137 lines
4.9 KiB
C
137 lines
4.9 KiB
C
/*
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* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <eduos/stdio.h>
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#include <eduos/string.h>
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#include <eduos/stdlib.h>
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#include <eduos/tasks.h>
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#include <eduos/errno.h>
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#include <eduos/processor.h>
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#include <eduos/time.h>
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#include <asm/gdt.h>
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#include <asm/tss.h>
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gdt_ptr_t gp;
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static tss_t task_state_segment __attribute__ ((aligned (PAGE_SIZE)));
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// currently, our kernel has full access to the ioports
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static gdt_entry_t gdt[GDT_ENTRIES] = {[0 ... GDT_ENTRIES-1] = {0, 0, 0, 0, 0, 0}};
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/*
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* This is defined in entry.asm. We use this to properly reload
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* the new segment registers
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*/
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extern void gdt_flush(void);
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/* Setup a descriptor in the Global Descriptor Table */
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void gdt_set_gate(int num, unsigned long base, unsigned long limit,
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unsigned char access, unsigned char gran)
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{
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configure_gdt_entry(&gdt[num], base, limit, access, gran);
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}
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void configure_gdt_entry(gdt_entry_t *dest_entry, unsigned long base, unsigned long limit,
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unsigned char access, unsigned char gran)
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{
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/* Setup the descriptor base address */
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dest_entry->base_low = (base & 0xFFFF);
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dest_entry->base_middle = (base >> 16) & 0xFF;
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dest_entry->base_high = (base >> 24) & 0xFF;
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/* Setup the descriptor limits */
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dest_entry->limit_low = (limit & 0xFFFF);
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dest_entry->granularity = ((limit >> 16) & 0x0F);
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/* Finally, set up the granularity and access flags */
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dest_entry->granularity |= (gran & 0xF0);
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dest_entry->access = access;
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}
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/*
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* This will setup the special GDT
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* pointer, set up the entries in our GDT, and then
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* finally call gdt_flush() in our assembler file in order
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* to tell the processor where the new GDT is and update the
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* new segment registers
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*/
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void gdt_install(void)
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{
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unsigned long mode, limit;
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memset(&task_state_segment, 0x00, sizeof(tss_t));
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mode = GDT_FLAG_32_BIT;
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limit = 0xFFFFFFFF;
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/* Setup the GDT pointer and limit */
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gp.limit = (sizeof(gdt_entry_t) * GDT_ENTRIES) - 1;
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gp.base = (size_t) &gdt;
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/* Our NULL descriptor */
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gdt_set_gate(0, 0, 0, 0, 0);
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/*
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* The second entry is our Code Segment. The base address
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* is 0, the limit is 4 GByte, it uses 4KByte granularity,
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* uses 32-bit opcodes, and is a Code Segment descriptor.
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*/
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gdt_set_gate(1, 0, limit,
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GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
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GDT_FLAG_4K_GRAN | mode);
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/*
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* The third entry is our Data Segment. It's EXACTLY the
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* same as our code segment, but the descriptor type in
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* this entry's access byte says it's a Data Segment
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*/
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gdt_set_gate(2, 0, limit,
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GDT_FLAG_RING0 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
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GDT_FLAG_4K_GRAN | mode);
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/*
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* Create code segement for userspace applications (ring 3)
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*/
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gdt_set_gate(3, 0, limit,
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GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_CODESEG | GDT_FLAG_PRESENT,
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GDT_FLAG_4K_GRAN | mode);
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/*
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* Create data segement for userspace applications (ring 3)
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*/
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gdt_set_gate(4, 0, limit,
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GDT_FLAG_RING3 | GDT_FLAG_SEGMENT | GDT_FLAG_DATASEG | GDT_FLAG_PRESENT,
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GDT_FLAG_4K_GRAN | mode);
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/* set default values */
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task_state_segment.eflags = 0x1202;
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task_state_segment.ss0 = 0x10; // data segment
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task_state_segment.esp0 = 0xDEADBEEF; // invalid pseudo address
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gdt_set_gate(5, (unsigned long) (&task_state_segment), sizeof(tss_t)-1,
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GDT_FLAG_PRESENT | GDT_FLAG_TSS | GDT_FLAG_RING0, mode);
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/* Flush out the old GDT and install the new changes! */
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gdt_flush();
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}
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