[PATCH] D95838: [WebAssembly] Prevent data inside text sections in assembly

[Wouter van Oortmerssen via Phabricator via llvm-commits]

aardappel created this revision.
aardappel added reviewers: dschuff, sbc100.
Herald added subscribers: ecnelises, sunfish, hiraditya, jgravelle-google.
aardappel requested review of this revision.
Herald added subscribers: llvm-commits, aheejin.
Herald added a project: LLVM.

This is not supported in Wasm, unless the data was encoded instructions, but that wouldn't work with the assembler's other functionality (enforcing nesting etc.).

Fixes: https://bugs.llvm.org/show_bug.cgi?id=48971


https://reviews.llvm.org/D95838

Files:
  llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
  llvm/lib/MC/MCParser/WasmAsmParser.cpp
  llvm/lib/MC/WasmObjectWriter.cpp
  llvm/test/MC/WebAssembly/debug-byval-struct.ll


Index: llvm/test/MC/WebAssembly/debug-byval-struct.ll
===================================================================
--- llvm/test/MC/WebAssembly/debug-byval-struct.ll
+++ llvm/test/MC/WebAssembly/debug-byval-struct.ll
@@ -103,11 +103,11 @@
 ; CHECK-NEXT:     DW_AT_name    ("x")
 
 ; CHECK-LABEL:  DW_TAG_formal_parameter
-; CHECK-NEXT:     DW_AT_location        (DW_OP_WASM_location 0x0 0x1, DW_OP_deref, DW_OP_stack_value)
+; CHECK-NEXT:     DW_AT_location        (DW_OP_WASM_location 0x0 0x1, DW_OP_deref)
 ; CHECK-NEXT:     DW_AT_name    ("some_union")
 
 ; CHECK-LABEL:  DW_TAG_formal_parameter
-; CHECK-NEXT:     DW_AT_location        (DW_OP_WASM_location 0x0 0x2, DW_OP_deref, DW_OP_stack_value)
+; CHECK-NEXT:     DW_AT_location        (DW_OP_WASM_location 0x0 0x2, DW_OP_deref)
 ; CHECK-NEXT:     DW_AT_name    ("some_struct")
 
 ; CHECK-LABEL:  DW_TAG_formal_parameter
Index: llvm/lib/MC/WasmObjectWriter.cpp
===================================================================
--- llvm/lib/MC/WasmObjectWriter.cpp
+++ llvm/lib/MC/WasmObjectWriter.cpp
@@ -488,10 +488,14 @@
 
     const MCSymbol *SectionSymbol = nullptr;
     const MCSection &SecA = SymA->getSection();
-    if (SecA.getKind().isText())
-      SectionSymbol = SectionFunctions.find(&SecA)->second;
-    else
+    if (SecA.getKind().isText()) {
+      auto &SecSymIt = SectionFunctions.find(&SecA);
+      if (SecSymIt == SectionFunctions.end())
+        report_fatal_error("section doesn\'t have defining symbol");
+      SectionSymbol = SecSymIt->second;
+    } else {
       SectionSymbol = SecA.getBeginSymbol();
+    }
     if (!SectionSymbol)
       report_fatal_error("section symbol is required for relocation");
 
Index: llvm/lib/MC/MCParser/WasmAsmParser.cpp
===================================================================
--- llvm/lib/MC/MCParser/WasmAsmParser.cpp
+++ llvm/lib/MC/MCParser/WasmAsmParser.cpp
@@ -221,18 +221,22 @@
           Lexer->is(AsmToken::Identifier)))
       return error("Expected label, at type declaration, got: ", Lexer->getTok());
     auto TypeName = Lexer->getTok().getString();
+    auto *Current =
+        cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
     if (TypeName == "function") {
       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
-      auto *Current =
-          cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
       if (Current->getGroup())
         WasmSym->setComdat(true);
-    } else if (TypeName == "global")
+    } else if (TypeName == "global") {
       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
-    else if (TypeName == "object")
+    } else if (TypeName == "object") {
+      if (Current->getKind().isText())
+        return error("WASM doesn\'t support data symbols in text sections: ",
+                     Lexer->getTok());
       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_DATA);
-    else
+    } else {
       return error("Unknown WASM symbol type: ", Lexer->getTok());
+    }
     Lex();
     return expect(AsmToken::EndOfStatement, "EOL");
   }
Index: llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -664,11 +664,15 @@
 }
 
 void DwarfExpression::addWasmLocation(unsigned Index, uint64_t Offset) {
-  assert(LocationKind == Implicit || LocationKind == Unknown);
-  LocationKind = Implicit;
   emitOp(dwarf::DW_OP_WASM_location);
   emitUnsigned(Index == 4/*TI_LOCAL_INDIRECT*/ ? 0/*TI_LOCAL*/ : Index);
   emitUnsigned(Offset);
-  if (Index == 4/*TI_LOCAL_INDIRECT*/)
+  if (Index == 4 /*TI_LOCAL_INDIRECT*/) {
     emitOp(dwarf::DW_OP_deref);
+    assert(LocationKind == Unknown);
+    LocationKind = Memory;
+  } else {
+    assert(LocationKind == Implicit || LocationKind == Unknown);
+    LocationKind = Implicit;
+  }
 }


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