x86/traps: Clarify KCFI instruction layout

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250904034656.3670313-2-kees@kernel.org

diff --git a/arch/x86/kernel/cfi.c b/arch/x86/kernel/cfi.c
index 77086cf565ec14ea9bfbbc5b0850f3b9158b92d9..638eb5c933e00977500cbd8f61265e8613f1751c 100644 (file)
--- 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: