maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/lld/ELF/LinkerScript.cpp

1932 lines
59 KiB
C++
Raw Blame History

//===- LinkerScript.cpp ---------------------------------------------------===//
//
// The LLVM Linker
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the parser/evaluator of the linker script.
//
//===----------------------------------------------------------------------===//
#include "LinkerScript.h"
#include "Config.h"
#include "Driver.h"
#include "InputSection.h"
#include "Memory.h"
#include "OutputSections.h"
#include "ScriptParser.h"
#include "Strings.h"
#include "SymbolTable.h"
#include "Symbols.h"
#include "Target.h"
#include "Writer.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <limits>
#include <memory>
#include <string>
#include <tuple>
#include <vector>
using namespace llvm;
using namespace llvm::ELF;
using namespace llvm::object;
using namespace llvm::support::endian;
using namespace lld;
using namespace lld::elf;
LinkerScriptBase *elf::ScriptBase;
ScriptConfiguration *elf::ScriptConfig;
template <class ELFT> static void addRegular(SymbolAssignment *Cmd) {
uint8_t Visibility = Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT;
Symbol *Sym = Symtab<ELFT>::X->addRegular(Cmd->Name, Visibility, STT_NOTYPE,
0, 0, STB_GLOBAL, nullptr, nullptr);
Cmd->Sym = Sym->body();
// If we have no SECTIONS then we don't have '.' and don't call
// assignAddresses(). We calculate symbol value immediately in this case.
if (!ScriptConfig->HasSections)
cast<DefinedRegular<ELFT>>(Cmd->Sym)->Value = Cmd->Expression(0);
}
template <class ELFT> static void addSynthetic(SymbolAssignment *Cmd) {
// If we have SECTIONS block then output sections haven't been created yet.
const OutputSectionBase *Sec =
ScriptConfig->HasSections ? nullptr : Cmd->Expression.Section();
Symbol *Sym = Symtab<ELFT>::X->addSynthetic(
Cmd->Name, Sec, 0, Cmd->Hidden ? STV_HIDDEN : STV_DEFAULT);
Cmd->Sym = Sym->body();
// If we already know section then we can calculate symbol value immediately.
if (Sec)
cast<DefinedSynthetic<ELFT>>(Cmd->Sym)->Value =
Cmd->Expression(0) - Sec->Addr;
}
template <class ELFT> static void addSymbol(SymbolAssignment *Cmd) {
if (Cmd->Expression.IsAbsolute())
addRegular<ELFT>(Cmd);
else
addSynthetic<ELFT>(Cmd);
}
// If a symbol was in PROVIDE(), we need to define it only when
// it is an undefined symbol.
template <class ELFT> static bool shouldDefine(SymbolAssignment *Cmd) {
if (Cmd->Name == ".")
return false;
if (!Cmd->Provide)
return true;
SymbolBody *B = Symtab<ELFT>::X->find(Cmd->Name);
return B && B->isUndefined();
}
bool SymbolAssignment::classof(const BaseCommand *C) {
return C->Kind == AssignmentKind;
}
bool OutputSectionCommand::classof(const BaseCommand *C) {
return C->Kind == OutputSectionKind;
}
bool InputSectionDescription::classof(const BaseCommand *C) {
return C->Kind == InputSectionKind;
}
bool AssertCommand::classof(const BaseCommand *C) {
return C->Kind == AssertKind;
}
bool BytesDataCommand::classof(const BaseCommand *C) {
return C->Kind == BytesDataKind;
}
template <class ELFT> LinkerScript<ELFT>::LinkerScript() = default;
template <class ELFT> LinkerScript<ELFT>::~LinkerScript() = default;
template <class ELFT> static StringRef basename(InputSectionBase<ELFT> *S) {
if (S->getFile())
return sys::path::filename(S->getFile()->getName());
return "";
}
template <class ELFT>
bool LinkerScript<ELFT>::shouldKeep(InputSectionBase<ELFT> *S) {
for (InputSectionDescription *ID : Opt.KeptSections)
if (ID->FilePat.match(basename(S)))
for (SectionPattern &P : ID->SectionPatterns)
if (P.SectionPat.match(S->Name))
return true;
return false;
}
static bool comparePriority(InputSectionData *A, InputSectionData *B) {
return getPriority(A->Name) < getPriority(B->Name);
}
static bool compareName(InputSectionData *A, InputSectionData *B) {
return A->Name < B->Name;
}
static bool compareAlignment(InputSectionData *A, InputSectionData *B) {
// ">" is not a mistake. Larger alignments are placed before smaller
// alignments in order to reduce the amount of padding necessary.
// This is compatible with GNU.
return A->Alignment > B->Alignment;
}
static std::function<bool(InputSectionData *, InputSectionData *)>
getComparator(SortSectionPolicy K) {
switch (K) {
case SortSectionPolicy::Alignment:
return compareAlignment;
case SortSectionPolicy::Name:
return compareName;
case SortSectionPolicy::Priority:
return comparePriority;
default:
llvm_unreachable("unknown sort policy");
}
}
template <class ELFT>
static bool matchConstraints(ArrayRef<InputSectionBase<ELFT> *> Sections,
ConstraintKind Kind) {
if (Kind == ConstraintKind::NoConstraint)
return true;
bool IsRW = llvm::any_of(Sections, [=](InputSectionData *Sec2) {
auto *Sec = static_cast<InputSectionBase<ELFT> *>(Sec2);
return Sec->Flags & SHF_WRITE;
});
return (IsRW && Kind == ConstraintKind::ReadWrite) ||
(!IsRW && Kind == ConstraintKind::ReadOnly);
}
static void sortSections(InputSectionData **Begin, InputSectionData **End,
SortSectionPolicy K) {
if (K != SortSectionPolicy::Default && K != SortSectionPolicy::None)
std::stable_sort(Begin, End, getComparator(K));
}
// Compute and remember which sections the InputSectionDescription matches.
template <class ELFT>
void LinkerScript<ELFT>::computeInputSections(InputSectionDescription *I) {
// Collects all sections that satisfy constraints of I
// and attach them to I.
for (SectionPattern &Pat : I->SectionPatterns) {
size_t SizeBefore = I->Sections.size();
for (InputSectionBase<ELFT> *S : Symtab<ELFT>::X->Sections) {
if (!S->Live || S->Assigned)
continue;
StringRef Filename = basename(S);
if (!I->FilePat.match(Filename) || Pat.ExcludedFilePat.match(Filename))
continue;
if (!Pat.SectionPat.match(S->Name))
continue;
I->Sections.push_back(S);
S->Assigned = true;
}
// Sort sections as instructed by SORT-family commands and --sort-section
// option. Because SORT-family commands can be nested at most two depth
// (e.g. SORT_BY_NAME(SORT_BY_ALIGNMENT(.text.*))) and because the command
// line option is respected even if a SORT command is given, the exact
// behavior we have here is a bit complicated. Here are the rules.
//
// 1. If two SORT commands are given, --sort-section is ignored.
// 2. If one SORT command is given, and if it is not SORT_NONE,
// --sort-section is handled as an inner SORT command.
// 3. If one SORT command is given, and if it is SORT_NONE, don't sort.
// 4. If no SORT command is given, sort according to --sort-section.
InputSectionData **Begin = I->Sections.data() + SizeBefore;
InputSectionData **End = I->Sections.data() + I->Sections.size();
if (Pat.SortOuter != SortSectionPolicy::None) {
if (Pat.SortInner == SortSectionPolicy::Default)
sortSections(Begin, End, Config->SortSection);
else
sortSections(Begin, End, Pat.SortInner);
sortSections(Begin, End, Pat.SortOuter);
}
}
}
template <class ELFT>
void LinkerScript<ELFT>::discard(ArrayRef<InputSectionBase<ELFT> *> V) {
for (InputSectionBase<ELFT> *S : V) {
S->Live = false;
reportDiscarded(S);
}
}
template <class ELFT>
std::vector<InputSectionBase<ELFT> *>
LinkerScript<ELFT>::createInputSectionList(OutputSectionCommand &OutCmd) {
std::vector<InputSectionBase<ELFT> *> Ret;
for (const std::unique_ptr<BaseCommand> &Base : OutCmd.Commands) {
auto *Cmd = dyn_cast<InputSectionDescription>(Base.get());
if (!Cmd)
continue;
computeInputSections(Cmd);
for (InputSectionData *S : Cmd->Sections)
Ret.push_back(static_cast<InputSectionBase<ELFT> *>(S));
}
return Ret;
}
template <class ELFT>
static SectionKey<ELFT::Is64Bits> createKey(InputSectionBase<ELFT> *C,
StringRef OutsecName) {
// When using linker script the merge rules are different.
