[glibc/arm/morello/main] aarch64: morello: add prctl with correct vararg handling

[Szabolcs Nagy <nsz@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f2c6fa2b30bc8123c178f8b9d88d206136b5c7bd

commit f2c6fa2b30bc8123c178f8b9d88d206136b5c7bd
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Oct 26 10:19:30 2022 +0100

    aarch64: morello: add prctl with correct vararg handling
    
    prctl is a variadic function and on morello args that were not passed
    cannot be accessed so the generic code does not work.

Diff:
---
 sysdeps/unix/sysv/linux/aarch64/morello/prctl.S | 44 +++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/sysdeps/unix/sysv/linux/aarch64/morello/prctl.S b/sysdeps/unix/sysv/linux/aarch64/morello/prctl.S
new file mode 100644
index 0000000000..f4e253af41
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/aarch64/morello/prctl.S
@@ -0,0 +1,44 @@
+/* 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>
+
+/* prctl (int option, ...) with 4 optional variadic arguments.  */
+
+ENTRY (__prctl)
+	mov	x8, #__NR_prctl
+	cbz	x9, L(skip_args)
+	gclen   x10, c9
+	ldr	c1, [c9]
+	cmp	x10, 16
+	bls	L(skip_args)
+	ldr	c2, [c9,16]
+	cmp	x10, 32
+	bls	L(skip_args)
+	ldr	c3, [c9,32]
+	cmp	x10, 48
+	bls	L(skip_args)
+	ldr	c4, [c9,48]
+L(skip_args):
+	svc	0x0
+	cmn	x0, #4095
+	b.cs	.Lsyscall_error
+	ret
+PSEUDO_END (__prctl)
+libc_hidden_def (__prctl)
+weak_alias (__prctl, prctl)