diff options
Diffstat (limited to 'src/kernel/arch/i386/gdt/gdt.c')
-rw-r--r-- | src/kernel/arch/i386/gdt/gdt.c | 130 |
1 files changed, 0 insertions, 130 deletions
diff --git a/src/kernel/arch/i386/gdt/gdt.c b/src/kernel/arch/i386/gdt/gdt.c deleted file mode 100644 index 3521052..0000000 --- a/src/kernel/arch/i386/gdt/gdt.c +++ /dev/null @@ -1,130 +0,0 @@ -#include <kernel/arch/generic.h> -#include <kernel/arch/i386/gdt.h> -#include <shared/mem.h> -#include <stdbool.h> -#include <stdint.h> - -extern char _isr_mini_stack; - -struct gdt_entry { - uint64_t limit_low : 16; - uint64_t base_low : 24; - uint64_t accessed : 1; // set by the processor - // CODE | DATA - uint64_t rw : 1; // readable? | writeable? - uint64_t conforming : 1; // conforming? | expands down? - uint64_t code : 1; // 1 | 0 - - uint64_t codeordata : 1; // 1 for everything other than TSS and LDT - uint64_t ring : 2; - uint64_t present : 1; // always 1 - uint64_t limit_high : 4; - uint64_t available : 1; // ??? - uint64_t long_mode : 1; - uint64_t x32 : 1; - uint64_t gran : 1; // 1 - 4kb, 0 - 1b - uint64_t base_high : 8; -} __attribute__((packed)); - -struct tss_entry { - uint32_t _unused0; - uint32_t esp0; // kernel mode stack pointer - uint32_t ss0; // kernel mode stack segment - uint8_t _unused1[0x5c]; -} __attribute__((packed)); - -struct lgdt_arg { - uint16_t limit; - uint32_t base; -} __attribute__((packed)); - -__attribute__((section(".shared"))) -static struct gdt_entry GDT[SEG_end]; -__attribute__((section(".shared"))) -static struct tss_entry TSS; -static struct lgdt_arg lgdt_arg; // probably doesn't need to be global - -static void gdt_fillout(struct gdt_entry* entry, uint8_t ring, bool code); -static void gdt_prepare(void); -static void gdt_load(void); - - -static void gdt_fillout(struct gdt_entry* entry, uint8_t ring, bool code) { - *entry = (struct gdt_entry) { - // set up the identity mapping - .limit_low = 0xFFFF, - .limit_high = 0xF, - .gran = 1, // 4KB * 0xFFFFF = (almost) 4GB - .base_low = 0, - .base_high = 0, - - .ring = ring, - .code = code, - - .accessed = 0, - .rw = 1, - .conforming = 0, - .codeordata = 1, - .present = 1, - .long_mode = 0, // ??? - .available = 1, // ??? - .x32 = 1, - }; -} - -static void gdt_prepare(void) { - GDT[SEG_null].present = 0; - - gdt_fillout(&GDT[SEG_r0code], 0, true); - gdt_fillout(&GDT[SEG_r0data], 0, false); - gdt_fillout(&GDT[SEG_r3code], 3, true); - gdt_fillout(&GDT[SEG_r3data], 3, false); - - // tss - memset(&TSS, 0, sizeof(TSS)); - TSS.ss0 = SEG_r0data << 3; // kernel data segment - TSS.esp0 = (uintptr_t) &_isr_mini_stack; - - GDT[SEG_TSS] = (struct gdt_entry) { - .limit_low = sizeof(TSS), - .limit_high = sizeof(TSS) >> 16, - .gran = 0, - .base_low = (uintptr_t) &TSS, - .base_high = ((uintptr_t) &TSS) >> 24, - - .accessed = 1, // 1 for TSS - .rw = 0, // 1 busy / 0 not busy - .conforming = 0, // 0 for TSS - .code = 1, // 32bit - .codeordata = 0, // is a system entry - .ring = 3, - .present = 1, - .available = 0, // 0 for TSS - .long_mode = 0, - .x32 = 0, // idk - }; -} - -static void gdt_load(void) { - lgdt_arg.limit = sizeof(GDT) - 1; - lgdt_arg.base = (uintptr_t) &GDT; - asm("lgdt (%0)" - : : "r" (&lgdt_arg) : "memory"); - - asm("ltr %%ax" - : : "a" (SEG_TSS << 3 | 3) : "memory"); - - // update all segment registers - gdt_farjump(SEG_r0code << 3); - asm("mov %0, %%ds;" - "mov %0, %%ss;" - "mov %0, %%es;" - "mov %0, %%fs;" - "mov %0, %%gs;" - : : "r" (SEG_r0data << 3) : "memory"); -} - -void gdt_init(void) { - gdt_prepare(); - gdt_load(); -} |