- `grub-pc-bin` and `grub-common` (x86 bootloader)
- Cross-compilers for ARM/RISC-V (optional, for non-x86 targets)
- `cppcheck` (optional, for static analysis)
+- `expect` (optional, for automated smoke tests)
+- `sparse` (optional, for kernel-style static analysis)
### On Ubuntu/Debian:
```bash
sudo apt update
sudo apt install build-essential bison flex libgmp3-dev libmpc-dev libmpfr-dev texinfo \
qemu-system-x86 qemu-system-arm qemu-system-misc \
- grub-common grub-pc-bin xorriso mtools cppcheck \
+ grub-common grub-pc-bin xorriso mtools cppcheck expect sparse \
gcc-aarch64-linux-gnu gcc-riscv64-linux-gnu
```
All tests print `[init] ... OK` on success. Any failure calls `sys_exit(1)`.
-Static analysis helper:
+### Testing
+
+Run all tests (static analysis + host unit tests + QEMU smoke tests):
```bash
-make ARCH=x86 cppcheck
+make test-all
+```
+
+Individual test targets:
+```bash
+make check # cppcheck + sparse + gcc -fanalyzer
+make test-host # 47 host-side unit tests (test_utils + test_security)
+make test # QEMU smoke test (4 CPUs, 40s timeout, 19 checks)
+make test-1cpu # Single-CPU smoke test (50s timeout)
+make test-gdb # GDB scripted integrity checks (heap, PMM, VGA)
```
-Additional analysis helpers:
+Static analysis helpers:
```bash
+make ARCH=x86 cppcheck
make ARCH=x86 scan-build
make ARCH=x86 mkinitrd-asan
```
# ---- Automated Smoke Test (QEMU + expect) ----
SMOKE_SMP ?= 4
-SMOKE_TIMEOUT ?= 40
+SMOKE_TIMEOUT ?= 60
test: iso
@echo "[TEST] Running smoke test (SMP=$(SMOKE_SMP), timeout=$(SMOKE_TIMEOUT)s)..."
- **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 userspace layout (separate RX/R and 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)
- - Minimal process lifecycle: parent/child tracking, zombies, `waitpid`
- - Basic shell with built-in commands (fallback when userspace fails)
-- **InitRD + VFS + mounts**
- - InitRD image in TAR/USTAR format (with directory support)
- - InitRD-backed filesystem node tree (`fs_node_t` + `finddir`)
- - Absolute path lookup (`vfs_lookup("/bin/init.elf")`)
- - Mount table support (`vfs_mount`) + `tmpfs` and `overlayfs`
-- **Syscalls (x86, `int 0x80`)**
- - **File I/O:** `open`, `openat`, `read`, `write`, `close`, `lseek`, `stat`, `fstat`, `fstatat`, `dup`, `dup2`, `dup3`, `pipe`, `pipe2`, `select`, `poll`, `ioctl`, `fcntl`
- - **Directory ops:** `mkdir`, `rmdir`, `unlink`, `unlinkat`, `rename`, `getdents`, `chdir`, `getcwd`
- - **Process:** `fork`, `execve`, `exit`, `waitpid` (incl. `WNOHANG`), `getpid`, `getppid`, `setsid`, `setpgid`, `getpgrp`
- - **Signals:** `sigaction`, `sigprocmask`, `kill`, `sigreturn` (trampoline-based return path)
- - **Modern POSIX:** `openat`/`fstatat`/`unlinkat` (`AT_FDCWD`), `dup3`, `pipe2` (with `O_NONBLOCK` flags)
- - Per-process fd table with refcounted file objects
- - Per-process current working directory (`cwd`) with relative path resolution
- - Non-blocking I/O (`O_NONBLOCK`) on pipes, TTY, and PTY via `fcntl`
