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Diffstat (limited to 'src/wasm-linker.h')
| -rw-r--r-- | src/wasm-linker.h | 342 |
1 files changed, 0 insertions, 342 deletions
diff --git a/src/wasm-linker.h b/src/wasm-linker.h deleted file mode 100644 index 89f1cb718..000000000 --- a/src/wasm-linker.h +++ /dev/null @@ -1,342 +0,0 @@ -/* - * Copyright 2016 WebAssembly Community Group participants - * - * Licensed under the Apache License, Version 2.0 (the "License"); - * you may not use this file except in compliance with the License. - * You may obtain a copy of the License at - * - * http://www.apache.org/licenses/LICENSE-2.0 - * - * Unless required by applicable law or agreed to in writing, software - * distributed under the License is distributed on an "AS IS" BASIS, - * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. - * See the License for the specific language governing permissions and - * limitations under the License. - */ - -// (very) basic linking functionality for s2wasm. -// Performs some of the tasks that will eventually be done by a real linker. -// Currently can allocate static variables and the stack, lay out memory -// and initial segment contents, and process relocations. (In particular, there -// is no merging of multiple modules). Currently this is only inteded to turn -// a .s file produced by LLVM into a usable wast file. - -#ifndef wasm_wasm_linker_h -#define wasm_wasm_linker_h - -#include "support/archive.h" -#include "support/name.h" -#include "support/utilities.h" -#include "wasm.h" - -namespace wasm { - -class S2WasmBuilder; - -inline void exportFunction(Module& wasm, Name name, bool must_export) { - if (!wasm.getFunctionOrNull(name)) { - assert(!must_export); - return; - } - if (wasm.getExportOrNull(name)) return; // Already exported - auto exp = new Export; - exp->name = exp->value = name; - exp->kind = ExternalKind::Function; - wasm.addExport(exp); -} - -// An "object file" for linking. Contains a wasm module, plus the associated -// information needed for linking/layout. -class LinkerObject { - public: - struct Relocation { - enum Kind { kData, kFunction }; - Kind kind; // Whether the symbol refers to data or a function. - // Instead of section offsets as relocation targets, for now this is just - // a pointer to the memory to rewrite. - uint32_t* data; - Name symbol; // Like the symbol index in ELF r_info field - int addend; // Like the ELF r_addend field - Relocation(Kind kind, uint32_t* data, Name symbol, int addend) : - kind(kind), data(data), symbol(symbol), addend(addend) {} - }; - struct SymbolAlias { - Name symbol; - Relocation::Kind kind; - Offset offset; - SymbolAlias(Name symbol, Relocation::Kind kind, Offset offset) : - symbol(symbol), kind(kind), offset(offset) {} - }; - // Information about symbols - struct SymbolInfo { - std::unordered_set<cashew::IString> implementedFunctions; - std::unordered_set<cashew::IString> undefinedFunctions; - std::unordered_set<cashew::IString> importedObjects; - // TODO: it's not clear that this really belongs here. - std::unordered_map<cashew::IString, SymbolAlias> aliasedSymbols; - - // For now, do not support weak symbols or anything special. Just directly - // merge the functions together, and remove any newly-defined functions - // from undefinedFunction - void merge(SymbolInfo& other) { - for (const auto& func : other.implementedFunctions) { - undefinedFunctions.erase(func); - } - implementedFunctions.insert(other.implementedFunctions.begin(), - other.implementedFunctions.end()); - importedObjects.insert(other.importedObjects.begin(), - other.importedObjects.end()); - aliasedSymbols.insert(other.aliasedSymbols.begin(), - other.aliasedSymbols.end()); - } - }; - - LinkerObject() {} - - // Allocate a static object - void addStatic(Address allocSize, Address alignment, Name name) { - staticObjects.emplace_back(allocSize, alignment, name); - } - - void addGlobal(Name name) { - globls.push_back(name); - } - - // This takes ownership of the added Relocation - void addRelocation(Relocation* relocation) { - relocations.emplace_back(relocation); - } - - bool