linux-kernel - Re: [PATCH] lkdtm: Fix targets for objcopy usage

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Date:	Fri, 29 Jul 2016 10:37:58 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Kees Cook <keescook@...omium.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lkdtm: Fix targets for objcopy usage

Hi,

On Thu, Jul 28, 2016 at 07:30:39PM -0700, Kees Cook wrote:
> The targets for lkdtm's objcopy were missing which caused them to always
> be rebuilt. This corrects the problem.
> 
> Additionally, commit f8fa70f392fa ("arm64: localise Image objcopy flags")
> has landed now, so this removes the work-around for the global OBJCOPY
> flag setting.
> 
> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Kees Cook <keescook@...omium.org>

With this applied, LKDTM builds fine for me on arm64, the redundant
rebuilds are gone, and the result appears to work. So FWIW:

Tested-by: Mark Rutland <mark.rutland@....com>

Thanks,
Mark.

> ---
>  drivers/misc/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 4387ccb79e64..132f4e3462ba 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -65,9 +65,9 @@ lkdtm-$(CONFIG_LKDTM)		+= lkdtm_perms.o
>  lkdtm-$(CONFIG_LKDTM)		+= lkdtm_rodata_objcopy.o
>  lkdtm-$(CONFIG_LKDTM)		+= lkdtm_usercopy.o
>  
> -OBJCOPYFLAGS :=
>  OBJCOPYFLAGS_lkdtm_rodata_objcopy.o := \
>  			--set-section-flags .text=alloc,readonly \
>  			--rename-section .text=.rodata
> -$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o
> +targets += lkdtm_rodata.o lkdtm_rodata_objcopy.o
> +$(obj)/lkdtm_rodata_objcopy.o: $(obj)/lkdtm_rodata.o FORCE
>  	$(call if_changed,objcopy)
> -- 
> 2.7.4
> 
> 
> -- 
> Kees Cook
> Brillo & Chrome OS Security
>