objdump not working on ELF 64-bit x86-64,

Question

I have a 64bits ELF object code from the Tiny C compiler. I can't get gobjdump to show the disassembled code. I'm using OS X 10.10.5.

$ file hello.o 
hello.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
$ gobjdump -d hello.o
gobjdump: hello.o: File format not recognized

$ greadelf -h hello.o
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00 
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              REL (Relocatable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x0
  Start of program headers:          0 (bytes into file)
  Start of section headers:          228 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           0 (bytes)
  Number of program headers:         0
  Size of section headers:           64 (bytes)
  Number of section headers:         7
  Section header string table index: 6

Extra Information:

$uname -a
Darwin Nawals-MacBook-Air.local 14.5.0 Darwin Kernel Version 14.5.0: 

Tue Sep  1 21:23:09 PDT 2015; root:xnu-2782.50.1~1/RELEASE_X86_64 x86_64

$ gobjdump -i
BFD header file version (GNU Binutils) 2.24
mach-o-x86-64
mach-o-i386
mach-o-le
mach-o-be
mach-o-fat
pef
pef-xlib
sym
srec
symbolsrec
verilog
tekhex
binary
ihex

I don't understand why stack overflow think my question is mostly code - I want to give as much information as possible to help people answer. I didn't think pastebin et al. were encouraged here.

The answer is simple. Your `gobjdump` was compiled with support for Mac OS X's Mach-O binary format _only_. Your `gobjdump` build does not support parsing ELF. — Iwillnotexist Idonotexist, Dec 18 '15 at 21:41
The native object file format on OSX is Mach-O, not ELF, so it's not surprising that it doesn't support ELF. — Ross Ridge, Dec 18 '15 at 21:41
I kinda thought that might be it - is there a way to compile binutils to support elf on OS X? I don't want to run the code, just compile it with tcc and then disassemble it. — Nawal, Dec 18 '15 at 21:48
See if tcc has an option to produce assembly output directly. — Ross Ridge, Dec 18 '15 at 22:34
Unfortunately, TCC is quite proud of producing the object code without outputting assembly for later assembling. But I managed to compile a binutils for elf64, as shown in a comment below. — Nawal, Dec 19 '15 at 22:45

score 5 · Accepted Answer · answered Dec 19 '15 at 01:01

the available output formats, per the man page are as follows:

  -Wl,--oformat,fmt
       Use fmt as output format. The supported output formats are:

       "elf32-i386"
           ELF output format (default)

       "binary"
           Binary image (only for executable output)

       "coff"
           COFF output format (only for executable output for TMS320C67xx
           target)

So, regardless of the online claim that the x86-64 is supported, the latest version does not support x86-64 output for the object file

Thanks! I had to compile binutils specifically for it, with a target=x86_64-elf for it to work. — Nawal, Dec 19 '15 at 22:44

objdump not working on ELF 64-bit x86-64,

1 Answers1