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

Kees Cook kees at kernel.org
Wed Sep 3 20:46:42 PDT 2025


The kernel-parameters.txt didn't have a section for the cfi= options.
Add it.

Signed-off-by: Kees Cook <kees at kernel.org>
---
Cc: Jonathan Corbet <corbet at lwn.net>
Cc: "Paul E. McKenney" <paulmck at kernel.org>
Cc: Randy Dunlap <rdunlap at infradead.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: <linux-doc at vger.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




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