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-rw-r--r--contrib/llvm/tools/lld/ELF/OutputSections.cpp437
1 files changed, 437 insertions, 0 deletions
diff --git a/contrib/llvm/tools/lld/ELF/OutputSections.cpp b/contrib/llvm/tools/lld/ELF/OutputSections.cpp
new file mode 100644
index 000000000000..c1442c078736
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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 "SymbolTable.h"
+#include "SyntheticSections.h"
+#include "Target.h"
+#include "lld/Common/Memory.h"
+#include "lld/Common/Strings.h"
+#include "lld/Common/Threads.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/Support/Compression.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;
+PhdrEntry *Out::TlsPhdr;
+OutputSection *Out::ElfHeader;
+OutputSection *Out::ProgramHeaders;
+OutputSection *Out::PreinitArray;
+OutputSection *Out::InitArray;
+OutputSection *Out::FiniArray;
+
+std::vector<OutputSection *> elf::OutputSections;
+
+uint32_t OutputSection::getPhdrFlags() const {
+ uint32_t Ret = 0;
+ if (Config->EMachine != EM_ARM || !(Flags & SHF_ARM_PURECODE))
+ 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)
+ : BaseCommand(OutputSectionKind),
+ SectionBase(Output, Name, Flags, /*Entsize*/ 0, /*Alignment*/ 1, Type,
+ /*Info*/ 0, /*Link*/ 0) {
+ Live = false;
+}
+
+// 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 OutputSection::addSection(InputSection *IS) {
+ if (!Live) {
+ // If IS is the first section to be added to this section,
+ // initialize Type, Entsize and flags from IS.
+ Live = true;
+ Type = IS->Type;
+ Entsize = IS->Entsize;
+ Flags = IS->Flags;
+ } else {
+ // Otherwise, check if new type or flags are compatible with existing ones.
+ unsigned Mask = SHF_TLS | SHF_LINK_ORDER;
+ if ((Flags & Mask) != (IS->Flags & Mask))
+ error("incompatible section flags for " + Name + "\n>>> " + toString(IS) +
+ ": 0x" + utohexstr(IS->Flags) + "\n>>> output section " + Name +
+ ": 0x" + utohexstr(Flags));
+
+ if (Type != IS->Type) {
+ if (!canMergeToProgbits(Type) || !canMergeToProgbits(IS->Type))
+ error("section type mismatch for " + IS->Name + "\n>>> " +
+ toString(IS) + ": " +
+ getELFSectionTypeName(Config->EMachine, IS->Type) +
+ "\n>>> output section " + Name + ": " +
+ getELFSectionTypeName(Config->EMachine, Type));
+ Type = SHT_PROGBITS;
+ }
+ }
+
+ IS->Parent = this;
+ uint64_t AndMask =
+ Config->EMachine == EM_ARM ? (uint64_t)SHF_ARM_PURECODE : 0;
+ uint64_t OrMask = ~AndMask;
+ uint64_t AndFlags = (Flags & IS->Flags) & AndMask;
+ uint64_t OrFlags = (Flags | IS->Flags) & OrMask;
+ Flags = AndFlags | OrFlags;
+
+ Alignment = std::max(Alignment, IS->Alignment);
+
+ // If this section contains a table of fixed-size entries, sh_entsize
+ // holds the element size. If it contains elements of different size we
+ // set sh_entsize to 0.
+ if (Entsize != IS->Entsize)
+ Entsize = 0;
+
+ if (!IS->Assigned) {
+ IS->Assigned = true;
+ if (SectionCommands.empty() ||
+ !isa<InputSectionDescription>(SectionCommands.back()))
+ SectionCommands.push_back(make<InputSectionDescription>(""));
+ auto *ISD = cast<InputSectionDescription>(SectionCommands.back());
+ ISD->Sections.push_back(IS);
+ }
+}
+
+static void sortByOrder(MutableArrayRef<InputSection *> In,
+ llvm::function_ref<int(InputSectionBase *S)> Order) {
+ typedef std::pair<int, InputSection *> Pair;
+ auto Comp = [](const Pair &A, const Pair &B) { return A.first < B.first; };
+
+ std::vector<Pair> V;
+ for (InputSection *S : In)
+ V.push_back({Order(S), S});
+ std::stable_sort(V.begin(), V.end(), Comp);
+
+ for (size_t I = 0; I < V.size(); ++I)
+ In[I] = V[I].second;
+}
+
+uint64_t elf::getHeaderSize() {
+ if (Config->OFormatBinary)
+ return 0;
+ return Out::ElfHeader->Size + Out::ProgramHeaders->Size;
+}
+
+bool OutputSection::classof(const BaseCommand *C) {
+ return C->Kind == OutputSectionKind;
+}
+
+void OutputSection::sort(llvm::function_ref<int(InputSectionBase *S)> Order) {
+ assert(Live);
+ for (BaseCommand *B : SectionCommands)
+ if (auto *ISD = dyn_cast<InputSectionDescription>(B))
+ sortByOrder(ISD->Sections, Order);
+}
+
+// Fill [Buf, Buf + Size) with Filler.
