74 lines
2.4 KiB
C
74 lines
2.4 KiB
C
#include <amd64/gdt.h>
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#include <amd64/smp.h>
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#include <aux/compiler.h>
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#include <libk/std.h>
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#include <libk/string.h>
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#define TSS 0x80
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#define TSS_PRESENT 0x89
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/* Set a GDT entry */
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static void gdt_set(volatile struct gdt_entry* ent, uint32_t base, uint32_t limit, uint8_t acc,
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uint8_t gran) {
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ent->baselow = (base & 0xFFFF);
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ent->basemid = (base >> 16) & 0xFF;
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ent->basehigh = (base >> 24) & 0xFF;
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ent->limitlow = (limit & 0xFFFF);
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ent->gran = ((limit >> 16) & 0x0F) | (gran & 0xF0);
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ent->access = acc;
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}
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/* Initialize GDT and TSS structures for a given CPU */
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void gdt_init(struct cpu* cpu) {
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volatile struct tss* tss = &cpu->tss;
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volatile struct gdt_extended* gdt = &cpu->gdt;
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memset((void*)gdt, 0, sizeof(*gdt));
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memset((void*)tss, 0, sizeof(*tss));
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tss->iopb_off = sizeof(*tss);
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tss->rsp0 = (uint64_t)((uintptr_t)cpu->kernel_stack + sizeof(cpu->kernel_stack));
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tss->ist[0] = (uint64_t)((uintptr_t)cpu->except_stack + sizeof(cpu->except_stack));
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tss->ist[1] = (uint64_t)((uintptr_t)cpu->irq_stack + sizeof(cpu->irq_stack));
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uint64_t tssbase = (uint64_t)tss;
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uint64_t tsslimit = sizeof(*tss) - 1;
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gdt_set(&gdt->old[0], 0, 0, 0, 0);
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gdt_set(&gdt->old[1], 0, 0xFFFFF, 0x9A, 0xA0);
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gdt_set(&gdt->old[2], 0, 0xFFFFF, 0x92, 0xC0);
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gdt_set(&gdt->old[3], 0, 0xFFFFF, 0xF2, 0xC0);
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gdt_set(&gdt->old[4], 0, 0xFFFFF, 0xFA, 0xA0);
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gdt_set(&gdt->tsslow, (tssbase & 0xFFFFFFFF), tsslimit, TSS_PRESENT | TSS, 0);
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uint32_t tssbasehigh = (tssbase >> 32);
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gdt->tsshigh.limitlow = (tssbasehigh & 0xFFFF);
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gdt->tsshigh.baselow = (tssbasehigh >> 16) & 0xFFFF;
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gdt->tsshigh.basemid = 0;
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gdt->tsshigh.basehigh = 0;
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gdt->tsshigh.access = 0;
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gdt->tsshigh.gran = 0;
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/* Load GDTR */
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struct gdt_ptr gdtr;
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gdtr.limit = sizeof(*gdt) - 1;
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gdtr.base = (uint64_t)gdt;
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__asm__ volatile("lgdt %0" ::"m"(gdtr) : "memory");
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/* Reload CS */
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__asm__ volatile("pushq %[kcode]\n"
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"lea 1f(%%rip), %%rax\n"
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"pushq %%rax\n"
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"lretq\n"
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"1:\n"
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"movw %[kdata], %%ax\n"
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"movw %%ax, %%ds\n"
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"movw %%ax, %%es\n"
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"movw %%ax, %%ss\n"
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:
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: [kcode] "i"(GDT_KCODE), [kdata] "i"(GDT_KDATA)
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: "rax", "memory");
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__asm__ volatile("ltr %0" ::"r"((uint16_t)GDT_TSS));
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}
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