[patch 1/3 v2] Add function get_bootparam
mingo at kernel.org
Mon Nov 11 22:53:44 EST 2013
* H. Peter Anvin <hpa at zytor.com> wrote:
> On 11/11/2013 05:27 PM, Toshi Kani wrote:
> > On Tue, 2013-11-05 at 16:29 +0800, dyoung at 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 .
> > 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.
No principial objections from me: anything that actually turns out to
prove itself in debugfs and ends up mattering for real ought to move to
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