svn commit: r296428 - head/sys/boot/common

[Dimitry Andric]

On 06 Mar 2016, at 20:57, Nikolai Lifanov <lifanov at mail.lifanov.com> wrote:
> 
> On 2016-03-06 11:17, Dimitry Andric wrote:
>> On 06 Mar 2016, at 17:00, Oliver Pinter <oliver.pinter at hardenedbsd.org> wrote:
>>> On 3/6/16, Dimitry Andric <dim at freebsd.org> wrote:
>>>> Author: dim
>>>> Date: Sun Mar  6 15:57:43 2016
>>>> New Revision: 296428
>>>> URL: https://svnweb.freebsd.org/changeset/base/296428
>>>> Log:
>>>> Since kernel modules can now contain sections of type SHT_AMD64_UNWIND,
>>>> the boot loader should not skip over these anymore while loading images.
>>>> Otherwise the kernel can still panic when it doesn't find the .eh_frame
>>>> section belonging to the .rela.eh_frame section.
>>>> Unfortunately this will require installing boot loaders from sys/boot
>>>> before attempting to boot with a new kernel.
>>> Could you please add a note about this to UPDATING file?
>> I am a bit torn on this, because normally we always tell people to
>> install the kernel first, reboot, then run make installworld (which also
>> installs the boot loaders).
>> However, in this case, people might depend on their boot loader loading
>> modules which are required to make the system boot at all.  So if they
>> happened to forget updating their boot loader first, a panic might be
>> the result.
>> I wonder what a failsafe and acceptable upgrade scenario is, in this
>> case.  Normally the procedure is something like:
>>  make buildworld
>>  make buildkernel (with KERNCONF=whatever, if needed)
>>  make installkernel (again with KERNCONF, if needed)
>>  reboot (to single user, but cheating is possible usually)
>>  mergemaster -p
>>  make installworld
>> This could maybe be modified to:
>>  make buildworld
>>  make buildkernel (with KERNCONF=whatever, if needed)
>>  make installkernel (again with KERNCONF, if needed)
>>  make -C sys/boot install
>>  reboot (to single user, but cheating is possible usually)
>>  mergemaster -p
>>  make installworld
>> E.g. insert the step which installs the boot loaders just after (or
>> before) the step which installs the kernel.
>> Is something like this acceptable as a one-time workaround, or maybe it
>> is better in general, in case we ever add other new features to the boot
>> loaders?
>> -Dimitry
> 
> In my opinion, boot *blocks* (boot1) should be updated seldomly and not on every install.
> All (?) instances of not updating these resulting in a failed boot have an UPDATING
> entry or a similar warning (like the one during "zpool upgrade").

Well, each time you run make installworld, almost all the files in /boot
(except for configuration) get reinstalled.  For e.g. mbr, boot1 and
such, this has no consequences at all, until you install them into some
partition using gpart, but changes to loader, loader.efi or zfsloader
*will* affect the next startup.

Per a suggestion from Kostik, maybe it would be nice to have a separate
"make installboot" target, which installs just the components in /boot.
This could then be used before or after "make installkernel".

-Dimitry

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