From b0e4b91660f4c04f9abf5022de547479282af9ca Mon Sep 17 00:00:00 2001
From: Rafael Auler <rafaelauler@fb.com>
Date: Fri, 9 Mar 2018 19:13:44 +0000
Subject: [PATCH] [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
---
 .../X86/disasm-specific-funcs.test            | 20 +++++++++
 llvm/tools/llvm-objdump/llvm-objdump.cpp      | 44 +++++++++++++------
 2 files changed, 50 insertions(+), 14 deletions(-)
 create mode 100644 llvm/test/tools/llvm-objdump/X86/disasm-specific-funcs.test

diff --git a/llvm/test/tools/llvm-objdump/X86/disasm-specific-funcs.test b/llvm/test/tools/llvm-objdump/X86/disasm-specific-funcs.test
new file mode 100644
index 000000000000..c46147fbe276
--- /dev/null
+++ b/llvm/test/tools/llvm-objdump/X86/disasm-specific-funcs.test
@@ -0,0 +1,20 @@
+// RUN: yaml2obj -o %t.out %p/Inputs/simple-executable-x86_64.yaml
+// RUN: llvm-objdump -d %t.out -df=main | FileCheck %s
+
+// CHECK:              Disassembly of section .anothertext:
+// CHECK-NEXT:         main:
+// CHECK-NEXT:         10:       55      pushq   %rbp
+// CHECK-NEXT:         11:       48 89 e5        movq    %rsp, %rbp
+// CHECK-NEXT:         14:       48 83 ec 20     subq    $32, %rsp
+// CHECK-NEXT:         18:       48 8d 04 25 a8 00 00 00         leaq    168, %rax
+// CHECK-NEXT:         20:       c7 45 fc 00 00 00 00    movl    $0, -4(%rbp)
+// CHECK-NEXT:         27:       48 89 45 f0     movq    %rax, -16(%rbp)
+// CHECK-NEXT:         2b:       48 8b 45 f0     movq    -16(%rbp), %rax
+// CHECK-NEXT:         2f:       8b 08   movl    (%rax), %ecx
+// CHECK-NEXT:         31:       89 4d ec        movl    %ecx, -20(%rbp)
+// CHECK-NEXT:         34:       e8 c7 ff ff ff  callq   -57
+// CHECK-NEXT:         39:       8b 4d ec        movl    -20(%rbp), %ecx
+// CHECK-NEXT:         3c:       01 c1   addl    %eax, %ecx
+// CHECK-NEXT:         3e:       89 c8   movl    %ecx, %eax
+// CHECK-NEXT:         40:       48 83 c4 20     addq    $32, %rsp
+// CHECK-NEXT:         44:       5d      popq    %rbp
diff --git a/llvm/tools/llvm-objdump/llvm-objdump.cpp b/llvm/tools/llvm-objdump/llvm-objdump.cpp
index 3be2c423bb5c..7764c1d6e101 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;