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References: <20221130023515.20217-1-palmer@rivosinc.com>
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From:   Khem Raj <raj.khem@gmail.com>
Date:   Tue, 29 Nov 2022 18:47:55 -0800
Message-ID: <CAMKF1srMj5aH4_+iwbFuu+AEgyyz85y+UPEszUGeQ7U=u19R3Q@mail.gmail.com>
Subject: Re: [PATCH 1/2] RISC-V: Align the shadow stack
To:     Palmer Dabbelt <palmer@rivosinc.com>
Cc:     jszhang@kernel.org, guoren@kernel.org,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org
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Hi Palmer

On Tue, Nov 29, 2022 at 6:36 PM Palmer Dabbelt <palmer@rivosinc.com> wrote:
>
> The standard RISC-V ABIs all require 16-byte stack alignment.  We're
> only calling that one function on the shadow stack so I doubt it'd
> result in a real issue, but might as well keep this lined up.

Is 16-byte alignment required on rv32 as well ?

>
> Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection")
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
>  arch/riscv/kernel/traps.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index be54ccea8c47..acdfcacd7e57 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -206,7 +206,7 @@ static DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
>   * shadow stack, handled_ kernel_ stack_ overflow(in kernel/entry.S) is used
>   * to get per-cpu overflow stack(get_overflow_stack).
>   */
> -long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)];
> +long shadow_stack[SHADOW_OVERFLOW_STACK_SIZE/sizeof(long)] __aligned(16);
>  asmlinkage unsigned long get_overflow_stack(void)
>  {
>         return (unsigned long)this_cpu_ptr(overflow_stack) +
> --
> 2.38.1
>
>
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