Building objdump on osx to allow disassembling arm64 objects

Question

I'm trying to disassemble openSSL that I've built for iOS targeting arm64 architecture with objdump (from GNU binutil) giving it following options:

./objdump openssl -f (file headers), -t (symbol table), and -h (section headers)

but getting following error:

BFD: bfd_mach_o_scan: unknown architecture 0x100000c/0x0
objdump: ./openssl: File format not recognized
TARGET: 
BFD: bfd_mach_o_scan: unknown architecture 0x100000c/0x0

The objdump -v 2.21.1 that I've built with following options:

./configure CC="gcc -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk -arch i386" CXX="g++ -arch i386" -disable-werror -enable-install-libiberty -enable-targets=arm-eabi

was working fine with all arm 32-bit architectures but failed to disassemble arm64.

Does anyone know how to build objdump to allow calling:

./objdump openssl -f (file headers), -t (symbol table), and -h (section headers)

for binary that was build targeting arm64?

Thanks in advance

Jason Molenda · Accepted Answer · 2014-11-26 00:44:53Z

1

The objdump you're using doesn't know about the arm64 arch. 0x100000c/0x0 is the cputype (CPU_TYPE_ARM64) and cpusubtype CPU_SUBTYPE_ARM64_ALL.

Why use objdump? The otool(1) program works well and is included in the Xcode developer tools / command line tools package. The command line options are a little different but one look at the man page will make it clear how to use it.

answered Nov 26, 2014 at 0:44

Jason Molenda

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3 Comments

marcin Over a year ago

Thanks for your answer but unfortunately I need to go with objdump. Do you know how to build it to recognize arm64 architecture? or do you know where I can get pre-build version of objdump that can do it?

Jason Molenda Over a year ago

Sorry, I don't know anything about the status of binutils or its releases. I don't know if objdump includes a disassembler -- that would be the most complicated part to add if you were supporting a new ISA like arm64 / AArch64. If objdump can't disassemble things, then adding arm64 support is very simple and I'd recommend looking for a newer version of it. But if it were me, I'd just find a way to use otool to do what you need - they're very similar in what they do.

marcin Over a year ago

Thanks for your answer. Would you happen to know how to translate objdump options: -f (file headers), -t (symbol table), and -h (section headers) to equivalent otool options?

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