>From 0a45e40834eeb8fc42f74645be715ca14432a767 Mon Sep 17 00:00:00 2001
From: Tom Bannink <tombann...@gmail.com>
Date: Tue, 12 Apr 2022 11:15:41 +0200
Subject: [PATCH] Fix bug in ARM memset implementation
The ARM implementation of memset has a bug when the fill-value is negative or
outside the
[0, 255] range. To reproduce:
char array[256];
memset(array, -5, 256);
This is supposed to fill the array with int8 values -5, -5, -5, ... . On ARM,
this does
not work because the implementation assumes the high bytes of the fill-value
argument are
already zero. However in this test case they are filled with 1-bits. The
aarch64 and x86_64
implementations do not have this problem: they first convert the fill-value to
an unsigned
byte following the specification of memset.
With GCC one can use `memset(ptr, (-5 & 0xFF), size)` as a workaround, but for
clang
users that does not work: clang optimizes the `& 0xFF` away because it assumes
that
memset will do it.
---
libc/string/arm/memset.S | 2 ++
1 file changed, 2 insertions(+)
diff --git a/libc/string/arm/memset.S b/libc/string/arm/memset.S
index 412270f50..f4b30b3dc 100644
--- a/libc/string/arm/memset.S
+++ b/libc/string/arm/memset.S
@@ -32,6 +32,7 @@ memset:
cmp r2, #8 @ at least 8 bytes to do?
bcc 2f
+ uxtb r1, r1
lsl r3, r1, #8
orr r1, r3
lsl r3, r1, #16
@@ -68,6 +69,7 @@ memset:
mov a4, a1
cmp a3, $8 @ at least 8 bytes to do?
blo 2f
+ uxtb a2, a2
orr a2, a2, a2, lsl $8
orr a2, a2, a2, lsl $16
1:
--
2.35.1
_______________________________________________
devel mailing list -- devel@uclibc-ng.org
To unsubscribe send an email to devel-le...@uclibc-ng.org
