynamicTag, addRelaSz(part.relaDyn));
bool isRela = config->isRela;
addInt(isRela ? DT_RELAENT : DT_RELENT,
@ -1426,8 +1394,8 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
if (part.relrDyn && !part.relrDyn->relocs.empty()) {
addInSec(config->useAndroidRelrTags ? DT_ANDROID_RELR : DT_RELR,
part.relrDyn);
addSize(config->useAndroidRelrTags ? DT_ANDROID_RELRSZ : DT_RELRSZ,
part.relrDyn->getParent());
addInt(config->useAndroidRelrTags ? DT_ANDROID_RELRSZ : DT_RELRSZ,
part.relrDyn->getParent()->size);
addInt(config->useAndroidRelrTags ? DT_ANDROID_RELRENT : DT_RELRENT,
sizeof(Elf_Relr));
}
@ -1439,7 +1407,7 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
// .rel[a].plt section.
if (isMain && (in.relaPlt->isNeeded() || in.relaIplt->isNeeded())) {
addInSec(DT_JMPREL, in.relaPlt);
entries.push_back({DT_PLTRELSZ, addPltRelSz});
entries.emplace_back(DT_PLTRELSZ, addPltRelSz());
switch (config->emachine) {
case EM_MIPS:
addInSec(DT_MIPS_PLTGOT, in.gotPlt);
@ -1481,24 +1449,24 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
if (isMain) {
if (Out::preinitArray) {
addOutSec(DT_PREINIT_ARRAY, Out::preinitArray);
addSize(DT_PREINIT_ARRAYSZ, Out::preinitArray);
addInt(DT_PREINIT_ARRAY, Out::preinitArray->addr);
addInt(DT_PREINIT_ARRAYSZ, Out::preinitArray->size);
}
if (Out::initArray) {
addOutSec(DT_INIT_ARRAY, Out::initArray);
addSize(DT_INIT_ARRAYSZ, Out::initArray);
addInt(DT_INIT_ARRAY, Out::initArray->addr);
addInt(DT_INIT_ARRAYSZ, Out::initArray->size);
}
if (Out::finiArray) {
addOutSec(DT_FINI_ARRAY, Out::finiArray);
addSize(DT_FINI_ARRAYSZ, Out::finiArray);
addInt(DT_FINI_ARRAY, Out::finiArray->addr);
addInt(DT_FINI_ARRAYSZ, Out::finiArray->size);
}
if (Symbol *b = symtab->find(config->init))
if (b->isDefined())
addSym(DT_INIT, b);
addInt(DT_INIT, b->getVA());
if (Symbol *b = symtab->find(config->fini))
if (b->isDefined())
addSym(DT_FINI, b);
addInt(DT_FINI, b->getVA());
}
if (part.verSym && part.verSym->isNeeded())
@ -1521,8 +1489,7 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
addInt(DT_MIPS_FLAGS, RHF_NOTPOT);
addInt(DT_MIPS_BASE_ADDRESS, target->getImageBase());
addInt(DT_MIPS_SYMTABNO, part.dynSymTab->getNumSymbols());
add(DT_MIPS_LOCAL_GOTNO, [] { return in.mipsGot->getLocalEntriesNum(); });
addInt(DT_MIPS_LOCAL_GOTNO, in.mipsGot->getLocalEntriesNum());
if (const Symbol *b = in.mipsGot->getFirstGlobalEntry())
addInt(DT_MIPS_GOTSYM, b->dynsymIndex);
@ -1534,37 +1501,39 @@ template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
addInSec(DT_MIPS_RLD_MAP, in.mipsRldMap);
// Store the offset to the .rld_map section
// relative to the address of the tag.
addInSecRelative(DT_MIPS_RLD_MAP_REL, in.mipsRldMap);
addInt(DT_MIPS_RLD_MAP_REL,
in.mipsRldMap->getVA() - (getVA() + entries.size() * entsize));
}
}
// DT_PPC_GOT indicates to glibc Secure PLT is used. If DT_PPC_GOT is absent,
// glibc assumes the old-style BSS PLT layout which we don't support.
if (config->emachine == EM_PPC)
add(DT_PPC_GOT, [] { return in.got->getVA(); });
addInSec(DT_PPC_GOT, in.got);
// Glink dynamic tag is required by the V2 abi if the plt section isn't empty.
if (config->emachine == EM_PPC64 && in.plt->isNeeded()) {
// The Glink tag points to 32 bytes before the first lazy symbol resolution
// stub, which starts directly after the header.
entries.push_back({DT_PPC64_GLINK, [=] {
unsigned offset = target->pltHeaderSize - 32;
return in.plt->getVA(0) + offset;
}});
addInt(DT_PPC64_GLINK, in.plt->getVA() + target->pltHeaderSize - 32);
}
addInt(DT_NULL, 0);
return entries;
}
getParent()->link = this->link;
this->size = entries.size() * this->entsize;
template <class ELFT> void DynamicSection<ELFT>::finalizeContents() {
if (OutputSection *sec = getPartition().dynStrTab->getParent())
getParent()->link = sec->sectionIndex;
this->size = computeContents().size() * this->entsize;
}
template <class ELFT> void DynamicSection<ELFT>::writeTo(uint8_t *buf) {
auto *p = reinterpret_cast<Elf_Dyn *>(buf);
for (std::pair<int32_t, std::function<uint64_t()>> &kv : entries) {
for (std::pair<int32_t, uint64_t> kv : computeContents()) {
p->d_tag = kv.first;
p->d_un.d_val = kv.second();
p->d_un.d_val = kv.second;
++p;
}
}

12
lld/ELF/SyntheticSections.h
View File

@ -493,9 +493,6 @@ private:
template <class ELFT> class DynamicSection final : public SyntheticSection {
LLVM_ELF_IMPORT_TYPES_ELFT(ELFT)
// finalizeContents() fills this vector with the section contents.
std::vector<std::pair<int32_t, std::function<uint64_t()>>> entries;
public:
DynamicSection();
void finalizeContents() override;
@ -503,14 +500,7 @@ public:
size_t getSize() const override { return size; }
private:
void add(int32_t tag, std::function<uint64_t()> fn);
void addInt(int32_t tag, uint64_t val);
void addInSec(int32_t tag, InputSection *sec);
void addInSecRelative(int32_t tag, InputSection *sec);
void addOutSec(int32_t tag, OutputSection *sec);
void addSize(int32_t tag, OutputSection *sec);
void addSym(int32_t tag, Symbol *sym);
std::vector<std::pair<int32_t, uint64_t>> computeContents();
uint64_t size = 0;
};