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#include "gdt.h"
struct __attribute__((packed)) Pointer {
uint16_t limit;
uint32_t base;
};
static struct SegmentDescriptor_t segments[8] __attribute__((aligned(32)));
void
gdt_install()
{
SegmentDescriptor(&segments[0], 0, 0, 0); // null segment
SegmentDescriptor(&segments[2], 0, 0xffffffff, 0x9a); // ktext
SegmentDescriptor(&segments[3], 0, 0xffffffff, 0x92); // kdata
const struct Pointer ptr = {.limit = sizeof(segments) - 1, .base = (unsigned)&segments};
asm volatile("lgdt (%0)" : : "a"(&ptr));
// load the kernel data segment
asm volatile(R"(mov %0, %%ds
mov %0, %%es
mov %0, %%fs
mov %0, %%gs
mov %0, %%ss
)"
:
: "ax"(kdataDescriptor));
// load the kernel code segment
asm volatile(R"(ljmp %0, $1f
1:)"
:
: "i"(ktextDescriptor));
}
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