isFunctionImplemented(Name name) { - return symbolInfo.implementedFunctions.count(name) != 0; - } - - // An object is considered implemented if it is not imported - bool isObjectImplemented(Name name) { - return symbolInfo.importedObjects.count(name) == 0; - } - - // If name is an alias, return what it points to. Otherwise return name. - Name resolveAlias(Name name, Relocation::Kind kind) { - auto aliased = symbolInfo.aliasedSymbols.find(name); - if (aliased != symbolInfo.aliasedSymbols.end() && aliased->second.kind == kind) return aliased->second.symbol; - return name; - } - - SymbolAlias *getAlias(Name name, Relocation::Kind kind) { - auto aliased = symbolInfo.aliasedSymbols.find(name); - if (aliased != symbolInfo.aliasedSymbols.end() && aliased->second.kind == kind) return &aliased->second; - return nullptr; - } - - // Add an initializer segment for the named static variable. - void addSegment(Name name, const char* data, Address size) { - segments[name] = wasm.memory.segments.size(); - wasm.memory.segments.emplace_back(wasm.allocator.alloc<Const>()->set(Literal(uint32_t(0))), data, size); - } - - void addSegment(Name name, std::vector<char>& data) { - segments[name] = wasm.memory.segments.size(); - wasm.memory.segments.emplace_back(wasm.allocator.alloc<Const>()->set(Literal(uint32_t(0))), data); - } - - void addInitializerFunction(Name name) { - initializerFunctions.emplace_back(name); - assert(symbolInfo.implementedFunctions.count(name)); - } - - void addUndefinedFunctionCall(Call* call) { - symbolInfo.undefinedFunctions.insert(call->target); - undefinedFunctionCalls[call->target].push_back(call); - } - - void addExternType(Name name, FunctionType* ty) { - externTypesMap[name] = ty; - } - FunctionType* getExternType(Name name) { - auto f = externTypesMap.find(name); - if (f == externTypesMap.end()) return nullptr; - return f->second; - } - - void addIndirectIndex(Name name, Address index) { - assert(!indirectIndexes.count(name)); - indirectIndexes[name] = index; - } - - bool isEmpty() { - return wasm.functions.empty(); - } - - std::vector<Name> const& getInitializerFunctions() const { - return initializerFunctions; - } - - friend class Linker; - - Module wasm; - - private: - struct StaticObject { - Address allocSize; - Address alignment; - Name name; - StaticObject(Address allocSize, Address alignment, Name name) : - allocSize(allocSize), alignment(alignment), name(name) {} - }; - - std::vector<Name> globls; - - std::vector<StaticObject> staticObjects; - std::vector<std::unique_ptr<Relocation>> relocations; - - SymbolInfo symbolInfo; - - using CallList = std::vector<Call*>; - std::map<Name, CallList> undefinedFunctionCalls; - - // Types of functions which are declared but not defined. - std::unordered_map<cashew::IString, FunctionType*> externTypesMap; - - std::map<Name, Address> segments; // name => segment index (in wasm module) - - // preassigned indexes for functions called indirectly - std::map<Name, Address> indirectIndexes; - - std::vector<Name> initializerFunctions; - - LinkerObject(const LinkerObject&) = delete; - LinkerObject& operator=(const LinkerObject&) = delete; - -}; - -// Class which performs some linker-like functionality; namely taking an object -// file with relocations, laying out the linear memory and segments, and -// applying the relocations, resulting in an executable wasm module. -class Linker { - public: - Linker(Address globalBase, Address stackAllocation, Address userInitialMemory, - Address userMaxMemory, bool importMemory, bool ignoreUnknownSymbols, - Name startFunction, bool debug) - : ignoreUnknownSymbols(ignoreUnknownSymbols), - startFunction(startFunction), - globalBase(globalBase), - nextStatic(globalBase), - userInitialMemory(userInitialMemory), - userMaxMemory(userMaxMemory), - importMemory(importMemory), - stackAllocation(stackAllocation), - debug(debug) { - if (userMaxMemory && userMaxMemory < userInitialMemory) { - Fatal() << "Specified max memory " << userMaxMemory << - " is < specified initial memory " << userInitialMemory; - } - if (roundUpToPageSize(userMaxMemory) != userMaxMemory) { - Fatal() << "Specified max memory " << userMaxMemory << - " is not a multiple of 64k"; - } - if (roundUpToPageSize(userInitialMemory) != userInitialMemory) { - Fatal() << "Specified initial memory " << userInitialMemory << - " is not a multiple of 64k"; - } - - // Don't allow anything to be allocated at address 0 - if (globalBase == 0) nextStatic = 1; - - // Place the stack pointer at the bottom of the linear memory, to keep its - // address small (and thus with a small encoding). - placeStackPointer(stackAllocation); - // Allocate __dso_handle. For asm.js, emscripten provides this in JS, but - // wasm modules can't import data objects. Its value is 0 for the main - // executable, which is all we have with static linking. In the future this - // can go in a crtbegin or similar file. - out.addStatic(4, 4, "__dso_handle"); - } - - // Return a reference to the LinkerObject for the main executable. If empty, - // it can be passed to an S2WasmBuilder and constructed. - LinkerObject& getOutput() { return out; } - - // Allocate the user stack, set up the initial memory size of the module, lay - // out the linear memory, process the relocations, and set up the indirect - // function table. - void layout(); - - // Add an object to the link by constructing it in-place with a builder. - // Returns false if an error occurred. - bool linkObject(S2WasmBuilder& builder); - - // Add an archive to the link. Any objects in the archive that satisfy a - // currently-undefined reference will be added to the link. - // Returns false if an error occurred. - bool linkArchive(Archive& archive); - - // Returns the address of the stack pointer. - Address getStackPointerAddress() const; - - // Returns the total size of all static allocations. - Address getStaticBump() const; - - private: - // Allocate a static variable and return its address in linear memory - Address allocateStatic(Address allocSize, Address alignment, Name name) { - Address address = alignAddr(nextStatic, alignment); - staticAddresses[name] = address; - nextStatic = address + allocSize; - return address; - } - - // Allocate space for a stack pointer and (if stackAllocation > 0) set up a - // relocation for it to point to the top of the stack. - void placeStackPointer(Address stackAllocation); - - void ensureFunctionImport(Name target, std::string signature); - void ensureObjectImport(Name target); - - // Makes sure the table has a single segment, with offset 0, - // to which we can add content. - void ensureTableSegment(); - - std::vector<Name>& getTableDataRef(); - std::vector<Name> getTableData(); - - // Retrieves (and assigns) an entry index in the indirect function table for - // a given function. - Index getFunctionIndex(Name name); - - // Adds a dummy function in the indirect table at slot 0 to prevent NULL - // pointer miscomparisons. - void makeDummyFunction(); - - static Address roundUpToPageSize(Address size) { - return (size + Memory::kPageSize - 1) & Memory::kPageMask; - } - - Function* getImportThunk(Name name, const FunctionType* t); - - // The output module (linked executable) - LinkerObject out; - - bool ignoreUnknownSymbols; - Name startFunction; - - // where globals can start to be statically allocated, i.e., the data segment - Address globalBase; - Address nextStatic; // location of next static allocation - Address userInitialMemory; // Initial memory size (in bytes) specified by the user. - Address userMaxMemory; // Max memory size (in bytes) specified by the user. - //(after linking, this is rounded and set on the wasm object in pages) - bool importMemory; // Whether the memory should be imported instead of - // defined. - Address stackAllocation; - bool debug; - - std::unordered_map<cashew::IString, int32_t> staticAddresses; // name => address - std::unordered_map<Address, Address> segmentsByAddress; // address => segment index - std::unordered_map<cashew::IString, Address> functionIndexes; - std::map<Address, cashew::IString> functionNames; -}; - -} - -#endif // wasm_wasm_linker_h |