[llvm] 4e8cb01 - [WebAssembly] Add symbol information for shared libraries (#75238)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Dec 20 11:13:12 PST 2023
Author: Sam Clegg
Date: 2023-12-20T11:13:09-08:00
New Revision: 4e8cb01b01458860ed3d3f6f54ca5405e50be605
URL: https://github.com/llvm/llvm-project/commit/4e8cb01b01458860ed3d3f6f54ca5405e50be605
DIFF: https://github.com/llvm/llvm-project/commit/4e8cb01b01458860ed3d3f6f54ca5405e50be605.diff
LOG: [WebAssembly] Add symbol information for shared libraries (#75238)
The current (experimental) spec for WebAssembly shared libraries does
not include a full symbol table like the object format. This change
extracts symbol information from the normal wasm exports.
This is the first step in having the linker report undefined symbols
when linking with shared libraries. The current behaviour is to ignore
all undefined symbols when linking with `-pie` or `-shared`.
See https://github.com/emscripten-core/emscripten/issues/18198
Added:
llvm/test/tools/llvm-nm/wasm/dylink.yaml
llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml
Modified:
llvm/include/llvm/Object/Wasm.h
llvm/lib/Object/WasmObjectFile.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Object/Wasm.h b/llvm/include/llvm/Object/Wasm.h
index dfab4c68d18f12..6b8edb90e144b5 100644
--- a/llvm/include/llvm/Object/Wasm.h
+++ b/llvm/include/llvm/Object/Wasm.h
@@ -144,7 +144,6 @@ class WasmObjectFile : public ObjectFile {
ArrayRef<wasm::WasmGlobal> globals() const { return Globals; }
ArrayRef<wasm::WasmTag> tags() const { return Tags; }
ArrayRef<wasm::WasmExport> exports() const { return Exports; }
- ArrayRef<WasmSymbol> syms() const { return Symbols; }
const wasm::WasmLinkingData &linkingData() const { return LinkingData; }
uint32_t getNumberOfSymbols() const { return Symbols.size(); }
ArrayRef<wasm::WasmElemSegment> elements() const { return ElemSegments; }
diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 168fb57935d6d2..05bd7302c49711 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -599,6 +599,10 @@ Error WasmObjectFile::parseLinkingSection(ReadContext &Ctx) {
Error WasmObjectFile::parseLinkingSectionSymtab(ReadContext &Ctx) {
uint32_t Count = readVaruint32(Ctx);
+ // Clear out any symbol information that was derived from the exports
+ // section.
+ LinkingData.SymbolTable.clear();
+ Symbols.clear();
LinkingData.SymbolTable.reserve(Count);
Symbols.reserve(Count);
StringSet<> SymbolNames;
@@ -1290,37 +1294,75 @@ Error WasmObjectFile::parseGlobalSection(ReadContext &Ctx) {
Error WasmObjectFile::parseExportSection(ReadContext &Ctx) {
uint32_t Count = readVaruint32(Ctx);
Exports.reserve(Count);
+ LinkingData.SymbolTable.reserve(Count);
+ Symbols.reserve(Count);
for (uint32_t I = 0; I < Count; I++) {
wasm::WasmExport Ex;
Ex.Name = readString(Ctx);
Ex.Kind = readUint8(Ctx);
Ex.Index = readVaruint32(Ctx);
+ const wasm::WasmSignature *Signature = nullptr;
+ const wasm::WasmGlobalType *GlobalType = nullptr;
+ const wasm::WasmTableType *TableType = nullptr;
+ wasm::WasmSymbolInfo Info;
+ Info.Name = Ex.Name;
+ Info.Flags = 0;
switch (Ex.Kind) {
- case wasm::WASM_EXTERNAL_FUNCTION:
-
+ case wasm::WASM_EXTERNAL_FUNCTION: {
if (!isDefinedFunctionIndex(Ex.Index))
return make_error<GenericBinaryError>("invalid function export",
object_error::parse_failed);
getDefinedFunction(Ex.Index).ExportName = Ex.Name;
+ Info.Kind = wasm::WASM_SYMBOL_TYPE_FUNCTION;
+ Info.ElementIndex = Ex.Index;
+ unsigned FuncIndex = Info.ElementIndex - NumImportedFunctions;
+ wasm::WasmFunction &Function = Functions[FuncIndex];
+ Signature = &Signatures[Function.SigIndex];
break;
- case wasm::WASM_EXTERNAL_GLOBAL:
+ }
+ case wasm::WASM_EXTERNAL_GLOBAL: {
if (!isValidGlobalIndex(Ex.Index))
return make_error<GenericBinaryError>("invalid global export",
object_error::parse_failed);
+ Info.Kind = wasm::WASM_SYMBOL_TYPE_DATA;
+ uint64_t Offset = 0;
+ if (isDefinedGlobalIndex(Ex.Index)) {
+ auto Global = getDefinedGlobal(Ex.Index);
+ if (!Global.InitExpr.Extended) {
+ auto Inst = Global.InitExpr.Inst;
+ if (Inst.Opcode == wasm::WASM_OPCODE_I32_CONST) {
+ Offset = Inst.Value.Int32;
+ } else if (Inst.Opcode == wasm::WASM_OPCODE_I64_CONST) {
+ Offset = Inst.Value.Int64;
