blob: 5297a03c2cfa7ff521f419e52498fb04e9beafe7 [file] [log] [blame]
//===- OutputSection.h ------------------------------------------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "Symbols.h"
#include "lld/Common/LLVM.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/TinyPtrVector.h"
#include <limits>
namespace lld::macho {
class Defined;
class InputSection;
class OutputSegment;
// The default order value for OutputSections that are not constructed from
// InputSections (i.e. SyntheticSections). We make it less than INT_MAX in order
// not to conflict with the ordering of zerofill sections, which must always be
// placed at the end of their segment.
constexpr int UnspecifiedInputOrder = std::numeric_limits<int>::max() - 1024;
// Output sections represent the finalized sections present within the final
// linked executable. They can represent special sections (like the symbol
// table), or represent coalesced sections from the various inputs given to the
// linker with the same segment / section name.
class OutputSection {
enum Kind {
OutputSection(Kind kind, StringRef name) : name(name), sectionKind(kind) {}
virtual ~OutputSection() = default;
Kind kind() const { return sectionKind; }
// These accessors will only be valid after finalizing the section.
uint64_t getSegmentOffset() const;
// How much space the section occupies in the address space.
virtual uint64_t getSize() const = 0;
// How much space the section occupies in the file. Most sections are copied
// as-is so their file size is the same as their address space size.
virtual uint64_t getFileSize() const { return getSize(); }
// Hidden sections omit header content, but body content may still be present.
virtual bool isHidden() const { return false; }
// Unneeded sections are omitted entirely (header and body).
virtual bool isNeeded() const { return true; }
// The implementations of this method can assume that it is only called right
// before addresses get assigned to this particular OutputSection. In
// particular, this means that it gets called only after addresses have been
// assigned to output sections that occur earlier in the output binary.
// Naturally, this means different sections' finalize() methods cannot execute
// concurrently with each other. As such, avoid using this method for
// operations that do not require this strict sequential guarantee.
// Operations that need to occur late in the linking process, but which do not
// need the sequential guarantee, should be named `finalizeContents()`. See
// e.g. LinkEditSection::finalizeContents() and
// CStringSection::finalizeContents().
virtual void finalize() {}
virtual void writeTo(uint8_t *buf) const = 0;
// Handle section$start$ and section$end$ symbols.
void assignAddressesToStartEndSymbols();
StringRef name;
llvm::TinyPtrVector<Defined *> sectionStartSymbols;
llvm::TinyPtrVector<Defined *> sectionEndSymbols;
OutputSegment *parent = nullptr;
// For output sections that don't have explicit ordering requirements, their
// output order should be based on the order of the input sections they
// contain.
int inputOrder = UnspecifiedInputOrder;
uint32_t index = 0;
uint64_t addr = 0;
uint64_t fileOff = 0;
uint32_t align = 1;
uint32_t flags = 0;
uint32_t reserved1 = 0;
uint32_t reserved2 = 0;
Kind sectionKind;
} // namespace lld::macho