[PATCH v2 2/9] x86/traps: Clarify KCFI instruction layout

Kees Cook
2025-09-04T03:46:57Z

Just a nit-picky change to the KCFI indirect call check instruction
documentation. The addl offset isn't always -4 (it depends on patchable
function entry configuration).

Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: Peter Zijlstra <peterz@infradead.org>
---
arch/x86/kernel/cfi.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cfi.c b/arch/x86/kernel/cfi.c
index 77086cf565ec..638eb5c933e0 100644
--- a/arch/x86/kernel/cfi.c
+++ b/arch/x86/kernel/cfi.c
@@ -27,7 +27,7 @@ static bool decode_cfi_insn(struct pt_regs *regs, unsigned long *target,
* for indirect call checks:
*
*   movl -<id>, %r10d ; 6 bytes
- * addl -4(%reg), %r10d ; 4 bytes
+ * addl -<pos>(%reg), %r10d; 4 bytes
* je .Ltmp1 ; 2 bytes
* ud2 ; <- regs->ip
* .Ltmp1:
--
2.34.1