// Unfortunately, linker scripts are name based. This means that expressions
// like *(.foo*) can refer to multiple input sections that would normally be
// placed in different output sections. We cannot put them in different
// output sections or we would produce wrong results for
// start = .; *(.foo.*) end = .; *(.bar)
// and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to
// another. The problem is that there is no way to layout those output
// sections such that the .foo sections are the only thing between the
// start and end symbols.
// An extra annoyance is that we cannot simply disable merging of the contents
// of SHF_MERGE sections, but our implementation requires one output section
// per "kind" (string or not, which size/aligment).
// Fortunately, creating symbols in the middle of a merge section is not
// supported by bfd or gold, so we can just create multiple section in that
// case.
typedef typename ELFT::uint uintX_t;
uintX_t Flags = C->Flags & (SHF_MERGE | SHF_STRINGS);
uintX_t Alignment = 0;
if (isa<MergeInputSection<ELFT>>(C))
Alignment = std::max<uintX_t>(C->Alignment, C->Entsize);
return SectionKey<ELFT::Is64Bits>{OutsecName, /*Type*/ 0, Flags, Alignment};
}
template <class ELFT>
void LinkerScript<ELFT>::addSection(OutputSectionFactory<ELFT> &Factory,
InputSectionBase<ELFT> *Sec,
StringRef Name) {
OutputSectionBase *OutSec;
bool IsNew;
std::tie(OutSec, IsNew) = Factory.create(createKey(Sec, Name), Sec);
if (IsNew)
OutputSections->push_back(OutSec);
OutSec->addSection(Sec);
}
template <class ELFT>
void LinkerScript<ELFT>::processCommands(OutputSectionFactory<ELFT> &Factory) {
for (unsigned I = 0; I < Opt.Commands.size(); ++I) {
auto Iter = Opt.Commands.begin() + I;
const std::unique_ptr<BaseCommand> &Base1 = *Iter;
// Handle symbol assignments outside of any output section.
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base1.get())) {
if (shouldDefine<ELFT>(Cmd))
addSymbol<ELFT>(Cmd);
continue;
}
if (auto *Cmd = dyn_cast<AssertCommand>(Base1.get())) {
// If we don't have SECTIONS then output sections have already been
// created by Writer<ELFT>. The LinkerScript<ELFT>::assignAddresses
// will not be called, so ASSERT should be evaluated now.
if (!Opt.HasSections)
Cmd->Expression(0);
continue;
}
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base1.get())) {
std::vector<InputSectionBase<ELFT> *> V = createInputSectionList(*Cmd);
// The output section name `/DISCARD/' is special.
// Any input section assigned to it is discarded.
if (Cmd->Name == "/DISCARD/") {
discard(V);
continue;
}
// This is for ONLY_IF_RO and ONLY_IF_RW. An output section directive
// ".foo : ONLY_IF_R[OW] { ... }" is handled only if all member input
// sections satisfy a given constraint. If not, a directive is handled
// as if it wasn't present from the beginning.
//
// Because we'll iterate over Commands many more times, the easiest
// way to "make it as if it wasn't present" is to just remove it.
if (!matchConstraints<ELFT>(V, Cmd->Constraint)) {
for (InputSectionBase<ELFT> *S : V)
S->Assigned = false;
Opt.Commands.erase(Iter);
--I;
continue;
}
// A directive may contain symbol definitions like this:
// ".foo : { ...; bar = .; }". Handle them.
for (const std::unique_ptr<BaseCommand> &Base : Cmd->Commands)
if (auto *OutCmd = dyn_cast<SymbolAssignment>(Base.get()))
if (shouldDefine<ELFT>(OutCmd))
addSymbol<ELFT>(OutCmd);
// Handle subalign (e.g. ".foo : SUBALIGN(32) { ... }"). If subalign
// is given, input sections are aligned to that value, whether the
// given value is larger or smaller than the original section alignment.
if (Cmd->SubalignExpr) {
uint32_t Subalign = Cmd->SubalignExpr(0);
for (InputSectionBase<ELFT> *S : V)
S->Alignment = Subalign;
}
// Add input sections to an output section.
for (InputSectionBase<ELFT> *S : V)
addSection(Factory, S, Cmd->Name);
}
}
}
// Add sections that didn't match any sections command.
template <class ELFT>
void LinkerScript<ELFT>::addOrphanSections(OutputSectionFactory<ELFT> &Factory) {
for (InputSectionBase<ELFT> *S : Symtab<ELFT>::X->Sections)
if (S->Live && !S->OutSec)
addSection(Factory, S, getOutputSectionName(S->Name));
}
// Sets value of a section-defined symbol. Two kinds of
// symbols are processed: synthetic symbols, whose value
// is an offset from beginning of section and regular
// symbols whose value is absolute.
template <class ELFT>
static void assignSectionSymbol(SymbolAssignment *Cmd,
typename ELFT::uint Value) {
if (!Cmd->Sym)
return;
if (auto *Body = dyn_cast<DefinedSynthetic<ELFT>>(Cmd->Sym)) {
Body->Section = Cmd->Expression.Section();
Body->Value = Cmd->Expression(Value) - Body->Section->Addr;
return;
}
auto *Body = cast<DefinedRegular<ELFT>>(Cmd->Sym);
Body->Value = Cmd->Expression(Value);
}
template <class ELFT> static bool isTbss(OutputSectionBase *Sec) {
return (Sec->Flags & SHF_TLS) && Sec->Type == SHT_NOBITS;
}
template <class ELFT> void LinkerScript<ELFT>::output(InputSection<ELFT> *S) {
if (!AlreadyOutputIS.insert(S).second)
return;
bool IsTbss = isTbss<ELFT>(CurOutSec);
uintX_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
Pos = alignTo(Pos, S->Alignment);
S->OutSecOff = Pos - CurOutSec->Addr;
Pos += S->getSize();
// Update output section size after adding each section. This is so that
// SIZEOF works correctly in the case below:
// .foo { *(.aaa) a = SIZEOF(.foo); *(.bbb) }
CurOutSec->Size = Pos - CurOutSec->Addr;
if (IsTbss)
ThreadBssOffset = Pos - Dot;
else
Dot = Pos;
}
template <class ELFT> void LinkerScript<ELFT>::flush() {
if (!CurOutSec || !AlreadyOutputOS.insert(CurOutSec).second)
return;
if (auto *OutSec = dyn_cast<OutputSection<ELFT>>(CurOutSec)) {
for (InputSection<ELFT> *I : OutSec->Sections)
output(I);
} else {
Dot += CurOutSec->Size;
}
}
template <class ELFT>
void LinkerScript<ELFT>::switchTo(OutputSectionBase *Sec) {
if (CurOutSec == Sec)
return;
if (AlreadyOutputOS.count(Sec))
return;
flush();
CurOutSec = Sec;
Dot = alignTo(Dot, CurOutSec->Addralign);
CurOutSec->Addr = isTbss<ELFT>(CurOutSec) ? Dot + ThreadBssOffset : Dot;
// If neither AT nor AT> is specified for an allocatable section, the linker
// will set the LMA such that the difference between VMA and LMA for the
// section is the same as the preceding output section in the same region
// https://sourceware.org/binutils/docs-2.20/ld/Output-Section-LMA.html
CurOutSec->setLMAOffset(LMAOffset);
}
template <class ELFT> void LinkerScript<ELFT>::process(BaseCommand &Base) {
// This handles the assignments to symbol or to a location counter (.)
if (auto *AssignCmd = dyn_cast<SymbolAssignment>(&Base)) {
if (AssignCmd->Name == ".") {
// Update to location counter means update to section size.
