Date: Mon, 4 Dec 2006 00:45:03 -0800
From: Andrew Morton <akpm@osdl.org>
To: Daniel Drake <dsd@gentoo.org>
Cc: sam@ravnborg.org, linux-kernel@vger.kernel.org, miraze@web.de
Subject: Re: [PATCH] kbuild: Write astest files to $(KBUILD_EXTMOD)
 directory
Message-Id: <20061204004503.11c1d6df.akpm@osdl.org>
In-Reply-To: <20061202194544.D9F057B40A0@zog.reactivated.net>
References: <20061202194544.D9F057B40A0@zog.reactivated.net>
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On Sat,  2 Dec 2006 19:45:44 +0000 (GMT)
Daniel Drake <dsd@gentoo.org> wrote:

> The astest code in 2.6.19 causes problems for Gentoo and other distributions
> building external kernel modules in sandboxes. kbuild has generally been
> pretty good at not violating the sandbox for quite a while, I hope we can
> keep it that way.
> 
> Right now it writes to a temporary astest file in the current directory
> (i.e. /usr/src/linux), this is because it is found that writing to /dev/null
> is not safe because as deletes its output file on failure.
> 
> To clarify what a sandbox is: Gentoo's package system compiles the package
> in /var/tmp/portage and while that package is building it restricts writes
> to parts of the filesystem outside of /var/tmp/portage and /tmp. If the
> external module tries to write to another location on the real filesystem such
> as /usr/src/linux, the build is aborted due to sandbox violation.
> 
> This patch prefixes the astest file path with the KBUILD_EXTMOD path if
> an external kernel module is being built. The behaviour in other situations
> is unmodified.
> 
> Signed-off-by: Daniel Drake <dsd@gentoo.org>
> 
> Index: linux-2.6.19/scripts/Kbuild.include
> ===================================================================
> --- linux-2.6.19.orig/scripts/Kbuild.include
> +++ linux-2.6.19/scripts/Kbuild.include
> @@ -66,9 +66,11 @@ as-option = $(shell if $(CC) $(CFLAGS) $
>  # as-instr
>  # Usage: cflags-y += $(call as-instr, instr, option1, option2)
>  
> -as-instr = $(shell if echo -e "$(1)" | $(AS) >/dev/null 2>&1 -W -Z -o astest$$$$.out ; \
> +as-instr = $(shell if echo -e "$(1)" | $(AS) >/dev/null 2>&1 -W -Z -o \
> +		   $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)astest$$$$.out ; \
>  		   then echo "$(2)"; else echo "$(3)"; fi; \
> -	           rm -f astest$$$$.out)
> +	           rm -f \
> +		   $(if $(KBUILD_EXTMOD),$(firstword $(KBUILD_EXTMOD))/)astest$$$$.out)
>  
>  # cc-option
>  # Usage: cflags-y += $(call cc-option, -march=winchip-c6, -march=i586)

What's the relationship between this patch and the fixes in this area in -mm?


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