[PATCH -next v19 06/24] riscv: Disable Vector Instructions for kernel itself

[Palmer Dabbelt]

On Tue, 09 May 2023 03:30:15 PDT (-0700), andy.chiu at sifive.com wrote:
> From: Guo Ren <guoren at linux.alibaba.com>
>
> Disable vector instructions execution for kernel mode at its entrances.
> This helps find illegal uses of vector in the kernel space, which is
> similar to the fpu.
>
> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> Co-developed-by: Vincent Chen <vincent.chen at sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> Co-developed-by: Han-Kuan Chen <hankuan.chen at sifive.com>
> Signed-off-by: Han-Kuan Chen <hankuan.chen at sifive.com>
> Co-developed-by: Greentime Hu <greentime.hu at sifive.com>
> Signed-off-by: Greentime Hu <greentime.hu at sifive.com>
> Signed-off-by: Vineet Gupta <vineetg at rivosinc.com>
> Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
> Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
> Reviewed-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
> Tested-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
> ---
> Changelog V19:
>  - Add description in commit msg (Heiko's suggestion on v17)
>
>  arch/riscv/kernel/entry.S |  6 +++---
>  arch/riscv/kernel/head.S  | 12 ++++++------
>  2 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 3fbb100bc9e4..e9ae284a55c1 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -48,10 +48,10 @@ _save_context:
>  	 * Disable user-mode memory access as it should only be set in the
>  	 * actual user copy routines.
>  	 *
> -	 * Disable the FPU to detect illegal usage of floating point in kernel
> -	 * space.
> +	 * Disable the FPU/Vector to detect illegal usage of floating point
> +	 * or vector in kernel space.
>  	 */
> -	li t0, SR_SUM | SR_FS
> +	li t0, SR_SUM | SR_FS_VS
>
>  	REG_L s0, TASK_TI_USER_SP(tp)
>  	csrrc s1, CSR_STATUS, t0
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 3fd6a4bd9c3e..e16bb2185d55 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -140,10 +140,10 @@ secondary_start_sbi:
>  	.option pop
>
>  	/*
> -	 * Disable FPU to detect illegal usage of
> -	 * floating point in kernel space
> +	 * Disable FPU & VECTOR to detect illegal usage of
> +	 * floating point or vector in kernel space
>  	 */
> -	li t0, SR_FS
> +	li t0, SR_FS_VS
>  	csrc CSR_STATUS, t0
>
>  	/* Set trap vector to spin forever to help debug */
> @@ -234,10 +234,10 @@ pmp_done:
>  .option pop
>
>  	/*
> -	 * Disable FPU to detect illegal usage of
> -	 * floating point in kernel space
> +	 * Disable FPU & VECTOR to detect illegal usage of
> +	 * floating point or vector in kernel space
>  	 */
> -	li t0, SR_FS
> +	li t0, SR_FS_VS
>  	csrc CSR_STATUS, t0
>
>  #ifdef CONFIG_RISCV_BOOT_SPINWAIT

Reviewed-by: Palmer Dabbelt <palmer at rivosinc.com>