[WebAssembly] Ensure relocation entries are ordered by offset

wasm-lld expects relocation entries to be sorted by offset.  In most
cases llvm produces them in order, but the CODE section (which combines
many MCSections) is an exception because we order the functions in
Symbol order, not in section order.  What is more, its not clear weather
`recordRelocation` is guaranteed to be called in offset order so this
sort of most likely needed in the general case too.

Differential Revision: https://reviews.llvm.org/D51065

llvm-svn: 340423

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Object/WasmObjectFile.cpp b/llvm/lib/Object/WasmObjectFile.cpp
index 1b32ae8afd9..f75dbfc3014 100644
--- a/llvm/lib/Object/WasmObjectFile.cpp
+++ b/llvm/lib/Object/WasmObjectFile.cpp
@@ -602,10 +602,15 @@ Error WasmObjectFile::parseRelocSection(StringRef Name, ReadContext &Ctx) {
   WasmSection& Section = Sections[SectionIndex];
   uint32_t RelocCount = readVaruint32(Ctx);
   uint32_t EndOffset = Section.Content.size();
+  uint32_t PreviousOffset = 0;
   while (RelocCount--) {
     wasm::WasmRelocation Reloc = {};
     Reloc.Type = readVaruint32(Ctx);
     Reloc.Offset = readVaruint32(Ctx);
+    if (Reloc.Offset < PreviousOffset)
+      return make_error<GenericBinaryError>("Relocations not in offset order",
+                                            object_error::parse_failed);
+    PreviousOffset = Reloc.Offset;
     Reloc.Index = readVaruint32(Ctx);
     switch (Reloc.Type) {
     case wasm::R_WEBASSEMBLY_FUNCTION_INDEX_LEB: