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Old 02-23-2009, 03:02 PM   #1
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How add assebly in linux kernel module program?


I am writing a linux kernel module program on Fedora core 6 and I am wondering if anyone could tell me how to add an assembly code shown below in my program. The assembly code was written for Windows and I have no idea how to convert to Linux kernel program.

#ifdef _MSC_VER

Unsigned char lookKbits(char k)
_asm {
mov dl, k
mov cl, 16
sub cl, dl
mov eax, [wordval]
shr eax, cl

Unsigned char WORD_hi_lo(char byte_high, char byte_low)
_asm {
mov ah,byte_high
mov al,byte_low

Last edited by aminoamide; 02-23-2009 at 03:05 PM. Reason: Title was not good
Old 02-24-2009, 04:56 AM   #2
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See C compiler documentation - because assembly format within C code differs on GCC/MSVC.
However you shouldn't use assembly in kernel modules - this makes modules non-portable (to other compilers and/or architectures). I recommend to use C instead, (because modern compiler can do better job optimizing code).
Old 02-24-2009, 08:13 AM   #3
Suresh Maniyath
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It is not recommended to use assembly coding. But to answer your question, GCC follows the standard as below.

__asm__ __volatile__ (assembler template
: output operands
: input operands
: list of clobbered registers

Suresh Maniyath
Old 02-24-2009, 10:39 AM   #4
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Moved: This thread is more suitable in Linux-Kernel and has been moved accordingly to help your thread/question get the exposure it deserves.


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