libpayload: The initial chunk of code writen by AMD

This is the initial chunk of code written by me and copyrighted
by AMD.  Includes everything but a few files that we pulled from
outside sources.

Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>


git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3170 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1

1 files changed, 85 insertions, 0 deletions

diff --git a/payloads/libpayload/i386/head.S b/payloads/libpayload/i386/head.S
new file mode 100644
index 0000000000..1278bdf4ed
--- /dev/null
+++ b/payloads/libpayload/i386/head.S
@@ -0,0 +1,85 @@
+/*
+ * This file is part of the libpayload project.
+ *
+ * Copyright (C) 2008 Advanced Micro Devices, Inc.
+ *
+ * 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. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 THE AUTHOR OR CONTRIBUTORS 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.
+ */
+	
+	.global _entry, _leave
+	.text
+	.align 4
+
+/* Our entry point - assume that the CPU is in
+ *  32 bit protected mode and all segments are in a
+ *  flat model.  Thats our operating mode, so we won't
+ *  change anything
+ */
+	
+_entry:
+	call _init
+
+	/* We're back - go back to the bootloader */
+	ret
+
+/* This function saves off the previous stack and
+   switches us to our own execution enviornment
+*/	
+
+_init:
+	/* No interrupts, please */
+	cli
+
+	/* Get the current stack pointer */
+	movl %esp, %esi
+
+	movl _istack, %ebx
+
+	/* lret needs %cs in the stack, so copy it over */
+	movw %cs, 4(%ebx)
+
+	/* Exchange the current stack pointer for the one in
+	   the initial stack (which happens to be the new
+	   stack pointer) */
+
+	xchgl %esi, 16(%ebx)
+
+	/* Set the new stack pointer */
+	movl %esi, %esp
+
+	/* Return into the main entry function
+	   and go
+	 */
+
+	lret
+
+_leave:
+	movl _istack, %ebx
+
+	/* Restore the stack pointer from the storage area */
+	movl 16(%ebx), %esp
+
+	/* Return to the original context */
+	lret
+