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/*
* Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
* 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 Hyra 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 THE COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
*/
.text
.globl gdt_load
gdt_load:
/*
* void gdt_load(GDTR *GDTR);
*/
push %r12
push %r13
push %r14
push %r15
push %rbx
push %rbp
lgdt (%rdi) /* Load our own GDT */
lea 1f(%rip), %rbx /* Save the drop point */
push $0x08 /* FRAME.CS */
push %rbx /* FRAME.RIP */
lretq /* Flush prefetch and update CS */
1: mov $0x10, %ax /* Our DS */
mov %ax, %ds /* Data segment */
mov %ax, %fs /* F segment */
mov %ax, %ss /* Stack segment */
mov %ax, %es /* Extra segment */
xor %ax, %ax /* We want GS in a known state */
mov %ax, %gs /* Load it with NULL */
pop %rbp
pop %rbx
pop %r15
pop %r14
pop %r13
pop %r12
retq
.section .data
.globl GDT
GDT:
.NULL:
.quad 0x0000000000000000
.CODE:
.quad 0x00209A0000000000
.DATA:
.quad 0x0000920000000000
.globl GDTR
GDTR:
.word . - GDT - 1
.quad GDT
/* vim: ft=gas :
*/
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