[lld] [lld-macho] Implement ObjC category merging (-objc_category_merging) (PR #82928)
Kyungwoo Lee via llvm-commits
llvm-commits at lists.llvm.org
Fri Mar 1 14:25:24 PST 2024
================
@@ -320,3 +332,915 @@ void objc::checkCategories() {
}
}
}
+
+namespace {
+
+class ObjcCategoryMerger {
+ // Information about an input category
+ struct InfoInputCategory {
+ ConcatInputSection *catBodyIsec;
+ ConcatInputSection *catListIsec;
+ uint32_t offCatListIsec = 0;
+
+ bool wasMerged = false;
+ };
+
+ // To write new (merged) categories or classes, we will try make limited
+ // assumptions about the alignment and the sections the various class/category
+ // info are stored in and . So we'll just reuse the same sections and
+ // alignment as already used in existing (input) categories. To do this we
+ // have InfoCategoryWriter which contains the various sections that the
+ // generated categories will be written to.
+ template <typename T> struct InfroWriteSection {
+ bool valid = false; // Data has been successfully collected from input
+ uint32_t align = 0;
+ const Section *inputSection;
+ Reloc relocTemplate;
+ T *outputSection;
+ };
+
+ struct InfoCategoryWriter {
+ InfroWriteSection<ConcatOutputSection> catListInfo;
+ InfroWriteSection<ConcatOutputSection> catBodyInfo;
+ InfroWriteSection<CStringSection> catNameInfo;
+ InfroWriteSection<ConcatOutputSection> catPtrListInfo;
+ };
+
+ // Information about a pointer list in the original categories (method lists,
+ // protocol lists, etc)
+ struct PointerListInfo {
+ PointerListInfo(const char *pszSymNamePrefix)
+ : namePrefix(pszSymNamePrefix) {}
+ const char *namePrefix;
+
+ uint32_t structSize = 0;
+ uint32_t structCount = 0;
+
+ std::vector<Symbol *> allPtrs;
+ };
+
+ // Full information about all the categories that are extending a class. This
+ // will have all the additional methods, protocols, proprieties that are
+ // contained in all the categories that extend a particular class.
+ struct ClassExtensionInfo {
+ // Merged names of containers. Ex: base|firstCategory|secondCategory|...
+ std::string mergedContainerName;
+ std::string baseClassName;
+ Symbol *baseClass = nullptr;
+ // In case we generate new data, mark the new data as belonging to this file
+ ObjFile *objFileForMergeData = nullptr;
+
+ PointerListInfo instanceMethods =
+ objc::symbol_names::categoryInstanceMethods;
+ PointerListInfo classMethods = objc::symbol_names::categoryClassMethods;
+ PointerListInfo protocols = objc::symbol_names::categoryProtocols;
+ PointerListInfo instanceProps = objc::symbol_names::listProprieties;
+ PointerListInfo classProps = objc::symbol_names::klassPropList;
+ };
+
+public:
+ ObjcCategoryMerger(std::vector<ConcatInputSection *> &_allInputSections);
+ void doMerge();
+ static void doCleanup();
+
+private:
+ void collectAndValidateCategoriesData();
+ void
+ mergeCategoriesIntoSingleCategory(std::vector<InfoInputCategory> &categories);
+
+ void eraseISec(ConcatInputSection *isec);
+ void eraseMergedCategories();
+
+ void generateCatListForNonErasedCategories(
+ std::map<ConcatInputSection *, std::set<uint64_t>>
+ catListToErasedOffsets);
+ template <typename T>
+ void collectSectionWriteInfoFromIsec(InputSection *isec,
+ InfroWriteSection<T> &catWriteInfo);
+ void collectCategoryWriterInfoFromCategory(InfoInputCategory &catInfo);
+ void parseCatInfoToExtInfo(InfoInputCategory &catInfo,
+ ClassExtensionInfo &extInfo);
+
+ void parseProtocolListInfo(ConcatInputSection *isec,
+ uint32_t symbolsPerStruct,
+ PointerListInfo &ptrList);
+
+ void parsePointerListInfo(ConcatInputSection *isec, uint32_t secOffset,
+ uint32_t symbolsPerStruct,
+ PointerListInfo &ptrList);
+
+ void emitAndLinkPointerList(Defined *parentSym, uint32_t linkAtOffset,
+ ClassExtensionInfo &extInfo,
+ PointerListInfo &ptrList);
+
+ void emitAndLinkProtocolList(Defined *parentSym, uint32_t linkAtOffset,
+ ClassExtensionInfo &extInfo,
+ PointerListInfo &ptrList);
+
+ void emitCategory(ClassExtensionInfo &extInfo, Defined *&catBodySym);
+ void emitCatListEntrySec(std::string &forCateogryName,
+ std::string &forBaseClassName, ObjFile *objFile,
+ Defined *&catListSym);
+ void emitCategoryBody(std::string &name, Defined *nameSym,
+ Symbol *baseClassSym, std::string &baseClassName,
+ ObjFile *objFile, Defined *&catBodySym);
+ void emitCategoryName(std::string &name, ObjFile *objFile,
+ Defined *&catNameSym);
+ void createSymbolReference(Defined *refFrom, Symbol *refTo, uint32_t offset,
+ Reloc &relocTemplate);
+ bool tryGetSymbolAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ Symbol *&sym);
+ bool tryGetDefinedAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ Defined *&defined);
+ void tryEraseDefinedAtIsecOffset(ConcatInputSection *isec, uint32_t offset,
+ bool stringOnly = false);
+
+ CategoryLayout catLayout;
+ ClassLayout classLayout;
+ ROClassLayout roClassLayout;
+ ListHeaderLayout listHeaderLayout;
+ MethodLayout methodLayout;
+ ProtocolListHeaderLayout protocolListHeaderLayout;
+
+ InfoCategoryWriter infoCategoryWriter;
+ std::vector<ConcatInputSection *> &allInputSections;
+ // Map of base class Symbol to list of InfoInputCategory's for it
+ std::map<const Symbol *, std::vector<InfoInputCategory>> categoryMap;
+
+ // Normally, the binary data comes from the input files, but since we're
+ // generating binary data ourselves, we use the below arrays to store it in.
