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SubjectRe: [RFC PATCH] kbuild: add -fno-PIE
On Fri, Oct 21, 2016 at 01:16:00PM +0200, Sebastian Andrzej Siewior wrote:
> Debian started to build the gcc with --enable-default-pie by default

To be exact: this is since gcc-6 6.2.0-7 dated Tue, 18 Oct 2016 13:53:00 +0200
on amd64 arm64 armel armhf i386 mips mipsel mips64el ppc64el s390x.

> so the kernel build ends before it starts properly with:
> |kernel/bounds.c:1:0: error: code model kernel does not support PIC mode
>
> Is this okay or do we want some kind of check to see if -fno-PIE is supported?
> It is mentioned in the 4.4.7 gcc manpage is it is not *that* new :)

A naive "git log -Sno-PIE" on gcc sources shows commit 3e7f6cce[1] from Feb
2004, and as gcc automatically supports no-XXX whenever XXX is added, it
appears the option is older than that.

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index bf6e44a421df..97296d66b586 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -398,7 +398,7 @@ KBUILD_CPPFLAGS := -D__KERNEL__
> KBUILD_CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
> -fno-strict-aliasing -fno-common \
> -Werror-implicit-function-declaration \
> - -Wno-format-security \
> + -Wno-format-security -fno-PIE \
> -std=gnu89
>
> KBUILD_AFLAGS_KERNEL :=
> --
> 2.9.3

The patch works for me. I haven't done any but most trivial testing,
though.


[1]. Using the https://gcc.gnu.org/git/gcc.git git gateway, commit hashes
may be different elsewhere.
--
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raspberries, 0.4kg sugar; put into a big jar for 1 month. Filter out and
throw away the fruits (can dump them into a cake, etc), let the drink age
at least 3-6 months.

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