[PATCH] ARM: Fix userspace enter on LPAE with CC_OPTIMIZE_FOR_SIZE=y

[Russell King (Oracle)]

On Wed, May 15, 2024 at 12:46:38PM -0700, Florian Fainelli wrote:
> On 5/15/24 07:02, Geert Uytterhoeven wrote:
> > Booting an LPAE-enabled kernel built with CONFIG_CC_OPTIMIZE_FOR_SIZE=y
> > fails when starting userspace:
> > 
> >      Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
> >      CPU: 1 PID: 1 Comm: init Tainted: G        W        N 6.9.0-rc1-koelsch-00004-g7af5b901e847 #1930
> >      Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
> >      Call trace:
> >       unwind_backtrace from show_stack+0x10/0x14
> >       show_stack from dump_stack_lvl+0x78/0xa8
> >       dump_stack_lvl from panic+0x118/0x398
> >       panic from do_exit+0x1ec/0x938
> >       do_exit from sys_exit_group+0x0/0x10
> >      ---[ end Kernel panic - not syncing: Attempted to kill init!  exitcode=0x00000004 ]---
> > 
> > Add the missing memory clobber to cpu_set_ttbcr(), as suggested by
> > Russell King.
> > 
> > Force inlining of uaccess_save_and_enable(), as suggested by Ard
> > Biesheuvel.
> > 
> > The latter fixes booting on Koelsch.
> > 
> > Fixes: 7af5b901e84743c6 ("ARM: 9358/2: Implement PAN for LPAE by TTBR0 page table walks disablement")
> > Closes: https://lore.kernel.org/r/CAMuHMdWTAJcZ9BReWNhpmsgkOzQxLNb5OhNYxzxv6D5TSh2fwQ@mail.gmail.com/
> > Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> 
> Tested-by: Florian Fainelli <florian.fainelli at broadcom.com>

This should be in linux-next now, if not by tomorrow - it was pushed
out yesterday.

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