Re: [PATCH v2 3/9] x86/cfi: Document the "cfi=" bootparam options

Nathan Chancellor
2025-09-05T02:17:24Z

On Wed, Sep 03, 2025 at 08:46:42PM -0700, Kees Cook wrote:
> The kernel-parameters.txt didn't have a section for the cfi= options.
> Add it.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
> Documentation/admin-guide/kernel-parameters.txt | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 747a55abf494..8bbffbb334ab 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -608,6 +608,23 @@
> ccw_timeout_log [S390]
> See Documentation/arch/s390/common_io.rst for details.
>
> + cfi= [X86-64] Set Control Flow Integrity checking features
> + when CONFIG_FINEIBT is enabled.
> + Format: feature[,feature...]
> + Default: auto
> +
> + auto: Use FineIBT if IBT available, otherwise kCFI.
> + Under FineIBT, enable "paranoid" mode when
> + FRED is not available.
> + off: Turn off CFI checking.
> + kcfi: Use kCFI (disable FineIBT).
> + fineibt: Use FineIBT (even if IBT not available).
> + norand: Do not re-randomize CFI hashes.
> + paranoid: Add caller hash checking under FineIBT.
> + bhi: Enable register poisoning to stop speculation
> + across FineIBT. (Disabled by default.)
> + warn: Do not enforce CFI checking: warn only.
> +
> cgroup_disable= [KNL] Disable a particular controller or optional feature
> Format: {name of the controller(s) or feature(s) to disable}
> The effects of cgroup_disable=foo are:
> --
> 2.34.1
>