+// This is used for linker script "=fillexp" command.
+static void fill(uint8_t *Buf, size_t Size,
+ const std::array<uint8_t, 4> &Filler) {
+ size_t I = 0;
+ for (; I + 4 < Size; I += 4)
+ memcpy(Buf + I, Filler.data(), 4);
+ memcpy(Buf + I, Filler.data(), Size - I);
+}
+
+// Compress section contents if this section contains debug info.
+template <class ELFT> void OutputSection::maybeCompress() {
+ typedef typename ELFT::Chdr Elf_Chdr;
+
+ // Compress only DWARF debug sections.
+ if (!Config->CompressDebugSections || (Flags & SHF_ALLOC) ||
+ !Name.startswith(".debug_"))
+ return;
+
+ // Create a section header.
+ ZDebugHeader.resize(sizeof(Elf_Chdr));
+ auto *Hdr = reinterpret_cast<Elf_Chdr *>(ZDebugHeader.data());
+ Hdr->ch_type = ELFCOMPRESS_ZLIB;
+ Hdr->ch_size = Size;
+ Hdr->ch_addralign = Alignment;
+
+ // Write section contents to a temporary buffer and compress it.
+ std::vector<uint8_t> Buf(Size);
+ writeTo<ELFT>(Buf.data());
+ if (Error E = zlib::compress(toStringRef(Buf), CompressedData))
+ fatal("compress failed: " + llvm::toString(std::move(E)));
+
+ // Update section headers.
+ Size = sizeof(Elf_Chdr) + CompressedData.size();
+ Flags |= SHF_COMPRESSED;
+}
+
+static void writeInt(uint8_t *Buf, uint64_t Data, uint64_t Size) {
+ if (Size == 1)
+ *Buf = Data;
+ else if (Size == 2)
+ write16(Buf, Data);
+ else if (Size == 4)
+ write32(Buf, Data);
+ else if (Size == 8)
+ write64(Buf, Data);
+ else
+ llvm_unreachable("unsupported Size argument");
+}
+
+template <class ELFT> void OutputSection::writeTo(uint8_t *Buf) {
+ if (Type == SHT_NOBITS)
+ return;
+
+ Loc = Buf;
+
+ // If -compress-debug-section is specified and if this is a debug seciton,
+ // we've already compressed section contents. If that's the case,
+ // just write it down.
+ if (!CompressedData.empty()) {
+ memcpy(Buf, ZDebugHeader.data(), ZDebugHeader.size());
+ memcpy(Buf + ZDebugHeader.size(), CompressedData.data(),
+ CompressedData.size());
+ return;
+ }
+
+ // Write leading padding.
+ std::vector<InputSection *> Sections = getInputSections(this);
+ std::array<uint8_t, 4> Filler = getFiller();
+ bool NonZeroFiller = read32(Filler.data()) != 0;
+ if (NonZeroFiller)
+ fill(Buf, Sections.empty() ? Size : Sections[0]->OutSecOff, Filler);
+
+ parallelForEachN(0, Sections.size(), [&](size_t I) {
+ InputSection *IS = Sections[I];
+ IS->writeTo<ELFT>(Buf);
+
+ // Fill gaps between sections.
+ if (NonZeroFiller) {
+ uint8_t *Start = Buf + IS->OutSecOff + IS->getSize();
+ uint8_t *End;
+ if (I + 1 == Sections.size())
+ End = Buf + Size;
+ else
+ End = Buf + Sections[I + 1]->OutSecOff;
+ fill(Start, End - Start, Filler);
+ }
+ });
+
+ // Linker scripts may have BYTE()-family commands with which you
+ // can write arbitrary bytes to the output. Process them if any.
