realmode _WAKEUP

Paul Bolle pebolle at
Wed Jan 7 13:57:26 EST 2015

On Wed, 2015-01-07 at 23:59 +0600, Alexander Kuleshov wrote:
> Yes i saw video-*.c files, but i can't understand how compilation of
> these video-*.c files depends on _WAKEUP macro...
> For example if'd remove -D_WAKEUP, i get errors during realmode.elf linking:
> arch/x86/realmode/rm/video-vga.o: In function `vga_probe':
> /home/alex/dev/linux/arch/x86/realmode/rm/../../boot/video-vga.c:259:
> undefined reference to `boot_params'
> As you wrote there are many #ifndef/#endif directives, but why there
> _WAKEUP is undefined everytime, but we pass it from command line with

Because these file also get compiled via arch/x86/boot/Makefile? Ie, I
_guess_ _WAKEUP is needed to ensure the compile started from
arch/x86/realmode/rm/Makefile differs from the compile started from
arch/x86/boot/Makefile. But [...]/boot/Makefile is sufficiently
complicated for me to stop me from looking at it too long!

You do realize that the Linux kernel is a treasure trove for people
wanting to know just how far make, gcc, etc can be pushed, don't you?

Paul Bolle

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