From 5fba45ad1107903e37a80e47bfb21477b7ee5062 Mon Sep 17 00:00:00 2001
From: Sam Parker <sam.parker@arm.com>
Date: Wed, 8 Feb 2017 09:44:18 +0000
Subject: 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

llvm-svn: 294430
---
 llvm/tools/llvm-objdump/llvm-objdump.cpp | 51 +++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

(limited to 'llvm/tools/llvm-objdump')

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 6b8a43ea1bd..fb144faca51 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/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;
-- 
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