Initial commit

2026-02-04 01:58:49 +01:00
commit 0e01345abf
117 changed files with 5076 additions and 0 deletions
@@ -0,0 +1,51 @@
+#include <kernel/percpu.h>
+#include <kernel/syscalls.h>
+#include <asm.h>
+#include <defs.h>
+#include <gdt.h>
+#include <stddef.h>
+#include <string.h>
+
+struct gdt main_gdt = {
+    .null = 0,
+    .kernel_code32 = 0x00cf9b000000ffff,
+    .kernel_data32 = 0x00cf93000000ffff,
+    .kernel_code64 = 0x00a09b0000000000,
+    .kernel_data64 = 0x0000930000000000,
+    .user_code = 0x00cffb000000ffff,
+    .user_data = 0x0000f30000000000,
+    .user_code64 = 0x0000fb0000000000,
+    .tss = {0x0000890000000000, 0},
+};
+
+void gdt_init() {
+    // Set initial values.
+    memcpy(&percpu_get()->arch.gdt, &main_gdt, sizeof(struct gdt));
+
+    struct gdtr gdtr = {
+        .limit = sizeof(struct gdt) - 1,
+        .base = &percpu_get()->arch.gdt,
+    };
+
+    asm volatile("lgdt [%0]" ::"r"(&gdtr));
+
+    // Save the contents of MSR_GS_BASE, as they get cleared by a write to `gs`.
+    virt_t gs = asm_rdmsr(MSR_GS_BASE);
+    asm volatile(
+        "push %0\n"
+        "lea rax, [rip + 1f]\n"
+        "push rax\n"
+        "retfq\n"
+        "1:\n"
+        "mov ax, %1\n"
+        "mov ds, ax\n"
+        "mov es, ax\n"
+        "mov fs, ax\n"
+        "mov gs, ax\n"
+        "mov ss, ax\n"
+        :
+        : "i"(offsetof(struct gdt, kernel_code64)), "i"(offsetof(struct gdt, kernel_data64))
+        : "rax", "memory"
+    );
+    asm_wrmsr(MSR_GS_BASE, gs);
+}