- - Centralized user-pointer access API (`user_range_ok`, `copy_from_user`, `copy_to_user`)
- - Ring3 init program (`/bin/init.elf`) with comprehensive smoke tests
- - Error returns use negative errno codes (Linux-style)
-- **TTY (canonical line discipline)**
- - Keyboard -> TTY input path
- - Canonical mode input (line-buffered until `\n`)
- - Echo + backspace handling
- - Blocking reads with a simple wait queue (multiple waiters)
- - `fd=0` wired to `tty_read`, `fd=1/2` wired to `tty_write`
- - Minimal termios/ioctl support (`TCGETS`, `TCSETS`, `TIOCGPGRP`, `TIOCSPGRP`)
- - Basic job control enforcement (`SIGTTIN`/`SIGTTOU` when background pgrp touches the controlling TTY)
-- **Devices (devfs)**
- - `/dev` mount with `readdir` support
- - `/dev/null`, `/dev/tty`
- - `/dev/ptmx` + `/dev/pts/0` (pseudo-terminal)
-- **PTY subsystem**
- - PTY master/slave pair (`/dev/ptmx` + `/dev/pts/0`)
- - Non-blocking I/O support
- - Used by userland smoke tests
-- **On-disk filesystem (diskfs)**
- - ATA PIO driver (primary master IDE)
- - Hierarchical inode-based filesystem mounted at `/disk`
- - Supports: `open` (create/truncate), `read`, `write`, `stat`, `mkdir`, `unlink`, `rmdir`, `rename`, `getdents`
- - Persistence filesystem mounted at `/persist` (smoke tests)
-- **Generic `readdir`/`getdents` across all VFS**
- - Works on diskfs, tmpfs, devfs, and overlayfs
- - Unified `struct vfs_dirent` format
-- **W^X (Option 1) for user ELFs (x86)**
- - User segments are mapped RW during load, then write permissions are dropped for non-writable segments
- - This provides "text is read-only" hardening without requiring NX/PAE
+
+### Boot & Architecture
+- **Multi-arch build system** — `make ARCH=x86|arm|riscv|mips` (x86 is the primary, working target)
+- **Multiboot2** (via GRUB), higher-half kernel mapping (3GB+)
+- **CPUID feature detection** — leaf 0/1/7/extended; SMEP/SMAP detection
+- **SYSENTER fast syscall path** — MSR setup + handler
+
+### Memory Management
+- **PMM** — bitmap allocator with spinlock protection and frame reference counting
+- **VMM** — recursive page directory, per-process address spaces, TLB flush
+- **Copy-on-Write (CoW) fork** — PTE bit 9 as CoW marker + page fault handler
+- **Kernel heap** — doubly-linked free list with coalescing, dynamic growth up to 64MB
+- **Slab allocator** — `slab_cache_t` with free-list-in-place and spinlock
+- **Shared memory** — System V IPC style (`shmget`/`shmat`/`shmdt`/`shmctl`)
+- **SMEP** — Supervisor Mode Execution Prevention enabled in CR4
+- **W^X** — user `.text` segments marked read-only after ELF load
+
+### Process & Scheduling
+- **O(1) scheduler** — bitmap + active/expired arrays, 32 priority levels
+- **Process model** — `fork` (CoW), `execve`, `exit`, `waitpid` (`WNOHANG`), `getpid`, `getppid`
+- **Sessions & groups** — `setsid`, `setpgid`, `getpgrp`
+- **User heap** — `brk`/`sbrk` syscall
+- **Time** — `nanosleep`, `clock_gettime` (`CLOCK_REALTIME`, `CLOCK_MONOTONIC`)
+
+### Syscalls (x86, `int 0x80` + SYSENTER)
