Luna/kernel/src/main.cpp

#include "ELF.h"
#include "InitRD.h"
#include "Log.h"
#include "arch/CPU.h"
#include "arch/MMU.h"
#include "arch/PCI.h"
#include "arch/Timer.h"
#include "boot/Init.h"
#include "config.h"
#include "fs/devices/DeviceRegistry.h"
#include "fs/tmpfs/FileSystem.h"
#include "memory/Heap.h"
#include "memory/KernelVM.h"
#include "memory/MemoryManager.h"
#include "thread/Scheduler.h"
#include "video/Framebuffer.h"
#include "video/TextConsole.h"
#include <luna/CString.h>
#include <luna/Result.h>
#include <luna/Units.h>

extern void set_host_name(StringView);

void reap_thread()
{
    while (true)
    {
        CPU::disable_interrupts();
        auto dying_threads = Scheduler::check_for_dying_threads();
        CPU::enable_interrupts();

        dying_threads.consume([](Thread* thread) { Scheduler::reap_thread(thread); });

        kernel_sleep(250);
    }
}

Result<void> init()
{
    kinfoln("Starting Moon %s, built on %s at %s", MOON_VERSION, __DATE__, __TIME__);

    // Default hostname if nobody from userspace changes it
    set_host_name("moon"_sv);

    kinfoln("Current platform: %s", CPU::platform_string());
    kinfoln("Current processor: %s", CPU::identify().value_or("(unknown)"));

    Timer::init();

    kinfoln("Total memory:    %s", to_dynamic_unit(MemoryManager::total()).release_value().chars());
    kinfoln("Free memory:     %s", to_dynamic_unit(MemoryManager::free()).release_value().chars());
    kinfoln("Used memory:     %s", to_dynamic_unit(MemoryManager::used()).release_value().chars());
    kinfoln("Reserved memory: %s", to_dynamic_unit(MemoryManager::reserved()).release_value().chars());

    Thread::init();
    Scheduler::init();

    VFS::root_fs = TRY(TmpFS::FileSystem::create());
    TRY(DeviceRegistry::init());
    InitRD::populate_vfs();

    auto init = TRY(VFS::resolve_path("/bin/init", Credentials {}));
    TRY(Scheduler::new_userspace_thread(init, "/bin/init"));

    Scheduler::new_kernel_thread(reap_thread, "[reap]").release_value();

    PCI::scan(
        [](const PCI::Device& device) {
            kinfoln("Found PCI mass storage device %.4x:%.4x, at address %u:%u:%u", device.id.vendor, device.id.device,
                    device.address.bus, device.address.slot, device.address.function);
        },
        { .klass = 1 });

    CPU::platform_finish_init();

    // Disable console logging before transferring control to userspace.
    setup_log(log_debug_enabled(), log_serial_enabled(), false);

    CPU::enable_interrupts();

    return {};
}

[[noreturn]] void init_wrapper()
{
    auto rc = init();
    if (rc.has_error()) kerrorln("Runtime error: %s", rc.error_string());
    CPU::idle_loop();
}

static constexpr u64 BOOTSTRAP_STACK_PAGES = 8;

// FIXME: Reclaim this memory as soon as we leave the init task (so as soon as the Scheduler runs a task switch)
static u64 allocate_initial_kernel_stack()
{
    u64 address = MemoryManager::alloc_for_kernel(BOOTSTRAP_STACK_PAGES + 1, MMU::ReadWrite | MMU::NoExecute).value();
    // First page is a guard page, the rest is stack.
    MMU::unmap(address); // Unmap (without deallocating VM) one guard page so that attempts to access it fail with a
                         // non-present page fault.

    // The actual stack.
    Stack stack { address + ARCH_PAGE_SIZE, BOOTSTRAP_STACK_PAGES * ARCH_PAGE_SIZE };

    return stack.top();
}

extern "C" [[noreturn]] void _start()
{
    Init::check_magic();
    Init::early_init();
    u64 bootstrap_stack_top = allocate_initial_kernel_stack();
    CPU::bootstrap_switch_stack(bootstrap_stack_top, (void*)init_wrapper);
}