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-rw-r--r--bolt/lib/Rewrite/CMakeLists.txt1
-rw-r--r--bolt/lib/Rewrite/GNUPropertyRewriter.cpp147
-rw-r--r--bolt/lib/Rewrite/RewriteInstance.cpp16
3 files changed, 152 insertions, 12 deletions
diff --git a/bolt/lib/Rewrite/CMakeLists.txt b/bolt/lib/Rewrite/CMakeLists.txt
index 7750360..5b15edc 100644
--- a/bolt/lib/Rewrite/CMakeLists.txt
+++ b/bolt/lib/Rewrite/CMakeLists.txt
@@ -25,6 +25,7 @@ add_llvm_library(LLVMBOLTRewrite
PseudoProbeRewriter.cpp
RewriteInstance.cpp
SDTRewriter.cpp
+ GNUPropertyRewriter.cpp
NO_EXPORT
DISABLE_LLVM_LINK_LLVM_DYLIB
diff --git a/bolt/lib/Rewrite/GNUPropertyRewriter.cpp b/bolt/lib/Rewrite/GNUPropertyRewriter.cpp
new file mode 100644
index 0000000..f61c08e
--- /dev/null
+++ b/bolt/lib/Rewrite/GNUPropertyRewriter.cpp
@@ -0,0 +1,147 @@
+//===- bolt/Rewrite/GNUPropertyRewriter.cpp -------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Read the .note.gnu.property section.
+//
+//===----------------------------------------------------------------------===//
+
+#include "bolt/Rewrite/MetadataRewriter.h"
+#include "bolt/Rewrite/MetadataRewriters.h"
+#include "llvm/Support/Errc.h"
+
+using namespace llvm;
+using namespace bolt;
+
+namespace {
+
+class GNUPropertyRewriter final : public MetadataRewriter {
+
+ Expected<uint32_t> decodeGNUPropertyNote(StringRef Desc);
+
+public:
+ GNUPropertyRewriter(StringRef Name, BinaryContext &BC)
+ : MetadataRewriter(Name, BC) {}
+
+ Error sectionInitializer() override;
+};
+
+Error GNUPropertyRewriter::sectionInitializer() {
+
+ ErrorOr<BinarySection &> Sec =
+ BC.getUniqueSectionByName(".note.gnu.property");
+ if (!Sec)
+ return Error::success();
+
+ // Accumulate feature bits
+ uint32_t FeaturesAcc = 0;
+
+ StringRef Buf = Sec->getContents();
+ DataExtractor DE(Buf, BC.AsmInfo->isLittleEndian(),
+ BC.AsmInfo->getCodePointerSize());
+ DataExtractor::Cursor Cursor(0);
+ while (Cursor && !DE.eof(Cursor)) {
+ const uint32_t NameSz = DE.getU32(Cursor);
+ const uint32_t DescSz = DE.getU32(Cursor);
+ const uint32_t Type = DE.getU32(Cursor);
+
+ StringRef Name =
+ NameSz ? Buf.slice(Cursor.tell(), Cursor.tell() + NameSz) : "<empty>";
+ Cursor.seek(alignTo(Cursor.tell() + NameSz, 4));
+
+ const uint64_t DescOffset = Cursor.tell();
+ StringRef Desc =
+ DescSz ? Buf.slice(DescOffset, DescOffset + DescSz) : "<empty>";
+ Cursor.seek(alignTo(DescOffset + DescSz, 4));
+ if (!Cursor)
+ return createStringError(
+ errc::executable_format_error,
+ "out of bounds while reading .note.gnu.property section: %s",
+ toString(Cursor.takeError()).c_str());
+
+ if (Type == ELF::NT_GNU_PROPERTY_TYPE_0 && Name.starts_with("GNU") &&
+ DescSz) {
+ auto Features = decodeGNUPropertyNote(Desc);
+ if (!Features)
+ return Features.takeError();
+ FeaturesAcc |= *Features;
+ }
+ }
+
+ if (BC.isAArch64()) {
+ BC.setUsesBTI(FeaturesAcc & llvm::ELF::GNU_PROPERTY_AARCH64_FEATURE_1_BTI);
+ if (BC.usesBTI())
+ BC.outs() << "BOLT-WARNING: binary is using BTI. Optimized binary may be "
+ "corrupted\n";
+ }
+
+ return Error::success();
+}
+
+/// \p Desc contains an array of property descriptors. Each member has the
+/// following structure:
+/// typedef struct {
+/// Elf_Word pr_type;
+/// Elf_Word pr_datasz;
+/// unsigned char pr_data[PR_DATASZ];
+/// unsigned char pr_padding[PR_PADDING];
+/// } Elf_Prop;
+///
+/// As there is no guarantee that the features are encoded in which element of
+/// the array, we have to read all, and OR together the result.
