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Strix OS Roadmap: Linux Application Compatibility

This roadmap outlines the path from the current kernel state to full Linux application compatibility.

Current State

The kernel has a solid foundation:

  • GDT/TSS/IDT properly configured
  • Interrupt handling (timer, keyboard, page fault exceptions)
  • VGA text mode output + serial debugging
  • PS/2 keyboard input with scancode translation

Missing for Linux compatibility: heap allocation, paging control, user-space, syscalls, processes, VFS, ELF loader.

Phase 1: Memory Management

1.1 - Page Table Access

  • Access bootloader's page tables via BootInfo
  • Implement page table walking (translate virtual → physical)
  • Create OffsetPageTable or RecursivePageTable mapper
  • Files: src/memory.rs

1.2 - Frame Allocator

  • Parse memory map from bootloader
  • Implement FrameAllocator trait
  • Track used/free physical frames (bitmap or linked list)
  • Files: src/memory/frame_allocator.rs

1.3 - Heap Allocator

  • Map heap region in virtual memory
  • Implement GlobalAlloc (linked_list_allocator crate or custom)
  • Enable alloc crate (Vec, Box, String, etc.)
  • Files: src/allocator.rs

Dependencies to add:

linked_list_allocator = "0.9.0"

Phase 2: User Space Foundation

2.1 - Ring 3 Transition

  • Set up user-mode GDT segments (ring 3 code/data)
  • Create per-process page tables
  • Implement context switch (save/restore registers)
  • Use IRET to jump to ring 3
  • Files: src/gdt.rs (extend), src/task/mod.rs

2.2 - System Call Interface

  • Set up SYSCALL/SYSRET MSRs (STAR, LSTAR, SFMASK)
  • Create syscall entry point in assembly
  • Implement syscall dispatcher
  • Start with: write, exit, mmap (minimal set)
  • Files: src/syscall/mod.rs, src/syscall/handler.S

2.3 - Basic Process Structure

  • Process struct (pid, page table, registers, state)
  • Process list/table
  • Simple round-robin scheduler
  • fork() and exit() syscalls
  • Files: src/task/process.rs, src/task/scheduler.rs

Phase 3: ELF Loading & exec()

3.1 - ELF Parser

  • Parse ELF64 header and program headers
  • Identify PT_LOAD segments
  • Handle static binaries first
  • Files: src/loader/elf.rs

3.2 - execve() Implementation

  • Load ELF into fresh address space
  • Set up user stack with argc/argv/envp
  • Set up auxiliary vector (AT_ENTRY, AT_PHDR, etc.)
  • Jump to entry point
  • Files: src/syscall/exec.rs

Dependencies to add:

xmas-elf = "0.9.0"  # or goblin for ELF parsing

Phase 4: Virtual File System

4.1 - VFS Layer

  • Define File, Inode, Superblock traits
  • File descriptor table per process
  • open(), read(), write(), close(), lseek()
  • Files: src/fs/vfs.rs, src/fs/fd.rs

4.2 - In-Memory Filesystems

  • ramfs/tmpfs for root filesystem
  • devfs (/dev/null, /dev/zero, /dev/console)
  • procfs (/proc/self/, /proc/[pid]/)
  • Files: src/fs/ramfs.rs, src/fs/devfs.rs, src/fs/procfs.rs

4.3 - Disk Filesystem

  • ATA/AHCI driver
  • ext2/ext4 read support (start read-only)
  • mount() syscall
  • Files: src/drivers/ata.rs, src/fs/ext2.rs

Phase 5: POSIX Essentials

5.1 - Signals

  • Signal delivery mechanism
  • Default handlers (SIGKILL, SIGTERM, SIGSEGV)
  • sigaction(), kill() syscalls
  • Files: src/task/signal.rs

5.2 - Pipes & IPC

  • pipe() syscall
  • dup(), dup2() for fd manipulation
  • Anonymous pipes for shell support
  • Files: src/fs/pipe.rs

5.3 - Wait & Process Groups

  • wait4(), waitpid() syscalls
  • Process groups, sessions
  • Foreground/background processes
  • Files: src/task/wait.rs

Phase 6: Init System Support (OpenRC)

6.1 - Required Syscalls & Filesystems

  • mount(), umount() syscalls
  • Working /proc and /sys
  • chroot(), pivot_root()
  • Basic TTY/PTY support
  • Files: src/syscall/mount.rs, src/fs/sysfs.rs

6.2 - Device Management

  • /dev population (static or dynamic)
  • ioctl() for device control
  • Console/TTY driver
  • Files: src/drivers/tty.rs

Suggested Directory Structure

src/
├── main.rs
├── lib.rs
├── memory/
│   ├── mod.rs
│   ├── paging.rs
│   ├── frame_allocator.rs
│   └── heap.rs
├── task/
│   ├── mod.rs
│   ├── process.rs
│   ├── scheduler.rs
│   ├── context.rs
│   └── signal.rs
├── syscall/
│   ├── mod.rs
│   ├── handler.rs
│   ├── table.rs          # syscall number → handler mapping
│   ├── fs.rs             # open, read, write, close
│   ├── process.rs        # fork, exec, exit, wait
│   └── memory.rs         # mmap, munmap, brk
├── fs/
│   ├── mod.rs
│   ├── vfs.rs
│   ├── fd.rs
│   ├── ramfs.rs
│   ├── devfs.rs
│   └── procfs.rs
├── loader/
│   └── elf.rs
└── drivers/
    ├── tty.rs
    └── ata.rs

Linux Syscall Priority List

Essential syscalls to implement (roughly in order of importance):

Tier 1 - Minimal Execution

Syscall Number Purpose
write 1 Output to console/files
exit 60 Terminate process
exit_group 231 Terminate all threads
brk 12 Heap memory allocation
mmap 9 Memory mapping
munmap 11 Unmap memory

Tier 2 - Process Management

Syscall Number Purpose
fork 57 Create child process
clone 56 Create thread/process
execve 59 Execute program
wait4 61 Wait for child
getpid 39 Get process ID
getppid 110 Get parent PID

Tier 3 - File Operations

Syscall Number Purpose
read 0 Read from fd
open 2 Open file
close 3 Close fd
stat 4 File information
fstat 5 File info by fd
lseek 8 Seek in file
dup 32 Duplicate fd
dup2 33 Duplicate to specific fd
pipe 22 Create pipe
ioctl 16 Device control

Tier 4 - Signals & Advanced

Syscall Number Purpose
rt_sigaction 13 Signal handlers
rt_sigprocmask 14 Block signals
kill 62 Send signal
getcwd 79 Current directory
chdir 80 Change directory
mount 165 Mount filesystem
umount2 166 Unmount filesystem

Resources

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