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[StaticMirror] Add support for GLOB_DAT relocations. #75905

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Merged
merged 1 commit into from
Sep 3, 2024
Merged

[StaticMirror] Add support for GLOB_DAT relocations. #75905

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37 changes: 37 additions & 0 deletions lib/StaticMirror/ObjectFileContext.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,20 @@ void Image::scanMachO(const llvm::object::MachOObjectFile *O) {
}
}

// We only support these for AArch64, ARM and x86-64 at present
static uint32_t getELFGlobDatRelocationType(uint32_t machine) {
switch (machine) {
case llvm::ELF::EM_AARCH64:
return llvm::ELF::R_AARCH64_GLOB_DAT;
case llvm::ELF::EM_ARM:
return llvm::ELF::R_ARM_GLOB_DAT;
case llvm::ELF::EM_X86_64:
return llvm::ELF::R_X86_64_GLOB_DAT;
default:
return 0;
}
}

template <typename ELFT>
void Image::scanELFType(const llvm::object::ELFObjectFile<ELFT> *O) {
using namespace llvm::ELF;
Expand Down Expand Up @@ -147,6 +161,7 @@ void Image::scanELFType(const llvm::object::ELFObjectFile<ELFT> *O) {

auto machine = O->getELFFile().getHeader().e_machine;
auto relativeRelocType = llvm::object::getELFRelativeRelocationType(machine);
auto globDatRelocType = getELFGlobDatRelocationType(machine);

for (auto &S : static_cast<const llvm::object::ELFObjectFileBase *>(O)
->dynamic_relocation_sections()) {
Expand All @@ -163,6 +178,28 @@ void Image::scanELFType(const llvm::object::ELFObjectFile<ELFT> *O) {
continue;
}

// `getRelocationResolver` doesn't handle GLOB_DAT relocations, so we
// also have to do that ourselves.
if (globDatRelocType && R.getType() == globDatRelocType) {
auto symbol = R.getSymbol();
auto name = symbol->getName();
if (!name) {
llvm::consumeError(name.takeError());
continue;
}

// On x86-64, this is just S, but on other architectures it is
// usually S + A.
uint64_t addend = 0;
if (isRela && machine != llvm::ELF::EM_X86_64) {
auto rela = O->getRela(R.getRawDataRefImpl());
addend = rela->r_addend;
}

DynamicRelocations.insert({R.getOffset(), {*name, addend}});
continue;
}

if (!resolverSupports(R.getType()))
continue;
auto symbol = R.getSymbol();
Expand Down