freebsd stable - Apr 2018 - gptboot broken when compiled with clang 6 and WITHOUT_LOADER_GELI -- clang 5 is OK

I have set up a new system disk for an i386 11.2-PRERELEASE box. I did the
usual

gpart create -s gpt $disk
gpart add -t freebsd-boot -s 984 $disk
gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 $disk
...

thing, just to notice that the box wouldn't boot. It seems to hang where
stage 2 should be run -- when the '\' should start spinning the screen
turns white and the box hangs (tested on two machines, an Asus P5W and a
Supermicro A2SAV).

So I replaced gptboot on the new disk by the one from an older machine
and everything was fine. I wanted to find out what is actually causing
the issue and recompiled /usr/src/stand after updating the old sources
in several steps.

Eventually it turned out that it depends on the compiler. When compiling
the latest /usr/src/stand with clang 5.0.1 the resulting gptboot works.
When using 6.0.0 it doesn't. To be exact, it's gptboot.o which is
causing
the problems. When using a gptboot.o from a clang 5 system it is OK, when
using a gptboot.o from a clang 6 system it fails. 

To add more confusion: I usually have WITHOUT_LOADER_GELI in my make.conf.
When removing this, the resulting gptboot works even when compiled with
clang 6...

I can reproduce this in case s.o. wants me to do some tests...

[This email is either empty or too large to be displayed at this time]

Andre, You're not alone.? I think there's a problem with clang6 on i386
FreeBSD 11.1X, refer:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=227552
https://forums.freebsd.org/threads/uptime-w-i386-breakage.65584/
and perhaps also on amd64, search for
https://bugs.freebsd.org/bugzilla/buglist.cgi?quicksearch=clang&list_id=226390.

Without time to investigate I've reverted userland
FreeBSD 11.2-PRERELEASE? r332843M??? amd64 1101515 1101509
FreeBSD 11.2-PRERELEASE? r332843M??? i386 1101515 1101509

Apologies for my earlier email, I'd missed setting content-type:
text/plain instead of text/html (the latter strips content to the
mailing list), too many management memo's! ;)

On 25 Apr 2018, at 18:58, Andre Albsmeier <Andre.Albsmeier at siemens.com>
wrote:
> 
> I have set up a new system disk for an i386 11.2-PRERELEASE box. I did the
> usual
> 
> gpart create -s gpt $disk
> gpart add -t freebsd-boot -s 984 $disk
> gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 $disk
> ...
> 
> thing, just to notice that the box wouldn't boot. It seems to hang
where
> stage 2 should be run -- when the '\' should start spinning the
screen
> turns white and the box hangs (tested on two machines, an Asus P5W and a
> Supermicro A2SAV).
> 
> So I replaced gptboot on the new disk by the one from an older machine
> and everything was fine. I wanted to find out what is actually causing
> the issue and recompiled /usr/src/stand after updating the old sources
> in several steps.
> 
> Eventually it turned out that it depends on the compiler. When compiling
> the latest /usr/src/stand with clang 5.0.1 the resulting gptboot works.
> When using 6.0.0 it doesn't. To be exact, it's gptboot.o which is
causing
> the problems. When using a gptboot.o from a clang 5 system it is OK, when
> using a gptboot.o from a clang 6 system it fails.
> 
> To add more confusion: I usually have WITHOUT_LOADER_GELI in my make.conf.
> When removing this, the resulting gptboot works even when compiled with
> clang 6...
> 
> I can reproduce this in case s.o. wants me to do some tests...
I can't reproduce it on my end, unfortunately.  I downloaded the latest
FreeBSD-11.2-PRERELEASE-i386-20180420-r332802 snapshot, installed it to
a GPT partitioned disk, and it boots just fine.

This snapshot corresponds to r332802, which has clang 6.0.0, with the
EFLAGS change still reverted, so I assume its copy of gptboot is also
compiled with that.

Which exact revision of the base system were you using?

-Dimitry

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