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

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Date:	Fri, 22 Nov 2013 21:42:52 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Vivek Goyal <vgoyal@...hat.com>
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 Wed, 20 Nov 2013, Vivek Goyal wrote:

> This patch implements the in kernel kexec functionality. It implements a
> new system call kexec_file_load. I think parameter list of this system
> call will change as I have not done the kernel image signature handling
> yet. I have been told that I might have to pass the detached signature
> and size as part of system call.
> 
> Previously segment list was prepared in user space. Now user space just
> passes kernel fd, initrd fd and command line and kernel will create a
> segment list internally.
> 
> This patch contains generic part of the code. Actual segment preparation
> and loading is done by arch and image specific loader. Which comes in
> next patch.
> 
> Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
[ ... snip ... ]
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index 6238927..50bcaa8 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
[ ... snip ... ]
> @@ -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.

Thanks a lot for pushing this patchset forward,

-- 
Jiri Kosina
SUSE Labs
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