[lld] r336631 - Report an error for an extremely large .gdb_index section.

[Rui Ueyama via llvm-commits]

Author: ruiu
Date: Mon Jul  9 18:22:25 2018
New Revision: 336631

URL: http://llvm.org/viewvc/llvm-project?rev=336631&view=rev
Log:
Report an error for an extremely large .gdb_index section.

I believe the only way to test this functionality is to create extremely
large object files and attempt to create a .gdb_index that is greater
than 4 GiB. But I think that's too much for most environments and buildbots,
so I'm commiting this without a test that actually triggers the new
error condition.

Modified:
    lld/trunk/ELF/SyntheticSections.cpp
    lld/trunk/ELF/SyntheticSections.h

Modified: lld/trunk/ELF/SyntheticSections.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=336631&r1=336630&r2=336631&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.cpp (original)
+++ lld/trunk/ELF/SyntheticSections.cpp Mon Jul  9 18:22:25 2018
@@ -2446,16 +2446,18 @@ GdbIndexSection::GdbIndexSection(std::ve
   SymtabOffset = CuTypesOffset + getAddressAreaSize(Chunks) * 20;
   ConstantPoolOffset = SymtabOffset + GdbSymtab.size() * 8;
 
-  size_t Off = 0;
   for (ArrayRef<uint32_t> Vec : CuVectors) {
-    CuVectorOffsets.push_back(Off);
-    Off += (Vec.size() + 1) * 4;
+    CuVectorOffsets.push_back(CuVectorsPoolSize);
+    CuVectorsPoolSize += (Vec.size() + 1) * 4;
   }
-  StringPoolOffset = ConstantPoolOffset + Off;
-}
 
-size_t GdbIndexSection::getSize() const {
-  return StringPoolOffset + StringPoolSize;
+  uint64_t PoolSize = CuVectorsPoolSize + StringPoolSize;
+  TotalSize = ConstantPoolOffset + PoolSize;
+
+  // Length fields in the .gdb_index section are only 4 byte long,
+  // so the section cannot contain very large contents.
+  if (ConstantPoolOffset > UINT32_MAX || PoolSize > UINT32_MAX)
+    error(".gdb_index section too large");
 }
 
 void GdbIndexSection::writeTo(uint8_t *Buf) {
@@ -2491,7 +2493,7 @@ void GdbIndexSection::writeTo(uint8_t *B
   // Write the symbol table.
   for (GdbSymbol *Sym : GdbSymtab) {
     if (Sym) {
-      write32le(Buf, Sym->NameOffset + StringPoolOffset - ConstantPoolOffset);
+      write32le(Buf, CuVectorsPoolSize + Sym->NameOffset);
       write32le(Buf + 4, CuVectorOffsets[Sym->CuVectorIndex]);
     }
     Buf += 8;

Modified: lld/trunk/ELF/SyntheticSections.h
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.h?rev=336631&r1=336630&r2=336631&view=diff
==============================================================================
--- lld/trunk/ELF/SyntheticSections.h (original)
+++ lld/trunk/ELF/SyntheticSections.h Mon Jul  9 18:22:25 2018
@@ -688,7 +688,7 @@ class GdbIndexSection final : public Syn
 public:
   GdbIndexSection(std::vector<GdbIndexChunk> &&Chunks);
   void writeTo(uint8_t *Buf) override;
-  size_t getSize() const override;
+  size_t getSize() const override { return TotalSize; }
   bool empty() const override;
 
 private:
@@ -709,12 +709,13 @@ private:
   // object and used to build different areas of gdb index.
   std::vector<GdbIndexChunk> Chunks;
 
-  static constexpr uint32_t CuListOffset = 24;
-  uint32_t CuTypesOffset;
-  uint32_t SymtabOffset;
-  uint32_t ConstantPoolOffset;
-  uint32_t StringPoolOffset;
-  uint32_t StringPoolSize;
+  uint64_t CuListOffset = 24;
+  uint64_t CuTypesOffset;
+  uint64_t SymtabOffset;
+  uint64_t ConstantPoolOffset;
+  uint64_t CuVectorsPoolSize = 0;
+  uint64_t StringPoolSize;
+  uint64_t TotalSize;
 
   std::vector<size_t> CuVectorOffsets;
 };