+- **File I/O:** `open`, `openat`, `read`, `write`, `close`, `lseek`, `stat`, `fstat`, `fstatat`, `dup`, `dup2`, `dup3`, `pipe`, `pipe2`, `select`, `poll`, `ioctl`, `fcntl`, `getdents`
+- **Directory ops:** `mkdir`, `rmdir`, `unlink`, `unlinkat`, `rename`, `chdir`, `getcwd`
+- **Signals:** `sigaction`, `sigprocmask`, `kill`, `sigreturn` (full trampoline with `SA_SIGINFO`)
+- **FD flags:** `O_NONBLOCK`, `O_CLOEXEC`, `FD_CLOEXEC` via `fcntl` (`F_GETFD`/`F_SETFD`/`F_GETFL`/`F_SETFL`)
+- **Shared memory:** `shmget`, `shmat`, `shmdt`, `shmctl`
+- Per-process fd table with atomic refcounted file objects
+- Centralized user-pointer access API (`user_range_ok`, `copy_from_user`, `copy_to_user`)
+- Error returns use negative errno codes (Linux-style)
+
+### TTY / PTY
+- **Canonical + raw mode** — `ICANON` clearable via `TCSETS`
+- **Signal characters** — Ctrl+C→SIGINT, Ctrl+Z→SIGTSTP, Ctrl+D→EOF, Ctrl+\\→SIGQUIT
+- **Job control** — `SIGTTIN`/`SIGTTOU` enforcement for background process groups
+- **PTY** — `/dev/ptmx` + `/dev/pts/0` with non-blocking I/O
+- **Window size** — `TIOCGWINSZ`/`TIOCSWINSZ`
+- **termios** — `TCGETS`, `TCSETS`, `TIOCGPGRP`, `TIOCSPGRP`
+
+### Filesystems (6 types)
+- **tmpfs** — in-memory filesystem
+- **devfs** — `/dev/null`, `/dev/tty`, `/dev/ptmx`, `/dev/pts/0`
+- **overlayfs** — copy-up semantics
+- **diskfs** — hierarchical inode-based on-disk filesystem at `/disk`
+- **persistfs** — minimal persistence at `/persist`
+- **procfs** — `/proc/meminfo`
+- Generic `readdir`/`getdents` across all VFS types
+
+### Drivers & Hardware
+- **PCI** — full bus/slot/func enumeration with BAR + IRQ
+- **ATA PIO + DMA** — Bus Master IDE with bounce buffer, PRDT, IRQ coordination
+- **LAPIC + IOAPIC** — replaces legacy PIC; ISA IRQ routing
+- **SMP** — 4 CPUs via INIT-SIPI-SIPI, per-CPU data via GS segment
+- **ACPI** — MADT parsing for CPU topology and IOAPIC discovery
+- **VBE framebuffer** — maps LFB, pixel drawing, font rendering
+- **UART**, **VGA text**, **PS/2 keyboard**, **PIT timer**, **LAPIC timer**
+
+### Userland
+- **ulibc** — `printf`, `malloc`/`free`/`calloc`/`realloc`, `string.h`, `unistd.h`, `errno.h`
+- **ELF32 loader** — secure with W^X enforcement, rejects kernel-range vaddrs
+- `/bin/init.elf` — comprehensive smoke test suite
+- `/bin/echo.elf` — argv/envp test
+
+### Security
+- **SMEP** enabled (prevents kernel executing user-mapped pages)
+- **user_range_ok** hardened (rejects kernel addresses)
+- **sigreturn eflags** sanitized (clears IOPL, ensures IF)
+- **Atomic file refcounts** (`__sync_*` builtins)
+- **PMM spinlock** for SMP safety
+
+### Testing
+- **47 host-side unit tests** — `test_utils.c` (28) + `test_security.c` (19)
+- **19 QEMU smoke tests** — 4-CPU, expect-based
+- **Static analysis** — cppcheck, sparse, gcc -fanalyzer
+- **GDB scripted checks** — heap/PMM/VGA integrity
+- `make test-all` runs everything
## Running (x86)
- `make ARCH=x86 iso`
See [POSIX_ROADMAP.md](docs/POSIX_ROADMAP.md) for a detailed checklist.
