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

From: Palmer Dabbelt
Date: Thu Oct 28 2021 - 01:05:28 EST

On Wed, 27 Oct 2021 21:15:28 PDT (-0700), alexandre.ghiti@xxxxxxxxxxxxx wrote:
On Thu, Oct 28, 2021 at 1:06 AM Palmer Dabbelt <palmer@xxxxxxxxxxx> wrote:

On Tue, 26 Oct 2021 21:58:42 PDT (-0700), alexandre.ghiti@xxxxxxxxxxxxx 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@xxxxxxxxxx>
> Signed-off-by: Alexandre Ghiti <alexandre.ghiti@xxxxxxxxxxxxx>
> ---
> 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.

Not sure if I'm missing something, but it's still not booting for me. I've put what I'm testing on palmer/to-test, it's these two on top of fixes and merged into Linus' tree

* 6d7d351902ff - (HEAD -> to-test, palmer/to-test) Merge remote-tracking branch 'palmer/fixes' into to-test (7 minutes ago) <Palmer Dabbelt>
|\
| * 782551edf8f8 - (palmer/fixes) riscv: Fix CONFIG_KASAN_STACK build (6 hours ago) <Alexandre Ghiti>
| * 47383e5b3c4f - riscv: Fix asan-stack clang build (6 hours ago) <Alexandre Ghiti>
| * 64a19591a293 - (riscv/fixes) riscv: fix misalgned trap vector base address (9 hours ago) <Chen Lu>
* | 1fc596a56b33 - (palmer/master, linus/master, linus/HEAD, master) Merge tag 'trace-v5.15-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace (11 hours ago) <Linus Torvalds>

Am I missing something else?


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),