linux-kernel - Re: [patch 2.6.19-rc6] Stop gcc 4.1.0 optimizing wait_hpet

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1164769705.2825.4.camel@entropy>
Date:	Tue, 28 Nov 2006 19:08:25 -0800
From:	Nicholas Miell <nmiell@...cast.net>
To:	Keith Owens <kaos@....com.au>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [patch 2.6.19-rc6] Stop gcc 4.1.0 optimizing wait_hpet_tick
	away

On Wed, 2006-11-29 at 13:22 +1100, Keith Owens wrote:
> Compiling 2.6.19-rc6 with gcc version 4.1.0 (SUSE Linux),
> wait_hpet_tick is optimized away to a never ending loop and the kernel
> hangs on boot in timer setup.
> 
> 0000001a <wait_hpet_tick>:
>   1a:   55                      push   %ebp
>   1b:   89 e5                   mov    %esp,%ebp
>   1d:   eb fe                   jmp    1d <wait_hpet_tick+0x3>
> 
> This is not a problem with gcc 3.3.5.  Adding barrier() calls to
> wait_hpet_tick does not help, making the variables volatile does.
> 
> Signed-off-by: Keith Owens <kaos@....com.au>
> 
> ---
>  arch/i386/kernel/time_hpet.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6/arch/i386/kernel/time_hpet.c
> ===================================================================
> --- linux-2.6.orig/arch/i386/kernel/time_hpet.c
> +++ linux-2.6/arch/i386/kernel/time_hpet.c
> @@ -51,7 +51,7 @@ static void hpet_writel(unsigned long d,
>   */
>  static void __devinit wait_hpet_tick(void)
>  {
> -	unsigned int start_cmp_val, end_cmp_val;
> +	unsigned volatile int start_cmp_val, end_cmp_val;
>  
>  	start_cmp_val = hpet_readl(HPET_T0_CMP);
>  	do {

When you examine the inlined functions involved, this looks an awful lot
like http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22278

Perhaps SUSE should fix their gcc instead of working around compiler
problems in the kernel?

-- 
Nicholas Miell <nmiell@...cast.net>

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/