From 0ad216b458445251e6f98d74382faf3606569731 Mon Sep 17 00:00:00 2001

From: Noah Goldstein <goldstein.w.n@gmail.com>

Date: Tue, 15 Feb 2022 08:18:15 -0600

Subject: [PATCH] x86: Fallback {str|wcs}cmp RTM in the ncmp overflow case [BZ

 #29127]

Re-cherry-pick commit c627209832 for strcmp-avx2.S change which was

omitted in intial cherry pick because at the time this bug was not

present on release branch.

Fixes BZ #29127.

In the overflow fallback strncmp-avx2-rtm and wcsncmp-avx2-rtm would

call strcmp-avx2 and wcscmp-avx2 respectively. This would have

not checks around vzeroupper and would trigger spurious

aborts. This commit fixes that.

test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass on

AVX2 machines with and without RTM.

Co-authored-by: H.J. Lu <hjl.tools@gmail.com>

(cherry picked from commit c6272098323153db373f2986c67786ea8c85f1cf)

---

 sysdeps/x86_64/multiarch/strcmp-avx2.S | 8 ++------

 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S

index 28cc98b6..e267c6cb 100644

--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S

+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S

@@ -345,10 +345,10 @@ L(one_or_less):

 	movq	%LOCALE_REG, %rdx

 #  endif

 	jb	L(ret_zero)

-#  ifdef USE_AS_WCSCMP

 	/* 'nbe' covers the case where length is negative (large

 	   unsigned).  */

-	jnbe	__wcscmp_avx2

+	jnbe	OVERFLOW_STRCMP

+#  ifdef USE_AS_WCSCMP

 	movl	(%rdi), %edx

 	xorl	%eax, %eax

 	cmpl	(%rsi), %edx

@@ -357,10 +357,6 @@ L(one_or_less):

 	negl	%eax

 	orl	$1, %eax

 #  else

-	/* 'nbe' covers the case where length is negative (large

-	   unsigned).  */

-

-	jnbe	__strcmp_avx2

 	movzbl	(%rdi), %eax

 	movzbl	(%rsi), %ecx

 	TOLOWER_gpr (%rax, %eax)

-- 

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