linux-kernel - Re: [PATCH] arch/x86/realmode: make trampoline code conditional for x86-32

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Date:	Wed, 15 Oct 2014 08:47:11 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
CC:	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch/x86/realmode: make trampoline code conditional for
 x86-32

On 10/15/2014 08:38 AM, Jarkko Sakkinen wrote:
> Trampoline code is only needed for SMP and in x86-64 for wakeup
> code. Make it conditional in order to minimize the kernel size.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>  arch/x86/realmode/rm/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile
> index 7c0d7be..82b7312 100644
> --- a/arch/x86/realmode/rm/Makefile
> +++ b/arch/x86/realmode/rm/Makefile
> @@ -20,7 +20,11 @@ wakeup-objs	+= video-vesa.o
>  wakeup-objs	+= video-bios.o
>  
>  realmode-y			+= header.o
> +ifdef CONFIG_X86_64
>  realmode-y			+= trampoline_$(BITS).o
> +else
> +realmode-$(CONFIG_SMP)		+= trampoline_$(BITS).o
> +endif
>  realmode-y			+= stack.o
>  realmode-y			+= reboot.o
>  realmode-$(CONFIG_ACPI_SLEEP)	+= $(wakeup-objs)
> 

It is usually preferred to make this a hidden config option (e.g.
CONFIG_X86_TRAMPOLINE) rather than use ifdef, especially since your
ifdef has another conditional inside it.

	-hpa

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