sortix-mirror/sortix/x86-family/gdt.h

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/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
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This file is part of Sortix.
Sortix 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 3 of the License, or (at your option) any later
version.
Sortix 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
Sortix. If not, see <http://www.gnu.org/licenses/>.
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x86-family/gdt.h
Initializes and handles the GDT and TSS.
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*******************************************************************************/
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#ifndef SORTIX_X86_FAMILY_GDT_H
#define SORTIX_X86_FAMILY_GDT_H
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namespace Sortix
{
namespace GDT
{
// This structure contains the value of one GDT entry.
// We use the attribute 'packed' to tell GCC not to change
// any of the alignment in the structure.
struct gdt_entry_struct
{
uint16_t limit_low; // The lower 16 bits of the limit.
uint16_t base_low; // The lower 16 bits of the base.
uint8_t base_middle; // The next 8 bits of the base.
uint8_t access; // Access flags, determine what ring this segment can be used in.
uint8_t granularity;
uint8_t base_high; // The last 8 bits of the base.
} __attribute__((packed));
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struct gdt_entry64_struct
{
uint16_t limit_low;
uint16_t base_low;
uint8_t base_middle;
uint8_t access;
uint8_t granularity;
uint8_t base_high;
uint32_t base_highest;
uint32_t zero1;
} __attribute__((packed));
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typedef struct gdt_entry_struct gdt_entry_t;
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typedef struct gdt_entry64_struct gdt_entry64_t;
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// This struct describes a GDT pointer. It points to the start of
// our array of GDT entries, and is in the format required by the
// lgdt instruction.
struct gdt_ptr_struct
{
uint16_t limit; // The upper 16 bits of all selector limits.
addr_t base; // The address of the first gdt_entry_t struct.
} __attribute__((packed));
typedef struct gdt_ptr_struct gdt_ptr_t;
// A struct describing a Task State Segment.
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#ifdef PLATFORM_X86
struct tss_entry_struct
{
uint32_t prev_tss; // The previous TSS - if we used hardware task switching this would form a linked list.
uint32_t esp0; // The stack pointer to load when we change to kernel mode.
uint32_t ss0; // The stack segment to load when we change to kernel mode.
uint32_t esp1; // Unused...
uint32_t ss1;
uint32_t esp2;
uint32_t ss2;
uint32_t cr3;
uint32_t eip;
uint32_t eflags;
uint32_t eax;
uint32_t ecx;
uint32_t edx;
uint32_t ebx;
uint32_t esp;
uint32_t ebp;
uint32_t esi;
uint32_t edi;
uint32_t es; // The value to load into ES when we change to kernel mode.
uint32_t cs; // The value to load into CS when we change to kernel mode.
uint32_t ss; // The value to load into SS when we change to kernel mode.
uint32_t ds; // The value to load into DS when we change to kernel mode.
uint32_t fs; // The value to load into FS when we change to kernel mode.
uint32_t gs; // The value to load into GS when we change to kernel mode.
uint32_t ldt; // Unused...
uint16_t trap;
uint16_t iomap_base;
} __attribute__((packed));
#else
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struct tss_entry_struct
{
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uint32_t reserved1;
uint64_t stack0;
uint64_t stack1;
uint64_t stack2;
uint64_t reserved2;
uint64_t ist[7];
uint64_t reserved3;
uint16_t reserved4;
uint16_t iomap_base;
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} __attribute__((packed));
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#endif
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typedef struct tss_entry_struct tss_entry_t;
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void Init();
void SetGate(int32_t num, uint32_t base, uint32_t limit, uint8_t access, uint8_t gran);
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void WriteTSS(int32_t num, uint16_t ss0, addr_t stack0);
void SetKernelStack(addr_t stacklower, size_t stacksize, addr_t stackhigher);
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}
}
#endif