glibc/glibc-RHEL-15696-49.patch

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From 08cbcd4dbc686bb38ec3093aff2f919fbff5ec17 Mon Sep 17 00:00:00 2001
From: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Wed, 23 Jun 2021 19:19:34 -0400
Subject: [PATCH] x86: Remove unnecessary overflow check from wcsnlen-sse4_1.S
Content-type: text/plain; charset=UTF-8
No bug. The way wcsnlen will check if near the end of maxlen
is the following macro:
mov %r11, %rsi; \
subq %rax, %rsi; \
andq $-64, %rax; \
testq $-64, %rsi; \
je L(strnlen_ret)
Which words independently of s + maxlen overflowing. So the
second overflow check is unnecissary for correctness and
just extra overhead in the common no overflow case.
test-strlen.c, test-wcslen.c, test-strnlen.c and test-wcsnlen.c are
all passing
Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
---
sysdeps/x86_64/multiarch/strlen-vec.S | 7 -------
1 file changed, 7 deletions(-)
diff --git a/sysdeps/x86_64/multiarch/strlen-vec.S b/sysdeps/x86_64/multiarch/strlen-vec.S
index 439e486a..b7657282 100644
--- a/sysdeps/x86_64/multiarch/strlen-vec.S
+++ b/sysdeps/x86_64/multiarch/strlen-vec.S
@@ -71,19 +71,12 @@ L(n_nonzero):
suffice. */
mov %RSI_LP, %R10_LP
sar $62, %R10_LP
- test %R10_LP, %R10_LP
jnz __wcslen_sse4_1
sal $2, %RSI_LP
# endif
-
/* Initialize long lived registers. */
-
add %RDI_LP, %RSI_LP
-# ifdef AS_WCSLEN
-/* Check for overflow again from s + maxlen * sizeof(wchar_t). */
- jbe __wcslen_sse4_1
-# endif
mov %RSI_LP, %R10_LP
and $-64, %R10_LP
mov %RSI_LP, %R11_LP
--
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