Re: [ANNOUNCE] 5.10.162-rt78

["Luis Claudio R. Goncalves" <lgoncalv@redhat.com>]

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On Thu, Jan 19, 2023 at 12:38:25PM +0100, Pavel Machek wrote:
> Hi!
> 
> > > I'm pleased to announce the 5.10.162-rt78 stable release.
> > > 
> > > You can get this release via the git tree at:
> > > 
> > >   git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git
> > > 
> > >   branch: v5.10-rt
> > >   Head SHA1: 143ef105f40a65f3ddd57121d4b4bc36eb10cc06
> > > 
> > > Or to build 5.10.162-rt78 directly, the following patches should be applied:
> 
> > I see that vanilla 5.10.162-rt78 fails to build with arm64 defconfig. [0] Full log [1]
> > Any pointers on what maybe wrong?
> 
> We see the same failure. 
> 
> >   AS      arch/arm64/kernel/entry.o
> > arch/arm64/kernel/entry.S: Assembler messages:
> > arch/arm64/kernel/entry.S:763: Error: immediate out of range at operand 3 -- `and x2,x19,#((1<<1)|(1<<0)|(1<<2)|(1<<3)|(1<<4)|(1<<5)|(1<<6)|(1<<13)|(1<<7))'
> > make[2]: *** [scripts/Makefile.build:367: arch/arm64/kernel/entry.o] Error 1
> > make[1]: *** [scripts/Makefile.build:503: arch/arm64/kernel] Error 2
> > make: *** [Makefile:1837: arch/arm64] Error 2
> 
> The line is:
> 
> >        and     x2, x19, #_TIF_WORK_MASK

I believe this is related to the arch/arm64/include/asm/thread_info.h
changes in 5.10.162-rt78, specifically:

    79a9991e87fe arm64: add support for TIF_NOTIFY_SIGNAL
    1ba44dcf789d Merge tag 'v5.10.162' into v5.10-rt

The first one is the original change, coming from stable v5.10.162 and the
second one has the merge conflict I fixed in that file due to the existence
of TIF_NEED_RESCHED_LAZY in PREEMPT_RT.

It escaped me that having TIF_NEED_RESCHED_LAZY set to 13 breaks the AND
statement reported above. Looking at

    b5a5a01d8e9a arm64: uaccess: remove addr_limit_user_check()

specially this note

    To ensure that _TIF_WORK_MASK can be used as an immediate value in an
    AND instruction (as it is in `ret_to_user`), TIF_MTE_ASYNC_FAULT is
    renumbered to keep the constituent bits of _TIF_WORK_MASK contiguous.

I understand that I need to either have to renumber TIF_NEED_RESCHED_LAZY
to 8, with the risk of breaking something else, or backport commit
b5a5a01d8e9a in order to remove TIF_FSCHECK and then safely renumber
TIF_NEED_RESCHED_LAZY.

Guidance is welcome here :)

Best regards,
Luis

> And I believe there were some cleanups in stable in that area. Let me
> search for them.
> 
> Best regards,
> 								Pavel
> -- 
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany


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