Dot = AssignCmd->Expression(Dot);
CurOutSec->Size = Dot - CurOutSec->Addr;
return;
}
assignSectionSymbol<ELFT>(AssignCmd, Dot);
return;
}
// Handle BYTE(), SHORT(), LONG(), or QUAD().
if (auto *DataCmd = dyn_cast<BytesDataCommand>(&Base)) {
DataCmd->Offset = Dot - CurOutSec->Addr;
Dot += DataCmd->Size;
CurOutSec->Size = Dot - CurOutSec->Addr;
return;
}
if (auto *AssertCmd = dyn_cast<AssertCommand>(&Base)) {
AssertCmd->Expression(Dot);
return;
}
// It handles single input section description command,
// calculates and assigns the offsets for each section and also
// updates the output section size.
auto &ICmd = cast<InputSectionDescription>(Base);
for (InputSectionData *ID : ICmd.Sections) {
auto *IB = static_cast<InputSectionBase<ELFT> *>(ID);
switchTo(IB->OutSec);
if (auto *I = dyn_cast<InputSection<ELFT>>(IB))
output(I);
else
flush();
}
}
template <class ELFT>
static std::vector<OutputSectionBase *>
findSections(StringRef Name, const std::vector<OutputSectionBase *> &Sections) {
std::vector<OutputSectionBase *> Ret;
for (OutputSectionBase *Sec : Sections)
if (Sec->getName() == Name)
Ret.push_back(Sec);
return Ret;
}
// This function assigns offsets to input sections and an output section
// for a single sections command (e.g. ".text { *(.text); }").
template <class ELFT>
void LinkerScript<ELFT>::assignOffsets(OutputSectionCommand *Cmd) {
if (Cmd->LMAExpr)
LMAOffset = Cmd->LMAExpr(Dot) - Dot;
std::vector<OutputSectionBase *> Sections =
findSections<ELFT>(Cmd->Name, *OutputSections);
if (Sections.empty())
return;
switchTo(Sections[0]);
// Find the last section output location. We will output orphan sections
// there so that end symbols point to the correct location.
auto E = std::find_if(Cmd->Commands.rbegin(), Cmd->Commands.rend(),
[](const std::unique_ptr<BaseCommand> &Cmd) {
return !isa<SymbolAssignment>(*Cmd);
})
.base();
for (auto I = Cmd->Commands.begin(); I != E; ++I)
process(**I);
for (OutputSectionBase *Base : Sections)
switchTo(Base);
flush();
std::for_each(E, Cmd->Commands.end(),
[this](std::unique_ptr<BaseCommand> &B) { process(*B.get()); });
}
template <class ELFT> void LinkerScript<ELFT>::removeEmptyCommands() {
// It is common practice to use very generic linker scripts. So for any
// given run some of the output sections in the script will be empty.
// We could create corresponding empty output sections, but that would
// clutter the output.
// We instead remove trivially empty sections. The bfd linker seems even
// more aggressive at removing them.
auto Pos = std::remove_if(
Opt.Commands.begin(), Opt.Commands.end(),
[&](const std::unique_ptr<BaseCommand> &Base) {
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
return findSections<ELFT>(Cmd->Name, *OutputSections).empty();
return false;
});
Opt.Commands.erase(Pos, Opt.Commands.end());
}
static bool isAllSectionDescription(const OutputSectionCommand &Cmd) {
for (const std::unique_ptr<BaseCommand> &I : Cmd.Commands)
if (!isa<InputSectionDescription>(*I))
return false;
return true;
}
template <class ELFT> void LinkerScript<ELFT>::adjustSectionsBeforeSorting() {
// If the output section contains only symbol assignments, create a
// corresponding output section. The bfd linker seems to only create them if
// '.' is assigned to, but creating these section should not have any bad
// consequeces and gives us a section to put the symbol in.
uintX_t Flags = SHF_ALLOC;
uint32_t Type = 0;
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd)
continue;
std::vector<OutputSectionBase *> Secs =
findSections<ELFT>(Cmd->Name, *OutputSections);
if (!Secs.empty()) {
Flags = Secs[0]->Flags;
Type = Secs[0]->Type;
continue;
}
if (isAllSectionDescription(*Cmd))
continue;
auto *OutSec = make<OutputSection<ELFT>>(Cmd->Name, Type, Flags);
OutputSections->push_back(OutSec);
}
}
template <class ELFT> void LinkerScript<ELFT>::adjustSectionsAfterSorting() {
placeOrphanSections();
// If output section command doesn't specify any segments,
// and we haven't previously assigned any section to segment,
// then we simply assign section to the very first load segment.
// Below is an example of such linker script:
// PHDRS { seg PT_LOAD; }
// SECTIONS { .aaa : { *(.aaa) } }
std::vector<StringRef> DefPhdrs;
auto FirstPtLoad =
std::find_if(Opt.PhdrsCommands.begin(), Opt.PhdrsCommands.end(),
[](const PhdrsCommand &Cmd) { return Cmd.Type == PT_LOAD; });
if (FirstPtLoad != Opt.PhdrsCommands.end())
DefPhdrs.push_back(FirstPtLoad->Name);
// Walk the commands and propagate the program headers to commands that don't
// explicitly specify them.
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd)
continue;
if (Cmd->Phdrs.empty())
Cmd->Phdrs = DefPhdrs;
else
DefPhdrs = Cmd->Phdrs;
}
removeEmptyCommands();
}
// When placing orphan sections, we want to place them after symbol assignments
// so that an orphan after
// begin_foo = .;
// foo : { *(foo) }
// end_foo = .;
// doesn't break the intended meaning of the begin/end symbols.
// We don't want to go over sections since Writer<ELFT>::sortSections is the
// one in charge of deciding the order of the sections.
// We don't want to go over alignments, since doing so in
// rx_sec : { *(rx_sec) }
// . = ALIGN(0x1000);
// /* The RW PT_LOAD starts here*/
// rw_sec : { *(rw_sec) }
// would mean that the RW PT_LOAD would become unaligned.
static bool shouldSkip(const BaseCommand &Cmd) {
if (isa<OutputSectionCommand>(Cmd))
return false;
const auto *Assign = dyn_cast<SymbolAssignment>(&Cmd);
if (!Assign)
return true;
return Assign->Name != ".";
}
// Orphan sections are sections present in the input files which are not
// explicitly placed into the output file by the linker script. This just
// places them in the order already decided in OutputSections.
template <class ELFT>
void LinkerScript<ELFT>::placeOrphanSections() {
// The OutputSections are already in the correct order.
// This loops creates or moves commands as needed so that they are in the
// correct order.
int CmdIndex = 0;
for (OutputSectionBase *Sec : *OutputSections) {
StringRef Name = Sec->getName();
// Find the last spot where we can insert a command and still get the
// correct result.
auto CmdIter = Opt.Commands.begin() + CmdIndex;
auto E = Opt.Commands.end();
while (CmdIter != E && shouldSkip(**CmdIter)) {
++CmdIter;
++CmdIndex;
}
auto Pos =
std::find_if(CmdIter, E, [&](const std::unique_ptr<BaseCommand> &Base) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
return Cmd && Cmd->Name == Name;
});
if (Pos == E) {
Opt.Commands.insert(CmdIter,
llvm::make_unique<OutputSectionCommand>(Name));
++CmdIndex;
continue;
}
// Continue from where we found it.
CmdIndex = (Pos - Opt.Commands.begin()) + 1;
}
}
template <class ELFT>
void LinkerScript<ELFT>::assignAddresses(std::vector<PhdrEntry<ELFT>> &Phdrs) {
// Assign addresses as instructed by linker script SECTIONS sub-commands.
