[WebAssembly] Encode numbers in ULEB128 in event section

[aheejin]

Summary

The number of events and the type index should be encoded in ULEB128,
but they were incorrctly encoded in LEB128. The smallest number with
which its LEB128 and ULEB128 encodings are different is 64.
There's no way we can generate 64 events in the C++ toolchain
implementation so we can't test that, but the attached test tests when
the type index is 64.

[sbc100]

Man, these kind of bug are so common, and so hard to test and occur across so many different tools.. I wonder if we would have made a different choice if we have known how many issues LEB128 would cause.

[aheejin]

Yes that's unfortunate... By the way the title should have been "decoding", not "encoding".

llvm/lib/Object/WasmObjectFile.cpp

Error WasmObjectFile::parseMemorySection(ReadContext &Ctx) {
   if (Ctx.Ptr != Ctx.End)
     return make_error<GenericBinaryError>("memory section ended prematurely",
                                           object_error::parse_failed);
   return Error::success();
 }
 
 Error WasmObjectFile::parseEventSection(ReadContext &Ctx) {
   EventSection = Sections.size();
-  uint32_t Count = readVarint32(Ctx);
+  uint32_t Count = readVaruint32(Ctx);
   Events.reserve(Count);
   while (Count--) {
     wasm::WasmEvent Event;
     Event.Index = NumImportedEvents + Events.size();
     Event.Type.Attribute = readVaruint32(Ctx);
-    Event.Type.SigIndex = readVarint32(Ctx);
+    Event.Type.SigIndex = readVaruint32(Ctx);
     Events.push_back(Event);
   }
 
   if (Ctx.Ptr != Ctx.End)
     return make_error<GenericBinaryError>("event section ended prematurely",
                                           object_error::parse_failed);
   return Error::success();
 }

llvm/test/MC/WebAssembly/event-section-encoding.ll

+; RUN: llc -filetype=obj -exception-model=wasm -mattr=+exception-handling %s -o - | obj2yaml | FileCheck %s
+
+; This is a regression test for an encoding bug that happens when an event's
+; sigindex is greater than 63, so we put 63 dummy functions with different
+; signatures before the function that contains the 'throw' instruction to make
+; the event's sigindex 64.
+
+target triple = "wasm32-unknown-unknown"
+
+declare void @llvm.wasm.throw(i32, i8*)
+
+define i32 @dummy0() {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy1(i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy2(i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy3(i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy4(i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy5(i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy6(i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy7(i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy8(i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy9(i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy10(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy11(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy12(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy13(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy14(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy15(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy16(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy17(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy18(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy19(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy20(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy21(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy22(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy23(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy24(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy25(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy26(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy27(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy28(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy29(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy30(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy31(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy32(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy33(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy34(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy35(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy36(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy37(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy38(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy39(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy40(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy41(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy42(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy43(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy44(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy45(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy46(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy47(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy48(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy49(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy50(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy51(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy52(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy53(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy54(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy55(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy56(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy57(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy58(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy59(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy60(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy61(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy62(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @dummy63(i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32, i32) {
+entry:
+  ret i32 0
+}
+
+define i32 @test_throw(i8* %p) {
+  call void @llvm.wasm.throw(i32 0, i8* %p)
+  ret i32 0
+}
+
+; Checks to see if the event index is correctly encoded in ULEB128. If it is
+; encoded with LEB128, 64 will not be correctly decoded. 64 is the smallest
+; number with which its LEB128 and ULEB128 encodings are different, because its
+; 7th least significant bit is not 0.
+; CHECK:      - Type:            EVENT
+; CHECK-NEXT:   Events:
+; CHECK-NEXT:     - Index:           0
+; CHECK-NEXT:       Attribute:       0
+; CHECK-NEXT:       SigIndex:        64