From 4df1fa6ddc8925a75f3da644d5da3bb16eb33f02 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Fri, 3 Dec 2021 15:29:25 -0800
Subject: [PATCH] x86-64: Use notl in EVEX strcmp [BZ #28646]
Content-type: text/plain; charset=UTF-8

Must use notl %edi here as lower bits are for CHAR comparisons
potentially out of range thus can be 0 without indicating mismatch.
This fixes BZ #28646.

Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
---
 sysdeps/x86_64/multiarch/strcmp-evex.S | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

Conflicts:
	string/test-strcmp.c
	(new check omitted)

diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index 82f12ac8..6f5c4bf9 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -656,12 +656,13 @@ L(loop_cross_page):
 	   in YMM3 and 32 bytes at VEC_SIZE(%rdx, %r10).  */
 	VPCMP	$0, VEC_SIZE(%rdx, %r10), %YMM3, %k3{%k4}
 	kmovd	%k3, %edi
+    /* Must use notl %edi here as lower bits are for CHAR
+	   comparisons potentially out of range thus can be 0 without
+	   indicating mismatch.  */
+	notl	%edi
 # ifdef USE_AS_WCSCMP
 	/* Don't use subl since it is the upper 8 bits of EDI below.  */
-	notl	%edi
 	andl	$0xff, %edi
-# else
-	incl	%edi
 # endif
 
 # ifdef USE_AS_WCSCMP
@@ -743,12 +744,13 @@ L(loop_cross_page_2_vec):
 	   in YMM1 and 32 bytes at (VEC_SIZE * 3)(%rdx, %r10).  */
 	VPCMP	$0, (VEC_SIZE * 3)(%rdx, %r10), %YMM1, %k3{%k4}
 	kmovd	%k3, %edi
+	/* Must use notl %edi here as lower bits are for CHAR
+	   comparisons potentially out of range thus can be 0 without
+	   indicating mismatch.  */
+	notl	%edi
 # ifdef USE_AS_WCSCMP
 	/* Don't use subl since it is the upper 8 bits of EDI below.  */
-	notl	%edi
 	andl	$0xff, %edi
-# else
-	incl	%edi
 # endif
 
 # ifdef USE_AS_WCSCMP
-- 
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