-- **Syscalls / POSIX gaps**
- - `brk`/`sbrk` (heap management)
- - `mmap`/`munmap` (memory-mapped I/O)
- - `access`, `chmod`, `chown`, `umask` (permissions)
- - `link`, `symlink`, `readlink` (hard/symbolic links)
- - `truncate`/`ftruncate`
- - `socket`/`bind`/`listen`/`accept`/`connect`/`send`/`recv` (networking)
- - Userspace `errno` variable + libc-style wrappers
-- **Filesystem**
- - Permissions/ownership (`uid/gid`, mode bits)
- - `/proc` filesystem
- - Real on-disk FS (ext2/FAT) as alternative to diskfs
-- **TTY / terminal**
- - Full termios flags (raw mode, VMIN/VTIME, signal chars)
- - Multiple PTY pairs
-- **Virtual memory hardening**
- - PAE + NX enforcement (execute disable for data/stack)
- - Guard pages, ASLR
-- **Multi-architecture kernel bring-up**
- - Implement VMM/interrupts/scheduler for ARM/RISC-V/MIPS
-- **Userland**
- - Minimal libc (`printf`, `malloc`, `string.h`, etc.)
- - Shell (sh-compatible)
- - Core utilities (`ls`, `cat`, `cp`, `mv`, `rm`, `echo`, `mkdir`)
-- **Observability & tooling**
- - Panic backtraces, symbolization
- - CI pipeline with `cppcheck`, `scan-build`
+### Near-term (unlock interactive use)
+- **Shell** (`sh`-compatible) — all required syscalls are implemented
+- **Core utilities** — `ls`, `cat`, `echo`, `mkdir`, `rm`
+- **`/dev/zero`**, **`/dev/random`** — simple device nodes
+- **Multiple PTY pairs** — currently only 1
+
+### Medium-term (POSIX compliance)
+- **`mmap`/`munmap`** — memory-mapped files
+- **Permissions** — `uid`/`gid`/mode, `chmod`, `chown`, `access`, `umask`
+- **`/proc` per-process** — `/proc/[pid]/status`, `/proc/[pid]/maps`
+- **Hard/symbolic links** — `link`, `symlink`, `readlink`
+- **VMIN/VTIME** — termios non-canonical timing
+
+### Long-term (full Unix experience)
+- **Networking** — socket API, TCP/IP stack
+- **Threads** — `clone`/`pthread`
+- **PAE + NX bit** — hardware W^X
+- **Dynamic linking** — `ld.so`
+- **ext2/FAT** filesystem support
## Directory Structure
-- `src/kernel/` - Architecture-independent kernel code (VFS, syscalls, scheduler, tmpfs, diskfs, devfs, overlayfs, PTY, TTY)
-- `src/arch/` - Architecture-specific code (boot, context switch, interrupts, VMM)
-- `src/hal/` - Hardware abstraction layer (CPU, keyboard, timer, UART, video)
-- `src/drivers/` - Device drivers (ATA, initrd, keyboard, timer, UART, VGA)
-- `src/mm/` - Memory management (PMM, heap)
-- `include/` - Header files
-- `user/` - Userland programs (`init.c`, `echo.c`)
-- `docs/` - Documentation (POSIX roadmap)
+- `src/kernel/` — Architecture-independent kernel (VFS, syscalls, scheduler, tmpfs, diskfs, devfs, overlayfs, PTY, TTY, shm, signals)
+- `src/arch/x86/` — x86-specific (boot, VMM, IDT, LAPIC, IOAPIC, SMP, ACPI, CPUID, SYSENTER)
+- `src/hal/x86/` — HAL x86 (CPU, keyboard, timer, UART, PCI, ATA PIO/DMA)
+- `src/drivers/` — Device drivers (VBE, initrd, VGA)
