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Diffstat (limited to 'payloads/libpayload/arch/x86/head.S')
| -rw-r--r-- | payloads/libpayload/arch/x86/head.S | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/payloads/libpayload/arch/x86/head.S b/payloads/libpayload/arch/x86/head.S new file mode 100644 index 0000000000..3dd61336f9 --- /dev/null +++ b/payloads/libpayload/arch/x86/head.S @@ -0,0 +1,104 @@ +/* + * 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. + */ + + .code32 + .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. That's our operating mode, so we won't + * change anything. + */ +_entry: + jmp _init + + .align 4 + +#define MB_MAGIC 0x1BADB002 +#define MB_FLAGS 0x00010003 + +mb_header: + .long MB_MAGIC + .long MB_FLAGS + .long -(MB_MAGIC + MB_FLAGS) + .long mb_header + .long _start + .long _edata + .long _end + .long _init + +/* + * This function saves off the previous stack and switches us to our + * own execution environment. + */ +_init: + /* No interrupts, please. */ + cli + + /* There is a bunch of stuff missing here to take arguments on the stack + * See http://www.coreboot.org/Payload_API and exec.S. + */ + /* Store current stack pointer. */ + movl %esp, %esi + + /* Store EAX and EBX */ + movl %eax,loader_eax + movl %ebx,loader_ebx + + /* Clear the bss */ + cld + movl $.bss, %edi + movl $_end, %ecx + subl %edi, %ecx + xor %ax, %ax + rep stosb + + /* Setup new stack. */ + movl $_stack, %ebx + + movl %ebx, %esp + + /* Save old stack pointer. */ + pushl %esi + + /* Let's rock. */ + call start_main + + /* %eax has the return value - pass it on unmolested */ +_leave: + /* Get old stack pointer. */ + popl %ebx + + /* Restore old stack. */ + movl %ebx, %esp + + /* Return to the original context. */ + ret |