linux-kernel - Re: [RFC PATCH 00/13][V3] kexec: A new system call to allow in kernel loading

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Date:	Fri, 6 Jun 2014 15:37:48 +0800
From:	Dave Young <dyoung@...hat.com>
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, bp@...en8.de, jkosina@...e.cz, chaowang@...hat.com,
	bhe@...hat.com, akpm@...ux-foundation.org
Subject: Re: [RFC PATCH 00/13][V3] kexec: A new system call to allow in
 kernel loading

On 06/05/14 at 11:01am, Vivek Goyal wrote:
> On Thu, Jun 05, 2014 at 04:31:34PM +0800, Dave Young wrote:
> 
> [..]
> > > +	ret = kexec_file_load(kernel_fd, info.initrd_fd, info.command_line,
> > > +			info.command_line_len, info.kexec_flags);
> > 
> > Vivek,
> > 
> > I tried your patch on my uefi test machine, but kexec load fails like below:
> > 
> > [root@...alhost ~]# kexec -l /boot/vmlinuz-3.15.0-rc8+ --use-kexec2-syscall
> > Could not find a free area of memory of 0xa000 bytes ...
> 
> Hi Dave,
> 
> I think this message is coming from kexec-tools from old loading path. I
> think somehow new path did not even kick in. I tried above and I got
> -EBADF as I did not pass initrd. Can you run gdb on kexec and see if
> you are getting to syscall or run strace.

Seems I can not reproduce the local hole fail issue but I'm sure it happens
before the new syscall callback.

This time I got -ENOEXEC. It's caused by CONFIG_EFI_MIXED=y. In case EFI_MIXED
64bit kernel runs on 32bit efi firmware thus XLF_CAN_BE_LOADED_ABOVE_4G is not
set thus bzImage probe will fail with NOEXEC.

> 
> > 
> > Another issue is that the syscall should allow load kernel only without initrd
> 
> Agreed. Currently my code is not handling it. I am thinking of ways how to
> make passing initrd fd optional.
> 
> > 
> > and
> > cmdline since kernel can mount root and embed cmdline in itself.
> 
> Passing command line is already optional. I tried it and kexec loaded
> successfully.
> 
> Thanks
> Vivek
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