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//===--------- JITLinkGeneric.cpp - Generic JIT linker utilities ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Generic JITLinker utility class.
//
//===----------------------------------------------------------------------===//
#include "JITLinkGeneric.h"
#include "llvm/Support/BinaryStreamReader.h"
#include "llvm/Support/MemoryBuffer.h"
#define DEBUG_TYPE "jitlink"
namespace llvm {
namespace jitlink {
JITLinkerBase::~JITLinkerBase() {}
void JITLinkerBase::linkPhase1(std::unique_ptr<JITLinkerBase> Self) {
// Build the link graph.
if (auto GraphOrErr = buildGraph(Ctx->getObjectBuffer()))
G = std::move(*GraphOrErr);
else
return Ctx->notifyFailed(GraphOrErr.takeError());
assert(G && "Graph should have been created by buildGraph above");
// Prune and optimize the graph.
if (auto Err = runPasses(Passes.PrePrunePasses))
return Ctx->notifyFailed(std::move(Err));
LLVM_DEBUG({
dbgs() << "Link graph \"" << G->getName() << "\" pre-pruning:\n";
dumpGraph(dbgs());
});
prune(*G);
LLVM_DEBUG({
dbgs() << "Link graph \"" << G->getName() << "\" post-pruning:\n";
dumpGraph(dbgs());
});
// Run post-pruning passes.
if (auto Err = runPasses(Passes.PostPrunePasses))
return Ctx->notifyFailed(std::move(Err));
// Sort blocks into segments.
auto Layout = layOutBlocks();
// Allocate memory for segments.
if (auto Err = allocateSegments(Layout))
return Ctx->notifyFailed(std::move(Err));
// Notify client that the defined symbols have been assigned addresses.
Ctx->notifyResolved(*G);
auto ExternalSymbols = getExternalSymbolNames();
// We're about to hand off ownership of ourself to the continuation. Grab a
// pointer to the context so that we can call it to initiate the lookup.
//
// FIXME: Once callee expressions are defined to be sequenced before argument
// expressions (c++17) we can simplify all this to:
//
// Ctx->lookup(std::move(UnresolvedExternals),
// [Self=std::move(Self)](Expected<AsyncLookupResult> Result) {
// Self->linkPhase2(std::move(Self), std::move(Result));
// });
auto *TmpCtx = Ctx.get();
TmpCtx->lookup(std::move(ExternalSymbols),
createLookupContinuation(
[S = std::move(Self), L = std::move(Layout)](
Expected<AsyncLookupResult> LookupResult) mutable {
auto &TmpSelf = *S;
TmpSelf.linkPhase2(std::move(S), std::move(LookupResult),
std::move(L));
}));
}
void JITLinkerBase::linkPhase2(std::unique_ptr<JITLinkerBase> Self,
Expected<AsyncLookupResult> LR,
SegmentLayoutMap Layout) {
// If the lookup failed, bail out.
if (!LR)
return deallocateAndBailOut(LR.takeError());
// Assign addresses to external addressables.
applyLookupResult(*LR);
LLVM_DEBUG({
dbgs() << "Link graph \"" << G->getName() << "\" before copy-and-fixup:\n";
dumpGraph(dbgs());
});
// Copy block content to working memory and fix up.
if (auto Err = copyAndFixUpBlocks(Layout, *Alloc))
return deallocateAndBailOut(std::move(Err));
LLVM_DEBUG({
dbgs() << "Link graph \"" << G->getName() << "\" after copy-and-fixup:\n";
dumpGraph(dbgs());
});
if (auto Err = runPasses(Passes.PostFixupPasses))
return deallocateAndBailOut(std::move(Err));
// FIXME: Use move capture once we have c++14.
auto *UnownedSelf = Self.release();
auto Phase3Continuation = [UnownedSelf](Error Err) {
std::unique_ptr<JITLinkerBase> Self(UnownedSelf);
UnownedSelf->linkPhase3(std::move(Self), std::move(Err));
};
Alloc->finalizeAsync(std::move(Phase3Continuation));
}
void JITLinkerBase::linkPhase3(std::unique_ptr<JITLinkerBase> Self, Error Err) {
if (Err)
return deallocateAndBailOut(std::move(Err));
Ctx->notifyFinalized(std::move(Alloc));
}
Error JITLinkerBase::runPasses(LinkGraphPassList &Passes) {
for (auto &P : Passes)
if (auto Err = P(*G))
return Err;
return Error::success();
}
JITLinkerBase::SegmentLayoutMap JITLinkerBase::layOutBlocks() {
SegmentLayoutMap Layout;
/// Partition blocks based on permissions and content vs. zero-fill.
