feat: main function

kernel/include/acpi/discovery.h

@@ -13,4 +13,7 @@ struct discovery_result_t {
     optional<Fadt> fadt;
 };
 
+void initDiscovery();
+const discovery_result_t& getDiscovery();
+
 } // namespace acpi

kernel/include/apic/core.h

@@ -3,6 +3,7 @@
 #include "memory/pointer.h"
 
 #include "acpi/discovery.h"
+#include "cpu/gdt.h"
 #include "memory/pagetable.h"
 
 namespace apic {
@@ -18,12 +19,13 @@ struct Core {
     core_id id;
     stack_t stack;
     PageTable kernelPageTable;
+    Gdt gdt;
 };
 
 optional<Core> initCore(acpi::Madt madt, core_id id);
 
 void initCores(acpi::discovery_result_t);
 
-void transitionStartupCore();
+[[noreturn]] void transitionStartupCore();
 
 } // namespace apic

kernel/include/cpu/gdt.h

@@ -56,3 +56,22 @@ struct [[gnu::packed]] tss_t {
 static_assert(sizeof(tss_t) == 104);
 
 void reloadSegments(Gdt::selector_t code_selector, Gdt::selector_t data_selector);
+
+[[noreturn]] inline void longjump(
+    uint64_t code, uint64_t stack, Gdt::selector_t code_selector, Gdt::selector_t stack_selector, uint64_t arg
+) {
+    uint64_t code_sel = code_selector;
+    uint16_t stack_sel = stack_selector;
+    asm volatile(
+        "mov %[stack_sel], %%ss\n"
+        "mov %[stack], %%rsp\n"
+        "pushq %[code_sel]\n"
+        "pushq %[code]\n"
+        "mov %[arg], %%rdi\n"
+        "lretq\n"
+        :
+        : [stack_sel] "r"(stack_sel), [stack] "r"(stack), [code_sel] "r"(code_sel), [code] "r"(code), [arg] "r"(arg)
+        : "memory", "rdi"
+    );
+    __builtin_unreachable();
+}

kernel/include/main.h

@@ -1,3 +1,5 @@
 #pragma once
 
-[[noreturn]] void main();
+#include "apic/core.h"
+
+[[noreturn]] void main(apic::Core* core);