[llvm] [WebAssembly] Add symbol information for shared libraries (PR #75238)
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llvm-commits at lists.llvm.org
Tue Dec 12 11:28:48 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-binary-utilities
Author: Sam Clegg (sbc100)
<details>
<summary>Changes</summary>
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`.
---
Full diff: https://github.com/llvm/llvm-project/pull/75238.diff
4 Files Affected:
- (modified) llvm/include/llvm/Object/Wasm.h (-1)
- (modified) llvm/lib/Object/WasmObjectFile.cpp (+47-3)
- (added) llvm/test/tools/llvm-nm/wasm/dylink.yaml (+69)
- (added) llvm/test/tools/llvm-objdump/wasm/dylink-symbol-table.yaml (+70)
``````````diff
diff --git a/llvm/include/llvm/Object/Wasm.h b/llvm/include/llvm/Object/Wasm.h
index dfab4c68d18f1..6b8edb90e144b 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 168fb57935d6d..07599d26442b1 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 0000000000000..2a8654526789a
--- /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 0000000000000..9c1e90a2d8967
--- /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: ''
``````````
</details>
https://github.com/llvm/llvm-project/pull/75238
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