How to generate a nasm compilable assembly code from c source code on Linux?

问题

Test platform is 32 bit Linux.

Basically, I know gcc can be used to generate both Intel and At&T style assembly code, but it seems that you can not directly use nasm/tasm to compile the Intel style assembly code gcc generated.

I am conducting a project analysis asm code on both windows and Linux platform, so I am thinking if they can be both compiled by platform independent assembler like nasm\yasm, I could have a much easier time...

So my question is how to generate a nasm compilable assembly code from c source code on Linux?

回答1:

I find it's a better approach to disassemble the object files rather than use assembly code generated by gcc.

First, generate an object file from your source code:
```
gcc -fno-asynchronous-unwind-tables -O2 -s -c -o main.o main.c
```
-fno-asynchronous-unwind-tables: do not generate unnecessary sections like .eh_frame

-O2 optimizes so the asm isn't horrible. Optionally use -Os (size over speed) or -O3 (full optimization including auto-vectorization). Also you can tune for a CPU and and use extensions it supports with -march=native or -march=haswell or -march=znver1 (Zen)

-s: make smaller executable (strip)

-c -o main.o: compile but don't link, generate an object file called main.o
Use objconv to generate nasm code:
```
objconv -fnasm main.o
```
The result will be stored in main.asm.
The result will be very close to Nasm syntax. However you might need to make some minor tweaks to eliminiate warnings/errors. Simply try to compile it with Nasm
```
nasm -f elf32 main.asm
```
and fix the errors/warnings by hand. For example:
- remove the align=N and execute/noexecute words from .SECTION lines.
- remove the text : function from global declarations
- remove the default rel line
- remove empty sections if you wish etc
Link the resulting main.o which generated by Nasm in step 3 using gcc:
```
gcc main.o
```
You can also link it using ld but it's much harder.

回答2:

If you're lazy: https://github.com/diogovk/c2nasm

There I have a script that does Babken Vardanyan's suggestion automatically.

回答3:

Heres a way to do it without objconv

ndisasm -u <(objdump -j .text -d main.o | cut -d: -f2 | cut -d$'\t' -f 2 | perl -ne 'next if /file/; s/\s+//g; print' | xxd -r -p)

来源：https://stackoverflow.com/questions/20737947/how-to-generate-a-nasm-compilable-assembly-code-from-c-source-code-on-linux

标签

assembly

nasm

gas

tasm

yasm