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//===- bolt/Rewrite/JITLinkLinker.cpp - BOLTLinker using JITLink ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "bolt/Rewrite/JITLinkLinker.h"
#include "bolt/Core/BinaryData.h"
#include "bolt/Rewrite/RewriteInstance.h"
#include "llvm/ExecutionEngine/JITLink/JITLink.h"
#include "llvm/ExecutionEngine/Orc/Shared/ExecutorAddress.h"
#include "llvm/ExecutionEngine/Orc/Shared/ExecutorSymbolDef.h"
#include "llvm/Support/Debug.h"
#define DEBUG_TYPE "bolt"
namespace llvm {
namespace bolt {
namespace {
bool hasSymbols(const jitlink::Block &B) {
return llvm::any_of(B.getSection().symbols(),
[&B](const auto &S) { return &S->getBlock() == &B; });
}
/// Liveness in JITLink is based on symbols so sections that do not contain
/// any symbols will always be pruned. This pass adds anonymous symbols to
/// needed sections to prevent pruning.
Error markSectionsLive(jitlink::LinkGraph &G) {
for (auto &Section : G.sections()) {
// We only need allocatable sections.
if (Section.getMemLifetimePolicy() == orc::MemLifetimePolicy::NoAlloc)
continue;
// Skip empty sections.
if (JITLinkLinker::sectionSize(Section) == 0)
continue;
for (auto *Block : Section.blocks()) {
// No need to add symbols if it already has some.
if (hasSymbols(*Block))
continue;
G.addAnonymousSymbol(*Block, /*Offset=*/0, /*Size=*/0,
/*IsCallable=*/false, /*IsLive=*/true);
}
}
return jitlink::markAllSymbolsLive(G);
}
void reassignSectionAddress(jitlink::LinkGraph &LG,
const BinarySection &BinSection, uint64_t Address) {
auto *JLSection = LG.findSectionByName(BinSection.getSectionID());
assert(JLSection && "cannot find section in LinkGraph");
auto BlockAddress = Address;
for (auto *Block : JITLinkLinker::orderedBlocks(*JLSection)) {
// FIXME it would seem to make sense to align here. However, in
// non-relocation mode, we simply use the original address of functions
// which might not be aligned with the minimum alignment used by
// BinaryFunction (2). Example failing test when aligning:
// bolt/test/X86/addr32.s
Block->setAddress(orc::ExecutorAddr(BlockAddress));
BlockAddress += Block->getSize();
}
}
} // anonymous namespace
struct JITLinkLinker::Context : jitlink::JITLinkContext {
JITLinkLinker &Linker;
JITLinkLinker::SectionsMapper MapSections;
Context(JITLinkLinker &Linker, JITLinkLinker::SectionsMapper MapSections)
: JITLinkContext(&Linker.Dylib), Linker(Linker),
MapSections(MapSections) {}
jitlink::JITLinkMemoryManager &getMemoryManager() override {
return *Linker.MM;
}
bool shouldAddDefaultTargetPasses(const Triple &TT) const override {
// The default passes manipulate DWARF sections in a way incompatible with
// BOLT.
// TODO check if we can actually use these passes to remove some of the
// DWARF manipulation done in BOLT.
return false;
}
Error modifyPassConfig(jitlink::LinkGraph &G,
jitlink::PassConfiguration &Config) override {
Config.PrePrunePasses.push_back(markSectionsLive);
return Error::success();
}
void notifyFailed(Error Err) override {
errs() << "BOLT-ERROR: JITLink failed: " << Err << '\n';
exit(1);
}
void
lookup(const LookupMap &Symbols,
std::unique_ptr<jitlink::JITLinkAsyncLookupContinuation> LC) override {
jitlink::AsyncLookupResult AllResults;
for (const auto &Symbol : Symbols) {
std::string SymName = Symbol.first.str();
LLVM_DEBUG(dbgs() << "BOLT: looking for " << SymName << "\n");
if (auto Address = Linker.lookupSymbol(SymName)) {
LLVM_DEBUG(dbgs() << "Resolved to address 0x"
<< Twine::utohexstr(*Address) << "\n");
AllResults[Symbol.first] = orc::ExecutorSymbolDef(
orc::ExecutorAddr(*Address), JITSymbolFlags());
continue;
}
if (const BinaryData *I = Linker.BC.getBinaryDataByName(SymName)) {
uint64_t Address = I->isMoved() && !I->isJumpTable()
? I->getOutputAddress()
: I->getAddress();
LLVM_DEBUG(dbgs() << "Resolved to address 0x"
<< Twine::utohexstr(Address) << "\n");
AllResults[Symbol.first] = orc::ExecutorSymbolDef(
orc::ExecutorAddr(Address), JITSymbolFlags());
continue;
}
LLVM_DEBUG(dbgs() << "Resolved to address 0x0\n");
AllResults[Symbol.first] =
orc::ExecutorSymbolDef(orc::ExecutorAddr(0), JITSymbolFlags());
}
LC->run(std::move(AllResults));
}
Error notifyResolved(jitlink::LinkGraph &G) override {
MapSections([&G](const BinarySection &Section, uint64_t Address) {
reassignSectionAddress(G, Section, Address);
});
for (auto *Symbol : G.defined_symbols()) {
Linker.Symtab.insert(
{Symbol->getName().str(), Symbol->getAddress().getValue()});
}
return Error::success();
}
void notifyFinalized(
jitlink::JITLinkMemoryManager::FinalizedAlloc Alloc) override {
Linker.Allocs.push_back(std::move(Alloc));
++Linker.MM->ObjectsLoaded;
}
};
JITLinkLinker::JITLinkLinker(BinaryContext &BC,
std::unique_ptr<ExecutableFileMemoryManager> MM)
: BC(BC), MM(std::move(MM)) {}
JITLinkLinker::~JITLinkLinker() { cantFail(MM->deallocate(std::move(Allocs))); }
void JITLinkLinker::loadObject(MemoryBufferRef Obj,
SectionsMapper MapSections) {
auto LG = jitlink::createLinkGraphFromObject(Obj);
if (auto E = LG.takeError()) {
errs() << "BOLT-ERROR: JITLink failed: " << E << '\n';
exit(1);
}
auto Ctx = std::make_unique<Context>(*this, MapSections);
jitlink::link(std::move(*LG), std::move(Ctx));
}
std::optional<uint64_t> JITLinkLinker::lookupSymbol(StringRef Name) const {
auto It = Symtab.find(Name.data());
if (It == Symtab.end())
return std::nullopt;
return It->second;
}
SmallVector<jitlink::Block *, 2>
JITLinkLinker::orderedBlocks(const jitlink::Section &Section) {
SmallVector<jitlink::Block *, 2> Blocks(Section.blocks());
llvm::sort(Blocks, [](const auto *LHS, const auto *RHS) {
return LHS->getAddress() < RHS->getAddress();
});
return Blocks;
}
size_t JITLinkLinker::sectionSize(const jitlink::Section &Section) {
size_t Size = 0;
for (const auto *Block : orderedBlocks(Section)) {
Size = jitlink::alignToBlock(Size, *Block);
Size += Block->getSize();
}
return Size;
}
} // namespace bolt
} // namespace llvm
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