[llvm-objdump] Support disassembling by symbol name

[rafauler]

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. Code originally written by Bill Nell.

[rafauler]

This is static because the function DisassembleObject potentially runs multiple times. So the static is to avoid re-creating the same set for each object, and it's also why it checks if it is empty.

On 3/7/18, 5:02 PM, "Rafael Avila de Espindola" <[e-mail]> wrote:

Rafael Auler via Phabricator via llvm-commits
<[e-mail]> writes:


> +    static StringSet<> DisasmFuncsSet;

Why static?

> +    if (DisasmFuncsSet.empty() && !DisassembleFunctions.empty())

DisasmFuncsSet has just been created, so it is empty.

Cheers,
Rafael

[• rafael]

Rafael Auler via Phabricator via llvm-commits
<[e-mail]> writes:

+ static StringSet<> DisasmFuncsSet;

Why static?

+ if (DisasmFuncsSet.empty() && !DisassembleFunctions.empty())

DisasmFuncsSet has just been created, so it is empty.

Cheers,
Rafael

[JDevlieghere]

tools/llvm-objdump/llvm-objdump.cpp

1420

Not a big fan of having a static var here. How about extracting this into a function:

static StringSet<> GetDisasmFuncsSet() {
	static StringSet<> DisasmFuncsSet;
  if (DisasmFuncsSet.empty() && !DisassembleFunctions.empty())
    DisasmFuncsSet.insert(DisassembleFunctions.begin(),
                          DisassembleFunctions.end());
  return DisasmFuncsSet;
}

[• rafael]

Rafael Auler <[e-mail]> writes:

This is static because the function DisassembleObject potentially runs multiple times. So the static is to avoid re-creating the same set for each object, and it's also why it checks if it is empty.

OK, that is a bit unusual. Please move the set initialization just
before

llvm::for_each(InputFilenames, DumpInput);

So that it can be done only once by more conventional means. I am OK
with the set being global.

Cheers,
Rafael

[rafauler]

Implement suggestions

[• rafael]

Rafael Auler via Phabricator <[e-mail]> writes:

+ if (!DisassembleFunctions.empty())
+ DisasmFuncsSet.insert(DisassembleFunctions.begin(),
+ DisassembleFunctions.end());

I don't think you need the if:

DisasmFuncsSet.insert(DisassembleFunctions.begin(),
                      DisassembleFunctions.end());

Will do nothing if DisassembleFunctions is empty.

LGTM with that.

Cheers,
Rafael

[rafauler]

Removing the if

[• rafael]

LGTM

Rafael Auler via Phabricator <[e-mail]> writes:

rafauler updated this revision to Diff 137799.
rafauler added a comment.

Removing the if

Repository:

rL LLVM

https://reviews.llvm.org/D44224

Files:

test/tools/llvm-objdump/X86/disasm-specific-funcs.test
tools/llvm-objdump/llvm-objdump.cpp

Index: tools/llvm-objdump/llvm-objdump.cpp

• tools/llvm-objdump/llvm-objdump.cpp

+++ 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 @@
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 @@

  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 @@

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 @@

  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 @@

  return 2;
}

+ DisasmFuncsSet.insert(DisassembleFunctions.begin(),
+ DisassembleFunctions.end());
+

llvm::for_each(InputFilenames, DumpInput);
 
return EXIT_SUCCESS;

Index: test/tools/llvm-objdump/X86/disasm-specific-funcs.test

• /dev/null

+++ 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

[rafauler]

Thank you Rafael and Jonas for reviewing

test/tools/llvm-objdump/X86/disasm-specific-funcs.test

+// 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

tools/llvm-objdump/llvm-objdump.cpp

 // binutils objdump.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm-objdump.h"
 #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"
 #include "llvm/DebugInfo/Symbolize/Symbolize.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
 #include "llvm/MC/MCDisassembler/MCRelocationInfo.h"

 
 cl::opt<bool>
 llvm::DisassembleAll("disassemble-all",
   cl::desc("Display assembler mnemonics for the machine instructions"));
 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"));
+
 cl::opt<bool>
 llvm::Relocations("r", cl::desc("Display the relocation entries in the file"));
 
 cl::opt<bool>
 llvm::SectionContents("s", cl::desc("Display the content of each section"));
 
 cl::opt<bool>
 llvm::SymbolTable("t", cl::desc("Display the symbol table"));
for (const SectionRef &Section : ToolSectionFilter(*Obj)) {
     // Sort relocations by address.
     std::sort(Rels.begin(), Rels.end(), RelocAddressLess);
 
     StringRef SegmentName = "";
     if (const MachOObjectFile *MachO = dyn_cast<const MachOObjectFile>(Obj)) {
       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;
     raw_svector_ostream CommentStream(Comments);
 
     StringRef BytesStr;
     error(Section.getContents(BytesStr));
     ArrayRef<uint8_t> Bytes(reinterpret_cast<const uint8_t *>(BytesStr.data()),
                             BytesStr.size());
 
     uint64_t Size;
     uint64_t Index;
+    bool PrintedSection = false;
+
+    static StringSet<> DisasmFuncsSet;
+    if (DisasmFuncsSet.empty() && !DisassembleFunctions.empty())
+      DisasmFuncsSet.insert(DisassembleFunctions.begin(),
+                            DisassembleFunctions.end());
 
     std::vector<RelocationRef>::const_iterator rel_cur = Rels.begin();
     std::vector<RelocationRef>::const_iterator rel_end = Rels.end();
     // Disassemble symbol by symbol.
     for (unsigned si = 0, se = Symbols.size(); si != se; ++si) {
       uint64_t Start = std::get<0>(Symbols[si]) - SectionAddr;
       // The end is either the section end or the beginning of the next
       // symbol.
       uint64_t End =
           (si == se - 1) ? SectSize : std::get<0>(Symbols[si + 1]) - SectionAddr;
       // Don't try to disassemble beyond the end of section contents.
       if (End > SectSize)
         End = SectSize;
       // If this symbol has the same address as the next symbol, then skip it.
       if (Start >= End)
         continue;
 
       // Check if we need to skip symbol
       // Skip if the symbol's data is not between StartAddress and StopAddress
       if (End + SectionAddr < StartAddress ||
           Start + SectionAddr > StopAddress) {
         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;
 
       if (Obj->isELF() && Obj->getArch() == Triple::amdgcn) {
         // make size 4 bytes folded
         End = Start + ((End - Start) & ~0x3ull);
         if (std::get<2>(Symbols[si]) == ELF::STT_AMDGPU_HSA_KERNEL) {