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/* Copyright (C) 2004 David Decotigny
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
USA.
*/
#include "segment.h"
#include "idt.h"
/**
* An entry in the IDT, or "IDTE" in the following, ie a reference to
* a interrupt/trap routine or a task gate to handle the sw/hw
* interrupts and exceptions.
*
* @see figure 5-2, intel x86 doc, vol 3
*/
struct x86_idt_entry
{
/* Low dword */
sos_ui16_t offset_low; /* 15..0, offset of the routine in the segment */
sos_ui16_t seg_sel; /* 31..16, the ID of the segment */
/* High dword */
sos_ui8_t reserved:5; /* 4..0 */
sos_ui8_t flags:3; /* 7..5 */
sos_ui8_t type:3; /* 10..8 (interrupt gate, trap gate...) */
sos_ui8_t op_size:1; /* 11 (0=16bits instructions, 1=32bits instr.) */
sos_ui8_t zero:1; /* 12 */
sos_ui8_t dpl:2; /* 14..13 */
sos_ui8_t present:1; /* 15 */
sos_ui16_t offset_high; /* 31..16 */
} __attribute__((packed));
/**
* The IDT register, which stores the address and size of the
* IDT.
*
* @see Intel x86 doc vol 3, section 2.4, figure 2-4
*/
struct x86_idt_register
{
/* The maximum GDT offset allowed to access an entry in the GDT */
sos_ui16_t limit;
/* This is not exactly a "virtual" address, ie an adddress such as
those of instructions and data; this is a "linear" address, ie an
address in the paged memory. However, in SOS we configure the
segmented memory as a "flat" space: the 0-4GB segment-based (ie
"virtual") addresses directly map to the 0-4GB paged memory (ie
"linear"), so that the "linear" addresses are numerically equal
to the "virtual" addresses: this base_addr will thus be the same
as the address of the gdt array */
sos_ui32_t base_addr;
} __attribute__((packed, aligned (8)));
static struct x86_idt_entry idt[SOS_IDTE_NUM];
sos_ret_t sos_idt_subsystem_setup()
{
struct x86_idt_register idtr;
int i;
for (i = 0 ;
i < SOS_IDTE_NUM ;
i++)
{
struct x86_idt_entry *idte = idt + i;
/* Setup an empty IDTE interrupt gate, see figure 5-2 in Intel
x86 doc, vol 3 */
idte->seg_sel = SOS_BUILD_SEGMENT_REG_VALUE(0, FALSE, SOS_SEG_KCODE);
idte->reserved = 0;
idte->flags = 0;
idte->type = 0x6; /* Interrupt gate (110b) */
idte->op_size = 1; /* 32bits instructions */
idte->zero = 0;
/* Disable this IDT entry for the moment */
sos_idt_set_handler(i, (sos_vaddr_t)NULL, 0/* Don't care */);
}
/*
* Setup the IDT register, see Intel x86 doc vol 3, section 5.8.
*/
/* Address of the IDT */
idtr.base_addr = (sos_ui32_t) idt;
/* The limit is the maximum offset in bytes from the base address of
the IDT */
idtr.limit = sizeof(idt) - 1;
/* Commit the IDT into the CPU */
asm volatile ("lidt %0\n"::"m"(idtr):"memory");
return SOS_OK;
}
sos_ret_t sos_idt_set_handler(int index,
sos_vaddr_t handler_address,
int lowest_priviledge /* 0..3 */)
{
struct x86_idt_entry *idte;
if ((index < 0) || (index >= SOS_IDTE_NUM))
return -SOS_EINVAL;
if ((lowest_priviledge < 0) || (lowest_priviledge > 3))
return -SOS_EINVAL;
idte = idt + index;
if (handler_address != (sos_vaddr_t)NULL)
{
idte->offset_low = handler_address & 0xffff;
idte->offset_high = (handler_address >> 16) & 0xffff;
idte->dpl = lowest_priviledge;
idte->present = 1; /* Yes, there is a handler */
}
else /* Disable this IDT entry */
{
idte->offset_low = 0;
idte->offset_high = 0;
idte->dpl = 0;
idte->present = 0; /* No, there is no handler */
}
return SOS_OK;
}
sos_ret_t sos_idt_get_handler(int index,
sos_vaddr_t *handler_address,
int *lowest_priviledge)
{
if ((index < 0) || (index >= SOS_IDTE_NUM))
return -SOS_EINVAL;
if (handler_address != NULL)
*handler_address = idt[index].offset_low
| (idt[index].offset_high << 16);
if (lowest_priviledge != NULL)
*lowest_priviledge = idt[index].dpl;
return SOS_OK;
}
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