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H A DMakefilebef5b54bd7bf8117c75cb943d64549134c6d9a1f Wed Jul 16 07:02:24 CDT 2008 Ralf Baechle <ralf@linux-mips.org> Fix MIPS cross-compile problem

Crosscompiling on a Fedora 9 machine running gcc 4.3.0 as its host compiler
and gcc 3.4.6 for the mips-linux target results in the following build
error:

$ make malta_defconfig
$ make
cc1: error: unrecognized command line option "-fno-stack-protector"
scripts/kconfig/conf -s arch/mips/Kconfig
cc1: error: unrecognized command line option "-fno-stack-protector"

The arch Makefile is included too late so the host compiler is feature
tested, not the crosscompiler as intended and thus the Makefile applies
adds -fno-stack-protector to crosscompiler's flags which fails for gcc
3.4.6. The bug was introduced by e06b8b98da071f7dd78fb7822991694288047df0
in 2.6.25; 35bb5b1e0e84cfa1a8906f7e6a77f391ff315791 did add more flags
testing before the arch Makefile inclusion.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
e06b8b98da071f7dd78fb7822991694288047df0 Wed Feb 13 15:43:28 CST 2008 Sam Ravnborg <sam@ravnborg.org> kbuild: allow -fstack-protector to take effect

Arjan van de Ven <arjan@infradead.org> wrote:
===
I just read the excellent LWN writeup of the vmsplice
security thing, and that got me wondering why this attack
wasn't stopped by the CONFIG_CC_STACKPROTECTOR option...
because it plain should have been...

Some analysis later.. it turns out that the following line
in the top level Makefile, added by you in October 2007,
entirely disables CONFIG_CC_STACKPROTECTOR ;(
With this line removed the exploit will be nicely stopped.

CFLAGS += $(call cc-option, -fno-stack-protector)

Now I realize that certain distros have patched gcc to
compensate for their lack of distro wide CFLAGS, and it's
great to work around that... but would there be a way to NOT
disable this for CONFIG_CC_STACKPROTECTOR please?
It would have made this exploit not possible for those kernels
that enable this feature (and that includes distros like Fedora)
===

Move the assignment to KBUILD_CFLAGS up before including
the arch specific Makefile so arch makefiles may override
the setting.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: stable@kernel.org