Re: [PATCH v11 24/27] riscv: create a config for shadow stack and landing pad instr support

[Zong Li]

On Mon, Mar 10, 2025 at 11:44 PM Deepak Gupta <debug@xxxxxxxxxxxx> wrote:
>
> This patch creates a config for shadow stack support and landing pad instr
> support. Shadow stack support and landing instr support can be enabled by
> selecting `CONFIG_RISCV_USER_CFI`. Selecting `CONFIG_RISCV_USER_CFI` wires
> up path to enumerate CPU support and if cpu support exists, kernel will
> support cpu assisted user mode cfi.
>
> If CONFIG_RISCV_USER_CFI is selected, select `ARCH_USES_HIGH_VMA_FLAGS`,
> `ARCH_HAS_USER_SHADOW_STACK` and DYNAMIC_SIGFRAME for riscv.
>
> Signed-off-by: Deepak Gupta <debug@xxxxxxxxxxxx>
> ---
>  arch/riscv/Kconfig | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 7612c52e9b1e..0a2e50f056e8 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -250,6 +250,26 @@ config ARCH_HAS_BROKEN_DWARF5
>         # https://github.com/llvm/llvm-project/commit/7ffabb61a5569444b5ac9322e22e5471cc5e4a77
>         depends on LD_IS_LLD && LLD_VERSION < 180000
>
> +config RISCV_USER_CFI
> +       def_bool y
> +       bool "riscv userspace control flow integrity"
> +       depends on 64BIT && $(cc-option,-mabi=lp64 -march=rv64ima_zicfiss)
> +       depends on RISCV_ALTERNATIVE
> +       select ARCH_HAS_USER_SHADOW_STACK
> +       select ARCH_USES_HIGH_VMA_FLAGS
> +       select DYNAMIC_SIGFRAME
> +       help
> +         Provides CPU assisted control flow integrity to userspace tasks.
> +         Control flow integrity is provided by implementing shadow stack for
> +         backward edge and indirect branch tracking for forward edge in program.
> +         Shadow stack protection is a hardware feature that detects function
> +         return address corruption. This helps mitigate ROP attacks.
> +         Indirect branch tracking enforces that all indirect branches must land
> +         on a landing pad instruction else CPU will fault. This mitigates against
> +         JOP / COP attacks. Applications must be enabled to use it, and old user-
> +         space does not get protection "for free".
> +         default y
> +
>  config ARCH_MMAP_RND_BITS_MIN
>         default 18 if 64BIT
>         default 8
>
LGTM.

Reviewed-by: Zong Li <zong.li@xxxxxxxxxx>
> --
> 2.34.1
>
>
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