AdrOS

Overview

AdrOS is a multi-architecture operating system developed for research and academic purposes. The goal is to build a secure, monolithic kernel from scratch, eventually serving as a platform for security testing and exploit development.

Architectures Targeted

• x86 (32-bit & 64-bit)
• ARM (32-bit & 64-bit)
• MIPS
• RISC-V (32-bit & 64-bit)

Technical Stack

• Language: C/C++ and Assembly
• Bootloader: GRUB2 (Multiboot2 compliant)
• Build System: Make + Cross-Compilers

Features

• Multi-arch build system
  • make ARCH=x86|arm|riscv|mips
  • x86 is the primary, working target
• x86 (i386) boot & memory layout
  • Multiboot2 (via GRUB)
  • Higher-half kernel mapping (3GB+)
  • Early paging + VMM initialization
  • W^X-oriented linker layout (separate RX/R/RW segments)
  • Non-executable stack markers in assembly (.note.GNU-stack)
• Memory management
  • Physical Memory Manager (PMM)
  • Virtual Memory Manager (x86)
  • Kernel heap allocator (kmalloc/kfree)
• Basic drivers & console
  • UART serial console logging
  • VGA text console (x86)
  • Keyboard driver + input callback
  • PIT timer + periodic tick
• Kernel services
  • Simple scheduler / multitasking (kernel threads)
  • Basic shell with built-in commands
• InitRD + VFS glue
  • InitRD-backed filesystem node tree
  • Minimal VFS helpers (vfs_read/vfs_write/open/close)
• Syscalls & ring3 bring-up (x86)
  • int 0x80 syscall gate
  • SYSCALL_WRITE, SYSCALL_EXIT, SYSCALL_GETPID
  • Centralized user-pointer access API (user_range_ok, copy_from_user, copy_to_user)
  • Ring3 stub test program with fault-injection for invalid pointers

TODO

• Multi-architecture kernel bring-up
  • Implement VMM/interrupts/scheduler for ARM/RISC-V/MIPS
  • Standardize arch entrypoint behavior (arch_start) across architectures
• Userspace
  • Real userspace loader (e.g., ELF)
  • Process address spaces + page fault handling
  • Safer syscall ABI expansion
• Virtual memory hardening
  • Reduce early identity mapping further (keep only what is required)
  • Guard pages, user/kernel separation checks beyond current page-walk
• Filesystem
  • Persisted storage (ATA/AHCI/virtio-blk or similar)
  • Path resolution, directories, permissions
• Observability & tooling
  • Better memory stats (mem shell command)
  • Debug facilities (panic backtraces, symbolization, structured logs)

Directory Structure

• src/kernel/ - Architecture-independent kernel code
• src/arch/ - Architecture-specific code (boot, context switch, interrupts)
• src/drivers/ - Device drivers
• include/ - Header files