Converting barebones boot.s to intel syntax

[Twicetimes]

Hi,

I followed the barebones guide and got the 'hello world' OS up and running.

As an exercise, I tried changing the boot.s file to intel syntax. As far as I can see, this just involved changing

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movl $stack_top, %esp

to

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mov esp, offset dword ptr stack_top

and then recompiling it with

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i686-elf-as -msyntax=intel

This all went fine. However, when it came to linking time, I received the following error:

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(.text+0x2): undefined reference to 'esp'

which instantly made me think it was still looking for ATT-syntax mnemonics like '%esp' instead of 'esp'. I tried combinations of adding '-masm=intel' to the i686-elf-gcc call, and '-mmnemonic=intel' to the i686-elf-as call, but these made no difference.

What finally did work was adding '.intel_syntax noprefix' to the top of the boot.s file. However, I'm assuming that the command line options are meant to make it so you don't have to specify this in each .s file. The flags seem to affect the general syntax, but not the register names somehow.

Any guidance on this would be much appreciated.

[mikegonta]

What finally did work was adding '.intel_syntax noprefix' to the top of the boot.s file. However, I'm assuming that the command line
options are meant to make it so you don't have to specify this in each .s file. The flags seem to affect the general syntax, but not the
register names somehow. Any guidance on this would be much appreciated.

Silly, but that's the way it is.
By the way, this is all you need to specify an offset.

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  mov esp, OFFSET stack_top

[Twicetimes]

Fair enough. Thanks for the tip about 'offset'.