a582419ac7
This is PR36768. Linker script OVERLAYs are described in 4.6.9. Overlay Description of the spec: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Using_ld_the_GNU_Linker/sections.html They are used to allow output sections which have different LMAs but the same VAs and used for embedded programming. Currently, LLD restricts overlapping of sections and that seems to be the most desired behaviour for defaults. My thoughts about possible approaches for PR36768 are on the bug page, this patch implements OVERLAY keyword and allows VAs overlapping for sections that within the overlay. Differential revision: https://reviews.llvm.org/D44780 llvm-svn: 335714
154 lines
4.5 KiB
C++
154 lines
4.5 KiB
C++
//===- OutputSections.h -----------------------------------------*- C++ -*-===//
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//
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// The LLVM Linker
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLD_ELF_OUTPUT_SECTIONS_H
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#define LLD_ELF_OUTPUT_SECTIONS_H
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#include "Config.h"
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#include "InputSection.h"
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#include "LinkerScript.h"
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#include "Relocations.h"
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#include "lld/Common/LLVM.h"
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#include "llvm/MC/StringTableBuilder.h"
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#include "llvm/Object/ELF.h"
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namespace lld {
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namespace elf {
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struct PhdrEntry;
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class Symbol;
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struct EhSectionPiece;
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class EhInputSection;
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class InputSection;
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class InputSectionBase;
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class MergeInputSection;
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class OutputSection;
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template <class ELFT> class ObjFile;
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template <class ELFT> class SharedFile;
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class SharedSymbol;
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class Defined;
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// This represents a section in an output file.
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// It is composed of multiple InputSections.
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// The writer creates multiple OutputSections and assign them unique,
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// non-overlapping file offsets and VAs.
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class OutputSection final : public BaseCommand, public SectionBase {
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public:
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OutputSection(StringRef Name, uint32_t Type, uint64_t Flags);
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static bool classof(const SectionBase *S) {
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return S->kind() == SectionBase::Output;
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}
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static bool classof(const BaseCommand *C);
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uint64_t getLMA() const { return PtLoad ? Addr + PtLoad->LMAOffset : Addr; }
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template <typename ELFT> void writeHeaderTo(typename ELFT::Shdr *SHdr);
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uint32_t SectionIndex = UINT32_MAX;
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unsigned SortRank;
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uint32_t getPhdrFlags() const;
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// Pointer to the PT_LOAD segment, which this section resides in. This field
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// is used to correctly compute file offset of a section. When two sections
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// share the same load segment, difference between their file offsets should
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// be equal to difference between their virtual addresses. To compute some
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// section offset we use the following formula: Off = Off_first + VA -
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// VA_first, where Off_first and VA_first is file offset and VA of first
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// section in PT_LOAD.
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PhdrEntry *PtLoad = nullptr;
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// Pointer to a relocation section for this section. Usually nullptr because
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// we consume relocations, but if --emit-relocs is specified (which is rare),
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// it may have a non-null value.
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OutputSection *RelocationSection = nullptr;
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// Initially this field is the number of InputSections that have been added to
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// the OutputSection so far. Later on, after a call to assignAddresses, it
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// corresponds to the Elf_Shdr member.
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uint64_t Size = 0;
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// The following fields correspond to Elf_Shdr members.
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uint64_t Offset = 0;
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uint64_t Addr = 0;
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uint32_t ShName = 0;
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void addSection(InputSection *IS);
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// Location in the output buffer.
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uint8_t *Loc = nullptr;
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// The following members are normally only used in linker scripts.
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MemoryRegion *MemRegion = nullptr;
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MemoryRegion *LMARegion = nullptr;
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Expr AddrExpr;
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Expr AlignExpr;
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Expr LMAExpr;
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Expr SubalignExpr;
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std::vector<BaseCommand *> SectionCommands;
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std::vector<StringRef> Phdrs;
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llvm::Optional<uint32_t> Filler;
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ConstraintKind Constraint = ConstraintKind::NoConstraint;
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std::string Location;
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std::string MemoryRegionName;
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std::string LMARegionName;
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bool NonAlloc = false;
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bool Noload = false;
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bool ExpressionsUseSymbols = false;
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bool InOverlay = false;
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template <class ELFT> void finalize();
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template <class ELFT> void writeTo(uint8_t *Buf);
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template <class ELFT> void maybeCompress();
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void sort(llvm::function_ref<int(InputSectionBase *S)> Order);
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void sortInitFini();
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void sortCtorsDtors();
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private:
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// Used for implementation of --compress-debug-sections option.
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std::vector<uint8_t> ZDebugHeader;
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llvm::SmallVector<char, 1> CompressedData;
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uint32_t getFiller();
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};
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int getPriority(StringRef S);
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std::vector<InputSection *> getInputSections(OutputSection* OS);
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// All output sections that are handled by the linker specially are
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// globally accessible. Writer initializes them, so don't use them
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// until Writer is initialized.
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struct Out {
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static uint8_t First;
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static PhdrEntry *TlsPhdr;
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static OutputSection *DebugInfo;
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static OutputSection *ElfHeader;
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static OutputSection *ProgramHeaders;
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static OutputSection *PreinitArray;
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static OutputSection *InitArray;
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static OutputSection *FiniArray;
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};
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} // namespace elf
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} // namespace lld
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namespace lld {
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namespace elf {
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uint64_t getHeaderSize();
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extern std::vector<OutputSection *> OutputSections;
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} // namespace elf
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} // namespace lld
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#endif
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