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Date: Mon, 14 Jan 2013 15:10:25 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Borislav Petkov <bp@alien8.de>, Yinghai Lu <yinghai@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jan Kiszka <jan.kiszka@web.de>,
        Jason Wessel <jason.wessel@windriver.com>,
        linux-kernel@vger.kernel.org, Rob Landley <rob@landley.net>,
        Matt Fleming <matt.fleming@intel.com>,
        Gokul Caushik <caushik1@gmail.com>,
        Josh Triplett <josh@joshtriplett.org>,
        Joe Millenbach <jmillenbach@gmail.com>
Subject: Re: [PATCH v7u1 22/31] x86, boot: add fields to support load bzImage
 and ramdisk above 4G
References: <1357260531-11115-1-git-send-email-yinghai@kernel.org> <1357260531-11115-23-git-send-email-yinghai@kernel.org> <20130113214132.GB17200@liondog.tnic>
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On 01/13/2013 01:41 PM, Borislav Petkov wrote:
>> diff --git a/arch/x86/boot/compressed/cmdline.c b/arch/x86/boot/compressed/cmdline.c
>> index b4c913c..bffd73b 100644
>> --- a/arch/x86/boot/compressed/cmdline.c
>> +++ b/arch/x86/boot/compressed/cmdline.c
>> @@ -17,6 +17,8 @@ static unsigned long get_cmd_line_ptr(void)
>>  {
>>  	unsigned long cmd_line_ptr = real_mode->hdr.cmd_line_ptr;
>>  
>> +	cmd_line_ptr |= (u64)real_mode->ext_cmd_line_ptr << 32;
>> +
>>  	return cmd_line_ptr;
>>  }
> 
> On 32-bit, this unsigned long cmd_line_ptr is 4 bytes and the OR doesn't
> have any effect on the final result. You probably want to do:
> 
> #ifdef CONFIG_64BIT
> 	cmd_line_ptr |= (u64)real_mode->ext_cmd_line_ptr << 32;
> #endif
> 
> right?
> 

Actually, on 32 bits the compiler will simply drop the statement on the
floor, no #ifdef required.  If gcc outputs a warning we should do
something about it, otherwise we can just plain ignore it.

	-hpa