integrity of the kernel's core initialization routines.

1. Symbol Verification and Availability

- isr.c : Confirmed that timer_get_ticks is correctly implemented and non-static.
- gdt.c : Verified gdt_init is present and correctly calls the assembly gdt_flush .
- idt.c : Fixed idt_init to ensure it registers all 32 exceptions, all 16 IRQs (after remapping the PIC), and the system call interrupt (128). Crucially, I added the missing call to idt_load , which actually tells the CPU where the IDT is located.
2. Build System Improvements in Makefile

- Unique Object Extensions : The build now uses .c.o and .s.o extensions. This prevents name collisions between C and Assembly files with the same name (like isr.c and isr.s ), which was likely the cause of the "undefined reference" errors.
- Link Order : The linker command now explicitly places -lgcc at the very end:
  ```
  kernel.bin: $(OBJS) linker.ld
      $(LD) $(LDFLAGS) $(OBJS) -lgcc
  ``` This ensures that libgcc's 64-bit math helper functions (like __udivdi3 ) are available to all object files.
3. Linker Script Standardization

- linker.ld : Confirmed that the script defines both kernel_start and kernel_end . These symbols are essential for the physical memory manager ( pmm.c ) to reserve the memory occupied by the kernel itself.

Author: PythonPlumber

src/cpu/idt.c

@@ -47,6 +47,7 @@ extern void irq6(void);
 extern void irq7(void);
 extern void irq8(void);
 extern void irq9(void);
+extern void idt_load(uint32_t);
 extern void irq10(void);
 extern void irq11(void);
 extern void irq12(void);