Comments update

1 files changed, 92 insertions, 0 deletions

diff --git a/asm/c_args.S b/asm/c_args.S
new file mode 100644
index 0000000..dabffd3
--- /dev/null
+++ b/asm/c_args.S
@@ -0,0 +1,92 @@
+/*
+ * ========================
+ * =====    ===============
+ * ======  ================
+ * ======  ================
+ * ======  ====   ====   ==
+ * ======  ===     ==  =  =
+ * ======  ===  =  ==     =
+ * =  ===  ===  =  ==  ====
+ * =  ===  ===  =  ==  =  =
+ * ==     =====   ====   ==
+ * ========================
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2020-2021 Joe
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the organization nor the
+ *    names of its contributors may be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY JOE ''AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL JOE BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * lowbat: asm/c_args.S
+ * Wed Feb 10 18:23:00 CET 2021
+ * Joe
+ */
+
+/*
+ * c_args(argc: rdi, *argv[]: rsi)
+ * -------------------------------
+ * returns 0 if args are invalid
+ * returns 1 if args are valid
+ */
+
+.text
+.extern strncmp
+.globl c_args
+
+c_args:
+	cmp		$0x2, %rdi
+	jle		no_args
+	xorq	%rax, %rax
+	pushq	%rcx
+	xorq	%rcx, %rcx
+	movb	$0x8, %cl
+	movq	(%rsi, %rcx, 2), %rax
+	cmpb	$0x0, (%rax)
+	je		no_args
+	pushq	%rdi
+	movq	(%rsi, %rcx, 1), %rdi
+	pushq	%rsi
+	movq	$reference, %rsi
+	pushq	%rdx
+	xorq	%rdx, %rdx
+	movb	$0x6, %dl
+	callq	strncmp
+	popq	%rdx
+	popq	%rsi
+	popq	%rdi
+	popq	%rcx
+	cmp		$0x0, %rax
+	jne		no_args
+	xorq	%rax, %rax
+	movb	$0x1, %al
+	jmp		return
+
+no_args:
+	xorq	%rax, %rax
+
+return:
+	retq
+
+.data
+	reference:	.asciz "--say"