+- `src/mm/` — Memory management (PMM, heap, slab)
+- `include/` — Header files
+- `user/` — Userland programs (`init.c`, `echo.c`)
+- `user/ulibc/` — Minimal C library (`printf`, `malloc`, `string.h`, `errno.h`)
+- `tests/` — Host unit tests, smoke tests, GDB scripted checks
+- `docs/` — Documentation (POSIX roadmap, audit report, supplementary analysis, testing plan)
| `pread`/`pwrite` | [ ] | |
| `readv`/`writev` | [ ] | |
| `truncate`/`ftruncate` | [ ] | |
-| `fsync`/`fdatasync` | [ ] | |
+| `fsync`/`fdatasync` | [ ] | No-op acceptable for now |
## 2. Syscalls — Directory & Path Operations
| Syscall | Status | Notes |
|---------|--------|-------|
-| `fork` | [x] | Full COW not implemented; copies address space |
-| `execve` | [~] | Loads ELF from VFS; minimal argv/envp; no `$PATH` search |
+| `fork` | [x] | Full COW implemented (`vmm_as_clone_user_cow` + `vmm_handle_cow_fault`) |
+| `execve` | [x] | Loads ELF from VFS; argv/envp; `O_CLOEXEC` FDs closed |
| `exit` / `_exit` | [x] | Closes FDs, marks zombie, notifies parent |
| `waitpid` | [x] | `-1` (any child), specific pid, `WNOHANG` |
| `getpid` | [x] | |
| `getpgrp` | [x] | |
| `getuid`/`getgid`/`geteuid`/`getegid` | [ ] | No user/group model yet |
| `setuid`/`setgid` | [ ] | |
-| `brk`/`sbrk` | [ ] | Heap management |
+| `brk`/`sbrk` | [x] | `syscall_brk_impl()` — per-process heap break |
| `mmap`/`munmap` | [ ] | Memory-mapped I/O |
| `clone` | [ ] | Thread creation |
-| `nanosleep`/`sleep` | [ ] | |
+| `nanosleep`/`sleep` | [x] | `syscall_nanosleep_impl()` with tick-based sleep |
+| `clock_gettime` | [x] | `CLOCK_REALTIME` and `CLOCK_MONOTONIC` |
| `alarm` | [ ] | |
| `times`/`getrusage` | [ ] | |
| `sigsuspend` | [ ] | |
| `sigqueue` | [ ] | |
| `sigaltstack` | [ ] | Alternate signal stack |
-| Signal defaults | [~] | `SIGKILL`/`SIGSEGV`/`SIGUSR1` handled; many signals missing default actions |
+| Signal defaults | [x] | `SIGKILL`/`SIGSEGV`/`SIGUSR1`/`SIGINT`/`SIGTSTP`/`SIGTTOU`/`SIGTTIN` handled |
## 5. File Descriptor Layer
| Refcounted file objects | [x] | Shared across `dup`/`fork` |
| File offset tracking | [x] | |
| `O_NONBLOCK` | [x] | Pipes, TTY, PTY via `fcntl` or `pipe2` |
-| `O_CLOEXEC` | [ ] | Close-on-exec flag |
+| `O_CLOEXEC` | [x] | Close-on-exec via `pipe2`, `open` flags |
| `O_APPEND` | [ ] | |
-| `FD_CLOEXEC` via `fcntl` | [ ] | |
+| `FD_CLOEXEC` via `fcntl` | [x] | `F_GETFD`/`F_SETFD` implemented; `execve` closes marked FDs |
| File locking (`flock`/`fcntl`) | [ ] | |
## 6. Filesystem / VFS
| **devfs** | [x] | `/dev/null`, `/dev/tty`, `/dev/ptmx`, `/dev/pts/0`; `readdir` |
| **diskfs** (on-disk) | [x] | Hierarchical inodes; `open`/`read`/`write`/`stat`/`mkdir`/`unlink`/`rmdir`/`rename`/`getdents` |
| **persistfs** | [x] | Minimal persistence at `/persist` |
+| **procfs** | [~] | `/proc/meminfo` exists; no per-process `/proc/[pid]` |