+Expected<uint32_t> GNUPropertyRewriter::decodeGNUPropertyNote(StringRef Desc) {
+ DataExtractor DE(Desc, BC.AsmInfo->isLittleEndian(),
+ BC.AsmInfo->getCodePointerSize());
+ DataExtractor::Cursor Cursor(0);
+ const uint32_t Align = DE.getAddressSize();
+
+ std::optional<uint32_t> Features = 0;
+ while (Cursor && !DE.eof(Cursor)) {
+ const uint32_t PrType = DE.getU32(Cursor);
+ const uint32_t PrDataSz = DE.getU32(Cursor);
+
+ const uint64_t PrDataStart = Cursor.tell();
+ const uint64_t PrDataEnd = PrDataStart + PrDataSz;
+ Cursor.seek(PrDataEnd);
+ if (!Cursor)
+ return createStringError(
+ errc::executable_format_error,
+ "out of bounds while reading .note.gnu.property section: %s",
+ toString(Cursor.takeError()).c_str());
+
+ if (PrType == llvm::ELF::GNU_PROPERTY_AARCH64_FEATURE_1_AND) {
+ if (PrDataSz != 4) {
+ return createStringError(
+ errc::executable_format_error,
+ "Property descriptor size has to be 4 bytes on AArch64\n");
+ }
+ DataExtractor::Cursor Tmp(PrDataStart);
+ // PrDataSz = 4 -> PrData is uint32_t
+ const uint32_t FeaturesItem = DE.getU32(Tmp);
+ if (!Tmp)
+ return createStringError(
+ errc::executable_format_error,
+ "failed to read property from .note.gnu.property section: %s",
+ toString(Tmp.takeError()).c_str());
+ Features = Features ? (*Features | FeaturesItem) : FeaturesItem;
+ }
+
+ Cursor.seek(alignTo(PrDataEnd, Align));
+ if (!Cursor)
+ return createStringError(errc::executable_format_error,
+ "out of bounds while reading property array in "
+ ".note.gnu.property section: %s",
+ toString(Cursor.takeError()).c_str());
+ }
+ return Features.value_or(0u);
+}
+} // namespace
+
+std::unique_ptr<MetadataRewriter>
+llvm::bolt::createGNUPropertyRewriter(BinaryContext &BC) {
+ return std::make_unique<GNUPropertyRewriter>("gnu-property-rewriter", BC);
+}
diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index 8b78c53..8a25d0b 100644
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -2274,8 +2274,7 @@ uint32_t getRelocationSymbol(const ELFObjectFileBase *Obj,
bool RewriteInstance::analyzeRelocation(
const RelocationRef &Rel, uint32_t &RType, std::string &SymbolName,
bool &IsSectionRelocation, uint64_t &SymbolAddress, int64_t &Addend,
- uint64_t &ExtractedValue, bool &Skip) const {
- Skip = false;
+ uint64_t &ExtractedValue) const {
if (!Relocation::isSupported(RType))
return false;
@@ -2707,9 +2706,8 @@ void RewriteInstance::handleRelocation(const SectionRef &RelocatedSection,
int64_t Addend;
uint64_t ExtractedValue;
bool IsSectionRelocation;
- bool Skip;
if (!analyzeRelocation(Rel, RType, SymbolName, IsSectionRelocation,
- SymbolAddress, Addend, ExtractedValue, Skip)) {
+ SymbolAddress, Addend, ExtractedValue)) {
LLVM_DEBUG({
dbgs() << "BOLT-WARNING: failed to analyze relocation @ offset = "
<< formatv("{0:x}; type name = {1}\n", Rel.getOffset(), TypeName);
@@ -2718,14 +2716,6 @@ void RewriteInstance::handleRelocation(const SectionRef &RelocatedSection,
return;
}
- if (Skip) {
- LLVM_DEBUG({
- dbgs() << "BOLT-DEBUG: skipping relocation @ offset = "
- << formatv("{0:x}; type name = {1}\n", Rel.getOffset(), TypeName);
- });
- return;
- }
-
if (!IsFromCode && !IsWritable && (IsX86 || IsAArch64) &&
Relocation::isPCRelative(RType)) {
BinaryData *BD = BC->getBinaryDataContainingAddress(Rel.getOffset());
@@ -3341,6 +3331,8 @@ void RewriteInstance::initializeMetadataManager() {
MetadataManager.registerRewriter(createPseudoProbeRewriter(*BC));
MetadataManager.registerRewriter(createSDTRewriter(*BC));
+
+ MetadataManager.registerRewriter(createGNUPropertyRewriter(*BC));
}
void RewriteInstance::processSectionMetadata() {
generated by cgit v1.1 at 2025-10-03 08:07:59 +0000