From 0bff8199e4a800d5ea1bd422dcf06643d6daf008 Mon Sep 17 00:00:00 2001 From: Aleksa Vučković Date: Mon, 10 Jan 2022 22:15:15 +0100 Subject: include/setup.sh --- include/03.gdt/gdt.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) create mode 100644 include/03.gdt/gdt.c (limited to 'include/03.gdt/gdt.c') diff --git a/include/03.gdt/gdt.c b/include/03.gdt/gdt.c new file mode 100644 index 0000000..e3d2b4c --- /dev/null +++ b/include/03.gdt/gdt.c @@ -0,0 +1,46 @@ +#include + +struct gdt_entry +{ + uint16_t limit; + uint16_t base1; + uint8_t base2; + uint8_t access; + uint8_t limit_flags; + uint8_t base3; +} __attribute__((packed)); + +struct gdt_pointer +{ + uint16_t size; + uint32_t offset; +} __attribute__((packed)); + +extern void load_gdt(struct gdt_pointer *gdtp); + +struct gdt_entry gdt[5]; +struct gdt_pointer gdtp; + +void init_gdt_entry(size_t num, uint32_t limit, uint32_t base, uint8_t access, uint8_t limit_flags) +{ + gdt[num].limit=limit; + gdt[num].base1=(base & 0xffff); + gdt[num].base2=(base & 0xff0000) >> 16; + gdt[num].access=access; + gdt[num].limit_flags=limit_flags; + gdt[num].base3=(base & 0xff000000) >> 24; +} + +void init_gdt_table() +{ + gdtp.size=sizeof(gdt)-1; + gdtp.offset=(uint32_t)&gdt; + + init_gdt_entry(0,0,0,0,0); // null segment + init_gdt_entry(1,0xffffffff,0,0b10011010,0b11001111); // code segment + init_gdt_entry(2,0xffffffff,0,0b10010010,0b11001111); // data segment + init_gdt_entry(3,0xffffffff,0,0b11111010,0b11001111); // user mode code segment + init_gdt_entry(4,0xffffffff,0,0b11110010,0b11001111); // user mode data segment + + load_gdt(&gdtp); +} -- cgit v1.2.3