aarch64: morello: purecap rawmemchr

Modified rawmemchr to support Arm Morello Capabilities.

diff --git a/sysdeps/aarch64/morello/rawmemchr.S b/sysdeps/aarch64/morello/rawmemchr.S
new file mode 100644 (file)
index 0000000..10e89ee
--- /dev/null
+++ b/sysdeps/aarch64/morello/rawmemchr.S
@@ -0,0 +1,43 @@
+/* rawmemchr - find a character in a memory zone
+
+   Copyright (C) 2022 Free Software Foundation, Inc.
+
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+/* Special case rawmemchr (s, 0) as strlen, otherwise tailcall memchr.
+   Call strlen without setting up a full frame - it preserves x14/x15.
+*/
+
+ENTRY (__rawmemchr)
+
+       cbz     w1, L(do_strlen)
+       mov     x2, -1
+       b       __memchr
+
+L(do_strlen):
+       mov     c15, c30
+       cfi_return_column (c15)
+       mov     c14, c0
+       bl      __strlen
+       add     c0, c14, x0
+       ret     c15
+
+END (__rawmemchr)
+weak_alias (__rawmemchr, rawmemchr)
+libc_hidden_builtin_def (__rawmemchr)