for (auto *B : G->blocks()) {
auto &SegLists = Layout[B->getSection().getProtectionFlags()];
if (!B->isZeroFill())
SegLists.ContentBlocks.push_back(B);
else
SegLists.ZeroFillBlocks.push_back(B);
}
/// Sort blocks within each list.
for (auto &KV : Layout) {
auto CompareBlocks = [](const Block *LHS, const Block *RHS) {
// Sort by section, address and size
if (LHS->getSection().getOrdinal() != RHS->getSection().getOrdinal())
return LHS->getSection().getOrdinal() < RHS->getSection().getOrdinal();
if (LHS->getAddress() != RHS->getAddress())
return LHS->getAddress() < RHS->getAddress();
return LHS->getSize() < RHS->getSize();
};
auto &SegLists = KV.second;
llvm::sort(SegLists.ContentBlocks, CompareBlocks);
llvm::sort(SegLists.ZeroFillBlocks, CompareBlocks);
}
LLVM_DEBUG({
dbgs() << "Segment ordering:\n";
for (auto &KV : Layout) {
dbgs() << " Segment "
<< static_cast<sys::Memory::ProtectionFlags>(KV.first) << ":\n";
auto &SL = KV.second;
for (auto &SIEntry :
{std::make_pair(&SL.ContentBlocks, "content block"),
std::make_pair(&SL.ZeroFillBlocks, "zero-fill block")}) {
dbgs() << " " << SIEntry.second << ":\n";
for (auto *B : *SIEntry.first)
dbgs() << " " << *B << "\n";
}
}
});
return Layout;
}
Error JITLinkerBase::allocateSegments(const SegmentLayoutMap &Layout) {
// Compute segment sizes and allocate memory.
LLVM_DEBUG(dbgs() << "JIT linker requesting: { ");
JITLinkMemoryManager::SegmentsRequestMap Segments;
for (auto &KV : Layout) {
auto &Prot = KV.first;
auto &SegLists = KV.second;
uint64_t SegAlign = 1;
// Calculate segment content size.
size_t SegContentSize = 0;
for (auto *B : SegLists.ContentBlocks) {
SegAlign = std::max(SegAlign, B->getAlignment());
SegContentSize = alignToBlock(SegContentSize, *B);
SegContentSize += B->getSize();
}
uint64_t SegZeroFillStart = SegContentSize;
uint64_t SegZeroFillEnd = SegZeroFillStart;
for (auto *B : SegLists.ZeroFillBlocks) {
SegAlign = std::max(SegAlign, B->getAlignment());
SegZeroFillEnd = alignToBlock(SegZeroFillEnd, *B);
SegZeroFillEnd += B->getSize();
}
Segments[Prot] = {SegAlign, SegContentSize,
SegZeroFillEnd - SegZeroFillStart};
LLVM_DEBUG({
dbgs() << (&KV == &*Layout.begin() ? "" : "; ")
<< static_cast<sys::Memory::ProtectionFlags>(Prot)
<< ": alignment = " << SegAlign
<< ", content size = " << SegContentSize
<< ", zero-fill size = " << (SegZeroFillEnd - SegZeroFillStart);
});
}
LLVM_DEBUG(dbgs() << " }\n");
if (auto AllocOrErr = Ctx->getMemoryManager().allocate(Segments))
Alloc = std::move(*AllocOrErr);
else
return AllocOrErr.takeError();
LLVM_DEBUG({
dbgs() << "JIT linker got working memory:\n";
for (auto &KV : Layout) {
auto Prot = static_cast<sys::Memory::ProtectionFlags>(KV.first);
dbgs() << " " << Prot << ": "
<< (const void *)Alloc->getWorkingMemory(Prot).data() << "\n";
}
});
// Update block target addresses.
for (auto &KV : Layout) {
auto &Prot = KV.first;
auto &SL = KV.second;
JITTargetAddress NextBlockAddr =
Alloc->getTargetMemory(static_cast<sys::Memory::ProtectionFlags>(Prot));
for (auto *SIList : {&SL.ContentBlocks, &SL.ZeroFillBlocks})
for (auto *B : *SIList) {
NextBlockAddr = alignToBlock(NextBlockAddr, *B);
B->setAddress(NextBlockAddr);
NextBlockAddr += B->getSize();
}
}
return Error::success();
}
JITLinkContext::LookupMap JITLinkerBase::getExternalSymbolNames() const {
// Identify unresolved external symbols.