Dot = 0;
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
if (auto *Cmd = dyn_cast<SymbolAssignment>(Base.get())) {
if (Cmd->Name == ".") {
Dot = Cmd->Expression(Dot);
} else if (Cmd->Sym) {
assignSectionSymbol<ELFT>(Cmd, Dot);
}
continue;
}
if (auto *Cmd = dyn_cast<AssertCommand>(Base.get())) {
Cmd->Expression(Dot);
continue;
}
auto *Cmd = cast<OutputSectionCommand>(Base.get());
if (Cmd->AddrExpr)
Dot = Cmd->AddrExpr(Dot);
assignOffsets(Cmd);
}
uintX_t MinVA = std::numeric_limits<uintX_t>::max();
for (OutputSectionBase *Sec : *OutputSections) {
if (Sec->Flags & SHF_ALLOC)
MinVA = std::min<uint64_t>(MinVA, Sec->Addr);
else
Sec->Addr = 0;
}
uintX_t HeaderSize = getHeaderSize();
auto FirstPTLoad =
std::find_if(Phdrs.begin(), Phdrs.end(), [](const PhdrEntry<ELFT> &E) {
return E.H.p_type == PT_LOAD;
});
if (FirstPTLoad == Phdrs.end())
return;
// If the linker script doesn't have PHDRS, add ElfHeader and ProgramHeaders
// now that we know we have space.
if (HeaderSize <= MinVA && !hasPhdrsCommands()) {
FirstPTLoad->First = Out<ELFT>::ElfHeader;
if (!FirstPTLoad->Last)
FirstPTLoad->Last = Out<ELFT>::ProgramHeaders;
}
// ELF and Program headers need to be right before the first section in
// memory. Set their addresses accordingly.
MinVA = alignDown(MinVA - HeaderSize, Config->MaxPageSize);
Out<ELFT>::ElfHeader->Addr = MinVA;
Out<ELFT>::ProgramHeaders->Addr = Out<ELFT>::ElfHeader->Size + MinVA;
if (!FirstPTLoad->First) {
// Sometimes the very first PT_LOAD segment can be empty.
// This happens if (all conditions met):
// - Linker script is used
// - First section in ELF image is not RO
// - Not enough space for program headers.
// The code below removes empty PT_LOAD segment and updates
// program headers size.
Phdrs.erase(FirstPTLoad);
Out<ELFT>::ProgramHeaders->Size =
sizeof(typename ELFT::Phdr) * Phdrs.size();
}
}
// Creates program headers as instructed by PHDRS linker script command.
template <class ELFT>
std::vector<PhdrEntry<ELFT>> LinkerScript<ELFT>::createPhdrs() {
std::vector<PhdrEntry<ELFT>> Ret;
// Process PHDRS and FILEHDR keywords because they are not
// real output sections and cannot be added in the following loop.
for (const PhdrsCommand &Cmd : Opt.PhdrsCommands) {
Ret.emplace_back(Cmd.Type, Cmd.Flags == UINT_MAX ? PF_R : Cmd.Flags);
PhdrEntry<ELFT> &Phdr = Ret.back();
if (Cmd.HasFilehdr)
Phdr.add(Out<ELFT>::ElfHeader);
if (Cmd.HasPhdrs)
Phdr.add(Out<ELFT>::ProgramHeaders);
if (Cmd.LMAExpr) {
Phdr.H.p_paddr = Cmd.LMAExpr(0);
Phdr.HasLMA = true;
}
}
// Add output sections to program headers.
for (OutputSectionBase *Sec : *OutputSections) {
if (!(Sec->Flags & SHF_ALLOC))
break;
// Assign headers specified by linker script
for (size_t Id : getPhdrIndices(Sec->getName())) {
Ret[Id].add(Sec);
if (Opt.PhdrsCommands[Id].Flags == UINT_MAX)
Ret[Id].H.p_flags |= Sec->getPhdrFlags();
}
}
return Ret;
}
template <class ELFT> bool LinkerScript<ELFT>::ignoreInterpSection() {
// Ignore .interp section in case we have PHDRS specification
// and PT_INTERP isn't listed.
return !Opt.PhdrsCommands.empty() &&
llvm::find_if(Opt.PhdrsCommands, [](const PhdrsCommand &Cmd) {
return Cmd.Type == PT_INTERP;
}) == Opt.PhdrsCommands.end();
}
template <class ELFT>
uint32_t LinkerScript<ELFT>::getFiller(StringRef Name) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->Name == Name)
return Cmd->Filler;
return 0;
}
template <class ELFT>
static void writeInt(uint8_t *Buf, uint64_t Data, uint64_t Size) {
const endianness E = ELFT::TargetEndianness;
switch (Size) {
case 1:
*Buf = (uint8_t)Data;
break;
case 2:
write16<E>(Buf, Data);
break;
case 4:
write32<E>(Buf, Data);
break;
case 8:
write64<E>(Buf, Data);
break;
default:
llvm_unreachable("unsupported Size argument");
}
}
template <class ELFT>
void LinkerScript<ELFT>::writeDataBytes(StringRef Name, uint8_t *Buf) {
int I = getSectionIndex(Name);
if (I == INT_MAX)
return;
auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I].get());
for (const std::unique_ptr<BaseCommand> &Base : Cmd->Commands)
if (auto *Data = dyn_cast<BytesDataCommand>(Base.get()))
writeInt<ELFT>(Buf + Data->Offset, Data->Data, Data->Size);
}
template <class ELFT> bool LinkerScript<ELFT>::hasLMA(StringRef Name) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get()))
if (Cmd->LMAExpr && Cmd->Name == Name)
return true;
return false;
}
// Returns the index of the given section name in linker script
// SECTIONS commands. Sections are laid out as the same order as they
// were in the script. If a given name did not appear in the script,
// it returns INT_MAX, so that it will be laid out at end of file.
template <class ELFT> int LinkerScript<ELFT>::getSectionIndex(StringRef Name) {
for (int I = 0, E = Opt.Commands.size(); I != E; ++I)
if (auto *Cmd = dyn_cast<OutputSectionCommand>(Opt.Commands[I].get()))
if (Cmd->Name == Name)
return I;
return INT_MAX;
}
template <class ELFT> bool LinkerScript<ELFT>::hasPhdrsCommands() {
return !Opt.PhdrsCommands.empty();
}
template <class ELFT>
const OutputSectionBase *LinkerScript<ELFT>::getOutputSection(StringRef Name) {
static OutputSectionBase FakeSec("", 0, 0);
for (OutputSectionBase *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec;
error("undefined section " + Name);
return &FakeSec;
}
// This function is essentially the same as getOutputSection(Name)->Size,
// but it won't print out an error message if a given section is not found.
//
// Linker script does not create an output section if its content is empty.
// We want to allow SIZEOF(.foo) where .foo is a section which happened to
// be empty. That is why this function is different from getOutputSection().
template <class ELFT>
uint64_t LinkerScript<ELFT>::getOutputSectionSize(StringRef Name) {
for (OutputSectionBase *Sec : *OutputSections)
if (Sec->getName() == Name)
return Sec->Size;
return 0;
}
template <class ELFT> uint64_t LinkerScript<ELFT>::getHeaderSize() {
return elf::getHeaderSize<ELFT>();
}
template <class ELFT> uint64_t LinkerScript<ELFT>::getSymbolValue(StringRef S) {
if (SymbolBody *B = Symtab<ELFT>::X->find(S))
return B->getVA<ELFT>();
error("symbol not found: " + S);
return 0;
}
template <class ELFT> bool LinkerScript<ELFT>::isDefined(StringRef S) {
return Symtab<ELFT>::X->find(S) != nullptr;
}
template <class ELFT> bool LinkerScript<ELFT>::isAbsolute(StringRef S) {
SymbolBody *Sym = Symtab<ELFT>::X->find(S);
auto *DR = dyn_cast_or_null<DefinedRegular<ELFT>>(Sym);
return DR && !DR->Section;
}
// Gets section symbol belongs to. Symbol "." doesn't belong to any
// specific section but isn't absolute at the same time, so we try
// to find suitable section for it as well.