+ for (BaseCommand *Base : SectionCommands)
+ if (auto *Data = dyn_cast<ByteCommand>(Base))
+ writeInt(Buf + Data->Offset, Data->Expression().getValue(), Data->Size);
+}
+
+template <class ELFT>
+static void finalizeShtGroup(OutputSection *OS,
+ InputSection *Section) {
+ assert(Config->Relocatable);
+
+ // sh_link field for SHT_GROUP sections should contain the section index of
+ // the symbol table.
+ OS->Link = In.SymTab->getParent()->SectionIndex;
+
+ // sh_info then contain index of an entry in symbol table section which
+ // provides signature of the section group.
+ ObjFile<ELFT> *Obj = Section->getFile<ELFT>();
+ ArrayRef<Symbol *> Symbols = Obj->getSymbols();
+ OS->Info = In.SymTab->getSymbolIndex(Symbols[Section->Info]);
+}
+
+template <class ELFT> void OutputSection::finalize() {
+ if (Type == SHT_NOBITS)
+ for (BaseCommand *Base : SectionCommands)
+ if (isa<ByteCommand>(Base))
+ Type = SHT_PROGBITS;
+
+ std::vector<InputSection *> V = getInputSections(this);
+ InputSection *First = V.empty() ? nullptr : V[0];
+
+ if (Flags & SHF_LINK_ORDER) {
+ // We must preserve the link order dependency of sections with the
+ // SHF_LINK_ORDER flag. The dependency is indicated by the sh_link field. We
+ // need to translate the InputSection sh_link to the OutputSection sh_link,
+ // all InputSections in the OutputSection have the same dependency.
+ if (auto *D = First->getLinkOrderDep())
+ Link = D->getParent()->SectionIndex;
+ }
+
+ if (Type == SHT_GROUP) {
+ finalizeShtGroup<ELFT>(this, First);
+ return;
+ }
+
+ if (!Config->CopyRelocs || (Type != SHT_RELA && Type != SHT_REL))
+ return;
+
+ if (isa<SyntheticSection>(First))
+ return;
+
+ Link = In.SymTab->getParent()->SectionIndex;
+ // sh_info for SHT_REL[A] sections should contain the section header index of
+ // the section to which the relocation applies.
+ InputSectionBase *S = First->getRelocatedSection();
+ Info = S->getOutputSection()->SectionIndex;
+ Flags |= SHF_INFO_LINK;
+}
+
+// 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);
+ 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() {
+ assert(SectionCommands.size() == 1);
+ auto *ISD = cast<InputSectionDescription>(SectionCommands[0]);
+ std::stable_sort(ISD->Sections.begin(), ISD->Sections.end(), compCtors);
+}
+
+// If an input string is in the form of "foo.N" where N is a number,
+// return N. Otherwise, returns 65536, which is one greater than the
+// lowest priority.
+int elf::getPriority(StringRef S) {
+ size_t Pos = S.rfind('.');
+ if (Pos == StringRef::npos)
+ return 65536;
+ int V;
+ if (!to_integer(S.substr(Pos + 1), V, 10))
+ return 65536;
+ return V;
+}
+
+std::vector<InputSection *> elf::getInputSections(OutputSection *OS) {
+ std::vector<InputSection *> Ret;
+ for (BaseCommand *Base : OS->SectionCommands)
+ if (auto *ISD = dyn_cast<InputSectionDescription>(Base))
+ Ret.insert(Ret.end(), ISD->Sections.begin(), ISD->Sections.end());
+ return Ret;
+}
+
+// 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); });
+}
+
+std::array<uint8_t, 4> OutputSection::getFiller() {
+ if (Filler)
+ return *Filler;
+ if (Flags & SHF_EXECINSTR)
+ return Target->TrapInstr;
+ return {0, 0, 0, 0};
+}
+
+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);
+
+template void OutputSection::writeTo<ELF32LE>(uint8_t *Buf);
+template void OutputSection::writeTo<ELF32BE>(uint8_t *Buf);
+template void OutputSection::writeTo<ELF64LE>(uint8_t *Buf);
+template void OutputSection::writeTo<ELF64BE>(uint8_t *Buf);
+
+template void OutputSection::maybeCompress<ELF32LE>();
+template void OutputSection::maybeCompress<ELF32BE>();
+template void OutputSection::maybeCompress<ELF64LE>();
+template void OutputSection::maybeCompress<ELF64BE>();
+
+template void OutputSection::finalize<ELF32LE>();
+template void OutputSection::finalize<ELF32BE>();
+template void OutputSection::finalize<ELF64LE>();
+template void OutputSection::finalize<ELF64BE>();
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