Re: git: 8a62a2a5659d - main - zfs: merge openzfs/zfs@f8e5af53e

On Sat, Mar 21, 2026 at 9:23 AM Shawn Webb <shawn.webb@hardenedbsd.org>
wrote:

> On Sat, Mar 21, 2026 at 09:18:20AM -0600, Warner Losh wrote:
> > On Sat, Mar 21, 2026, 9:08 AM Shawn Webb <shawn.webb@hardenedbsd.org>
> wrote:
> >
> > > On Sat, Mar 21, 2026 at 09:04:17AM +0100, A FreeBSD User wrote:
> > > > Am Tage des Herren Fri, 20 Mar 2026 23:27:20 -0400
> > > > Charlie Li <vishwin@freebsd.org> schrieb:
> > > >
> > > > > Shawn Webb wrote:
> > > > > > On Tue, Mar 17, 2026 at 04:52:16PM +0000, Shawn Webb wrote:
> > > > > >> On Tue, Mar 17, 2026 at 10:44:59AM -0600, Warner Losh wrote:
> > > > > >>> On Tue, Mar 17, 2026 at 10:36 AM Shawn Webb <
> > > shawn.webb@hardenedbsd.org>
> > > > > >>> wrote:
> > > > > >>>
> > > > > >>>> Hey Martin,
> > > > > >>>>
> > > > > >>>> On Sat, Mar 14, 2026 at 01:26:23PM +0000, Martin Matuska
> wrote:
> > > > > >>>>> The branch main has been updated by mm:
> > > > > >>>>>
> > > > > >>>>> URL:
> > > > > >>>>
> > >
> https://cgit.FreeBSD.org/src/commit/?id=8a62a2a5659d1839d8799b4274c04469d7f17c78
> > >
> > > > > >>>>>
> > > > > >>>>> commit 8a62a2a5659d1839d8799b4274c04469d7f17c78
> > > > > >>>>> Merge: f91464171d61 f8e5af53e92f
> > > > > >>>>> Author:     Martin Matuska <mm@FreeBSD.org>
> > > > > >>>>> AuthorDate: 2026-03-14 12:14:56 +0000
> > > > > >>>>> Commit:     Martin Matuska <mm@FreeBSD.org>
> > > > > >>>>> CommitDate: 2026-03-14 12:14:56 +0000
> > > > > >>>>>
> > > > > >>>>> [snip for brevity]
> > > > > >>>>>
> > > > > >>>>>      Obtained from:  OpenZFS
> > > > > >>>>>      OpenZFS commit: f8e5af53e92fa7c03393fbd4922cb9c1d0c15920
> > > > > >>>>
> > > > > >>>> This commit seems to cause issues when building boot loader
> > > related
> > > > > >>>> code:
> > > > > >>>>
> > > > > >>>> ==== BEGIN LOG ====
> > > > > >>>> 114232 bytes available
> > > > > >>>> btxld -v -f aout -e 0x200000 -o loader_simp -l
> > > > > >>>> /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btxldr/btxldr  -b
> > > > > >>>> /usr/obj/usr/src/amd64.amd64/stand/i386/btx/btx/btx
> > > loader_simp.bin
> > > > > >>>> kernel: ver=1.02 size=690 load=9000 entry=9010 map=16M
> pgctl=0:58
> > > > > >>>> client: fmt=elf size=5e2e8 text=57930 data=514c bss=7470
> entry=0
> > > > > >>>> output: fmt=aout size=61000 text=1000 data=5f000 org=200000
> > > entry=200000
> > > > > >>>> ===> stand/i386/pxeldr (all)
> > > > > >>>> -560 bytes available
> > > > > >>>> *** Error code 1
> > > > > >>>>
> > > > > >>>
> > > > > >>> What all do you have enabled? The defaults aren't even close to
> > > running out
> > > > > >>> of space (though I've not looked at this).
> > > > > >>
> > > > > >> Hey Warner,
> > > > > >>
> > > > > >> Thanks for reaching out! I've uploaded `make showconfig` here:
> > > > > >> https://hardenedbsd.org/~shawn/2026-03-17_srcconf-r01.txt
> > > > > >>
> > > > > >> The following options are specific to HardenedBSD (in no
> particular
> > > > > >> order):
> > > > > >>
> > > > > >> 1. MK_HBSD_UPDATE
> > > > > >> 2. MK_HBSDCONTROL
> > > > > >> 3. MK_PIE
> > > > > >> 4. MK_RELRO
> > > > > >> 5. MK_SHLIBRANDOM
> > > > > >> 6. MK_ZERO_REGS
