linux-kernel - [PATCH] stackprotector: fix multi-word cross-builds

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Date:	Wed, 11 Feb 2009 12:18:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <tj@...nel.org>
Cc:	hpa@...or.com, jeremy@...p.org, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, x86@...nel.org, rusty@...tcorp.com.au
Subject: [PATCH] stackprotector: fix multi-word cross-builds


* Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Tejun Heo <tj@...nel.org> wrote:
> 
> > Ingo Molnar wrote:
> > >>> I'll try other compilers but which version are you using?  The
> > >>> difference is that before the patchset, -fno-stack-protector was
> > >>> always added whether stackprotector was enabled or not so this problem
> > >>> wasn't visible (at the cost of bogus stackprotector of course).  We'll
> > >>> probably need to add __stack_chk_guard or disable if gcc generates
> > >>> such symbol.  I'll play with different gccs.
> > >> Can't reproduce with gcc-4.1 or 4.2.  Any chance you're using distcc
> > >> w/ a build machine w/ glibc < 2.4?  __stack_chk_guard is the symbol
> > >> gcc fetches stack canary from if TLS is not supported, so somehow gcc
> > >> thought that TLS wasn't available while building head64.
> > > 
> > > yeah - i also used distcc. Maybe the nostackp makefile magic gets confused
> > > about that?
> > 
> > It seems that even with the same gcc versions, gcc built against libc
> > w/o TLS support generates __stack_chk_guard, so if you mix the two
> > flavors, the has-stack-protector check can be compiled on machines w/
> > TLS while some other files end up being built on machines w/o TLS
> > support thus circumventing the support check.  Can you please see
> > whether non-distcc build fails too?
> 
> That build succeeds:
> 
> rhea:~/tip> make -j30 bzImage ARCH=x86_64 CROSS_COMPILE='/opt/crosstool/gcc-4.2.3-glibc-2.3.6/x86_64-unknown-linux-gnu/bin/x86_64-unknown-linux-gnu-'
> /home/mingo/tip/arch/x86/Makefile:82: stack protector enabled but no compiler support
>   CHK     include/linux/version.h
> [...]
> BFD: arch/x86/boot/compressed/vmlinux.bin: warning: allocated section `.bss' not in segment
> [...]
> Root device is (8, 3)
> Setup is 11996 bytes (padded to 12288 bytes).
> System is 5690 kB
> CRC be1b2e21
> Kernel: arch/x86/boot/bzImage is ready  (#3)
> 
> Some shell variable expansion bug? If CROSS_COMPILE is not a single word
> we fail to detect the compiler borkage at arch/x86/Makefile line 82?

Yep - i'm testing the fix below now - it's looking good so far.

	Ingo

---------->
>From ebd9026d9f8499abc60d82d949bd37f88fe34a41 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@...e.hu>
Date: Wed, 11 Feb 2009 12:17:29 +0100
Subject: [PATCH] stackprotector: fix multi-word cross-builds

Stackprotector builds were failing if CROSS_COMPILER was more than
a single world (such as when distcc was used) - because the check
scripts used $1 instead of $*.

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 scripts/gcc-x86_32-has-stack-protector.sh |    2 +-
 scripts/gcc-x86_64-has-stack-protector.sh |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/gcc-x86_32-has-stack-protector.sh b/scripts/gcc-x86_32-has-stack-protector.sh
index 4fdf6ce..29493dc 100644
--- a/scripts/gcc-x86_32-has-stack-protector.sh
+++ b/scripts/gcc-x86_32-has-stack-protector.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-echo "int foo(void) { char X[200]; return 3; }" | $1 -S -xc -c -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
+echo "int foo(void) { char X[200]; return 3; }" | $* -S -xc -c -O0 -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
 if [ "$?" -eq "0" ] ; then
 	echo y
 else
diff --git a/scripts/gcc-x86_64-has-stack-protector.sh b/scripts/gcc-x86_64-has-stack-protector.sh
index 2d69fcd..afaec61 100644
--- a/scripts/gcc-x86_64-has-stack-protector.sh
+++ b/scripts/gcc-x86_64-has-stack-protector.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 
-echo "int foo(void) { char X[200]; return 3; }" | $1 -S -xc -c -O0 -mcmodel=kernel -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
+echo "int foo(void) { char X[200]; return 3; }" | $* -S -xc -c -O0 -mcmodel=kernel -fstack-protector - -o - 2> /dev/null | grep -q "%gs"
 if [ "$?" -eq "0" ] ; then
 	echo y
 else
--
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