llvm-jitlink-elf.cpp
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//===---- llvm-jitlink-elf.cpp -- ELF parsing support for llvm-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
//
//===----------------------------------------------------------------------===//
//
// ELF parsing support for llvm-jitlink.
//
//===----------------------------------------------------------------------===//
#include "llvm-jitlink.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/Path.h"
#define DEBUG_TYPE "llvm_jitlink"
using namespace llvm;
using namespace llvm::jitlink;
static bool isELFGOTSection(Section &S) { return S.getName() == "$__GOT"; }
static bool isELFStubsSection(Section &S) { return S.getName() == "$__STUBS"; }
static Expected<Edge &> getFirstRelocationEdge(LinkGraph &G, Block &B) {
auto EItr = std::find_if(B.edges().begin(), B.edges().end(),
[](Edge &E) { return E.isRelocation(); });
if (EItr == B.edges().end())
return make_error<StringError>("GOT entry in " + G.getName() + ", \"" +
B.getSection().getName() +
"\" has no relocations",
inconvertibleErrorCode());
return *EItr;
}
static Expected<Symbol &> getELFGOTTarget(LinkGraph &G, Block &B) {
auto E = getFirstRelocationEdge(G, B);
if (!E)
return E.takeError();
auto &TargetSym = E->getTarget();
if (!TargetSym.hasName())
return make_error<StringError>(
"GOT entry in " + G.getName() + ", \"" +
TargetSym.getBlock().getSection().getName() +
"\" points to anonymous "
"symbol",
inconvertibleErrorCode());
return TargetSym;
}
static Expected<Symbol &> getELFStubTarget(LinkGraph &G, Block &B) {
auto E = getFirstRelocationEdge(G, B);
if (!E)
return E.takeError();
auto &GOTSym = E->getTarget();
if (!GOTSym.isDefined() || !isELFGOTSection(GOTSym.getBlock().getSection()))
return make_error<StringError>(
"Stubs entry in " + G.getName() + ", \"" +
GOTSym.getBlock().getSection().getName() +
"\" does not point to GOT entry",
inconvertibleErrorCode());
return getELFGOTTarget(G, GOTSym.getBlock());
}
namespace llvm {
Error registerELFGraphInfo(Session &S, LinkGraph &G) {
auto FileName = sys::path::filename(G.getName());
if (S.FileInfos.count(FileName)) {
return make_error<StringError>("When -check is passed, file names must be "
"distinct (duplicate: \"" +
FileName + "\")",
inconvertibleErrorCode());
}
auto &FileInfo = S.FileInfos[FileName];
LLVM_DEBUG({
dbgs() << "Registering ELF file info for \"" << FileName << "\"\n";
});
for (auto &Sec : G.sections()) {
LLVM_DEBUG({
dbgs() << " Section \"" << Sec.getName() << "\": "
<< (llvm::empty(Sec.symbols()) ? "empty. skipping."
: "processing...")
<< "\n";
});
// Skip empty sections.
if (llvm::empty(Sec.symbols()))
continue;
if (FileInfo.SectionInfos.count(Sec.getName()))
return make_error<StringError>("Encountered duplicate section name \"" +
Sec.getName() + "\" in \"" + FileName +
"\"",
inconvertibleErrorCode());
bool isGOTSection = isELFGOTSection(Sec);
bool isStubsSection = isELFStubsSection(Sec);
bool SectionContainsContent = false;
bool SectionContainsZeroFill = false;
auto *FirstSym = *Sec.symbols().begin();
auto *LastSym = FirstSym;
for (auto *Sym : Sec.symbols()) {
if (Sym->getAddress() < FirstSym->getAddress())
FirstSym = Sym;
if (Sym->getAddress() > LastSym->getAddress())
LastSym = Sym;
if (isGOTSection) {
if (Sym->isSymbolZeroFill())
return make_error<StringError>("zero-fill atom in GOT section",
inconvertibleErrorCode());
if (auto TS = getELFGOTTarget(G, Sym->getBlock()))
FileInfo.GOTEntryInfos[TS->getName()] = {Sym->getSymbolContent(),
Sym->getAddress()};
else
return TS.takeError();
SectionContainsContent = true;
} else if (isStubsSection) {
if (Sym->isSymbolZeroFill())
return make_error<StringError>("zero-fill atom in Stub section",
inconvertibleErrorCode());
if (auto TS = getELFStubTarget(G, Sym->getBlock()))
FileInfo.StubInfos[TS->getName()] = {Sym->getSymbolContent(),
Sym->getAddress()};
else
return TS.takeError();
SectionContainsContent = true;
} else if (Sym->hasName()) {
dbgs() << "Symbol: " << Sym->getName() << "\n";
if (Sym->isSymbolZeroFill()) {
S.SymbolInfos[Sym->getName()] = {Sym->getSize(), Sym->getAddress()};
SectionContainsZeroFill = true;
} else {
S.SymbolInfos[Sym->getName()] = {Sym->getSymbolContent(),
Sym->getAddress()};
SectionContainsContent = true;
}
}
}
JITTargetAddress SecAddr = FirstSym->getAddress();
uint64_t SecSize =
(LastSym->getBlock().getAddress() + LastSym->getBlock().getSize()) -
SecAddr;
if (SectionContainsZeroFill && SectionContainsContent)
return make_error<StringError>("Mixed zero-fill and content sections not "
"supported yet",
inconvertibleErrorCode());
if (SectionContainsZeroFill)
FileInfo.SectionInfos[Sec.getName()] = {SecSize, SecAddr};
else
FileInfo.SectionInfos[Sec.getName()] = {
StringRef(FirstSym->getBlock().getContent().data(), SecSize),
SecAddr};
}
return Error::success();
}
} // end namespace llvm