+ }
+ }
+ }
+ Info.DataRef = wasm::WasmDataReference{0, Offset, 0};
break;
+ }
case wasm::WASM_EXTERNAL_TAG:
if (!isValidTagIndex(Ex.Index))
return make_error<GenericBinaryError>("invalid tag export",
object_error::parse_failed);
+ Info.Kind = wasm::WASM_SYMBOL_TYPE_TAG;
+ Info.ElementIndex = Ex.Index;
break;
case wasm::WASM_EXTERNAL_MEMORY:
+ break;
case wasm::WASM_EXTERNAL_TABLE:
+ Info.Kind = wasm::WASM_SYMBOL_TYPE_TABLE;
break;
default:
return make_error<GenericBinaryError>("unexpected export kind",
object_error::parse_failed);
}
Exports.push_back(Ex);
+ if (Ex.Kind != wasm::WASM_EXTERNAL_MEMORY) {
+ LinkingData.SymbolTable.emplace_back(Info);
+ Symbols.emplace_back(LinkingData.SymbolTable.back(), GlobalType,
+ TableType, Signature);
+ LLVM_DEBUG(dbgs() << "Adding symbol: " << Symbols.back() << "\n");
+ }
}
if (Ctx.Ptr != Ctx.End)
return make_error<GenericBinaryError>("export section ended prematurely",
@@ -1644,6 +1686,8 @@ uint64_t WasmObjectFile::getWasmSymbolValue(const WasmSymbol &Sym) const {
return Segment.Offset.Inst.Value.Int32 + Sym.Info.DataRef.Offset;
} else if (Segment.Offset.Inst.Opcode == wasm::WASM_OPCODE_I64_CONST) {
return Segment.Offset.Inst.Value.Int64 + Sym.Info.DataRef.Offset;
+ } else if (Segment.Offset.Inst.Opcode == wasm::WASM_OPCODE_GLOBAL_GET) {
+ return Sym.Info.DataRef.Offset;
} else {
llvm_unreachable("unknown init expr opcode");
}
diff --git a/llvm/test/tools/llvm-nm/wasm/dylink.yaml b/llvm/test/tools/llvm-nm/wasm/dylink.yaml
new file mode 100644
index 00000000000000..2a8654526789a4
--- /dev/null
+++ b/llvm/test/tools/llvm-nm/wasm/dylink.yaml
@@ -0,0 +1,69 @@
+# RUN: yaml2obj %s -o %t.so
+# RUN: llvm-nm %t.so | FileCheck %s
+#
+# CHECK: 00000001 T my_func_export
+# CHECK: 0000002a D my_global_export
+
+--- !WASM
+FileHeader:
+ Version: 0x1
+Sections:
+ - Type: CUSTOM
+ Name: dylink.0
+ MemorySize: 15
+ MemoryAlignment: 0
+ TableSize: 0
+ TableAlignment: 0
+ Needed: []
+ - Type: TYPE
+ Signatures:
+ - Index: 0
+ ParamTypes: []
+ ReturnTypes: []
+ - Type: IMPORT
+ Imports:
+ - Module: env
+ Field: foo
+ Kind: FUNCTION
+ SigIndex: 0
+ - Module: env
+ Field: bar
+ Kind: GLOBAL
+ GlobalType: I32
+ GlobalMutable: true
+ - Module: env
+ Field: memory
+ Kind: MEMORY
+ Memory:
+ Minimum: 0x1
+ - Type: FUNCTION
+ FunctionTypes: [ 0 ]
+ - Type: GLOBAL
+ Globals:
+ - Index: 1
+ Mutable: false
+ Type: I32
+ InitExpr:
+ Opcode: I32_CONST
+ Value: 42
+ - Type: EXPORT
+ Exports:
+ - Name: my_func_export
+ Kind: FUNCTION
+ Index: 1
+ - Name: my_global_export
+ Kind: GLOBAL
+ Index: 1
+ - Type: CODE
+ Functions:
+ - Index: 1
+ Locals:
+ Body: 00
+ - Type: DATA
+ Segments:
+ - SectionOffset: 0
+ InitFlags: 0
+ Offset:
+ Opcode: I32_CONST
+ Value: 0
+ Content: ''
diff --git a/llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml b/llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml
new file mode 100644
index 00000000000000..9c1e90a2d89675
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml
@@ -0,0 +1,70 @@
+# RUN: yaml2obj %s -o %t.so
+# RUN: llvm-objdump -t %t.so | FileCheck %s
+#
+# CHECK: SYMBOL TABLE:
+# CHECK-NEXT: 00000001 g F CODE my_func_export
+# CHECK-NEXT: 0000002a g O DATA my_global_export
+
+--- !WASM
+FileHeader:
+ Version: 0x1
+Sections:
+ - Type: CUSTOM
+ Name: dylink.0
+ MemorySize: 15
+ MemoryAlignment: 0
+ TableSize: 0
+ TableAlignment: 0
+ Needed: []
+ - Type: TYPE
+ Signatures:
+ - Index: 0
+ ParamTypes: []
+ ReturnTypes: []
+ - Type: IMPORT
+ Imports:
+ - Module: env
+ Field: foo
+ Kind: FUNCTION
+ SigIndex: 0
+ - Module: env
+ Field: bar
+ Kind: GLOBAL
+ GlobalType: I32
+ GlobalMutable: true
+ - Module: env
+ Field: memory
+ Kind: MEMORY
+ Memory:
+ Minimum: 0x1
+ - Type: FUNCTION
+ FunctionTypes: [ 0 ]
+ - Type: GLOBAL
+ Globals:
+ - Index: 1
+ Mutable: false
+ Type: I32
+ InitExpr:
+ Opcode: I32_CONST
+ Value: 42
+ - Type: EXPORT
+ Exports:
+ - Name: my_func_export
+ Kind: FUNCTION
+ Index: 1
+ - Name: my_global_export
+ Kind: GLOBAL
+ Index: 1
+ - Type: CODE
+ Functions:
+ - Index: 1
+ Locals:
+ Body: 00
+ - Type: DATA
+ Segments:
+ - SectionOffset: 0
+ InitFlags: 0
+ Offset:
+ Opcode: I32_CONST
+ Value: 0
+ Content: ''
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