| Permissions (`uid`/`gid`/mode) | [ ] | No permission model |
| Hard links | [ ] | |
| Symbolic links | [ ] | |
-| `/proc` filesystem | [ ] | |
| ext2 / FAT support | [ ] | |
## 7. TTY / PTY
| `isatty` (via `ioctl TCGETS`) | [x] | |
| PTY master/slave | [x] | `/dev/ptmx` + `/dev/pts/0` |
| Non-blocking PTY I/O | [x] | |
-| Raw mode (non-canonical) | [ ] | |
+| Raw mode (non-canonical) | [x] | Clear `ICANON` via `TCSETS` |
| VMIN/VTIME | [ ] | |
-| Signal characters (Ctrl+C → `SIGINT`, etc.) | [ ] | |
+| Signal characters (Ctrl+C → `SIGINT`, etc.) | [x] | Ctrl+C→SIGINT, Ctrl+Z→SIGTSTP, Ctrl+D→EOF, Ctrl+\\→SIGQUIT |
| Multiple PTY pairs | [ ] | Only 1 pair currently |
-| Window size (`TIOCGWINSZ`/`TIOCSWINSZ`) | [ ] | |
+| Window size (`TIOCGWINSZ`/`TIOCSWINSZ`) | [x] | Get/set `struct winsize` |
## 8. Memory Management
| Feature | Status | Notes |
|---------|--------|-------|
-| PMM (bitmap allocator) | [x] | |
-| VMM (x86 paging) | [x] | Higher-half kernel |
+| PMM (bitmap allocator) | [x] | Spinlock-protected, frame refcounting |
+| VMM (x86 paging) | [x] | Higher-half kernel, recursive page directory |
| Per-process address spaces | [x] | Page directory per process |
-| Kernel heap (`kmalloc`/`kfree`) | [x] | 10MB heap |
+| Kernel heap (`kmalloc`/`kfree`) | [x] | Dynamic growth up to 64MB |
+| Slab allocator | [x] | `slab_cache_t` with free-list-in-place |
| W^X for user ELFs | [x] | Text segments read-only after load |
-| `brk`/`sbrk` | [ ] | |
+| SMEP | [x] | Enabled in CR4 if CPU supports |
+| `brk`/`sbrk` | [x] | Per-process heap break |
| `mmap`/`munmap` | [ ] | |
-| Copy-on-write (COW) fork | [ ] | Currently full-copy |
+| Shared memory (`shmget`/`shmat`/`shmdt`) | [x] | System V IPC style |
+| Copy-on-write (COW) fork | [x] | PTE bit 9 as CoW marker + page fault handler |
| PAE + NX bit | [ ] | |
| Guard pages | [ ] | |
| ASLR | [ ] | |
| VGA text console (x86) | [x] | |
| PS/2 keyboard | [x] | |
| PIT timer | [x] | |
+| LAPIC timer | [x] | Calibrated, used when APIC available |
| ATA PIO (IDE) | [x] | Primary master |
+| ATA DMA (Bus Master IDE) | [x] | Bounce buffer, PRDT, IRQ-coordinated |
+| PCI enumeration | [x] | Full bus/slot/func scan with BAR + IRQ |
+| ACPI (MADT parsing) | [x] | CPU topology + IOAPIC discovery |
+| LAPIC + IOAPIC | [x] | Replaces legacy PIC |
+| SMP (multi-CPU boot) | [x] | 4 CPUs via INIT-SIPI-SIPI, per-CPU data via GS |
+| CPUID feature detection | [x] | Leaf 0/1/7/extended; SMEP/SMAP detection |
+| VBE framebuffer | [x] | Maps LFB, pixel drawing, font rendering |
+| SYSENTER fast syscall | [x] | MSR setup + handler |
| RTC (real-time clock) | [ ] | |
-| PCI enumeration | [ ] | |
-| Framebuffer / VESA | [ ] | |
| Network (e1000/virtio-net) | [ ] | |
| Virtio-blk | [ ] | |
| Feature | Status | Notes |
|---------|--------|-------|
-| ELF32 loader | [x] | |
