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/*
* Copyright (c) 2023 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.
*/
#include <machine/tss.h>
#include <machine/cpu.h>
#include <lib/string.h>
#include <vm/dynalloc.h>
#include <sys/panic.h>
__MODULE_NAME("TSS");
__KERNEL_META("$Hyra$: tss.c, Ian Marco Moffett, "
"AMD64 Task state segment code");
static void
alloc_resources(struct cpu_info *cpu)
{
struct tss_entry *tss;
/*
* Allocate TSS entries for this CPU
*/
if (cpu->tss == NULL) {
/* Allocate a TSS for this CPU */
tss = dynalloc(sizeof(*tss));
if (tss == NULL)
panic("Failed to alloc %d bytes for TSS\n", sizeof(*tss));
memset(tss, 0, sizeof(*tss));
cpu->tss = tss;
}
}
void
write_tss(struct cpu_info *cpu, struct tss_desc *desc)
{
uintptr_t tss_base;
alloc_resources(cpu);
tss_base = (uintptr_t)cpu->tss;
/*
* XXX: The AVL (Available for use by system software)
* bit is ignored by hardware and it is up to us
* to decide how to use it... As of now, it is useless
* to us and shall remain 0.
*/
desc->seglimit = sizeof(struct tss_entry);
desc->p = 1; /* Must be present to be valid! */
desc->g = 0; /* Granularity -> 0 */
desc->avl = 0; /* Not used */
desc->dpl = 0; /* Descriptor Privilege Level -> 0 */
desc->type = 0x9; /* For TSS -> 0x9 (0b1001) */
desc->base_lo16 = __SHIFTOUT(tss_base, __MASK(16));
desc->base_mid8 = __SHIFTOUT(tss_base, __MASK(8) << 16);
desc->base_hi_mid8 = __SHIFTOUT(tss_base, __MASK(8) << 24);
desc->base_hi32 = __SHIFTOUT(tss_base, __MASK(32) << 32);
}
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