template <class ELFT>
const OutputSectionBase *LinkerScript<ELFT>::getSymbolSection(StringRef S) {
SymbolBody *Sym = Symtab<ELFT>::X->find(S);
if (!Sym) {
if (OutputSections->empty())
return nullptr;
return CurOutSec ? CurOutSec : (*OutputSections)[0];
}
if (auto *DR = dyn_cast_or_null<DefinedRegular<ELFT>>(Sym))
return DR->Section ? DR->Section->OutSec : nullptr;
if (auto *DS = dyn_cast_or_null<DefinedSynthetic<ELFT>>(Sym))
return DS->Section;
return nullptr;
}
// Returns indices of ELF headers containing specific section, identified
// by Name. Each index is a zero based number of ELF header listed within
// PHDRS {} script block.
template <class ELFT>
std::vector<size_t> LinkerScript<ELFT>::getPhdrIndices(StringRef SectionName) {
for (const std::unique_ptr<BaseCommand> &Base : Opt.Commands) {
auto *Cmd = dyn_cast<OutputSectionCommand>(Base.get());
if (!Cmd || Cmd->Name != SectionName)
continue;
std::vector<size_t> Ret;
for (StringRef PhdrName : Cmd->Phdrs)
Ret.push_back(getPhdrIndex(PhdrName));
return Ret;
}
return {};
}
template <class ELFT>
size_t LinkerScript<ELFT>::getPhdrIndex(StringRef PhdrName) {
size_t I = 0;
for (PhdrsCommand &Cmd : Opt.PhdrsCommands) {
if (Cmd.Name == PhdrName)
return I;
++I;
}
error("section header '" + PhdrName + "' is not listed in PHDRS");
return 0;
}
class elf::ScriptParser final : public ScriptParserBase {
typedef void (ScriptParser::*Handler)();
public:
ScriptParser(MemoryBufferRef MB, bool B)
: ScriptParserBase(MB), IsUnderSysroot(B) {}
void readLinkerScript();
void readVersionScript();
private:
void addFile(StringRef Path);
void readAsNeeded();
void readEntry();
void readExtern();
void readGroup();
void readInclude();
void readOutput();
void readOutputArch();
void readOutputFormat();
void readPhdrs();
void readSearchDir();
void readSections();
void readVersion();
void readVersionScriptCommand();
SymbolAssignment *readAssignment(StringRef Name);
BytesDataCommand *readBytesDataCommand(StringRef Tok);
uint32_t readFill();
OutputSectionCommand *readOutputSectionDescription(StringRef OutSec);
uint32_t readOutputSectionFiller(StringRef Tok);
std::vector<StringRef> readOutputSectionPhdrs();
InputSectionDescription *readInputSectionDescription(StringRef Tok);
StringMatcher readFilePatterns();
std::vector<SectionPattern> readInputSectionsList();
InputSectionDescription *readInputSectionRules(StringRef FilePattern);
unsigned readPhdrType();
SortSectionPolicy readSortKind();
SymbolAssignment *readProvideHidden(bool Provide, bool Hidden);
SymbolAssignment *readProvideOrAssignment(StringRef Tok);
void readSort();
Expr readAssert();
Expr readExpr();
Expr readExpr1(Expr Lhs, int MinPrec);
StringRef readParenLiteral();
Expr readPrimary();
Expr readTernary(Expr Cond);
Expr readParenExpr();
// For parsing version script.
std::vector<SymbolVersion> readVersionExtern();
void readAnonymousDeclaration();
void readVersionDeclaration(StringRef VerStr);
std::vector<SymbolVersion> readSymbols();
ScriptConfiguration &Opt = *ScriptConfig;
bool IsUnderSysroot;
std::vector<std::unique_ptr<MemoryBuffer>> OwningMBs;
};
void ScriptParser::readVersionScript() {
readVersionScriptCommand();
if (!atEOF())
setError("EOF expected, but got " + next());
}
void ScriptParser::readVersionScriptCommand() {
if (consume("{")) {
readAnonymousDeclaration();
return;
}
while (!atEOF() && !Error && peek() != "}") {
StringRef VerStr = next();
if (VerStr == "{") {
setError("anonymous version definition is used in "
"combination with other version definitions");
return;
}
expect("{");
readVersionDeclaration(VerStr);
}
}
void ScriptParser::readVersion() {
expect("{");
readVersionScriptCommand();
expect("}");
}
void ScriptParser::readLinkerScript() {
while (!atEOF()) {
StringRef Tok = next();
if (Tok == ";")
continue;
if (Tok == "ASSERT") {
Opt.Commands.emplace_back(new AssertCommand(readAssert()));
} else if (Tok == "ENTRY") {
readEntry();
} else if (Tok == "EXTERN") {
readExtern();
} else if (Tok == "GROUP" || Tok == "INPUT") {
readGroup();
} else if (Tok == "INCLUDE") {
readInclude();
} else if (Tok == "OUTPUT") {
readOutput();
} else if (Tok == "OUTPUT_ARCH") {
readOutputArch();
} else if (Tok == "OUTPUT_FORMAT") {
readOutputFormat();
} else if (Tok == "PHDRS") {
readPhdrs();
} else if (Tok == "SEARCH_DIR") {
readSearchDir();
} else if (Tok == "SECTIONS") {
readSections();
} else if (Tok == "VERSION") {
readVersion();
} else if (SymbolAssignment *Cmd = readProvideOrAssignment(Tok)) {
Opt.Commands.emplace_back(Cmd);
} else {
setError("unknown directive: " + Tok);
}
}
}
void ScriptParser::addFile(StringRef S) {
if (IsUnderSysroot && S.startswith("/")) {
SmallString<128> PathData;
StringRef Path = (Config->Sysroot + S).toStringRef(PathData);
if (sys::fs::exists(Path)) {
Driver->addFile(Saver.save(Path));
return;
}
}
if (sys::path::is_absolute(S)) {
Driver->addFile(S);
} else if (S.startswith("=")) {
if (Config->Sysroot.empty())
Driver->addFile(S.substr(1));
else
Driver->addFile(Saver.save(Config->Sysroot + "/" + S.substr(1)));
} else if (S.startswith("-l")) {
Driver->addLibrary(S.substr(2));
} else if (sys::fs::exists(S)) {
Driver->addFile(S);
} else {
if (Optional<std::string> Path = findFromSearchPaths(S))
Driver->addFile(Saver.save(*Path));
else
setError("unable to find " + S);
}
}
void ScriptParser::readAsNeeded() {
expect("(");
bool Orig = Config->AsNeeded;
Config->AsNeeded = true;
while (!Error && !consume(")"))
addFile(unquote(next()));
Config->AsNeeded = Orig;
}
void ScriptParser::readEntry() {
// -e <symbol> takes predecence over ENTRY(<symbol>).
expect("(");
StringRef Tok = next();
if (Config->Entry.empty())
Config->Entry = Tok;
expect(")");
}
void ScriptParser::readExtern() {
expect("(");
while (!Error && !consume(")"))
Config->Undefined.push_back(next());
}
void ScriptParser::readGroup() {
expect("(");
while (!Error && !consume(")")) {
StringRef Tok = next();
if (Tok == "AS_NEEDED")
readAsNeeded();
else
addFile(unquote(Tok));
}
}
void ScriptParser::readInclude() {
StringRef Tok = next();
auto MBOrErr = MemoryBuffer::getFile(unquote(Tok));
if (!MBOrErr) {
setError("cannot open " + Tok);
return;
}
std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
tokenize(MB->getMemBufferRef());
OwningMBs.push_back(std::move(MB));
}
void ScriptParser::readOutput() {
// -o <file> takes predecence over OUTPUT(<file>).
expect("(");
StringRef Tok = next();
if (Config->OutputFile.empty())
Config->OutputFile = unquote(Tok);
expect(")");
}
void ScriptParser::readOutputArch() {
// Error checking only for now.
expect("(");
skip();
expect(")");
}
void ScriptParser::readOutputFormat() {
// Error checking only for now.
expect("(");
skip();
StringRef Tok = next();
if (Tok == ")")
return;
if (Tok != ",") {
setError("unexpected token: " + Tok);
return;
}
skip();
expect(",");
skip();
expect(")");
}
void ScriptParser::readPhdrs() {
expect("{");
while (!Error && !consume("}")) {
StringRef Tok = next();
Opt.PhdrsCommands.push_back(
{Tok, PT_NULL, false, false, UINT_MAX, nullptr});
PhdrsCommand &PhdrCmd = Opt.PhdrsCommands.back();
PhdrCmd.Type = readPhdrType();
do {
Tok = next();
if (Tok == ";")
break;
if (Tok == "FILEHDR")
PhdrCmd.HasFilehdr = true;
else if (Tok == "PHDRS")
PhdrCmd.HasPhdrs = true;
else if (Tok == "AT")
PhdrCmd.LMAExpr = readParenExpr();
else if (Tok == "FLAGS") {
expect("(");
// Passing 0 for the value of dot is a bit of a hack. It means that
// we accept expressions like ".|1".
