From 6e9b3275d75e0cdbae1e8f7e4dda8880bb6346bc Mon Sep 17 00:00:00 2001 From: Aleksa Vuckovic Date: Sat, 3 Sep 2022 23:53:53 +0200 Subject: gdt & tss --- kernel/src/cpu/gdt.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 kernel/src/cpu/gdt.c (limited to 'kernel/src/cpu/gdt.c') diff --git a/kernel/src/cpu/gdt.c b/kernel/src/cpu/gdt.c new file mode 100644 index 0000000..b4f1ec0 --- /dev/null +++ b/kernel/src/cpu/gdt.c @@ -0,0 +1,53 @@ +#include +#include + +gdt_seg_entry gdt[7]; +gdt_p gdt_pointer; + +void add_gdt_entry(uint32_t num, uint32_t offset, uint32_t limit, uint8_t access, uint8_t flags) +{ + gdt[num].offset1 = offset & 0xffff; + gdt[num].offset2 = (offset >> 16) & 0xff; + gdt[num].offset3 = (uint8_t)(offset >> 24) & 0xff; + gdt[num].limit = limit & 0xffff; + gdt[num].limitflags = (limit >> 16) & 0xf; + gdt[num].access = access; + gdt[num].limitflags = flags << 4; +} + +void add_gdt_tss(uint32_t num, uint64_t offset, uint32_t limit, uint8_t access, uint8_t flags) +{ + add_gdt_entry(num, offset & 0xffffffff, limit, access, flags); +} + +void reload_gdt() +{ + __asm__ volatile ( + "mov $0x10, %ax;" + "mov %ax, %ds;" + "mov %ax, %es;" + "mov %ax, %ss;" + ); +} + +void load_gdt(gdt_p* pointer) +{ + __asm__ volatile ("lgdt (%0);" : : "r"(pointer) : ); + reload_gdt(); +} + +void init_gdt() +{ + gdt_pointer.offset = (uint64_t)&gdt; + gdt_pointer.size = sizeof(gdt) - 1; + + add_gdt_entry(0, 0, 0, 0, 0); + add_gdt_entry(1, 0, 0xfffff, 0x9a, 0xa); + add_gdt_entry(2, 0, 0xfffff, 0x92, 0xc); + add_gdt_entry(3, 0, 0xfffff, 0xfa, 0xa); + add_gdt_entry(4, 0, 0xfffff, 0xf2, 0xc); + add_gdt_tss(5, (uint64_t)&tss, sizeof(tss_type), 0x89, 0); + + load_gdt(&gdt_pointer); + init_tss(); +} -- cgit v1.2.3