Writing x86_64 linux kernel module in assembler

发布于 2012-12-02 10:28:12

I try write simple kernel module (v3.6) in nasm, but insmod say me:

$ sudo insmod  ./hello.ko
insmod: ERROR: could not insert module ./hello.ko: Invalid module format
$ echo $?
1

I compile my code with:

$ nasm -f elf64 -o hello.m hello.asm
$ ld -m elf_x86_64 -r -o hello.ko hello.m

and my module code:

section .modinfo
    __mod_kernel_version db "kernel_version=3.6.8", 0
    __mod_license        db "license=GPL", 0
    __mod_author         db "author=actics", 0
    __mod_description    db "description=hello world module in nasm", 0


section .data
    init_mess    db "init_module", 10, 0
    cleanup_mess db "cleanup_module", 10, 0


section .text
    global init_module
    global cleanup_module

    extern printk

init_module:
    push rbp
    mov rbp, rsp

    xor rax, rax
    mov rdi, init_mess
    call printk

    xor rax, rax
    mov rsp, rbp
    pop rbp
    ret

cleanup_module:
    push rbp
    mov rbp, rsp

    xor rax, rax
    mov rdi, cleanup_mess
    call printk

    xor rax, rax
    mov rsp, rbp
    pop rbp
    ret

Please help. In internets i found 1 link with equal code for 2.4, but he doesnt work too My system - archlinux with 3.6.8 kernel

UPDATE: in nasm forum i find thread with interesting solution. It's work for me, if my module do return 0 and exit :) But if i try add "extern printk" the insmod say me next:

ERROR: could not insert module hello.ko: Invalid parameters

What i'm doing wrong? my code:

[bits 64]

global init_module
global cleanup_module

;extern printk

section .modinfo
    __mod_description8  db   'description=Simple module',0
    align 16,db 0
    __mod_author7       db   'author=That´s me',0
    __mod_license6      db   'license=GPL',0
    align 16,db 0
    __module_depends    db   'depends=',0
    align 32,db 0
    __mod_vermagic5     db   'vermagic=3.6.8-1-ARCH SMP preempt mod_unload modversions ',0   ;from a .ko module of my system

section __versions
    ____versions      db   0xdf, 0xbc, 0xbf, 0x8c, 0, 0, 0, 0, "module_layout"   ;from a .ko module of my system
    align 64,db 0

section .data
    init_mess    db "init_module", 10, 0
    cleanup_mess db "cleanup_module", 10, 0


section .text

init_module:
    xor rax, rax
    ret

cleanup_module:
    xor rax, rax
    ret

section .gnu.linkonce.this_module
    times 24 db 0
__name:         db  'Simple', 0
    times (0x168 - 24 - 7) db 0
__init_module:      dq  init_module
    times 0x2ac db 0
__cleanup_module:   dq  cleanup_module
    times 1152 db 0

this code work with: nasm -f elf64 hello.asm -o hello.o

but if i uncomment printk this no working!)

Questioner

Alexander Lavrukov

Viewed

Original

#include <linux/module.h> MODULE_AUTHOR("A. U. Thor"); MODULE_DESCRIPTION("Description"); MODULE_LICENSE("GPL"); extern int asm_init(void); int main_init(void) { return asm_init(); } module_init(main_init);

obj-m += test.o test-objs := module.o main.o $(KBUILD_EXTMOD)/main.o: main.asm nasm -f elf64 -o $@ $^ obj-m += memory_asm.o memory_asm-objs := module.o main.o $(KBUILD_EXTMOD)/main.o: $(src)/main.asm nasm -f elf64 -o $@ $^ && echo "" > $(src)/.main.o.cmd

Alexander Lavrukov 2012-12-04 09:54:25

Jester, thank you, its very good solution. In my case it's work, but with some problems. I'll try to do it good.

Alexander Lavrukov 2012-12-19 22:23:31

All works good. But we can define in module.c only include and MODULE macros. I dont use extern because in asm file i named function like init_module

Writing x86_64 linux kernel module in assembler

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