PhdrCmd.Flags = readExpr()(0);
expect(")");
} else
setError("unexpected header attribute: " + Tok);
} while (!Error);
}
}
void ScriptParser::readSearchDir() {
expect("(");
StringRef Tok = next();
if (!Config->Nostdlib)
Config->SearchPaths.push_back(unquote(Tok));
expect(")");
}
void ScriptParser::readSections() {
Opt.HasSections = true;
expect("{");
while (!Error && !consume("}")) {
StringRef Tok = next();
BaseCommand *Cmd = readProvideOrAssignment(Tok);
if (!Cmd) {
if (Tok == "ASSERT")
Cmd = new AssertCommand(readAssert());
else
Cmd = readOutputSectionDescription(Tok);
}
Opt.Commands.emplace_back(Cmd);
}
}
static int precedence(StringRef Op) {
return StringSwitch<int>(Op)
.Cases("*", "/", 5)
.Cases("+", "-", 4)
.Cases("<<", ">>", 3)
.Cases("<", "<=", ">", ">=", "==", "!=", 2)
.Cases("&", "|", 1)
.Default(-1);
}
StringMatcher ScriptParser::readFilePatterns() {
std::vector<StringRef> V;
while (!Error && !consume(")"))
V.push_back(next());
return StringMatcher(V);
}
SortSectionPolicy ScriptParser::readSortKind() {
if (consume("SORT") || consume("SORT_BY_NAME"))
return SortSectionPolicy::Name;
if (consume("SORT_BY_ALIGNMENT"))
return SortSectionPolicy::Alignment;
if (consume("SORT_BY_INIT_PRIORITY"))
return SortSectionPolicy::Priority;
if (consume("SORT_NONE"))
return SortSectionPolicy::None;
return SortSectionPolicy::Default;
}
// Method reads a list of sequence of excluded files and section globs given in
// a following form: ((EXCLUDE_FILE(file_pattern+))? section_pattern+)+
// Example: *(.foo.1 EXCLUDE_FILE (*a.o) .foo.2 EXCLUDE_FILE (*b.o) .foo.3)
// The semantics of that is next:
// * Include .foo.1 from every file.
// * Include .foo.2 from every file but a.o
// * Include .foo.3 from every file but b.o
std::vector<SectionPattern> ScriptParser::readInputSectionsList() {
std::vector<SectionPattern> Ret;
while (!Error && peek() != ")") {
StringMatcher ExcludeFilePat;
if (consume("EXCLUDE_FILE")) {
expect("(");
ExcludeFilePat = readFilePatterns();
}
std::vector<StringRef> V;
while (!Error && peek() != ")" && peek() != "EXCLUDE_FILE")
V.push_back(next());
if (!V.empty())
Ret.push_back({std::move(ExcludeFilePat), StringMatcher(V)});
else
setError("section pattern is expected");
}
return Ret;
}
// Reads contents of "SECTIONS" directive. That directive contains a
// list of glob patterns for input sections. The grammar is as follows.
//
// <patterns> ::= <section-list>
// | <sort> "(" <section-list> ")"
// | <sort> "(" <sort> "(" <section-list> ")" ")"
//
// <sort> ::= "SORT" | "SORT_BY_NAME" | "SORT_BY_ALIGNMENT"
// | "SORT_BY_INIT_PRIORITY" | "SORT_NONE"
//
// <section-list> is parsed by readInputSectionsList().
InputSectionDescription *
ScriptParser::readInputSectionRules(StringRef FilePattern) {
auto *Cmd = new InputSectionDescription(FilePattern);
expect("(");
while (!Error && !consume(")")) {
SortSectionPolicy Outer = readSortKind();
SortSectionPolicy Inner = SortSectionPolicy::Default;
std::vector<SectionPattern> V;
if (Outer != SortSectionPolicy::Default) {
expect("(");
Inner = readSortKind();
if (Inner != SortSectionPolicy::Default) {
expect("(");
V = readInputSectionsList();
expect(")");
} else {
V = readInputSectionsList();
}
expect(")");
} else {
V = readInputSectionsList();
}
for (SectionPattern &Pat : V) {
Pat.SortInner = Inner;
Pat.SortOuter = Outer;
}
std::move(V.begin(), V.end(), std::back_inserter(Cmd->SectionPatterns));
}
return Cmd;
}
InputSectionDescription *
ScriptParser::readInputSectionDescription(StringRef Tok) {
// Input section wildcard can be surrounded by KEEP.
// https://sourceware.org/binutils/docs/ld/Input-Section-Keep.html#Input-Section-Keep
if (Tok == "KEEP") {
expect("(");
StringRef FilePattern = next();
InputSectionDescription *Cmd = readInputSectionRules(FilePattern);
expect(")");
Opt.KeptSections.push_back(Cmd);
return Cmd;
}
return readInputSectionRules(Tok);
}
void ScriptParser::readSort() {
expect("(");
expect("CONSTRUCTORS");
expect(")");
}
Expr ScriptParser::readAssert() {
expect("(");
Expr E = readExpr();
expect(",");
StringRef Msg = unquote(next());
expect(")");
return [=](uint64_t Dot) {
uint64_t V = E(Dot);
if (!V)
error(Msg);
return V;
};
}
// Reads a FILL(expr) command. We handle the FILL command as an
// alias for =fillexp section attribute, which is different from
// what GNU linkers do.
// https://sourceware.org/binutils/docs/ld/Output-Section-Data.html
uint32_t ScriptParser::readFill() {
expect("(");
uint32_t V = readOutputSectionFiller(next());
expect(")");
expect(";");
return V;
}
OutputSectionCommand *
ScriptParser::readOutputSectionDescription(StringRef OutSec) {
OutputSectionCommand *Cmd = new OutputSectionCommand(OutSec);
// Read an address expression.
// https://sourceware.org/binutils/docs/ld/Output-Section-Address.html#Output-Section-Address
if (peek() != ":")
Cmd->AddrExpr = readExpr();
expect(":");
if (consume("AT"))
Cmd->LMAExpr = readParenExpr();
if (consume("ALIGN"))
Cmd->AlignExpr = readParenExpr();
if (consume("SUBALIGN"))
Cmd->SubalignExpr = readParenExpr();
// Parse constraints.
if (consume("ONLY_IF_RO"))
Cmd->Constraint = ConstraintKind::ReadOnly;
if (consume("ONLY_IF_RW"))
Cmd->Constraint = ConstraintKind::ReadWrite;
expect("{");
while (!Error && !consume("}")) {
StringRef Tok = next();
if (SymbolAssignment *Assignment = readProvideOrAssignment(Tok)) {
Cmd->Commands.emplace_back(Assignment);
} else if (BytesDataCommand *Data = readBytesDataCommand(Tok)) {
Cmd->Commands.emplace_back(Data);
} else if (Tok == "ASSERT") {
Cmd->Commands.emplace_back(new AssertCommand(readAssert()));
expect(";");
} else if (Tok == "FILL") {
Cmd->Filler = readFill();
} else if (Tok == "SORT") {
readSort();
} else if (peek() == "(") {
Cmd->Commands.emplace_back(readInputSectionDescription(Tok));
} else {
setError("unknown command " + Tok);
}
}
Cmd->Phdrs = readOutputSectionPhdrs();
if (consume("="))
Cmd->Filler = readOutputSectionFiller(next());
else if (peek().startswith("="))
Cmd->Filler = readOutputSectionFiller(next().drop_front());
return Cmd;
}
// Read "=<number>" where <number> is an octal/decimal/hexadecimal number.
