linux-kernel - Re: [PATCH 1/2] riscv: Fix asan-stack clang build

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Date:   Thu, 28 Oct 2021 06:15:28 +0200
From:   Alexandre Ghiti <alexandre.ghiti@...onical.com>
To:     Palmer Dabbelt <palmer@...belt.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>, aou@...s.berkeley.edu,
        ryabinin.a.a@...il.com, glider@...gle.com, andreyknvl@...il.com,
        dvyukov@...gle.com, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        nathan@...nel.org
Subject: Re: [PATCH 1/2] riscv: Fix asan-stack clang build

On Thu, Oct 28, 2021 at 1:06 AM Palmer Dabbelt <palmer@...belt.com> wrote:
>
> On Tue, 26 Oct 2021 21:58:42 PDT (-0700), alexandre.ghiti@...onical.com wrote:
> > Nathan reported that because KASAN_SHADOW_OFFSET was not defined in
> > Kconfig, it prevents asan-stack from getting disabled with clang even
> > when CONFIG_KASAN_STACK is disabled: fix this by defining the
> > corresponding config.
> >
> > Reported-by: Nathan Chancellor <nathan@...nel.org>
> > Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
> > ---
> >  arch/riscv/Kconfig             | 6 ++++++
> >  arch/riscv/include/asm/kasan.h | 3 +--
> >  arch/riscv/mm/kasan_init.c     | 3 +++
> >  3 files changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index c1abbc876e5b..79250b1ed54e 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -162,6 +162,12 @@ config PAGE_OFFSET
> >       default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
> >       default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
> >
> > +config KASAN_SHADOW_OFFSET
> > +     hex
> > +     depends on KASAN_GENERIC
> > +     default 0xdfffffc800000000 if 64BIT
> > +     default 0xffffffff if 32BIT
>
> I thought I posted this somewhere, but this is exactly what my first
> guess was.  The problem is that it's hanging on boot for me.  I don't
> really have anything exotic going on, it's just a defconfig with
> CONFIG_KASAN=y running in QEMU.
>
> Does this boot for you?

Yes with the 2nd patch of this series which fixes the issue
encountered here. And that's true I copied/pasted this part of your
patch which was better than what I had initially done, sorry I should
have mentioned you did that, please add a Codeveloped-by or something
like that.

Thanks,

Alex

>
> > +
> >  config ARCH_FLATMEM_ENABLE
> >       def_bool !NUMA
> >
> > diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
> > index a2b3d9cdbc86..b00f503ec124 100644
> > --- a/arch/riscv/include/asm/kasan.h
> > +++ b/arch/riscv/include/asm/kasan.h
> > @@ -30,8 +30,7 @@
> >  #define KASAN_SHADOW_SIZE    (UL(1) << ((CONFIG_VA_BITS - 1) - KASAN_SHADOW_SCALE_SHIFT))
> >  #define KASAN_SHADOW_START   KERN_VIRT_START
> >  #define KASAN_SHADOW_END     (KASAN_SHADOW_START + KASAN_SHADOW_SIZE)
> > -#define KASAN_SHADOW_OFFSET  (KASAN_SHADOW_END - (1ULL << \
> > -                                     (64 - KASAN_SHADOW_SCALE_SHIFT)))
> > +#define KASAN_SHADOW_OFFSET  _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
> >
> >  void kasan_init(void);
> >  asmlinkage void kasan_early_init(void);
> > diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> > index d7189c8714a9..8175e98b9073 100644
> > --- a/arch/riscv/mm/kasan_init.c
> > +++ b/arch/riscv/mm/kasan_init.c
> > @@ -17,6 +17,9 @@ asmlinkage void __init kasan_early_init(void)
> >       uintptr_t i;
> >       pgd_t *pgd = early_pg_dir + pgd_index(KASAN_SHADOW_START);
> >
> > +     BUILD_BUG_ON(KASAN_SHADOW_OFFSET !=
> > +             KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
> > +
> >       for (i = 0; i < PTRS_PER_PTE; ++i)
> >               set_pte(kasan_early_shadow_pte + i,
> >                       mk_pte(virt_to_page(kasan_early_shadow_page),