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From: Frans Pop <elendil@planet.nl>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org,
	linux-kbuild@vger.kernel.org, barryn@pobox.com,
	bugme-daemon@bugzilla.kernel.org
Subject: [PATCH,v2] Only add '-fwrapv' to gcc CFLAGS for gcc 4.2 and later
Date: Fri, 10 Jul 2009 22:05:47 +0200	[thread overview]
Message-ID: <200907102205.49642.elendil@planet.nl> (raw)
In-Reply-To: <200907100928.07369.elendil@planet.nl>

On Friday 10 July 2009, Frans Pop wrote:
> The discussion on issue looks to have died, but it has bitten Debian
> stable ("Lenny") [1] as it causes init to die on s390 after a kernel
> update.
>
> Here's a possible patch. The exact gcc version to check for is still a
> bit open I guess. For the s390 issue I've confirmed that 4.2.4 is OK,
> but for safety and because of Andrew's comment above I've set the test
> for 4.3 in the patch.

Here's an updated patch as I found the gcc version check was incorrect 
(0430 should have been 0403; sorry).

I've now changed the check to allow -fwrapv for gcc 4.2 as that has been 
shown to work and because of the consideration mentioned in my previous 
mail.

---
From: Frans Pop <elendil@planet.nl>
Subject: Only add '-fwrapv' to gcc CFLAGS for gcc 4.2 and later

This flag has been shown to cause init to segfault for kernels
compiled with gcc-4.1. gcc version 4.2.4 has been shown to be OK.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=13012.

Reported-by: Barry K. Nathan <barryn@pobox.com>
Signed-off-by: Frans Pop <elendil@planet.nl>

diff --git a/Makefile b/Makefile
index 0aeec59..2519fde 100644
--- a/Makefile
+++ b/Makefile
@@ -565,7 +565,8 @@ KBUILD_CFLAGS += $(call 
cc-option,-Wdeclaration-after-statement,)
 KBUILD_CFLAGS += $(call cc-option,-Wno-pointer-sign,)
 
 # disable invalid "can't wrap" optimizations for signed / pointers
-KBUILD_CFLAGS	+= $(call cc-option,-fwrapv)
+KBUILD_CFLAGS  += $(shell if [ $(call cc-version) -ge 0402 ]; then \
+		    echo $(call cc-option,-fwrapv); fi ;)
 
 # revert to pre-gcc-4.4 behaviour of .eh_frame
 KBUILD_CFLAGS	+= $(call cc-option,-fno-dwarf2-cfi-asm)

  parent reply	other threads:[~2009-07-10 20:05 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-10  7:28 [Bug 13012] 2.6.28.9 causes init to segfault on Debian etch; 2.6.28.8 OK Frans Pop
2009-07-10 14:59 ` Frans Pop
2009-07-12 17:58   ` Linus Torvalds
2009-07-12 17:58     ` Linus Torvalds
2009-07-12 18:24     ` Linus Torvalds
2009-07-13  5:29     ` Ian Lance Taylor
2009-07-25  3:23       ` Dave Jones
2009-07-25 16:49         ` Linus Torvalds
2009-07-10 20:05 ` Frans Pop [this message]
2009-07-17 22:18   ` [PATCH,v2] Only add '-fwrapv' to gcc CFLAGS for gcc 4.2 and later Sam Ravnborg
2009-07-17 22:43     ` Frans Pop
2009-07-18  6:59       ` Sam Ravnborg
2009-07-23 12:46         ` Frans Pop
2009-07-23 14:27           ` Sam Ravnborg

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