// https://sourceware.org/binutils/docs/ld/Output-Section-Fill.html
//
// ld.gold is not fully compatible with ld.bfd. ld.bfd handles
// hexstrings as blobs of arbitrary sizes, while ld.gold handles them
// as 32-bit big-endian values. We will do the same as ld.gold does
// because it's simpler than what ld.bfd does.
uint32_t ScriptParser::readOutputSectionFiller(StringRef Tok) {
uint32_t V;
if (!Tok.getAsInteger(0, V))
return V;
setError("invalid filler expression: " + Tok);
return 0;
}
SymbolAssignment *ScriptParser::readProvideHidden(bool Provide, bool Hidden) {
expect("(");
SymbolAssignment *Cmd = readAssignment(next());
Cmd->Provide = Provide;
Cmd->Hidden = Hidden;
expect(")");
expect(";");
return Cmd;
}
SymbolAssignment *ScriptParser::readProvideOrAssignment(StringRef Tok) {
SymbolAssignment *Cmd = nullptr;
if (peek() == "=" || peek() == "+=") {
Cmd = readAssignment(Tok);
expect(";");
} else if (Tok == "PROVIDE") {
Cmd = readProvideHidden(true, false);
} else if (Tok == "HIDDEN") {
Cmd = readProvideHidden(false, true);
} else if (Tok == "PROVIDE_HIDDEN") {
Cmd = readProvideHidden(true, true);
}
return Cmd;
}
static uint64_t getSymbolValue(StringRef S, uint64_t Dot) {
if (S == ".")
return Dot;
return ScriptBase->getSymbolValue(S);
}
static bool isAbsolute(StringRef S) {
if (S == ".")
return false;
return ScriptBase->isAbsolute(S);
}
SymbolAssignment *ScriptParser::readAssignment(StringRef Name) {
StringRef Op = next();
Expr E;
assert(Op == "=" || Op == "+=");
if (consume("ABSOLUTE")) {
// The RHS may be something like "ABSOLUTE(.) & 0xff".
// Call readExpr1 to read the whole expression.
E = readExpr1(readParenExpr(), 0);
E.IsAbsolute = [] { return true; };
} else {
E = readExpr();
}
if (Op == "+=")
E = [=](uint64_t Dot) { return getSymbolValue(Name, Dot) + E(Dot); };
return new SymbolAssignment(Name, E);
}
// This is an operator-precedence parser to parse a linker
// script expression.
Expr ScriptParser::readExpr() { return readExpr1(readPrimary(), 0); }
static Expr combine(StringRef Op, Expr L, Expr R) {
if (Op == "*")
return [=](uint64_t Dot) { return L(Dot) * R(Dot); };
if (Op == "/") {
return [=](uint64_t Dot) -> uint64_t {
uint64_t RHS = R(Dot);
if (RHS == 0) {
error("division by zero");
return 0;
}
return L(Dot) / RHS;
};
}
if (Op == "+")
return {[=](uint64_t Dot) { return L(Dot) + R(Dot); },
[=] { return L.IsAbsolute() && R.IsAbsolute(); },
[=] {
const OutputSectionBase *S = L.Section();
return S ? S : R.Section();
}};
if (Op == "-")
return [=](uint64_t Dot) { return L(Dot) - R(Dot); };
if (Op == "<<")
return [=](uint64_t Dot) { return L(Dot) << R(Dot); };
if (Op == ">>")
return [=](uint64_t Dot) { return L(Dot) >> R(Dot); };
if (Op == "<")
return [=](uint64_t Dot) { return L(Dot) < R(Dot); };
if (Op == ">")
return [=](uint64_t Dot) { return L(Dot) > R(Dot); };
if (Op == ">=")
return [=](uint64_t Dot) { return L(Dot) >= R(Dot); };
if (Op == "<=")
return [=](uint64_t Dot) { return L(Dot) <= R(Dot); };
if (Op == "==")
return [=](uint64_t Dot) { return L(Dot) == R(Dot); };
if (Op == "!=")
return [=](uint64_t Dot) { return L(Dot) != R(Dot); };
if (Op == "&")
return [=](uint64_t Dot) { return L(Dot) & R(Dot); };
if (Op == "|")
return [=](uint64_t Dot) { return L(Dot) | R(Dot); };
llvm_unreachable("invalid operator");
}
// This is a part of the operator-precedence parser. This function
// assumes that the remaining token stream starts with an operator.
Expr ScriptParser::readExpr1(Expr Lhs, int MinPrec) {
while (!atEOF() && !Error) {
// Read an operator and an expression.
if (consume("?"))
return readTernary(Lhs);
StringRef Op1 = peek();
if (precedence(Op1) < MinPrec)
break;
skip();
Expr Rhs = readPrimary();
// Evaluate the remaining part of the expression first if the
// next operator has greater precedence than the previous one.
// For example, if we have read "+" and "3", and if the next
// operator is "*", then we'll evaluate 3 * ... part first.
while (!atEOF()) {
StringRef Op2 = peek();
if (precedence(Op2) <= precedence(Op1))
break;
Rhs = readExpr1(Rhs, precedence(Op2));
}
Lhs = combine(Op1, Lhs, Rhs);
}
return Lhs;
}
uint64_t static getConstant(StringRef S) {
if (S == "COMMONPAGESIZE")
return Target->PageSize;
if (S == "MAXPAGESIZE")
return Config->MaxPageSize;
error("unknown constant: " + S);
return 0;
}
// Parses Tok as an integer. Returns true if successful.
// It recognizes hexadecimal (prefixed with "0x" or suffixed with "H")
// and decimal numbers. Decimal numbers may have "K" (kilo) or
// "M" (mega) prefixes.
static bool readInteger(StringRef Tok, uint64_t &Result) {
// Negative number
if (Tok.startswith("-")) {
if (!readInteger(Tok.substr(1), Result))
return false;
Result = -Result;
return true;
}
// Hexadecimal
if (Tok.startswith_lower("0x"))
return !Tok.substr(2).getAsInteger(16, Result);
if (Tok.endswith_lower("H"))
return !Tok.drop_back().getAsInteger(16, Result);
// Decimal
int Suffix = 1;
if (Tok.endswith_lower("K")) {
Suffix = 1024;
Tok = Tok.drop_back();
} else if (Tok.endswith_lower("M")) {
Suffix = 1024 * 1024;
Tok = Tok.drop_back();
}
if (Tok.getAsInteger(10, Result))
return false;
Result *= Suffix;
return true;
}
BytesDataCommand *ScriptParser::readBytesDataCommand(StringRef Tok) {
int Size = StringSwitch<unsigned>(Tok)
.Case("BYTE", 1)
.Case("SHORT", 2)
.Case("LONG", 4)
.Case("QUAD", 8)
.Default(-1);
if (Size == -1)
return nullptr;
expect("(");
uint64_t Val = 0;
StringRef S = next();
if (!readInteger(S, Val))
setError("unexpected value: " + S);
expect(")");
return new BytesDataCommand(Val, Size);
}
StringRef ScriptParser::readParenLiteral() {
expect("(");
StringRef Tok = next();
expect(")");
return Tok;
}
Expr ScriptParser::readPrimary() {
if (peek() == "(")
return readParenExpr();
StringRef Tok = next();
if (Tok == "~") {
Expr E = readPrimary();
return [=](uint64_t Dot) { return ~E(Dot); };
}
if (Tok == "-") {
Expr E = readPrimary();
return [=](uint64_t Dot) { return -E(Dot); };
}
// Built-in functions are parsed here.
