[patch 1/3 v2] Add function get_bootparam

[Dave Young]

On 11/11/13 at 06:27pm, 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 [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).

Toshi, Thanks for your suggestion, it make sense. Will fix it.

> 
> [1]
> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_MRG/2/html/Realtime_Tuning_Guide/sect-Realtime_Tuning_Guide-Realtime_Specific_Tuning-Mount_debugfs.html
> 
> Thanks,
> Toshi
>