bastion: initial implementation

ready project skeleton
dual-arch build system with Linux-config style configuration
UEFI EFI stub loader (PE32+) for x86_64 and AArch64
ELF64 kernel parser
Temporary framebuffer console
freestanding string and c++ abi stubs

For now, kernel boots, prints banner, memory map and go halt

1 files changed, 113 insertions, 0 deletions

diff --git a/kernel/core/kernel_main.cpp b/kernel/core/kernel_main.cpp
new file mode 100644
index 0000000..9c744c7
--- /dev/null
+++ b/kernel/core/kernel_main.cpp
@@ -0,0 +1,113 @@
+// ============================================================================
+// core/kernel_main.cpp - Kernel entry point
+//
+// Called by arch-specific entry.S after stack setup.
+// Receives BootInfo* by the UEFI loader (or in future from other loader).
+// ============================================================================
+
+#include <boot/boot_info.h>
+#include <kernel/kprint.h>
+#include <kernel/arch.h>
+
+// ── Memory region type names ───────────────────────────────────────────────
+
+namespace {
+//TODO: Move it to another cpp/h file
+//TODO: use reflection to get field name
+[[nodiscard]] constexpr const char* mem_type_name(MemoryRegionType type) {
+    switch (type) {
+        case MemoryRegionType::Usable:                return "Usable";
+        case MemoryRegionType::Reserved:              return "Reserved";
+        case MemoryRegionType::AcpiReclaimable:       return "ACPI Reclaimable";
+        case MemoryRegionType::AcpiNvs:               return "ACPI NVS";
+        case MemoryRegionType::BootloaderReclaimable: return "Boot Reclaimable";
+        case MemoryRegionType::KernelAndModules:      return "Kernel";
+        case MemoryRegionType::Framebuffer:           return "Framebuffer";
+    }
+    return "Unknown";
+}
+
+} // anonymous namespace
+
+// ── Kernel entry ───────────────────────────────────────────────────────────
+// Called from entry.S with BootInfo* in RDI (x86_64) / X0 (AArch64).
+extern "C" void kernel_main(BootInfo* boot_info) {
+    // Validate magic — if wrong we can't print, just halt.
+    if (boot_info->magic != BOOT_INFO_MAGIC)
+        arch::halt();
+
+    // Initialize framebuffer console.
+    // TODO: Add driver skeleton and move framebuffer to early drivers.
+    kcon::init(boot_info->framebuffer);
+
+    // ── Banner ─────────────────────────────────────────────────────────
+
+    kcon::println("========================================");
+    kcon::println("  Bastion Kernel " CONFIG_KERNEL_VERSION);
+    kcon::kprintf("  Architecture: %s\n", arch::name());
+    kcon::println("========================================");
+    kcon::putchar('\n');
+
+    // ── Framebuffer info ───────────────────────────────────────────────
+
+    kcon::kprintf("Framebuffer: %ux%u, pitch=%u, base=%x\n",
+        boot_info->framebuffer.width,
+        boot_info->framebuffer.height,
+        boot_info->framebuffer.pitch,
+        boot_info->framebuffer.base);
+    kcon::putchar('\n');
+
+    // ── Firmware tables ────────────────────────────────────────────────
+
+#ifdef CONFIG_X86
+    if (boot_info->rsdp_address)
+        kcon::kprintf("ACPI RSDP at: %x\n", boot_info->rsdp_address);
+#elif CONFIG_AARCH64
+    if (boot_info->fdt_address)
+        kcon::kprintf("Device Tree at: %x\n", boot_info->fdt_address);
+#endif
+    kcon::putchar('\n');
+
+    // ── Memory map ─────────────────────────────────────────────────────
+
+    kcon::kprintf("Memory map (%u entries):\n", boot_info->memory_map_count);
+
+    uint64_t total_usable = 0;
+    for (uint64_t i = 0; i < boot_info->memory_map_count; i++) {
+        const auto& region = boot_info->memory_map[i];
+
+        // Skip tiny reserved regions to avoid flooding the console.
+        if (region.type == MemoryRegionType::Reserved && region.length < 0x10000)
+            continue;
+
+        kcon::kprintf("  %x - %x  [%s]\n",
+            region.base,
+            region.base + region.length,
+            mem_type_name(region.type));
+
+        if (region.type == MemoryRegionType::Usable)
+            total_usable += region.length;
+    }
+
+    kcon::putchar('\n');
+    kcon::kprintf("Total usable memory: %u MiB\n", total_usable / (1024u * 1024u));
+
+    // ── Kernel info ────────────────────────────────────────────────────
+
+    kcon::putchar('\n');
+    kcon::kprintf("Kernel loaded at phys %x, virt %x, size %u KiB\n",
+        boot_info->kernel_phys_base,
+        boot_info->kernel_virt_base,
+        boot_info->kernel_size / 1024u);
+
+    // ── Done (for now) ─────────────────────────────────────────────────
+
+    kcon::putchar('\n');
+    kcon::println("Hello, World from BastionOS!");
+    kcon::putchar('\n');
+    kcon::println("Kernel initialized successfully.");
+    kcon::println("Next: GDT, IDT, paging, memory allocator...");
+    kcon::println("Halting.");
+
+    arch::halt(); // [[noreturn]] — never comes back
+}