// https://sourceware.org/binutils/docs/ld/Builtin-Functions.html.
if (Tok == "ADDR") {
StringRef Name = readParenLiteral();
return {
[=](uint64_t Dot) { return ScriptBase->getOutputSection(Name)->Addr; },
[=] { return false; },
[=] { return ScriptBase->getOutputSection(Name); }};
}
if (Tok == "LOADADDR") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) {
return ScriptBase->getOutputSection(Name)->getLMA();
};
}
if (Tok == "ASSERT")
return readAssert();
if (Tok == "ALIGN") {
Expr E = readParenExpr();
return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
}
if (Tok == "CONSTANT") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return getConstant(Name); };
}
if (Tok == "DEFINED") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return ScriptBase->isDefined(Name) ? 1 : 0; };
}
if (Tok == "SEGMENT_START") {
expect("(");
skip();
expect(",");
Expr E = readExpr();
expect(")");
return [=](uint64_t Dot) { return E(Dot); };
}
if (Tok == "DATA_SEGMENT_ALIGN") {
expect("(");
Expr E = readExpr();
expect(",");
readExpr();
expect(")");
return [=](uint64_t Dot) { return alignTo(Dot, E(Dot)); };
}
if (Tok == "DATA_SEGMENT_END") {
expect("(");
expect(".");
expect(")");
return [](uint64_t Dot) { return Dot; };
}
// GNU linkers implements more complicated logic to handle
// DATA_SEGMENT_RELRO_END. We instead ignore the arguments and just align to
// the next page boundary for simplicity.
if (Tok == "DATA_SEGMENT_RELRO_END") {
expect("(");
readExpr();
expect(",");
readExpr();
expect(")");
return [](uint64_t Dot) { return alignTo(Dot, Target->PageSize); };
}
if (Tok == "SIZEOF") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) { return ScriptBase->getOutputSectionSize(Name); };
}
if (Tok == "ALIGNOF") {
StringRef Name = readParenLiteral();
return [=](uint64_t Dot) {
return ScriptBase->getOutputSection(Name)->Addralign;
};
}
if (Tok == "SIZEOF_HEADERS")
return [=](uint64_t Dot) { return ScriptBase->getHeaderSize(); };
// Tok is a literal number.
uint64_t V;
if (readInteger(Tok, V))
return [=](uint64_t Dot) { return V; };
// Tok is a symbol name.
if (Tok != "." && !isValidCIdentifier(Tok))
setError("malformed number: " + Tok);
return {[=](uint64_t Dot) { return getSymbolValue(Tok, Dot); },
[=] { return isAbsolute(Tok); },
[=] { return ScriptBase->getSymbolSection(Tok); }};
}
Expr ScriptParser::readTernary(Expr Cond) {
Expr L = readExpr();
expect(":");
Expr R = readExpr();
return [=](uint64_t Dot) { return Cond(Dot) ? L(Dot) : R(Dot); };
}
Expr ScriptParser::readParenExpr() {
expect("(");
Expr E = readExpr();
expect(")");
return E;
}
std::vector<StringRef> ScriptParser::readOutputSectionPhdrs() {
std::vector<StringRef> Phdrs;
while (!Error && peek().startswith(":")) {
StringRef Tok = next();
Phdrs.push_back((Tok.size() == 1) ? next() : Tok.substr(1));
}
return Phdrs;
}
// Read a program header type name. The next token must be a
// name of a program header type or a constant (e.g. "0x3").
unsigned ScriptParser::readPhdrType() {
StringRef Tok = next();
uint64_t Val;
if (readInteger(Tok, Val))
return Val;
unsigned Ret = StringSwitch<unsigned>(Tok)
.Case("PT_NULL", PT_NULL)
.Case("PT_LOAD", PT_LOAD)
.Case("PT_DYNAMIC", PT_DYNAMIC)
.Case("PT_INTERP", PT_INTERP)
.Case("PT_NOTE", PT_NOTE)
.Case("PT_SHLIB", PT_SHLIB)
.Case("PT_PHDR", PT_PHDR)
.Case("PT_TLS", PT_TLS)
.Case("PT_GNU_EH_FRAME", PT_GNU_EH_FRAME)
.Case("PT_GNU_STACK", PT_GNU_STACK)
.Case("PT_GNU_RELRO", PT_GNU_RELRO)
.Case("PT_OPENBSD_RANDOMIZE", PT_OPENBSD_RANDOMIZE)
.Case("PT_OPENBSD_WXNEEDED", PT_OPENBSD_WXNEEDED)
.Default(-1);
if (Ret == (unsigned)-1) {
setError("invalid program header type: " + Tok);
return PT_NULL;
}
return Ret;
}
// Reads a list of symbols, e.g. "{ global: foo; bar; local: *; };".
void ScriptParser::readAnonymousDeclaration() {
// Read global symbols first. "global:" is default, so if there's
// no label, we assume global symbols.
if (consume("global:") || peek() != "local:")
Config->VersionScriptGlobals = readSymbols();
// Next, read local symbols.
if (consume("local:")) {
if (consume("*")) {
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
expect(";");
} else {
setError("local symbol list for anonymous version is not supported");
}
}
expect("}");
expect(";");
}
// Reads a list of symbols, e.g. "VerStr { global: foo; bar; local: *; };".
void ScriptParser::readVersionDeclaration(StringRef VerStr) {
// Identifiers start at 2 because 0 and 1 are reserved
// for VER_NDX_LOCAL and VER_NDX_GLOBAL constants.
uint16_t VersionId = Config->VersionDefinitions.size() + 2;
Config->VersionDefinitions.push_back({VerStr, VersionId});
// Read global symbols.
if (consume("global:") || peek() != "local:")
Config->VersionDefinitions.back().Globals = readSymbols();
// Read local symbols.
if (consume("local:")) {
if (consume("*")) {
Config->DefaultSymbolVersion = VER_NDX_LOCAL;
expect(";");
} else {
for (SymbolVersion V : readSymbols())
Config->VersionScriptLocals.push_back(V);
}
}
expect("}");
// Each version may have a parent version. For example, "Ver2"
// defined as "Ver2 { global: foo; local: *; } Ver1;" has "Ver1"
// as a parent. This version hierarchy is, probably against your
// instinct, purely for hint; the runtime doesn't care about it
// at all. In LLD, we simply ignore it.
if (peek() != ";")
skip();
expect(";");
}
// Reads a list of symbols for a versions cript.
std::vector<SymbolVersion> ScriptParser::readSymbols() {
std::vector<SymbolVersion> Ret;
for (;;) {
if (consume("extern"))
for (SymbolVersion V : readVersionExtern())
Ret.push_back(V);
if (peek() == "}" || peek() == "local:" || Error)
break;
StringRef Tok = next();
Ret.push_back({unquote(Tok), false, hasWildcard(Tok)});
expect(";");
}
return Ret;
}
// Reads an "extern C++" directive, e.g.,
// "extern "C++" { ns::*; "f(int, double)"; };"
std::vector<SymbolVersion> ScriptParser::readVersionExtern() {
expect("\"C++\"");
expect("{");
std::vector<SymbolVersion> Ret;
while (!Error && peek() != "}") {
StringRef Tok = next();
bool HasWildcard = !Tok.startswith("\"") && hasWildcard(Tok);
Ret.push_back({unquote(Tok), true, HasWildcard});
expect(";");
}
expect("}");
expect(";");
return Ret;
}
static bool isUnderSysroot(StringRef Path) {
if (Config->Sysroot == "")
return false;
for (; !Path.empty(); Path = sys::path::parent_path(Path))
if (sys::fs::equivalent(Config->Sysroot, Path))
return true;
return false;
}
void elf::readLinkerScript(MemoryBufferRef MB) {
StringRef Path = MB.getBufferIdentifier();
ScriptParser(MB, isUnderSysroot(Path)).readLinkerScript();
}
void elf::readVersionScript(MemoryBufferRef MB) {
ScriptParser(MB, false).readVersionScript();
}
template class elf::LinkerScript<ELF32LE>;
template class elf::LinkerScript<ELF32BE>;
template class elf::LinkerScript<ELF64LE>;
template class elf::LinkerScript<ELF64BE>;
Reference in New Issue View Git Blame Copy Permalink