1 files changed, 48 insertions, 0 deletions
diff --git a/kernel/arch/x86_64/entry.S b/kernel/arch/x86_64/entry.S
new file mode 100644
index 0000000..50cdd47
--- /dev/null
+++ b/kernel/arch/x86_64/entry.S
@@ -0,0 +1,48 @@
+// ============================================================================
+// arch/x86_64/entry.S - Kernel entry point (x86_64)
+//
+// Called by the UEFI loader after ExitBootServices.
+//   - Long mode active, paging on (identity map from UEFI)
+//   - RDI = pointer to BootInfo structure
+//   - Interrupts disabled
+// ============================================================================
+
+.section .text
+.global _start
+.extern kernel_main
+
+_start:
+    // Disable interrupts
+    cli
+
+    // Set up kernel stack
+    // Load Effective Address quadword
+    // the address RIP (current exec instruction) + offset_to_stack_top
+    // to the Stack pointer register (rsp)
+    //(AT&T syntax: lea symbol(%rip), %reg)
+    leaq    _stack_top(%rip), %rsp
+
+    // Align stack to 16 bytes (System V ABI)
+    // Because ABI mandates that rsp must be 16-byte aligned at the point of a call instruction
+    andq    $-16, %rsp
+
+    // The UEFI boot loader (PE/MS x64 ABI) passes BootInfo* in RCX.
+    // kernel_main uses System V ABI and expects it in RDI.
+    movq    %rcx, %rdi
+    call    kernel_main
+
+    // Should never return
+.Lhalt:
+    cli
+    hlt
+    jmp     .Lhalt
+
+// ============================================================================
+// Kernel stack (16 KiB)
+// ============================================================================
+
+.section .bss
+.align 4096
+_stack_bottom:
+    .space CONFIG_KERNEL_STACK_SIZE
+_stack_top: