linux-kernel - Re: [PATCH] ARM: mm: proc-macros: ensure *_tlb

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Date:   Wed, 29 Sep 2021 12:14:36 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Fangrui Song <maskray@...gle.com>,
        Peter Smith <Peter.Smith@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Richard Henderson <richard.henderson@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...nel.org>,
        YiFei Zhu <yifeifz2@...inois.edu>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, Nicolas Pitre <nico@...xnic.net>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Dave Martin <dave.martin@....com>
Subject: Re: [PATCH] ARM: mm: proc-macros: ensure *_tlb_fns are 4B aligned

On Wed, Sep 29, 2021 at 12:10 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> + Dave (Dave, I got a bounceback on your linaro.org email address.
> Consider sending a patch updating the .mailmap)
>
> On Wed, Sep 29, 2021 at 12:08 PM Nick Desaulniers
> <ndesaulniers@...gle.com> wrote:
> >
> > QEMU 6.1.0 is more correct about trapping on misaligned accesses. A
> > kernel built with CONFIG_THUMB2_KERNEL=y and using clang as the
> > assembler could generate non-naturally-aligned v7wbi_tlb_fns which
> > results in a boot failure. The original commit adding the macro missed
> > the .align directive on this data.
> >
> > Fixes: 66a625a88174 ("ARM: mm: proc-macros: Add generic proc/cache/tlb struct definition macros")
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1447
> > Link: https://lore.kernel.org/all/0699da7b-354f-aecc-a62f-e25693209af4@linaro.org/
> > Debugged-by: Ard Biesheuvel <ardb@...nel.org>
> > Debugged-by: Nathan Chancellor <nathan@...nel.org>
> > Debugged-by: Richard Henderson <richard.henderson@...aro.org>
> > Suggested-by: Ard Biesheuvel <ardb@...nel.org>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > ---
> >  arch/arm/Kconfig          | 1 +

d'oh, had an unintentional `-a` when I did `git commit`. Will resend a v2...

> >  arch/arm/mm/proc-macros.S | 1 +
> >  2 files changed, 2 insertions(+)
> >
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index fc196421b2ce..b760dd45b734 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -92,6 +92,7 @@ config ARM
> >         select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
> >         select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
> >         select HAVE_FUNCTION_TRACER if !XIP_KERNEL
> > +       select HAVE_FUTEX_CMPXCHG if FUTEX
> >         select HAVE_GCC_PLUGINS
> >         select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)
> >         select HAVE_IRQ_TIME_ACCOUNTING
> > diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> > index e2c743aa2eb2..d9f7dfe2a7ed 100644
> > --- a/arch/arm/mm/proc-macros.S
> > +++ b/arch/arm/mm/proc-macros.S
> > @@ -340,6 +340,7 @@ ENTRY(\name\()_cache_fns)
> >
> >  .macro define_tlb_functions name:req, flags_up:req, flags_smp
> >         .type   \name\()_tlb_fns, #object
> > +       .align 2
> >  ENTRY(\name\()_tlb_fns)
> >         .long   \name\()_flush_user_tlb_range
> >         .long   \name\()_flush_kern_tlb_range
> > --
> > 2.33.0.685.g46640cef36-goog
> >
>
>
> --
> Thanks,
> ~Nick Desaulniers



-- 
Thanks,
~Nick Desaulniers