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//===- LinkerScript.h -------------------------------------------*- C++ -*-===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLD_ELF_LINKER_SCRIPT_H
#define LLD_ELF_LINKER_SCRIPT_H
#include "Config.h"
#include "Writer.h"
#include "lld/Common/LLVM.h"
#include "lld/Common/Strings.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/MemoryBuffer.h"
#include <cstddef>
#include <cstdint>
#include <functional>
#include <memory>
#include <vector>
namespace lld {
namespace elf {
class Defined;
class Symbol;
class InputSectionBase;
class InputSection;
class OutputSection;
class InputSectionBase;
class SectionBase;
// This represents an r-value in the linker script.
struct ExprValue {
ExprValue(SectionBase *Sec, bool ForceAbsolute, uint64_t Val,
const Twine &Loc)
: Sec(Sec), ForceAbsolute(ForceAbsolute), Val(Val), Loc(Loc.str()) {}
ExprValue(uint64_t Val) : ExprValue(nullptr, false, Val, "") {}
bool isAbsolute() const { return ForceAbsolute || Sec == nullptr; }
uint64_t getValue() const;
uint64_t getSecAddr() const;
uint64_t getSectionOffset() const;
// If a value is relative to a section, it has a non-null Sec.
SectionBase *Sec;
// True if this expression is enclosed in ABSOLUTE().
// This flag affects the return value of getValue().
bool ForceAbsolute;
uint64_t Val;
uint64_t Alignment = 1;
// Original source location. Used for error messages.
std::string Loc;
};
// This represents an expression in the linker script.
// ScriptParser::readExpr reads an expression and returns an Expr.
// Later, we evaluate the expression by calling the function.
typedef std::function<ExprValue()> Expr;
// This enum is used to implement linker script SECTIONS command.
// https://sourceware.org/binutils/docs/ld/SECTIONS.html#SECTIONS
enum SectionsCommandKind {
AssignmentKind, // . = expr or <sym> = expr
OutputSectionKind,
InputSectionKind,
ByteKind // BYTE(expr), SHORT(expr), LONG(expr) or QUAD(expr)
};
struct BaseCommand {
BaseCommand(int K) : Kind(K) {}
int Kind;
};
// This represents ". = <expr>" or "<symbol> = <expr>".
struct SymbolAssignment : BaseCommand {
SymbolAssignment(StringRef Name, Expr E, std::string Loc)
: BaseCommand(AssignmentKind), Name(Name), Expression(E), Location(Loc) {}
static bool classof(const BaseCommand *C) {
return C->Kind == AssignmentKind;
}
// The LHS of an expression. Name is either a symbol name or ".".
StringRef Name;
Defined *Sym = nullptr;
// The RHS of an expression.
Expr Expression;
// Command attributes for PROVIDE, HIDDEN and PROVIDE_HIDDEN.
bool Provide = false;
bool Hidden = false;
// Holds file name and line number for error reporting.
std::string Location;
// A string representation of this command. We use this for -Map.
std::string CommandString;
// Address of this assignment command.
unsigned Addr;
// Size of this assignment command. This is usually 0, but if
// you move '.' this may be greater than 0.
unsigned Size;
};
// Linker scripts allow additional constraints to be put on ouput sections.
// If an output section is marked as ONLY_IF_RO, the section is created
// only if its input sections are read-only. Likewise, an output section
// with ONLY_IF_RW is created if all input sections are RW.
enum class ConstraintKind { NoConstraint, ReadOnly, ReadWrite };
// This struct is used to represent the location and size of regions of
// target memory. Instances of the struct are created by parsing the
// MEMORY command.
struct MemoryRegion {
MemoryRegion(StringRef Name, uint64_t Origin, uint64_t Length, uint32_t Flags,
uint32_t NegFlags)
: Name(Name), Origin(Origin), Length(Length), Flags(Flags),
NegFlags(NegFlags) {}
std::string Name;
uint64_t Origin;
uint64_t Length;
uint32_t Flags;
uint32_t NegFlags;
uint64_t CurPos = 0;
};
// This struct represents one section match pattern in SECTIONS() command.
// It can optionally have negative match pattern for EXCLUDED_FILE command.
// Also it may be surrounded with SORT() command, so contains sorting rules.
struct SectionPattern {
SectionPattern(StringMatcher &&Pat1, StringMatcher &&Pat2)
: ExcludedFilePat(Pat1), SectionPat(Pat2) {}
StringMatcher ExcludedFilePat;
StringMatcher SectionPat;
SortSectionPolicy SortOuter;
SortSectionPolicy SortInner;
};
class ThunkSection;
struct InputSectionDescription : BaseCommand {
InputSectionDescription(StringRef FilePattern)
: BaseCommand(InputSectionKind), FilePat(FilePattern) {}
static bool classof(const BaseCommand *C) {
return C->Kind == InputSectionKind;
}
StringMatcher FilePat;
// Input sections that matches at least one of SectionPatterns
// will be associated with this InputSectionDescription.
