objdump and ARM vs Thumb

assembly arm objdump binutils thumb
David Given picture David Given · Aug 25, 2011 · Viewed 11.2k times · Source

I'm trying to disassemble an object built for ARM with gcc. Unfortunately, objdump is trying to guess whether the code is ARM and Thumb, and is getting it wrong: it thinks my code is Thumb when it's actually ARM.

I see that objdump has an option to force it to interpret all instructions as Thumb (-Mforce-thumb), but it doesn't have one to force ARM mode!

This seems like a really weird omission to me, and it's seriously hampering my ability to get work done (I'm on an embedded device and my only means of debugging is to look at the disassembly). I've tried various approaches, including trying to tell objdump to use an ARM architecture that doesn't support Thumb, but nothing seems to work. Any ideas?

(And yes, I know that the instructions really are ARM...)

Answer

JaviMerino picture JaviMerino · Mar 6, 2013

arm-linux-gnueabi-objdump -marm -b binary -D does the trick for me. It doesn't preserve the symbol information though, so it's not quite what you are looking for, but it gives you the disassemble, which is a start.

Related questions

What are SP (stack) and LR in ARM?

I am reading definitions over and over again and I still not getting what are SP and LR in ARM? I understand PC (it shows next instruction's address), SP and LR probably are similar, but I just don't get what …

Read More
What registers to save in the ARM C calling convention?

It's been a while since I last coded arm assembler and I'm a little rusty on the details. If I call a C function from arm, I only have to worry about saving r0-r3 and lr, right? If the …

Read More
Why do ARM chips have an instruction with Javascript in the name (FJCVTZS)?

FJCVTZS is "Floating-point Javascript Convert to Signed fixed-point, rounding toward Zero". It is supported in Arm v8.3-A chips and later. Which is odd, because you don't expect to see JavaScript so close to the bare metal. I can find …

Read More