+ // Need this to be 'static' so the data survives past the ObjcCategoryMerger
+ // object, as the data will be read by the Writer when the final binary is
+ // generated.
+ static SmallVector<SmallString<0>> generatedNames;
+ static SmallVector<SmallVector<uint8_t>> generatedSectionData;
+};
+
+SmallVector<SmallString<0>> ObjcCategoryMerger::generatedNames;
+SmallVector<SmallVector<uint8_t>> ObjcCategoryMerger::generatedSectionData;
+
+ObjcCategoryMerger::ObjcCategoryMerger(
+ std::vector<ConcatInputSection *> &_allInputSections)
+ : catLayout(target->wordSize), classLayout(target->wordSize),
+ roClassLayout(target->wordSize), listHeaderLayout(target->wordSize),
+ methodLayout(target->wordSize),
+ protocolListHeaderLayout(target->wordSize),
+ allInputSections(_allInputSections) {}
+
+// This is a template so that it can be used both for CStringSection and
+// ConcatOutputSection
+template <typename T>
+void ObjcCategoryMerger::collectSectionWriteInfoFromIsec(
+ InputSection *isec, InfroWriteSection<T> &catWriteInfo) {
+
+ catWriteInfo.inputSection = &isec->section;
+ catWriteInfo.align = isec->align;
+ catWriteInfo.outputSection = dyn_cast_or_null<T>(isec->parent);
+
+ assert(catWriteInfo.outputSection &&
+ "outputSection may not be null in collectSectionWriteInfoFromIsec.");
+
+ if (isec->relocs.size())
+ catWriteInfo.relocTemplate = isec->relocs[0];
+
+ catWriteInfo.valid = true;
+}
+
+bool ObjcCategoryMerger::tryGetSymbolAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ Symbol *&sym) {
+ const Reloc *reloc = isec->getRelocAt(offset);
+
+ if (!reloc)
+ return false;
+
+ sym = reloc->referent.get<Symbol *>();
+ return sym != nullptr;
+}
+
+bool ObjcCategoryMerger::tryGetDefinedAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ Defined *&defined) {
+ Symbol *sym;
+ if (!tryGetSymbolAtIsecOffset(isec, offset, sym))
+ return false;
+
+ defined = dyn_cast_or_null<Defined>(sym);
+ return defined != nullptr;
+}
+
+// Given an ConcatInputSection and an offset, if there is a symbol(Defined) at
+// that offset, then erase the symbol (mark it not live) from the final output.
+// Used for easely erasing already merged strings, method lists, etc ...