std::vector<SectionPattern> SectionPatterns;
std::vector<InputSection *> Sections;
// Temporary record of synthetic ThunkSection instances and the pass that
// they were created in. This is used to insert newly created ThunkSections
// into Sections at the end of a createThunks() pass.
std::vector<std::pair<ThunkSection *, uint32_t>> ThunkSections;
};
// Represents BYTE(), SHORT(), LONG(), or QUAD().
struct ByteCommand : BaseCommand {
ByteCommand(Expr E, unsigned Size, std::string CommandString)
: BaseCommand(ByteKind), CommandString(CommandString), Expression(E),
Size(Size) {}
static bool classof(const BaseCommand *C) { return C->Kind == ByteKind; }
// Keeps string representing the command. Used for -Map" is perhaps better.
std::string CommandString;
Expr Expression;
// This is just an offset of this assignment command in the output section.
unsigned Offset;
// Size of this data command.
unsigned Size;
};
struct PhdrsCommand {
StringRef Name;
unsigned Type = llvm::ELF::PT_NULL;
bool HasFilehdr = false;
bool HasPhdrs = false;
llvm::Optional<unsigned> Flags;
Expr LMAExpr = nullptr;
};
class LinkerScript final {
// Temporary state used in processSectionCommands() and assignAddresses()
// that must be reinitialized for each call to the above functions, and must
// not be used outside of the scope of a call to the above functions.
struct AddressState {
AddressState();
uint64_t ThreadBssOffset = 0;
OutputSection *OutSec = nullptr;
MemoryRegion *MemRegion = nullptr;
MemoryRegion *LMARegion = nullptr;
uint64_t LMAOffset = 0;
};
llvm::DenseMap<StringRef, OutputSection *> NameToOutputSection;
void addSymbol(SymbolAssignment *Cmd);
void assignSymbol(SymbolAssignment *Cmd, bool InSec);
void setDot(Expr E, const Twine &Loc, bool InSec);
void expandOutputSection(uint64_t Size);
void expandMemoryRegions(uint64_t Size);
std::vector<InputSection *>
computeInputSections(const InputSectionDescription *);
std::vector<InputSection *> createInputSectionList(OutputSection &Cmd);
std::vector<size_t> getPhdrIndices(OutputSection *Sec);
MemoryRegion *findMemoryRegion(OutputSection *Sec);
void switchTo(OutputSection *Sec);
uint64_t advance(uint64_t Size, unsigned Align);
void output(InputSection *Sec);
void assignOffsets(OutputSection *Sec);
// Ctx captures the local AddressState and makes it accessible
// deliberately. This is needed as there are some cases where we cannot just
// thread the current state through to a lambda function created by the
// script parser.
// This should remain a plain pointer as its lifetime is smaller than
// LinkerScript.
AddressState *Ctx = nullptr;
OutputSection *Aether;
uint64_t Dot;
public:
OutputSection *createOutputSection(StringRef Name, StringRef Location);
OutputSection *getOrCreateOutputSection(StringRef Name);
bool hasPhdrsCommands() { return !PhdrsCommands.empty(); }
uint64_t getDot() { return Dot; }
void discard(ArrayRef<InputSection *> V);
ExprValue getSymbolValue(StringRef Name, const Twine &Loc);
void addOrphanSections();
void adjustSectionsBeforeSorting();
void adjustSectionsAfterSorting();
std::vector<PhdrEntry *> createPhdrs();
bool needsInterpSection();
bool shouldKeep(InputSectionBase *S);
void assignAddresses();
void allocateHeaders(std::vector<PhdrEntry *> &Phdrs);
void processSectionCommands();
void declareSymbols();
// Used to handle INSERT AFTER statements.
void processInsertCommands();
// SECTIONS command list.
std::vector<BaseCommand *> SectionCommands;
// PHDRS command list.
std::vector<PhdrsCommand> PhdrsCommands;
bool HasSectionsCommand = false;
bool ErrorOnMissingSection = false;
// List of section patterns specified with KEEP commands. They will
// be kept even if they are unused and --gc-sections is specified.
std::vector<InputSectionDescription *> KeptSections;
// A map from memory region name to a memory region descriptor.
llvm::MapVector<llvm::StringRef, MemoryRegion *> MemoryRegions;
// A list of symbols referenced by the script.
std::vector<llvm::StringRef> ReferencedSymbols;
// Used to implement INSERT [AFTER|BEFORE]. Contains commands that need
// to be inserted into SECTIONS commands list.
llvm::DenseMap<StringRef, std::vector<BaseCommand *>> InsertAfterCommands;
llvm::DenseMap<StringRef, std::vector<BaseCommand *>> InsertBeforeCommands;
};
extern LinkerScript *Script;
} // end namespace elf
} // end namespace lld
#endif // LLD_ELF_LINKER_SCRIPT_H