> > > > > >> 7. MK_SPECTREV1_FIX
> > > > > >> 8. MK_SAFESTACK
> > > > > >> 9. MK_RETPOLINE
> > > > > >> 10. MK_LTOLIB
> > > > > >> 11. MK_CFI
> > > > > >
> > > > > > MK_RETPOLINE was the culprit. Something about this ZFS commit
> causes
> > > > > > LLVM to emit more retpoline entries than before--too many for a
> > > little
> > > > > > bootloader. That might be something to investigate later, but
> only to
> > > > > > satisfy a curious mind, not to actuall fix anything (since
> nothing's
> > > > > > actually broken.)
> > > > > >
> > > > > > Since it doesn't really make sense to apply speculative execution
> > > > > > mitigations to a bootloader, I disabled retpoline for a
> components
> > > > > > in stand/.
> > > > > >
> > > > > > Good to go.
> > > > > >
> > > > > Also just got bit by this, albeit during the lua loader, since I
> have
> > > > > WITH_RETPOLINE in my src.conf.
> > > > >
> > > >
> > > > Hello,
> > > >
> > > > I do not have WITH_RETPOLINE in my /etc/src.conf, but since I got
> this
> > > mysterious error about
> > > > not enough bytes left, I use WITHOUT_LOADER_PXEBOOT= YES (due to
> issues
> > > with WITH_BEARSSL=YES
> > > > also used).
> > > > Despite not using any WITH_RETPOLINE I also catch the error ...
> > >
> > > Something about this ZFS commit causes the boot laoder to be too big.
> > > I guess the first sign of trouble was with retpolines, but there seem
> > > to now be additional signs.
> > >
> > > What's the process for filing a bug report against OpenzFS for
> > > something like this? (Not asking you directly, just a general question
> > > for the thread.)
> > >
> >
> > That's a good question. We are rapidly aporoaching the day we will have
> to
> > freeze the set of zfs feature that we can boot with the BIOS path.
> There's
> > only so much space.
> >
> > Right now,  there's little to no bootloader testing, let alone analysis
> > done and that will need to change.
>
> Another question might also be: is it worth the time and effort? Are
> people really using a ZFS-enabled traditional MBR BIOS bootloader on
> FreeBSD 16-CURRENT (or eventual 16.0-RELEASE)? From my rather naive
> (and ignorant, since I don't know FreeBSD's userbase well), it seems
> like folks use either loader.efi or u-boot (or both!)
>

Nobody uses MBR BIOS bootloader. It's totally unsupported. They all use the
GPT one, which is used for all kinds of things, most recently several
light-weight
VM systems that don't have UEFI. BIOS is what imposes the limit, not MBR.

But there's a huge number of systems that are already in the field that need
to be upgradeable, but we will eventually need to draw a line in the sand
for
that.


> Not a question I can answer, of course, because everyone likely has a
> different take on what "worth the time and effort" means to them. :-)
>

Yea, the BIOS path is stubbornly hanging around.

Warner


> Thanks,
>
> --
> Shawn Webb
> Cofounder / Security Engineer
> HardenedBSD
>
> Signal Username:  shawn_webb.74
> Tor-ified Signal: +1 303-901-1600 / shawn_webb_opsec.50
>
> https://git.hardenedbsd.org/hardenedbsd/pubkeys/-/raw/master/Shawn_Webb/03A4CBEBB82EA5A67D9F3853FF2E67A277F8E1FA.pub.asc
>