linux-kernel - Re: [PATCH 4/6] kexec: A new system call, kexec_file

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Date:	Fri, 17 Jan 2014 14:17:14 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	ebiederm@...ssion.com, hpa@...or.com, mjg59@...f.ucam.org,
	greg@...ah.com
Subject: Re: [PATCH 4/6] kexec: A new system call, kexec_file_load, for in
 kernel kexec

On Fri, Nov 22, 2013 at 09:42:52PM +0100, Jiri Kosina wrote:

[..]
> > @@ -843,7 +1075,11 @@ static int kimage_load_normal_segment(struct kimage *image,
> >  				PAGE_SIZE - (maddr & ~PAGE_MASK));
> >  		uchunk = min(ubytes, mchunk);
> >  
> > -		result = copy_from_user(ptr, buf, uchunk);
> > +		/* For file based kexec, source pages are in kernel memory */
> > +		if (image->file_mode)
> > +			memcpy(ptr, buf, uchunk);
> 
> Very minor nit I came across when going through the patchset -- can't we 
> use some different buffer for the file-based kexec that's not marked 
> __user here? This really causes some eye-pain when looking at the code.

Hi Jiri,

Sorry, responding to your comment after a very long time.

Now I have made buf field a union as it can either be a user pointer or
a kernel pointer depending on which kexec syscall has been used. Now
caller needs to either use segment->buf or segment->kbuf based on the
context of code.

	kexec_segment {
		union {
			void __user *buf;
			void *kbuf;
		};
	}

Thanks
Vivek
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