From fc500368485bd2ebafea6a37da30f49c8be75aac Mon Sep 17 00:00:00 2001
From: Raoul Strackx <raoul.strackx@fortanix.com>
Date: Mon, 21 Oct 2019 15:10:32 +0200
Subject: fixed ac vulnerability

---
 src/libstd/sys/sgx/abi/entry.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'src/libstd')

diff --git a/src/libstd/sys/sgx/abi/entry.S b/src/libstd/sys/sgx/abi/entry.S
index c35e49b1dc6..4f8673a1907 100644
--- a/src/libstd/sys/sgx/abi/entry.S
+++ b/src/libstd/sys/sgx/abi/entry.S
@@ -121,6 +121,16 @@ sgx_entry:
     fnstcw %gs:tcsls_user_fcw
 /*  reset user state */
     cld /* x86-64 ABI requires DF to be unset at function entry/exit */
+
+/*  making sure AC flag is not set in rflags */
+/*  avoid using the 'clac' instruction to be compatible with older compilers */
+    push %rcx
+    pushfq
+    popq %rcx
+    and $0xFFFFFFFFFFFBFFFF, %rcx
+    push %rcx
+    popfq
+
 /*  check for debug buffer pointer */
     testb  $0xff,DEBUG(%rip)
     jz .Lskip_debug_init
-- 
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