From: Rusty Russell <rusty@rustcorp.com.au>
To: Andi Kleen <ak@muc.de>
Cc: torvalds@transmeta.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix RELOC_HIDE miscompilation
Date: Mon, 02 Sep 2002 12:11:28 +1000 [thread overview]
Message-ID: <20020901215535.24D4C2C182@lists.samba.org> (raw)
In-Reply-To: Your message of "Sun, 01 Sep 2002 11:42:42 +0200." <20020901114242.21242@colin.muc.de>
In message <20020901114242.21242@colin.muc.de> you write:
>
> [resend due to mailer problems]
>
> RELOC_HIDE got miscompiled on gcc3.1/x86-64 in the access to softirq.c's per
> cpu variables. This patch fixes the problem.
>
> Clearly to hide the relocation the addition needs to be done after the
> value obfuscation, not before.
>
> I don't know if it triggers on other architectures (x86-64 is especially
> stressf here because it has negative kernel addresses), but seems like the
> right thing to do.
Yes, agreed. Linus, please apply.
--- linux/include/linux/compiler.h-o Sun Apr 14 21:18:44 2002
+++ linux/include/linux/compiler.h Sun Sep 1 02:52:31 2002
@@ -16,7 +16,7 @@
/* This macro obfuscates arithmetic on a variable address so that gcc
shouldn't recognize the original var, and make assumptions about it */
#define RELOC_HIDE(ptr, off) \
- ({ __typeof__(ptr) __ptr; \
- __asm__ ("" : "=g"(__ptr) : "0"((void *)(ptr) + (off))); \
- __ptr; })
+ ({ unsigned long __ptr; \
+ __asm__ ("" : "=g"(__ptr) : "0"(ptr)); \
+ (typeof(ptr)) (__ptr + (off)); })
#endif /* __LINUX_COMPILER_H */
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
prev parent reply other threads:[~2002-09-02 2:50 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-01 9:42 Andi Kleen
2002-09-02 2:11 ` Rusty Russell [this message]
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