linux-kernel - Re: [PATCH 2/3] x86, boot: Don't compile aslr.c when !CONFIG_RANDOMIZE

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Message-ID: <CAGXu5jJgoWk89Oh_RjQN7Kn7AZJt_g37O+X_K=7V+asW=8wsUg@mail.gmail.com>
Date:	Mon, 10 Mar 2014 13:45:37 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Josh Triplett <josh@...htriplett.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
	Jan Beulich <JBeulich@...e.com>,
	Kyungsik Lee <kyungsik.lee@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Wei Yongjun <yongjun_wei@...ndmicro.com.cn>,
	LKML <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 2/3] x86, boot: Don't compile aslr.c when !CONFIG_RANDOMIZE_BASE

On Mon, Mar 10, 2014 at 1:32 PM, Josh Triplett <josh@...htriplett.org> wrote:
> All the code in aslr.c gets compiled out if !CONFIG_RANDOMIZE_BASE, but
> aslr.o itself still gets compiled in.  Eliminate it from the compile
> entirely in that case.
>
> This does not change the generated code at all, in either case.
>
> Signed-off-by: Josh Triplett <josh@...htriplett.org>

Good clean-up! This makes things quite a bit more readable. Thanks!

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
>  arch/x86/boot/compressed/Makefile | 4 +++-
>  arch/x86/boot/compressed/aslr.c   | 3 ---
>  2 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index 7c50279..42e738d 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -28,7 +28,9 @@ HOST_EXTRACFLAGS += -I$(srctree)/tools/include
>
>  vmlinux-objs-y := $(obj)/vmlinux.lds $(obj)/head_$(BITS).o $(obj)/misc.o \
>         $(obj)/string.o $(obj)/cmdline.o $(obj)/early_serial_console.o \
> -       $(obj)/piggy.o $(obj)/cpuflags.o $(obj)/aslr.o
> +       $(obj)/piggy.o $(obj)/cpuflags.o
> +
> +vmlinux-objs-$(CONFIG_RANDOMIZE_BASE) += $(obj)/aslr.o
>
>  $(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone
>
> diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c
> index 4dbf967..d0f8923 100644
> --- a/arch/x86/boot/compressed/aslr.c
> +++ b/arch/x86/boot/compressed/aslr.c
> @@ -1,6 +1,5 @@
>  #include "misc.h"
>
> -#ifdef CONFIG_RANDOMIZE_BASE
>  #include <asm/msr.h>
>  #include <asm/archrandom.h>
>  #include <asm/e820.h>
> @@ -313,5 +312,3 @@ unsigned char *choose_kernel_location(unsigned char *input,
>  out:
>         return (unsigned char *)choice;
>  }
> -
> -#endif /* CONFIG_RANDOMIZE_BASE */
> --
> 1.9.0
>



-- 
Kees Cook
Chrome OS Security
--
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