linux-kernel - Re: [PATCH -fixes v2 4/4] riscv: Fix config KASAN && DEBUG

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Message-ID: <CANp29Y7M=wSLBE8m0-CHKtYPkqgcxNiUPEyRNv-VHeR5O2BTYQ@mail.gmail.com>
Date:   Tue, 22 Feb 2022 11:28:33 +0100
From:   Aleksandr Nogikh <nogikh@...gle.com>
To:     Alexandre Ghiti <alexandre.ghiti@...onical.com>
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Nick Hu <nickhu@...estech.com>,
        linux-riscv@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>
Subject: Re: [PATCH -fixes v2 4/4] riscv: Fix config KASAN && DEBUG_VIRTUAL

Hi Alexandre,

Thanks for the series!

However, I still haven't managed to boot the kernel. What I did:
1) Checked out the riscv/fixes branch (this is the one we're using on
syzbot). The latest commit was
6df2a016c0c8a3d0933ef33dd192ea6606b115e3.
2) Applied all 4 patches.
3) Used the config from the cover letter:
https://gist.github.com/a-nogikh/279c85c2d24f47efcc3e865c08844138
4) Built with `make -j32 ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu-`
5) Ran with `qemu-system-riscv64 -m 2048 -smp 1 -nographic -no-reboot
-device virtio-rng-pci -machine virt -device
virtio-net-pci,netdev=net0 -netdev
user,id=net0,restrict=on,hostfwd=tcp:127.0.0.1:12529-:22 -device
virtio-blk-device,drive=hd0 -drive
file=~/kernel-image/riscv64,if=none,format=raw,id=hd0 -snapshot
-kernel ~/linux-riscv/arch/riscv/boot/Image -append "root=/dev/vda
console=ttyS0 earlyprintk=serial"` (this is similar to how syzkaller
runs qemu).

Can you please hint at what I'm doing differently?

A simple config with KASAN, KASAN_OUTLINE and DEBUG_VIRTUAL now indeed
leads to a booting kernel, which was not the case before.
make defconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu-
./scripts/config -e KASAN -e KASAN_OUTLINE -e DEBUG_VIRTUAL
make olddefconfig ARCH=riscv CROSS_COMPILE=riscv64-linux-gnu-

--
Best Regards,
Aleksandr

On Mon, Feb 21, 2022 at 5:17 PM Alexandre Ghiti
<alexandre.ghiti@...onical.com> wrote:
>
> __virt_to_phys function is called very early in the boot process (ie
> kasan_early_init) so it should not be instrumented by KASAN otherwise it
> bugs.
>
> Fix this by declaring phys_addr.c as non-kasan instrumentable.
>
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@...onical.com>
> ---
>  arch/riscv/mm/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index 7ebaef10ea1b..ac7a25298a04 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -24,6 +24,9 @@ obj-$(CONFIG_KASAN)   += kasan_init.o
>  ifdef CONFIG_KASAN
>  KASAN_SANITIZE_kasan_init.o := n
>  KASAN_SANITIZE_init.o := n
> +ifdef CONFIG_DEBUG_VIRTUAL
> +KASAN_SANITIZE_physaddr.o := n
> +endif
>  endif
>
>  obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
> --
> 2.32.0
>