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From: "H. Peter Anvin" <hpa@zytor.com>
To: Toshi Kani <toshi.kani@hp.com>, dyoung@redhat.com
Cc: mjg59@srcf.ucam.org, linux-efi@vger.kernel.org,
	Greg KH <greg@kroah.com>,
	x86@kernel.org, kexec@lists.infradead.org,
	James.Bottomley@HansenPartnership.com, horms@verge.net.au,
	bp@alien8.de, ebiederm@xmission.com,
	Ingo Molnar <mingo@kernel.org>,
	vgoyal@redhat.com
Subject: Re: [patch 1/3 v2] Add function get_bootparam
Date: Mon, 11 Nov 2013 19:20:17 -0800	[thread overview]
Message-ID: <52819E71.70201@zytor.com> (raw)
In-Reply-To: <1384219658.1847.84.camel@misato.fc.hp.com>

On 11/11/2013 05:27 PM, Toshi Kani wrote:
> On Tue, 2013-11-05 at 16:29 +0800, dyoung@redhat.com wrote:
>> Not only setup_subarch will get data from debugfs file
>> boot_params/data, later code for adding efi_info will
>> also need do same thing. Thus add a common function here
>> for later use.
> 
> get_bootparam() calls find_mnt_by_fsname("debugfs"), which assumes that
> debugfs is mounted with device name "debugfs".  This function fails
> when:
>  - debugfs is not mounted, or
>  - debugfs is mounted with a different device name, such as nodev [1].
> 
> This issue is not introduced by this patch.  But the original code,
> which sets hardware_subarch, seems to work even if it failed to access
> debugfs (which is ignored) since hardware_subarch is zero most of the
> cases anyway.  With this change, however, this failure now makes the 2nd
> kernel unbootable.  So, it needs to be addressed to make this code path
> work reliably (or kexec should fail at least).
> 

Greg, Ingo,

Since there is now a legitimate user of this stuff, can we actually
export this in sysfs (or something else other than sploit^Wdebugfs)?

kexec-tools can have a fallback to debugfs if we really need it, but
making people mount debugfs to have some essential piece of
functionality scares the heck out of me.

	-hpa



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kexec mailing list
kexec@lists.infradead.org
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WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: Toshi Kani <toshi.kani-VXdhtT5mjnY@public.gmane.org>,
	dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Cc: mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org,
	linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Greg KH <greg-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>,
	x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	James.Bottomley-d9PhHud1JfjCXq6kfMZ53/egYHeGw8Jk@public.gmane.org,
	horms-/R6kz+dDXgpPR4JQBCEnsQ@public.gmane.org,
	bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org,
	ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org,
	Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org
Subject: Re: [patch 1/3 v2] Add function get_bootparam
Date: Mon, 11 Nov 2013 19:20:17 -0800	[thread overview]
Message-ID: <52819E71.70201@zytor.com> (raw)
In-Reply-To: <1384219658.1847.84.camel-RbGIw1UOYPVo/CpIj0byZw@public.gmane.org>

On 11/11/2013 05:27 PM, Toshi Kani wrote:
> On Tue, 2013-11-05 at 16:29 +0800, dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org wrote:
>> Not only setup_subarch will get data from debugfs file
>> boot_params/data, later code for adding efi_info will
>> also need do same thing. Thus add a common function here
>> for later use.
> 
> get_bootparam() calls find_mnt_by_fsname("debugfs"), which assumes that
> debugfs is mounted with device name "debugfs".  This function fails
> when:
>  - debugfs is not mounted, or
>  - debugfs is mounted with a different device name, such as nodev [1].
> 
> This issue is not introduced by this patch.  But the original code,
> which sets hardware_subarch, seems to work even if it failed to access
> debugfs (which is ignored) since hardware_subarch is zero most of the
> cases anyway.  With this change, however, this failure now makes the 2nd
> kernel unbootable.  So, it needs to be addressed to make this code path
> work reliably (or kexec should fail at least).
> 

Greg, Ingo,

Since there is now a legitimate user of this stuff, can we actually
export this in sysfs (or something else other than sploit^Wdebugfs)?

kexec-tools can have a fallback to debugfs if we really need it, but
making people mount debugfs to have some essential piece of
functionality scares the heck out of me.

	-hpa

  parent reply	other threads:[~2013-11-12  3:21 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-05  8:29 [patch 0/3 v2] kexec-tools: efi runtime support dyoung
2013-11-05  8:29 ` dyoung-H+wXaHxf7aLQT0dZR+AlfA
2013-11-05  8:29 ` [patch 1/3 v2] Add function get_bootparam dyoung
2013-11-05  8:29   ` dyoung-H+wXaHxf7aLQT0dZR+AlfA
2013-11-12  1:27   ` Toshi Kani
2013-11-12  1:27     ` Toshi Kani
2013-11-12  2:14     ` Dave Young
2013-11-12  2:14       ` Dave Young
2013-11-12  3:20     ` H. Peter Anvin [this message]
2013-11-12  3:20       ` H. Peter Anvin
2013-11-12  3:53       ` Ingo Molnar
2013-11-12  3:53         ` Ingo Molnar
     [not found]         ` <aa0ccca4-b27b-41b6-8adb-3c969eb29bf7@email.android.com>
2013-11-12 14:26           ` Vivek Goyal
2013-11-12 14:26             ` Vivek Goyal
2013-11-12  7:58       ` Greg KH
2013-11-12  7:58         ` Greg KH
2013-11-12  8:08         ` Dave Young
2013-11-12  8:08           ` Dave Young
2013-11-12  8:30           ` Greg KH
2013-11-12  8:30             ` Greg KH
2013-11-12  8:50             ` Dave Young
2013-11-12  8:50               ` Dave Young
2013-11-12  9:37             ` H. Peter Anvin
2013-11-12  9:37               ` H. Peter Anvin
2013-11-12  9:51               ` Greg KH
2013-11-12  9:51                 ` Greg KH
2013-11-13  0:50                 ` Dave Young
2013-11-13  0:50                   ` Dave Young
2013-11-18  2:22                   ` Dave Young
2013-11-18  2:22                     ` Dave Young
2013-11-18  3:29                     ` H. Peter Anvin
2013-11-18  3:29                       ` H. Peter Anvin
2013-11-18  5:29                       ` Dave Young
2013-11-18  5:29                         ` Dave Young
2013-11-18  5:36                         ` H. Peter Anvin
2013-11-18  5:36                           ` H. Peter Anvin
2013-11-05  8:29 ` [patch 2/3 v2] Add efi_info in x86 setup header dyoung
2013-11-05  8:29   ` dyoung-H+wXaHxf7aLQT0dZR+AlfA
2013-11-05  8:29 ` [patch 3/3 v2] Passing efi related data via setup_data dyoung
2013-11-05  8:29   ` dyoung-H+wXaHxf7aLQT0dZR+AlfA

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