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[ELF] addRelIpltSymbols: make it explicit some passes are for non-relocatable links. NFC 

and prepare for __global_pointer$ and _TLS_MODULE_BASE_ fix.
This commit is contained in:
Fangrui Song 2022-11-22 11:38:57 -08:00
parent 6327d263f5
commit 9015e41f0f
1 changed files with 61 additions and 59 deletions
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120
lld/ELF/Writer.cpp
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@ -1005,7 +1005,7 @@ void PhdrEntry::add(OutputSection *sec) {
// need these symbols, since IRELATIVE relocs are resolved through GOT
// and PLT. For details, see http://www.airs.com/blog/archives/403.
template <class ELFT> void Writer<ELFT>::addRelIpltSymbols() {
if (config->relocatable || config->isPic)
if (config->isPic)
return;
// By default, __rela_iplt_{start,end} belong to a dummy section 0
@ -1826,31 +1826,34 @@ static void removeUnusedSyntheticSections() {
// Create output section objects and add them to OutputSections.
template <class ELFT> void Writer<ELFT>::finalizeSections() {
Out::preinitArray = findSection(".preinit_array");
Out::initArray = findSection(".init_array");
Out::finiArray = findSection(".fini_array");
// The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
// symbols for sections, so that the runtime can get the start and end
// addresses of each section by section name. Add such symbols.
if (!config->relocatable) {
Out::preinitArray = findSection(".preinit_array");
Out::initArray = findSection(".init_array");
Out::finiArray = findSection(".fini_array");
// The linker needs to define SECNAME_start, SECNAME_end and SECNAME_stop
// symbols for sections, so that the runtime can get the start and end
// addresses of each section by section name. Add such symbols.
addStartEndSymbols();
for (SectionCommand *cmd : script->sectionCommands)
if (auto *osd = dyn_cast<OutputDesc>(cmd))
addStartStopSymbols(osd->osec);
// Add _DYNAMIC symbol. Unlike GNU gold, our _DYNAMIC symbol has no type.
// It should be okay as no one seems to care about the type.
// Even the author of gold doesn't remember why gold behaves that way.
// https://sourceware.org/ml/binutils/2002-03/msg00360.html
if (mainPart->dynamic->parent) {
Symbol *s = symtab.addSymbol(Defined{
/*file=*/nullptr, "_DYNAMIC", STB_WEAK, STV_HIDDEN, STT_NOTYPE,
/*value=*/0, /*size=*/0, mainPart->dynamic.get()});
s->isUsedInRegularObj = true;
}
// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();
}
// Add _DYNAMIC symbol. Unlike GNU gold, our _DYNAMIC symbol has no type.
// It should be okay as no one seems to care about the type.
// Even the author of gold doesn't remember why gold behaves that way.
// https://sourceware.org/ml/binutils/2002-03/msg00360.html
if (mainPart->dynamic->parent)
symtab.addSymbol(Defined{/*file=*/nullptr, "_DYNAMIC", STB_WEAK, STV_HIDDEN,
STT_NOTYPE, /*value=*/0, /*size=*/0, mainPart->dynamic.get()})->isUsedInRegularObj = true;
// Define __rel[a]_iplt_{start,end} symbols if needed.
addRelIpltSymbols();
// RISC-V's gp can address +/- 2 KiB, set it to .sdata + 0x800. This symbol
// should only be defined in an executable. If .sdata does not exist, its
// value/section does not matter but it has to be relative, so set its
@ -1883,67 +1886,66 @@ template <class ELFT> void Writer<ELFT>::finalizeSections() {
}
}
{
if (!config->relocatable) {
llvm::TimeTraceScope timeScope("Finalize .eh_frame");
// This responsible for splitting up .eh_frame section into
// pieces. The relocation scan uses those pieces, so this has to be
// earlier.
for (Partition &part : partitions)
finalizeSynthetic(part.ehFrame.get());
}
if (config->hasDynSymTab) {
parallelForEach(symtab.getSymbols(), [](Symbol *sym) {
sym->isPreemptible = computeIsPreemptible(*sym);
});
if (config->hasDynSymTab) {
parallelForEach(symtab.getSymbols(), [](Symbol *sym) {
sym->isPreemptible = computeIsPreemptible(*sym);
});
}
}
// Change values of linker-script-defined symbols from placeholders (assigned
// by declareSymbols) to actual definitions.
script->processSymbolAssignments();
{
if (!config->relocatable) {
llvm::TimeTraceScope timeScope("Scan relocations");
// Scan relocations. This must be done after every symbol is declared so
// that we can correctly decide if a dynamic relocation is needed. This is
// called after processSymbolAssignments() because it needs to know whether
// a linker-script-defined symbol is absolute.
ppc64noTocRelax.clear();
if (!config->relocatable) {
scanRelocations<ELFT>();
reportUndefinedSymbols();
postScanRelocations();
}
}
scanRelocations<ELFT>();
reportUndefinedSymbols();
postScanRelocations();
if (in.plt && in.plt->isNeeded())
in.plt->addSymbols();
if (in.iplt && in.iplt->isNeeded())
in.iplt->addSymbols();
if (in.plt && in.plt->isNeeded())
in.plt->addSymbols();
if (in.iplt && in.iplt->isNeeded())
in.iplt->addSymbols();
if (config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore) {
auto diagnose =
config->unresolvedSymbolsInShlib == UnresolvedPolicy::ReportError
? errorOrWarn
: warn;
// Error on undefined symbols in a shared object, if all of its DT_NEEDED
// entries are seen. These cases would otherwise lead to runtime errors
// reported by the dynamic linker.
//
// ld.bfd traces all DT_NEEDED to emulate the logic of the dynamic linker to
// catch more cases. That is too much for us. Our approach resembles the one
// used in ld.gold, achieves a good balance to be useful but not too smart.
for (SharedFile *file : ctx.sharedFiles) {
bool allNeededIsKnown =
llvm::all_of(file->dtNeeded, [&](StringRef needed) {
return symtab.soNames.count(CachedHashStringRef(needed));
});
if (!allNeededIsKnown)
continue;
for (Symbol *sym : file->requiredSymbols)
if (sym->isUndefined() && !sym->isWeak())
diagnose("undefined reference due to --no-allow-shlib-undefined: " +
toString(*sym) + "\n>>> referenced by " + toString(file));
if (config->unresolvedSymbolsInShlib != UnresolvedPolicy::Ignore) {
auto diagnose =
config->unresolvedSymbolsInShlib == UnresolvedPolicy::ReportError
? errorOrWarn
: warn;
// Error on undefined symbols in a shared object, if all of its DT_NEEDED
// entries are seen. These cases would otherwise lead to runtime errors
// reported by the dynamic linker.
//
// ld.bfd traces all DT_NEEDED to emulate the logic of the dynamic linker
// to catch more cases. That is too much for us. Our approach resembles
// the one used in ld.gold, achieves a good balance to be useful but not
// too smart.
for (SharedFile *file : ctx.sharedFiles) {
bool allNeededIsKnown =
llvm::all_of(file->dtNeeded, [&](StringRef needed) {
return symtab.soNames.count(CachedHashStringRef(needed));
});
if (!allNeededIsKnown)
continue;
for (Symbol *sym : file->requiredSymbols)
if (sym->isUndefined() && !sym->isWeak())
diagnose("undefined reference due to --no-allow-shlib-undefined: " +
toString(*sym) + "\n>>> referenced by " + toString(file));
}
}
}