forked from OSchip/llvm-project
85 lines
2.8 KiB
C++
85 lines
2.8 KiB
C++
//===- Thunks.h --------------------------------------------------------===//
|
|
//
|
|
// 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_ELF_THUNKS_H
|
|
#define LLD_ELF_THUNKS_H
|
|
|
|
#include "llvm/ADT/SmallVector.h"
|
|
#include "Relocations.h"
|
|
|
|
namespace lld {
|
|
namespace elf {
|
|
class Defined;
|
|
class InputFile;
|
|
class Symbol;
|
|
class ThunkSection;
|
|
// Class to describe an instance of a Thunk.
|
|
// A Thunk is a code-sequence inserted by the linker in between a caller and
|
|
// the callee. The relocation to the callee is redirected to the Thunk, which
|
|
// after executing transfers control to the callee. Typical uses of Thunks
|
|
// include transferring control from non-pi to pi and changing state on
|
|
// targets like ARM.
|
|
//
|
|
// Thunks can be created for Defined, Shared and Undefined Symbols.
|
|
// Thunks are assigned to synthetic ThunkSections
|
|
class Thunk {
|
|
public:
|
|
Thunk(Symbol &destination, int64_t addend);
|
|
virtual ~Thunk();
|
|
|
|
virtual uint32_t size() = 0;
|
|
virtual void writeTo(uint8_t *buf) = 0;
|
|
|
|
// All Thunks must define at least one symbol, known as the thunk target
|
|
// symbol, so that we can redirect relocations to it. The thunk may define
|
|
// additional symbols, but these are never targets for relocations.
|
|
virtual void addSymbols(ThunkSection &isec) = 0;
|
|
|
|
void setOffset(uint64_t offset);
|
|
Defined *addSymbol(StringRef name, uint8_t type, uint64_t value,
|
|
InputSectionBase §ion);
|
|
|
|
// Some Thunks must be placed immediately before their Target as they elide
|
|
// a branch and fall through to the first Symbol in the Target.
|
|
virtual InputSection *getTargetInputSection() const { return nullptr; }
|
|
|
|
// To reuse a Thunk the InputSection and the relocation must be compatible
|
|
// with it.
|
|
virtual bool isCompatibleWith(const InputSection &,
|
|
const Relocation &) const {
|
|
return true;
|
|
}
|
|
|
|
Defined *getThunkTargetSym() const { return syms[0]; }
|
|
|
|
Symbol &destination;
|
|
int64_t addend;
|
|
llvm::SmallVector<Defined *, 3> syms;
|
|
uint64_t offset = 0;
|
|
// The alignment requirement for this Thunk, defaults to the size of the
|
|
// typical code section alignment.
|
|
uint32_t alignment = 4;
|
|
};
|
|
|
|
// For a Relocation to symbol S create a Thunk to be added to a synthetic
|
|
// ThunkSection.
|
|
Thunk *addThunk(const InputSection &isec, Relocation &rel);
|
|
|
|
void writePPC32PltCallStub(uint8_t *buf, uint64_t gotPltVA,
|
|
const InputFile *file, int64_t addend);
|
|
void writePPC64LoadAndBranch(uint8_t *buf, int64_t offset);
|
|
|
|
static inline uint16_t computeHiBits(uint32_t toCompute) {
|
|
return (toCompute + 0x8000) >> 16;
|
|
}
|
|
|
|
} // namespace elf
|
|
} // namespace lld
|
|
|
|
#endif
|