JITLinkContext::LookupMap UnresolvedExternals;
for (auto *Sym : G->external_symbols()) {
assert(Sym->getAddress() == 0 &&
"External has already been assigned an address");
assert(Sym->getName() != StringRef() && Sym->getName() != "" &&
"Externals must be named");
SymbolLookupFlags LookupFlags =
Sym->getLinkage() == Linkage::Weak
? SymbolLookupFlags::WeaklyReferencedSymbol
: SymbolLookupFlags::RequiredSymbol;
UnresolvedExternals[Sym->getName()] = LookupFlags;
}
return UnresolvedExternals;
}
void JITLinkerBase::applyLookupResult(AsyncLookupResult Result) {
for (auto *Sym : G->external_symbols()) {
assert(Sym->getOffset() == 0 &&
"External symbol is not at the start of its addressable block");
assert(Sym->getAddress() == 0 && "Symbol already resolved");
assert(!Sym->isDefined() && "Symbol being resolved is already defined");
auto ResultI = Result.find(Sym->getName());
if (ResultI != Result.end())
Sym->getAddressable().setAddress(ResultI->second.getAddress());
else
assert(Sym->getLinkage() == Linkage::Weak &&
"Failed to resolve non-weak reference");
}
LLVM_DEBUG({
dbgs() << "Externals after applying lookup result:\n";
for (auto *Sym : G->external_symbols())
dbgs() << " " << Sym->getName() << ": "
<< formatv("{0:x16}", Sym->getAddress()) << "\n";
});
assert(llvm::all_of(G->external_symbols(),
[](Symbol *Sym) {
return Sym->getAddress() != 0 ||
Sym->getLinkage() == Linkage::Weak;
}) &&
"All strong external symbols should have been resolved by now");
}
void JITLinkerBase::deallocateAndBailOut(Error Err) {
assert(Err && "Should not be bailing out on success value");
assert(Alloc && "can not call deallocateAndBailOut before allocation");
Ctx->notifyFailed(joinErrors(std::move(Err), Alloc->deallocate()));
}
void JITLinkerBase::dumpGraph(raw_ostream &OS) {
assert(G && "Graph is not set yet");
G->dump(dbgs(), [this](Edge::Kind K) { return getEdgeKindName(K); });
}
void prune(LinkGraph &G) {
std::vector<Symbol *> Worklist;
DenseSet<Block *> VisitedBlocks;
// Build the initial worklist from all symbols initially live.
for (auto *Sym : G.defined_symbols())
if (Sym->isLive())
Worklist.push_back(Sym);
// Propagate live flags to all symbols reachable from the initial live set.
while (!Worklist.empty()) {
auto *Sym = Worklist.back();
Worklist.pop_back();
auto &B = Sym->getBlock();
// Skip addressables that we've visited before.
if (VisitedBlocks.count(&B))
continue;
VisitedBlocks.insert(&B);
for (auto &E : Sym->getBlock().edges()) {
if (E.getTarget().isDefined() && !E.getTarget().isLive()) {
E.getTarget().setLive(true);
Worklist.push_back(&E.getTarget());
}
}
}
// Collect all the symbols to remove, then remove them.
{
LLVM_DEBUG(dbgs() << "Dead-stripping symbols:\n");
std::vector<Symbol *> SymbolsToRemove;
for (auto *Sym : G.defined_symbols())
if (!Sym->isLive())
SymbolsToRemove.push_back(Sym);
for (auto *Sym : SymbolsToRemove) {
LLVM_DEBUG(dbgs() << " " << *Sym << "...\n");
G.removeDefinedSymbol(*Sym);
}
}
// Delete any unused blocks.
{
LLVM_DEBUG(dbgs() << "Dead-stripping blocks:\n");
std::vector<Block *> BlocksToRemove;
for (auto *B : G.blocks())
if (!VisitedBlocks.count(B))
BlocksToRemove.push_back(B);
for (auto *B : BlocksToRemove) {
LLVM_DEBUG(dbgs() << " " << *B << "...\n");
G.removeBlock(*B);
}
}
}
} // end namespace jitlink
} // end namespace llvm