Use dynamic symbols for ELF disassembly

Disassembly currently begins from addresses obtained from the objects
symbol table. For ELF, add the dynamic symbols to the list if no
static symbols are available so that we can more successfully
disassemble stripped binaries.

Differential Revision: https://reviews.llvm.org/D29632

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294430 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/test/tools/llvm-objdump/Inputs/stripped-elf.so b/test/tools/llvm-objdump/Inputs/stripped-elf.so
new file mode 100644 (file)
index 0000000..b88b775
Binary files /dev/null and b/test/tools/llvm-objdump/Inputs/stripped-elf.so differ

diff --git a/test/tools/llvm-objdump/stripped-shared.test b/test/tools/llvm-objdump/stripped-shared.test
new file mode 100644 (file)
index 0000000..c57155f
--- /dev/null
+++ b/test/tools/llvm-objdump/stripped-shared.test
@@ -0,0 +1,10 @@
+// This test checks that dynamic symbols are used when disassembling elf files.
+// RUN: llvm-objdump -d %p/Inputs/stripped-elf.so | FileCheck %s
+
+# CHECK: .init
+# CHECK: .plt
+# CHECK: .text
+# CHECK: func0
+# CHECK: func1
+# CHECK: func2
+# CHECK: .fini

diff --git a/tools/llvm-objdump/llvm-objdump.cpp b/tools/llvm-objdump/llvm-objdump.cpp
index 6b8a43ea1bdd35d03b673e9a152d6775bb65c33d..fb144faca5115da3ec0f9bd94e3d96ae19ea12a5 100644 (file)
--- a/tools/llvm-objdump/llvm-objdump.cpp
+++ b/tools/llvm-objdump/llvm-objdump.cpp
@@ -213,6 +213,8 @@ cl::opt<unsigned long long>
                 cl::value_desc("address"), cl::init(UINT64_MAX));
 static StringRef ToolName;
 
+typedef std::vector<std::tuple<uint64_t, StringRef, uint8_t>> SectionSymbolsTy;
+
 namespace {
 typedef std::function<bool(llvm::object::SectionRef const &)> FilterPredicate;
 
@@ -1108,6 +1110,52 @@ static uint8_t getElfSymbolType(const ObjectFile *Obj, const SymbolRef &Sym) {
   llvm_unreachable("Unsupported binary format");
 }
 
+template <class ELFT> static void
+addDynamicElfSymbols(const ELFObjectFile<ELFT> *Obj,
+                     std::map<SectionRef, SectionSymbolsTy> &AllSymbols) {
+  for (auto Symbol : Obj->getDynamicSymbolIterators()) {
+    uint8_t SymbolType = Symbol.getELFType();
+    if (SymbolType != ELF::STT_FUNC || Symbol.getSize() == 0)
+      continue;
+
+    Expected<uint64_t> AddressOrErr = Symbol.getAddress();
+    if (!AddressOrErr)
+      report_error(Obj->getFileName(), AddressOrErr.takeError());
+    uint64_t Address = *AddressOrErr;
+
+    Expected<StringRef> Name = Symbol.getName();
+    if (!Name)
+      report_error(Obj->getFileName(), Name.takeError());
+    if (Name->empty())
+      continue;
+
+    Expected<section_iterator> SectionOrErr = Symbol.getSection();
+    if (!SectionOrErr)
+      report_error(Obj->getFileName(), SectionOrErr.takeError());
+    section_iterator SecI = *SectionOrErr;
+    if (SecI == Obj->section_end())
+      continue;
+
+    AllSymbols[*SecI].emplace_back(Address, *Name, SymbolType);
+  }
+}
+
+static void
+addDynamicElfSymbols(const ObjectFile *Obj,
+                     std::map<SectionRef, SectionSymbolsTy> &AllSymbols) {
+  assert(Obj->isELF());
+  if (auto *Elf32LEObj = dyn_cast<ELF32LEObjectFile>(Obj))
+    addDynamicElfSymbols(Elf32LEObj, AllSymbols);
+  else if (auto *Elf64LEObj = dyn_cast<ELF64LEObjectFile>(Obj))
+    addDynamicElfSymbols(Elf64LEObj, AllSymbols);
+  else if (auto *Elf32BEObj = dyn_cast<ELF32BEObjectFile>(Obj))
+    addDynamicElfSymbols(Elf32BEObj, AllSymbols);
+  else if (auto *Elf64BEObj = cast<ELF64BEObjectFile>(Obj))
+    addDynamicElfSymbols(Elf64BEObj, AllSymbols);
+  else
+    llvm_unreachable("Unsupported binary format");
+}
+
 static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
   if (StartAddress > StopAddress)
     error("Start address should be less than stop address");
@@ -1182,7 +1230,6 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
 
   // Create a mapping from virtual address to symbol name.  This is used to
   // pretty print the symbols while disassembling.
-  typedef std::vector<std::tuple<uint64_t, StringRef, uint8_t>> SectionSymbolsTy;
   std::map<SectionRef, SectionSymbolsTy> AllSymbols;
   for (const SymbolRef &Symbol : Obj->symbols()) {
     Expected<uint64_t> AddressOrErr = Symbol.getAddress();
@@ -1210,6 +1257,8 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
     AllSymbols[*SecI].emplace_back(Address, *Name, SymbolType);
 
   }
+  if (AllSymbols.empty() && Obj->isELF())
+    addDynamicElfSymbols(Obj, AllSymbols);
 
   // Create a mapping from virtual address to section.
   std::vector<std::pair<uint64_t, SectionRef>> SectionAddresses;