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-rw-r--r--contrib/llvm/tools/lld/ELF/OutputSections.cpp370
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diff --git a/contrib/llvm/tools/lld/ELF/OutputSections.cpp b/contrib/llvm/tools/lld/ELF/OutputSections.cpp
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+++ b/contrib/llvm/tools/lld/ELF/OutputSections.cpp
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+//===- OutputSections.cpp -------------------------------------------------===//
+//
+// The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "OutputSections.h"
+#include "Config.h"
+#include "LinkerScript.h"
+#include "Memory.h"
+#include "Strings.h"
+#include "SymbolTable.h"
+#include "SyntheticSections.h"
+#include "Target.h"
+#include "Threads.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/Support/MD5.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/SHA1.h"
+
+using namespace llvm;
+using namespace llvm::dwarf;
+using namespace llvm::object;
+using namespace llvm::support::endian;
+using namespace llvm::ELF;
+
+using namespace lld;
+using namespace lld::elf;
+
+uint8_t Out::First;
+OutputSection *Out::Opd;
+uint8_t *Out::OpdBuf;
+PhdrEntry *Out::TlsPhdr;
+OutputSection *Out::DebugInfo;
+OutputSection *Out::ElfHeader;
+OutputSection *Out::ProgramHeaders;
+OutputSection *Out::PreinitArray;
+OutputSection *Out::InitArray;
+OutputSection *Out::FiniArray;
+
+uint32_t OutputSection::getPhdrFlags() const {
+ uint32_t Ret = PF_R;
+ if (Flags & SHF_WRITE)
+ Ret |= PF_W;
+ if (Flags & SHF_EXECINSTR)
+ Ret |= PF_X;
+ return Ret;
+}
+
+template <class ELFT>
+void OutputSection::writeHeaderTo(typename ELFT::Shdr *Shdr) {
+ Shdr->sh_entsize = Entsize;
+ Shdr->sh_addralign = Alignment;
+ Shdr->sh_type = Type;
+ Shdr->sh_offset = Offset;
+ Shdr->sh_flags = Flags;
+ Shdr->sh_info = Info;
+ Shdr->sh_link = Link;
+ Shdr->sh_addr = Addr;
+ Shdr->sh_size = Size;
+ Shdr->sh_name = ShName;
+}
+
+OutputSection::OutputSection(StringRef Name, uint32_t Type, uint64_t Flags)
+ : SectionBase(Output, Name, Flags, /*Entsize*/ 0, /*Alignment*/ 1, Type,
+ /*Info*/ 0,
+ /*Link*/ 0),
+ SectionIndex(INT_MAX) {}
+
+static uint64_t updateOffset(uint64_t Off, InputSection *S) {
+ Off = alignTo(Off, S->Alignment);
+ S->OutSecOff = Off;
+ return Off + S->getSize();
+}
+
+void OutputSection::addSection(InputSection *S) {
+ assert(S->Live);
+ Sections.push_back(S);
+ S->Parent = this;
+ this->updateAlignment(S->Alignment);
+
+ // The actual offsets will be computed by assignAddresses. For now, use
+ // crude approximation so that it is at least easy for other code to know the
+ // section order. It is also used to calculate the output section size early
+ // for compressed debug sections.
+ this->Size = updateOffset(Size, S);
+
+ // If this section contains a table of fixed-size entries, sh_entsize
+ // holds the element size. Consequently, if this contains two or more
+ // input sections, all of them must have the same sh_entsize. However,
+ // you can put different types of input sections into one output
+ // sectin by using linker scripts. I don't know what to do here.
+ // Probably we sholuld handle that as an error. But for now we just
+ // pick the largest sh_entsize.
+ this->Entsize = std::max(this->Entsize, S->Entsize);
+}
+
+// This function is called after we sort input sections
+// and scan relocations to setup sections' offsets.
+void OutputSection::assignOffsets() {
+ OutputSectionCommand *Cmd = Script->getCmd(this);
+ uint64_t Off = 0;
+ for (BaseCommand *Base : Cmd->Commands)
+ if (auto *ISD = dyn_cast<InputSectionDescription>(Base))
+ for (InputSection *S : ISD->Sections)
+ Off = updateOffset(Off, S);
+ this->Size = Off;
+}
+
+void OutputSection::sort(std::function<int(InputSectionBase *S)> Order) {
+ typedef std::pair<unsigned, InputSection *> Pair;
+ auto Comp = [](const Pair &A, const Pair &B) { return A.first < B.first; };
+
+ std::vector<Pair> V;
+ for (InputSection *S : Sections)
+ V.push_back({Order(S), S});
+ std::stable_sort(V.begin(), V.end(), Comp);
+ Sections.clear();
+ for (Pair &P : V)
+ Sections.push_back(P.second);
+}
+
+// Sorts input sections by section name suffixes, so that .foo.N comes
+// before .foo.M if N < M. Used to sort .{init,fini}_array.N sections.
+// We want to keep the original order if the priorities are the same
+// because the compiler keeps the original initialization order in a
+// translation unit and we need to respect that.
+// For more detail, read the section of the GCC's manual about init_priority.
+void OutputSection::sortInitFini() {
+ // Sort sections by priority.
+ sort([](InputSectionBase *S) { return getPriority(S->Name); });
+}
+
+// Returns true if S matches /Filename.?\.o$/.
+static bool isCrtBeginEnd(StringRef S, StringRef Filename) {
+ if (!S.endswith(".o"))
+ return false;
+ S = S.drop_back(2);
+ if (S.endswith(Filename))
+ return true;
+ return !S.empty() && S.drop_back().endswith(Filename);
+}
+
+static bool isCrtbegin(StringRef S) { return isCrtBeginEnd(S, "crtbegin"); }
+static bool isCrtend(StringRef S) { return isCrtBeginEnd(S, "crtend"); }
+
+// .ctors and .dtors are sorted by this priority from highest to lowest.
+//
+// 1. The section was contained in crtbegin (crtbegin contains
+// some sentinel value in its .ctors and .dtors so that the runtime
+// can find the beginning of the sections.)
+//
+// 2. The section has an optional priority value in the form of ".ctors.N"
+// or ".dtors.N" where N is a number. Unlike .{init,fini}_array,
+// they are compared as string rather than number.
+//
+// 3. The section is just ".ctors" or ".dtors".
+//
+// 4. The section was contained in crtend, which contains an end marker.
+//
+// In an ideal world, we don't need this function because .init_array and
+// .ctors are duplicate features (and .init_array is newer.) However, there
+// are too many real-world use cases of .ctors, so we had no choice to
+// support that with this rather ad-hoc semantics.
+static bool compCtors(const InputSection *A, const InputSection *B) {
+ bool BeginA = isCrtbegin(A->File->getName());
+ bool BeginB = isCrtbegin(B->File->getName());
+ if (BeginA != BeginB)
+ return BeginA;
+ bool EndA = isCrtend(A->File->getName());
+ bool EndB = isCrtend(B->File->getName());
+ if (EndA != EndB)
+ return EndB;
+ StringRef X = A->Name;
+ StringRef Y = B->Name;
+ assert(X.startswith(".ctors") || X.startswith(".dtors"));
+ assert(Y.startswith(".ctors") || Y.startswith(".dtors"));
+ X = X.substr(6);
+ Y = Y.substr(6);
+ if (X.empty() && Y.empty())
+ return false;
+ return X < Y;
+}
+
+// Sorts input sections by the special rules for .ctors and .dtors.
+// Unfortunately, the rules are different from the one for .{init,fini}_array.
+// Read the comment above.
+void OutputSection::sortCtorsDtors() {
+ std::stable_sort(Sections.begin(), Sections.end(), compCtors);
+}
+
+static SectionKey createKey(InputSectionBase *C, StringRef OutsecName) {
+ // The ELF spec just says
+ // ----------------------------------------------------------------
+ // In the first phase, input sections that match in name, type and
+ // attribute flags should be concatenated into single sections.