+| ELF32 loader | [x] | Secure with W^X enforcement |
| `/bin/init.elf` (smoke tests) | [x] | Comprehensive test suite |
| `/bin/echo.elf` | [x] | Minimal argv/envp test |
-| Minimal libc | [ ] | No libc; userland uses raw syscall wrappers |
+| Minimal libc (ulibc) | [x] | `printf`, `malloc`/`free`/`calloc`/`realloc`, `string.h`, `unistd.h`, `errno.h` |
| Shell (`sh`) | [ ] | |
| Core utilities (`ls`, `cat`, `cp`, `mv`, `rm`, `mkdir`) | [ ] | |
| Dynamic linking | [ ] | |
## Priority Roadmap (next steps)
### Near-term (unlock a usable shell)
-1. **Minimal libc** — `printf`, `malloc`/`free`, `string.h`, `stdio.h` wrappers
-2. **Shell** — `sh`-compatible; needs `fork`+`execve`+`waitpid`+`pipe`+`dup2`+`chdir` (all implemented)
-3. **Core utilities** — `ls` (uses `getdents`), `cat`, `echo`, `mkdir`, `rm`, `mv`, `cp`
-4. **Signal characters** — Ctrl+C → `SIGINT`, Ctrl+Z → `SIGTSTP`, Ctrl+D → EOF
-5. **Raw TTY mode** — needed for interactive editors and proper shell line editing
+1. ~~Minimal libc~~ ✅ ulibc implemented (`printf`, `malloc`, `string.h`, `unistd.h`, `errno.h`)
+2. **Shell** — `sh`-compatible; all required syscalls are implemented
+3. **Core utilities** — `ls` (uses `getdents`), `cat`, `echo`, `mkdir`, `rm`
+4. ~~Signal characters~~ ✅ Ctrl+C→SIGINT, Ctrl+Z→SIGTSTP, Ctrl+D→EOF
+5. ~~Raw TTY mode~~ ✅ ICANON clearable via TCSETS
+6. **`/dev/zero`** + **`/dev/random`** — simple device nodes
+7. **Multiple PTY pairs** — currently only 1
### Medium-term (real POSIX compliance)
-6. **`brk`/`sbrk`** — userland heap
-7. **`mmap`/`munmap`** — memory-mapped files, shared memory
-8. **Permissions** — `uid`/`gid`, mode bits, `chmod`, `chown`, `access`, `umask`
-9. **`O_CLOEXEC`** — close-on-exec for fd hygiene
-10. **`/proc`** — process information filesystem
-11. **Hard/symbolic links** — `link`, `symlink`, `readlink`
+8. ~~`brk`/`sbrk`~~ ✅ Implemented
+9. **`mmap`/`munmap`** — memory-mapped files, shared memory
+10. **Permissions** — `uid`/`gid`, mode bits, `chmod`, `chown`, `access`, `umask`
+11. ~~`O_CLOEXEC`~~ ✅ Implemented
+12. **`/proc` per-process** — `/proc/[pid]/status`, `/proc/[pid]/maps`
+13. **Hard/symbolic links** — `link`, `symlink`, `readlink`
+14. **VMIN/VTIME** — termios non-canonical timing
+15. **Generic wait queue abstraction** — replace ad-hoc blocking
### Long-term (full Unix experience)
-12. **Networking** — socket API, TCP/IP stack
-13. **Multi-arch bring-up** — ARM/RISC-V functional kernels
-14. **COW fork + demand paging**
-15. **Threads** (`clone`/`pthread`)
-16. **Dynamic linking** (`ld.so`)
-17. **ext2/FAT** filesystem support
+16. **Networking** — socket API, TCP/IP stack
+17. **Multi-arch bring-up** — ARM/RISC-V functional kernels
+18. ~~COW fork~~ ✅ Implemented
+19. **Threads** (`clone`/`pthread`)
+20. **Dynamic linking** (`ld.so`)
+21. **ext2/FAT** filesystem support
+22. **PAE + NX bit** — hardware W^X
