Date: Tue, 4 Jun 2019 17:40:06 +0200 From: Jan Martin Mikkelsen <janm@transactionware.com> To: Warner Losh <imp@bsdimp.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: UEFI boot1 vs. GPT bootme/bootonce flags Message-ID: <74732E11-5735-46CB-AA54-2B49F30CB10A@transactionware.com> In-Reply-To: <CANCZdfoVdDjR8D_ju1i7%2BAKA9Va0rWwqo-H3KX=Mu4%2BMQY%2B_4g@mail.gmail.com> References: <33262C24-8B1E-4C3D-9E3F-549BD8B9F26D@transactionware.com> <CANCZdfoVdDjR8D_ju1i7%2BAKA9Va0rWwqo-H3KX=Mu4%2BMQY%2B_4g@mail.gmail.com>
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> On 4 Jun 2019, at 16:10, Warner Losh <imp@bsdimp.com> wrote: >=20 >=20 > On Tue, Jun 4, 2019 at 1:06 AM Jan Martin Mikkelsen = <janm@transactionware.com <mailto:janm@transactionware.com>> wrote: > Hi, >=20 > The UEFI boot1 loader does not support the GPT = bootme/bootonce/bootfailed flags for selecting which partition to boot. >=20 > Is there a reason for this? >=20 > Yes. There's three. >=20 > First, UEFI provides no way to get to these flags via their block = interfaces. Second, the block interfaces are independent, so there was = no easy way to know w/o jumping through a bunch of hoops. Third, the = UEFI Boot Manager Protocol was championed as being the one-true way to = select a boot partition. It's significantly more flexible and reliable = than rewriting the partition table from time to time. >=20 > However, there's significant drawbacks to the UEFI scheme. Vendors = suck at not mucking up the UEFI Boot Manager Protocol (I'm looking at = you SuperMicro). And the trend in embedded where UEFI has a foothold has = been to move away from writable variables at all... Finally, the UEFI = Boot Protocol assumes a host + media. There's no media-agnostic way to = produce an image with multiple partitions that you ping-pong between = (say a recovery USB stick that moves from system to system). >=20 > So against my better judgement, I've been working on making = gptboot.efi. It's not as terrible as I thought it would be, but it shows = another issue: loader.efi and boot1.efi process all the partitions they = find, but gptboot just does one disk's worth and stops when it = successfully boots something: this has required a restructuring of the = boot1 code that I started with to rearrange the loops used to find = things. An no, the gptboot.efi will not support ZFS, which has its own = way to do this outside of UEFI Boot Manager Protocol. >=20 > If you don't want to wait, there's now a mechanism for loading loader = environment variables from a file called \efi\freebsd\loader.env in the = ESP that can accomplish much the same thing. OK. I am looking at similar situations: Supermicro servers and various = flavours of embedded systems. For some of the newer embedded systems = UEFI is the necessary approach. I am not at all interested in writable = variables in firmware. I=E2=80=99m also not interested in booting from = ZFS. My question was because I have been reading the efi/boot1 source code = and deciding what to do to duplicate the bootme/bootonce functionality. = That there were lots of hoops to jump through was clear. However, I was = coming to the conclusion that boot1.efi needed to duplicate the = functionality of gptboot, and was getting ready to implement. How far have you gone with your gptboot.efi? What=E2=80=99s missing? Regards, Jan M.
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