+ // ----------------------------------------------------------------
+ //
+ // However, it is clear that at least some flags have to be ignored for
+ // section merging. At the very least SHF_GROUP and SHF_COMPRESSED have to be
+ // ignored. We should not have two output .text sections just because one was
+ // in a group and another was not for example.
+ //
+ // It also seems that that wording was a late addition and didn't get the
+ // necessary scrutiny.
+ //
+ // Merging sections with different flags is expected by some users. One
+ // reason is that if one file has
+ //
+ // int *const bar __attribute__((section(".foo"))) = (int *)0;
+ //
+ // gcc with -fPIC will produce a read only .foo section. But if another
+ // file has
+ //
+ // int zed;
+ // int *const bar __attribute__((section(".foo"))) = (int *)&zed;
+ //
+ // gcc with -fPIC will produce a read write section.
+ //
+ // Last but not least, when using linker script the merge rules are forced by
+ // the script. Unfortunately, linker scripts are name based. This means that
+ // expressions like *(.foo*) can refer to multiple input sections with
+ // different flags. We cannot put them in different output sections or we
+ // would produce wrong results for
+ //
+ // start = .; *(.foo.*) end = .; *(.bar)
+ //
+ // and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to
+ // another. The problem is that there is no way to layout those output
+ // sections such that the .foo sections are the only thing between the start
+ // and end symbols.
+ //
+ // Given the above issues, we instead merge sections by name and error on
+ // incompatible types and flags.
+
+ uint32_t Alignment = 0;
+ uint64_t Flags = 0;
+ if (Config->Relocatable && (C->Flags & SHF_MERGE)) {
+ Alignment = std::max<uint64_t>(C->Alignment, C->Entsize);
+ Flags = C->Flags & (SHF_MERGE | SHF_STRINGS);
+ }
+
+ return SectionKey{OutsecName, Flags, Alignment};
+}
+
+OutputSectionFactory::OutputSectionFactory(
+ std::vector<OutputSection *> &OutputSections)
+ : OutputSections(OutputSections) {}
+
+static uint64_t getIncompatibleFlags(uint64_t Flags) {
+ return Flags & (SHF_ALLOC | SHF_TLS);
+}
+
+// We allow sections of types listed below to merged into a
+// single progbits section. This is typically done by linker
+// scripts. Merging nobits and progbits will force disk space
+// to be allocated for nobits sections. Other ones don't require
+// any special treatment on top of progbits, so there doesn't
+// seem to be a harm in merging them.
+static bool canMergeToProgbits(unsigned Type) {
+ return Type == SHT_NOBITS || Type == SHT_PROGBITS || Type == SHT_INIT_ARRAY ||
+ Type == SHT_PREINIT_ARRAY || Type == SHT_FINI_ARRAY ||
+ Type == SHT_NOTE;
+}
+
+void elf::reportDiscarded(InputSectionBase *IS) {
+ if (!Config->PrintGcSections)
+ return;
+ message("removing unused section from '" + IS->Name + "' in file '" +
+ IS->File->getName());
+}
+
+void OutputSectionFactory::addInputSec(InputSectionBase *IS,
+ StringRef OutsecName) {
+ // Sections with the SHT_GROUP attribute reach here only when the - r option
+ // is given. Such sections define "section groups", and InputFiles.cpp has
+ // dedup'ed section groups by their signatures. For the -r, we want to pass
+ // through all SHT_GROUP sections without merging them because merging them
+ // creates broken section contents.
+ if (IS->Type == SHT_GROUP) {
+ OutputSection *Out = nullptr;
+ addInputSec(IS, OutsecName, Out);
+ return;
+ }
+
+ // Imagine .zed : { *(.foo) *(.bar) } script. Both foo and bar may have
+ // relocation sections .rela.foo and .rela.bar for example. Most tools do
+ // not allow multiple REL[A] sections for output section. Hence we
+ // should combine these relocation sections into single output.
