Re: [PATCH] i386:kexec-bzImage: Use "\0" as command line instead of empty command line

From: Wang YanQing <udknight@gmail.com>
To: Zhang Yanfei <zhangyanfei.yes@gmail.com>
Cc: jbarnes@sgi.com, tjd21@cl.cam.ac.uk, khalid.aziz@hp.com,
	kexec@lists.infradead.org, horms@verge.net.au,
	ebiederm@xmission.com, hari@in.ibm.com
Subject: Re: [PATCH] i386:kexec-bzImage: Use "\0" as command line instead of empty command line
Date: Sun, 7 Apr 2013 09:01:03 +0800	[thread overview]
Message-ID: <20130407010103.GA2176@udknight> (raw)
In-Reply-To: <515FB809.3020103@gmail.com>

On Sat, Apr 06, 2013 at 01:52:09PM +0800, Zhang Yanfei wrote:
> 于 2013年04月03日 17:43, Wang YanQing 写道:
> > I get garbage output of /proc/cmdline and in dmesg when I
> > use kexec to load new kernel bzImage without append command
> > line like below:
> > 
> > kexec -l bzImage --initrd=initramfs.
> 
> Hello Wang
> 
> I tried this:
> 
> ./build/sbin/kexec -l /boot/vmlinuz-2.6.32-279.el6.i686 --initrd=/boot/initramfs-2.6.32-279.el6.i686.img 
> 
> But nothing happened and it seemed the command loaded the kernel successfully.
> Can you describe your situation more concretely, please?
Yes, it will load the kernel successfully, but when you use kexec -e to run into
the loaded kernel, in the new kernel context, you will get garbage output when 
execute `cat /proc/cmdline`, and you also can see the garbage in "Kernel command
line" from dmesg. 

I am sure you will see this issue, because when user pass no cmdline, and cmdline_len
will because zero, so the line below in setup_linux_bootloader_parameters_high will
not work:
cmdline_ptr[cmdline_len - 1] = '\0';

Thanks

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