I had been playing about with assembler after many years of missing it and decided to try and find an IDE that works with using a C/C++ project with assembler code.
Well, I found one.
Eclipse Oxygen (may work with earlier versions too)
- Create a new C project. You can do this with C++ projects too if you remember to use extern “C”.
You will get a default project file like this:
/* ============================================================================ Name : testasm.c Author : WLGfx Version : Copyright : Your copyright notice Description : Hello World in C, Ansi-style ============================================================================ */ #include#include int main(void) { puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */ return EXIT_SUCCESS; }
2. Set up NASM for 64 bit using Project->Properties->Settings->GCC Assembler
Change ‘as’ to ‘nasm’. That is only if you already have installed NASM.
3. Set NASM to build for 64 bit.
From the screenshot showing the change from ‘as’ to ‘nasm’, now click on ‘General’ just under ‘GCC Assembler’. Now in the ‘Assembler flags’ you just add ‘-f elf64’ and click ‘Apply’. That’s the assembler setup to use the intel syntax in Eclipse.
4. Create a new file called ‘test.asm’ and copy the code below into it. If you’re in the C/C++ perspective view in eclipse you have to go round the houses to create an empty file. ie. File->New->Other->General->File and finally you are there.
EDIT: Actually, if you right click on the ‘src’ folder then you can add a blank file from there.
You now have an assembler file, empty, but it’s there.
Don’t worry at this point about things getting complicated, because Eclipse still handles the build and linking of these assembler files automatically.
Copy this code into that empty file:
; random number generator to be used in crypto transmission
; of sensitive data over the internet
; WLGfx 2017-Nov-19
section .text
global _testmain:function
extern printf
srand: mov [seed],rax ; set random seed
ret
arand: mov rax,[seed] ; get seed
mov rbx,qword 0x023defca321acfed
add rax,rbx ; add 64 bit value
rol rax,19 ; rotate bits
mov rbx,qword 0xbead6789
add rax,rbx ; another add
imul rax,qword 0x1234567c ; a multiple this time
mov rbx,rax ; copy into rbx
xor rax,qword 0x5ecdab73 ; flip some bits
rol rax,48 ; rotate bits again
mov rcx,rax ; copy to rcx
and rax,0x3 ; mask and test with 0
jnz .notz ; 25% chance of other ops
mov rax,rbx
add rcx,rax
mov rbx,qword 0x87650027
imul rax,rbx
jmp .cont
.notz mov rax,rcx ; back into rax
.cont mov [seed],rax ; store into seed
and rax,0xff ; return byte value only
ret
_testmain:
mov rax,9 ; set seed
call srand
mov dword[lc],10 ; set loop counter
.loop call arand ; get random byte
push rbp ; stack frame
mov rsi,rax ; random number
mov rdi,pf_msg ; format string
xor rax,rax ; 0
call printf ; call printf
pop rbp ; stack frame
sub dword[lc],1 ; dec loop counter
jnz .loop
ret
section .data
seed dq 0,0,0,0 ; random seed value 64 bit
lc dd 10 ; loop counter
pf_msg db "Number: 0x%02x",10,0
In the above code I’ve declared and external function as you can see. Fortunately the underscore is still seen from C so the function name stays the same as you will see. I’m using the underscores as a note to myself that I am calling an assembler function. In future I will use a double underscore so that it doesn’t pollute other names withing the C/C++ libraries and headers.
5. Change your C file to this:
#include#include _testmain(); int main(void) { puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */ _testmain(); return EXIT_SUCCESS; }
6. Build and Run and you get the output (if you’re on 64 bit)
!!!Hello World!!! Number: 0xe0 Number: 0x5b Number: 0xca Number: 0x7c Number: 0xfc Number: 0x2d Number: 0x79 Number: 0xa5 Number: 0x62 Number: 0x7f
7. Enjoy because I am now…