llvm-project/lld/MachO/OutputSection.h

110 lines
3.3 KiB
C++

//===- OutputSection.h ------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLD_MACHO_OUTPUT_SECTION_H
#define LLD_MACHO_OUTPUT_SECTION_H
#include "lld/Common/LLVM.h"
#include "llvm/ADT/DenseMap.h"
namespace lld {
namespace macho {
class InputSection;
class OutputSegment;
// 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 {
public:
enum Kind {
MergedKind,
SyntheticKind,
};
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; }
// Some sections may allow coalescing other raw input sections.
virtual void mergeInput(InputSection *input);
// Specifically finalizes addresses and section size, not content.
virtual void finalize() {
// TODO investigate refactoring synthetic section finalization logic into
// overrides of this function.
}
virtual void writeTo(uint8_t *buf) const = 0;
StringRef name;
OutputSegment *parent = nullptr;
uint32_t index = 0;
uint64_t addr = 0;
uint64_t fileOff = 0;
uint32_t align = 1;
uint32_t flags = 0;
private:
Kind sectionKind;
};
class OutputSectionComparator {
public:
OutputSectionComparator(uint32_t segmentOrder,
const std::vector<StringRef> &sectOrdering)
: segmentOrder(segmentOrder) {
for (uint32_t j = 0, m = sectOrdering.size(); j < m; ++j)
sectionOrdering[sectOrdering[j]] = j;
}
uint32_t sectionOrder(StringRef secname) {
auto sectIt = sectionOrdering.find(secname);
if (sectIt != sectionOrdering.end())
return sectIt->second;
return sectionOrdering.size();
}
// Sort sections within a common segment, which stores them in
// a MapVector of section name -> section
bool operator()(const std::pair<StringRef, OutputSection *> &a,
const std::pair<StringRef, OutputSection *> &b) {
return sectionOrder(a.first) < sectionOrder(b.first);
}
bool operator<(const OutputSectionComparator &b) {
return segmentOrder < b.segmentOrder;
}
private:
uint32_t segmentOrder;
llvm::DenseMap<StringRef, uint32_t> sectionOrdering;
};
} // namespace macho
} // namespace lld
#endif