CODEWITHSUNDEEP
assemblyarmcross-compilingqemueabi
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Reputation: 21

How to write and compile THUMB assembly programs on x86 architecture with qemu?

I am trying to write THUMB assembly code and I want to run it on Linux (x86). I can write ARM assembly and it works fine, but when compiling with the -mthumb option, nothing works. I can't find any tutorial online, so any resources would be great.

Here is the assembly code I am using :

.text

.globl _start
_start:
add r0, r0, $0

Here are the compilation options I am using :

arm-linux-gnueabihf-as -march=armv7-m -mcpu=cortex-m0 -mthumb -o main.o main.s
arm-linux-gnueabihf-ld -o main main.o

Here is how I try to run the binary :

LD_LIBRARY_PATH=/lib/arm-linux-gnueabihf qemu-arm main

Though, I did try to specify the CPU here as well (and also tried all sorts of combinations). I get the following error message :

qemu: uncaught target signal 4 (Illegal instruction) - core dumped
Illegal instruction

Finally, using gdb-multiarch, all instructions are indeed shown as invalid (but I am unsure how to actually use gdb-multiarch, just followed a guide online).

I am obviously doing something wrong (whether it is the format of instructions or along with the compilation), I hope someone can clarify what is wrong and maybe give some online resources. Note that I don't have any issue with ARM/THUMB per se, I have been studying it for a bit, but never tried to write any code.

Upvotes: 1

Views: 351

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