[llvm-objdump] Support disassembling by symbol name

Summary:
Add a new option -df to llvm-objdump that takes function names
as arguments and instructs the disassembler to only dump those function
contents. Based on code originally written by Bill Nell.

Reviewers: espindola, JDevlieghere

Differential Revision: https://reviews.llvm.org/D44224

llvm-svn: 327164

1 files changed, 30 insertions, 14 deletions

diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 3be2c423bb5..7764c1d6e10 100644
--- a/llvm/tools/llvm-objdump/llvm-objdump.cpp
+++ b/llvm/tools/llvm-objdump/llvm-objdump.cpp
@@ -20,6 +20,7 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/CodeGen/FaultMaps.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
@@ -85,6 +86,12 @@ static cl::alias
 DisassembleAlld("D", cl::desc("Alias for --disassemble-all"),
              cl::aliasopt(DisassembleAll));
 
+static cl::list<std::string>
+DisassembleFunctions("df",
+                     cl::CommaSeparated,
+                     cl::desc("List of functions to disassemble"));
+static StringSet<> DisasmFuncsSet;
+
 cl::opt<bool>
 llvm::Relocations("r", cl::desc("Display the relocation entries in the file"));
 
@@ -1388,23 +1395,15 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
       DataRefImpl DR = Section.getRawDataRefImpl();
       SegmentName = MachO->getSectionFinalSegmentName(DR);
     }
-    StringRef name;
-    error(Section.getName(name));
-
-    if ((SectionAddr <= StopAddress) &&
-        (SectionAddr + SectSize) >= StartAddress) {
-    outs() << "Disassembly of section ";
-    if (!SegmentName.empty())
-      outs() << SegmentName << ",";
-    outs() << name << ':';
-    }
+    StringRef SectionName;
+    error(Section.getName(SectionName));
 
     // If the section has no symbol at the start, just insert a dummy one.
     if (Symbols.empty() || std::get<0>(Symbols[0]) != 0) {
-      Symbols.insert(Symbols.begin(),
-                     std::make_tuple(SectionAddr, name, Section.isText()
-                                                            ? ELF::STT_FUNC
-                                                            : ELF::STT_OBJECT));
+      Symbols.insert(
+          Symbols.begin(),
+          std::make_tuple(SectionAddr, SectionName,
+                          Section.isText() ? ELF::STT_FUNC : ELF::STT_OBJECT));
     }
 
     SmallString<40> Comments;
@@ -1417,6 +1416,7 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
 
     uint64_t Size;
     uint64_t Index;
+    bool PrintedSection = false;
 
     std::vector<RelocationRef>::const_iterator rel_cur = Rels.begin();
     std::vector<RelocationRef>::const_iterator rel_end = Rels.end();
@@ -1441,6 +1441,19 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
         continue;
       }
 
+      /// Skip if user requested specific symbols and this is not in the list
+      if (!DisasmFuncsSet.empty() &&
+          !DisasmFuncsSet.count(std::get<1>(Symbols[si])))
+        continue;
+
+      if (!PrintedSection) {
+        PrintedSection = true;
+        outs() << "Disassembly of section ";
+        if (!SegmentName.empty())
+          outs() << SegmentName << ",";
+        outs() << SectionName << ':';
+      }
+
       // Stop disassembly at the stop address specified
       if (End + SectionAddr > StopAddress)
         End = StopAddress - SectionAddr;
@@ -2203,6 +2216,9 @@ int main(int argc, char **argv) {
     return 2;
   }
 
+  DisasmFuncsSet.insert(DisassembleFunctions.begin(),
+                        DisassembleFunctions.end());
+
   llvm::for_each(InputFilenames, DumpInput);
 
   return EXIT_SUCCESS;