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Date: Wed, 28 Jan 2015 22:10:59 +0000 (UTC)
From: Scot Doyle <lkml14@scotdoyle.com>
To: Vivek Goyal <vgoyal@redhat.com>
cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
        lkml <linux-kernel@vger.kernel.org>,
        "linux-man@vger.kernel.org" <linux-man@vger.kernel.org>,
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        Andy Lutomirski <luto@amacapital.net>, Dave Young <dyoung@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Borislav Petkov <bp@alien8.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Andi Kleen <andi@firstfloor.org>
Subject: Re: Edited kexec_load(2) [kexec_file_load()] man page for review
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On Wed, 28 Jan 2015, Vivek Goyal wrote:
> On Wed, Jan 28, 2015 at 09:14:03PM +0000, Scot Doyle wrote:
> > On Wed, 28 Jan 2015, Vivek Goyal wrote:
> > > On Wed, Jan 28, 2015 at 04:49:34PM +0100, Michael Kerrisk (man-pages) wrote:
> > > > Hello Vivek,
> > > > 
> > > > >> I've made various adjustments to the page in the light of your comments
> > > > >> above. Thanks!
> > > > >
> > > > > Thank you for following it up and improving kexec man page.
> > > > 
> > > > You're welcome. So, by now, I've made quite a lot of changes
> > > > (including adding a number of cases under ERRORS). I think the revised
> > > > kexec_load/kexec_file_load page is pretty much ready to go, but would
> > > > you be willing to give the text below a check over first?
> > > > 
> > > 
> > > Hi Michael,
> > > 
> > > I had a quick look and it looks good to me.
> > > 
> > > Thanks
> > > Vivek
> > 
> > When I tested, kexec_file_load required CONFIG_RELOCATABLE. Is the same 
> > true for kexec_load? Would it make sense to note this in the man pages 
> > along with the need for CONFIG_KEXEC_FILE, etc? Or as an error message?
> 
> Hmm.., I can't see an explicity dependency between RELOCATABLE and
> KEXEC. Both KEXEC and KEXEC_FILE should be able to load a kernel
> even if it had RELOCATABLE=n.
> 
> Just that kernel will run from the address it has been built for.
> 
> Thanks
> Vivek

Confusing, right? kexec_file_load returns -ENOEXEC and dmesg says 
"kexec-bzImage64: XLF_CAN_BE_LOADED_ABOVE_4G is not set." which leads to
arch/x86/boot/header.S line 396:

#if defined(CONFIG_RELOCATABLE) && defined(CONFIG_X86_64)  
   /* kernel/boot_param/ramdisk could be loaded above 4g */
# define XLF1 XLF_CAN_BE_LOADED_ABOVE_4G
#else
# define XLF1 0
#endif