On 12/4/25 12:04 PM, Deepak Gupta 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.
>
> Reviewed-by: Zong Li <[email protected]>
> Tested-by: Andreas Korb <[email protected]>
> Tested-by: Valentin Haudiquet <[email protected]>
> Signed-off-by: Deepak Gupta <[email protected]>
> ---
> arch/riscv/Kconfig | 22 ++++++++++++++++++++++
> arch/riscv/configs/hardening.config | 4 ++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 0c6038dc5dfd..f5574c6f66d8 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -1146,6 +1146,28 @@ config RANDOMIZE_BASE
>
> If unsure, say N.
>
> +config RISCV_USER_CFI
> + def_bool y
> + bool "riscv userspace control flow integrity"
> + depends on 64BIT && \
> + $(cc-option,-mabi=lp64 -march=rv64ima_zicfiss_zicfilp
> -fcf-protection=full)
> + depends on RISCV_ALTERNATIVE
> + select RISCV_SBI
> + 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.
CPU-assisted
> + 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.
Default is y if hardware supports it.
?
> +
> endmenu # "Kernel features"
--
~Randy
