From 2c97077e00c2fa6920f36e1481159f980b3e744a Mon Sep 17 00:00:00 2001
From: Hanno Becker <beckphan@amazon.co.uk>
Date: Thu, 21 Nov 2024 05:05:11 +0000
Subject: [PATCH] Add warning about use of LTO in verify.c

Signed-off-by: Hanno Becker <beckphan@amazon.co.uk>
---
 mlkem/verify.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/mlkem/verify.c b/mlkem/verify.c
index b6b51fddb..b66ca429f 100644
--- a/mlkem/verify.c
+++ b/mlkem/verify.c
@@ -3,6 +3,17 @@
 #include <stddef.h>
 #include <stdint.h>
 
+//
+// WARNING:
+//
+// The functions in this compilation unit may be susceptible to
+// compiler-induced variable-time code when inlined into their call-sites.
+// The purpose of having a separate compilation here is to prevent
+// such potentially insecure inlining.
+//
+// You MUST NOT compile this file using link time optimization.
+//
+
 int verify(const uint8_t *a, const uint8_t *b, const size_t len) {
   uint8_t r = 0;
   uint64_t u;