+ // We skip synthetic sections because it can be .rela.dyn/.rela.plt or any
+ // other REL[A] sections created by linker itself.
+ if (!isa<SyntheticSection>(IS) &&
+ (IS->Type == SHT_REL || IS->Type == SHT_RELA)) {
+ auto *Sec = cast<InputSection>(IS);
+ OutputSection *Out = Sec->getRelocatedSection()->getOutputSection();
+ addInputSec(IS, OutsecName, Out->RelocationSection);
+ return;
+ }
+
+ SectionKey Key = createKey(IS, OutsecName);
+ OutputSection *&Sec = Map[Key];
+ return addInputSec(IS, OutsecName, Sec);
+}
+
+void OutputSectionFactory::addInputSec(InputSectionBase *IS,
+ StringRef OutsecName,
+ OutputSection *&Sec) {
+ if (!IS->Live) {
+ reportDiscarded(IS);
+ return;
+ }
+
+ if (Sec) {
+ if (getIncompatibleFlags(Sec->Flags) != getIncompatibleFlags(IS->Flags))
+ error("incompatible section flags for " + Sec->Name +
+ "\n>>> " + toString(IS) + ": 0x" + utohexstr(IS->Flags) +
+ "\n>>> output section " + Sec->Name + ": 0x" +
+ utohexstr(Sec->Flags));
+ if (Sec->Type != IS->Type) {
+ if (canMergeToProgbits(Sec->Type) && canMergeToProgbits(IS->Type))
+ Sec->Type = SHT_PROGBITS;
+ else
+ error("section type mismatch for " + IS->Name +
+ "\n>>> " + toString(IS) + ": " +
+ getELFSectionTypeName(Config->EMachine, IS->Type) +
+ "\n>>> output section " + Sec->Name + ": " +
+ getELFSectionTypeName(Config->EMachine, Sec->Type));
+ }
+ Sec->Flags |= IS->Flags;
+ } else {
+ Sec = make<OutputSection>(OutsecName, IS->Type, IS->Flags);
+ OutputSections.push_back(Sec);
+ }
+
+ Sec->addSection(cast<InputSection>(IS));
+}
+
+OutputSectionFactory::~OutputSectionFactory() {}
+
+SectionKey DenseMapInfo<SectionKey>::getEmptyKey() {
+ return SectionKey{DenseMapInfo<StringRef>::getEmptyKey(), 0, 0};
+}
+
+SectionKey DenseMapInfo<SectionKey>::getTombstoneKey() {
+ return SectionKey{DenseMapInfo<StringRef>::getTombstoneKey(), 0, 0};
+}
+
+unsigned DenseMapInfo<SectionKey>::getHashValue(const SectionKey &Val) {
+ return hash_combine(Val.Name, Val.Flags, Val.Alignment);
+}
+
+bool DenseMapInfo<SectionKey>::isEqual(const SectionKey &LHS,
+ const SectionKey &RHS) {
+ return DenseMapInfo<StringRef>::isEqual(LHS.Name, RHS.Name) &&
+ LHS.Flags == RHS.Flags && LHS.Alignment == RHS.Alignment;
+}
+
+uint64_t elf::getHeaderSize() {
+ if (Config->OFormatBinary)
+ return 0;
+ return Out::ElfHeader->Size + Out::ProgramHeaders->Size;
+}
+
+template void OutputSection::writeHeaderTo<ELF32LE>(ELF32LE::Shdr *Shdr);
+template void OutputSection::writeHeaderTo<ELF32BE>(ELF32BE::Shdr *Shdr);
+template void OutputSection::writeHeaderTo<ELF64LE>(ELF64LE::Shdr *Shdr);
+template void OutputSection::writeHeaderTo<ELF64BE>(ELF64BE::Shdr *Shdr);
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