+void ObjcCategoryMerger::tryEraseDefinedAtIsecOffset(ConcatInputSection *isec,
+ uint32_t offset,
+ bool stringOnly) {
+ const Reloc *reloc = isec->getRelocAt(offset);
+
+ if (!reloc)
+ return;
+
+ Defined *sym = dyn_cast_or_null<Defined>(reloc->referent.get<Symbol *>());
+ if (!sym)
+ return;
+
+ auto *cisec = dyn_cast_or_null<ConcatInputSection>(sym->isec);
+ if (!stringOnly && cisec) {
+ eraseISec(cisec);
+ return;
+ }
+
+ if (auto *cisec = dyn_cast_or_null<CStringInputSection>(sym->isec)) {
+ uint32_t totalOffset = sym->value + reloc->addend;
+ StringPiece &piece = cisec->getStringPiece(totalOffset);
+ piece.live = false;
+ return;
+ }
+}
+
+void ObjcCategoryMerger::collectCategoryWriterInfoFromCategory(
+ InfoInputCategory &catInfo) {
+
+ collectSectionWriteInfoFromIsec<ConcatOutputSection>(
+ catInfo.catListIsec, infoCategoryWriter.catListInfo);
+ collectSectionWriteInfoFromIsec<ConcatOutputSection>(
+ catInfo.catBodyIsec, infoCategoryWriter.catBodyInfo);
+
+ if (!infoCategoryWriter.catNameInfo.valid) {
+ const Reloc *catNameReloc =
+ catInfo.catBodyIsec->getRelocAt(catLayout.nameOffset);
+
+ assert(catNameReloc && "Category does not have a reloc at nameOffset");
+
+ lld::macho::Defined *catDefSym =
+ dyn_cast_or_null<Defined>(catNameReloc->referent.dyn_cast<Symbol *>());
+ assert(catDefSym && "Reloc of category name is not a valid Defined symbol");
+
+ collectSectionWriteInfoFromIsec<CStringSection>(
+ catDefSym->isec, infoCategoryWriter.catNameInfo);
+ }
+
+ // Collect writer info from all the category lists (we're assuming they all
+ // would provide the same info)
+ if (!infoCategoryWriter.catPtrListInfo.valid) {
+ for (uint32_t off = catLayout.instanceMethodsOffset;
+ off <= catLayout.classPropsOffset; off += target->wordSize) {
+ Defined *ptrList;
+ if (tryGetDefinedAtIsecOffset(catInfo.catBodyIsec, off, ptrList)) {
+ collectSectionWriteInfoFromIsec<ConcatOutputSection>(
+ ptrList->isec, infoCategoryWriter.catPtrListInfo);
+ // we've successfully collected data, so we can break
+ break;
+ }
+ }
+ }
+}
+
+// Parse a protocol list that might be linked to at a ConcatInputSection given
+// offset. The format of the protocol list is different than other lists (prop
+// lists, method lists) so we need to parse it differently
+void ObjcCategoryMerger::parseProtocolListInfo(ConcatInputSection *isec,
+ uint32_t secOffset,
+ PointerListInfo &ptrList) {
+ if (!isec || (secOffset + target->wordSize > isec->data.size()))
+ assert("Tried to read pointer list beyond protocol section end");
+
+ const Reloc *reloc = isec->getRelocAt(secOffset);
+ if (!reloc)
+ return; // List is null, nothing to do
+
+ auto *ptrListSym = dyn_cast_or_null<Defined>(reloc->referent.get<Symbol *>());
+ assert(ptrListSym && "Protocol list reloc does not have a valid Defined");
+
+ // Theoretically protocol count can be either 32b or 64b, but reading the
+ // first 32b is good enough
+ uint32_t protocolCount = *reinterpret_cast<const uint32_t *>(
+ ptrListSym->isec->data.data() + listHeaderLayout.structSizeOffset);
+
+ ptrList.structCount += protocolCount;
+ ptrList.structSize = target->wordSize;
+
+ uint32_t expectedListSize =
+ (protocolCount * target->wordSize) +
+ /*header(count)*/ protocolListHeaderLayout.totalSize +
+ /*extra null value*/ target->wordSize;
+ assert(expectedListSize == ptrListSym->isec->data.size() &&
+ "Protocol list does not match expected size");
+
+ uint32_t off = protocolListHeaderLayout.totalSize;
+ for (uint32_t inx = 0; inx < protocolCount; inx++) {
+ const Reloc *reloc = ptrListSym->isec->getRelocAt(off);
+ assert(reloc && "No reloc found at protocol list offset");
+
+ auto *listSym = dyn_cast_or_null<Defined>(reloc->referent.get<Symbol *>());
+ assert(listSym && "Protocol list reloc does not have a valid Defined");
+
+ ptrList.allPtrs.push_back(listSym);
+ off += target->wordSize;
+ }
+}
+
+// Parse a pointer list that might be linked to at a ConcatInputSection given
+// offset. This can be used for instance methods, class methods, instance props
+// and class props since they have the same format.
+void ObjcCategoryMerger::parsePointerListInfo(ConcatInputSection *isec,
+ uint32_t secOffset,
+ uint32_t symbolsPerStruct,
----------------
kyulee-com wrote:
Can we use an enum to handle 4 each case -- instance methods, class methods, instance props
and class props, and use it to specialize code inside this function, instead of individually passing offset, size, and output value, etc, which are error-prone?
Basically, you could attach `extInfo` to `ObjcCategoryMerger`, which you can avoid passing output parameters all over the place, and call something like:
```
parsePointerListInfo(catInfo.catBodyIsec, InstanceMethods);
parsePointerListInfo(catInfo.catBodyIsec, ClassMethods);
parsePointerListInfo(catInfo.catBodyIsec, InstanceProps);
parsePointerListInfo(catInfo.catBodyIsec, ClassProps);
```
https://github.com/llvm/llvm-project/pull/82928
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