+23. **Per-thread errno** (needs TLS)
+24. **vDSO** — fast `clock_gettime` without syscall
| Bitmap allocator | ✅ Bitmap-based | ✅ Bitmap-based (`src/mm/pmm.c`) | None |
| Multiboot memory map parsing | ✅ Parse MMAP entries | ✅ Full Multiboot2 MMAP parsing, clamping, fallback | None |
| Kernel/module protection | ✅ Reserve kernel + initrd | ✅ Protects kernel (`_start`–`_end`), modules, low 1MB | None |
-| Frame reference counting | â\9c\85 `uint16_t frame_ref_count[]` for CoW | â\9d\8c Not implemented | **Critical for CoW fork** |
-| Contiguous block allocation | ✅ `pmm_alloc_blocks(count)` for DMA | ❌ Only single-frame `pmm_alloc_page()` | Needed for DMA drivers |
-| Atomic ref operations | â\9c\85 `__sync_fetch_and_add` | â\9d\8c N/A (no refcount) | Future |
-| Spinlock protection | â\9c\85 `spinlock_acquire(&pmm_lock)` | â\9d\8c PMM has no lock (single-core safe only) | Needed for SMP |
+| Frame reference counting | â\9c\85 `uint16_t frame_ref_count[]` for CoW | â\9c\85 `pmm_incref`/`pmm_decref`/`pmm_get_refcount` | None |
+| Contiguous block allocation | ✅ `pmm_alloc_blocks(count)` for DMA | ❌ Only single-frame `pmm_alloc_page()` | Needed for multi-page DMA |
+| Atomic ref operations | â\9c\85 `__sync_fetch_and_add` | â\9c\85 File refcounts use `__sync_*` builtins | None |
+| Spinlock protection | â\9c\85 `spinlock_acquire(&pmm_lock)` | â\9c\85 `pmm_lock` with `spin_lock_irqsave` | None |
-**Summary:** AdrOS PMM is solid for single-core use. Missing ref-counting (blocks CoW) and contiguous allocation (blocks DMA).
+**Summary:** AdrOS PMM is SMP-safe with spinlock protection and frame refcounting for CoW. Only missing contiguous block allocation.
---
| Per-process address spaces | ✅ Clone kernel PD | ✅ `vmm_as_create_kernel_clone()`, `vmm_as_clone_user()` | None |
| W^X logical policy | ✅ `vmm_apply_wx_policy()` rejects RWX | ✅ ELF loader maps `.text` as RO after load via `vmm_protect_range()` | Partial — no policy function, but effect achieved |
| W^X hardware (NX bit) | ✅ PAE + NX via EFER MSR | ❌ 32-bit paging, no PAE, no NX | Long-term |
-| CPUID feature detection | ✅ `cpu_get_features()` for PAE/NX | ❌ Not implemented | Long-term |
+| CPUID feature detection | ✅ `cpu_get_features()` for PAE/NX | ✅ Full CPUID leaf 0/1/7/extended; SMEP/SMAP detection | None |
+| SMEP | Not discussed | ✅ Enabled in CR4 if CPU supports | **AdrOS is ahead** |
+| Copy-on-Write (CoW) | ✅ Full implementation | ✅ `vmm_as_clone_user_cow()` + `vmm_handle_cow_fault()` | None |
| `vmm_find_free_area()` | ✅ Scan user VA space for holes | ❌ Not implemented | Needed for `mmap` |
| `vmm_map_dma_buffer()` | ✅ Map phys into user VA | ❌ Not implemented | Needed for zero-copy I/O |
| TLB flush | ✅ `invlpg` + full flush | ✅ `invlpg()` per page | None |
| Spinlock on VMM ops | ✅ `vmm_kernel_lock` | ❌ No lock | Needed for SMP |
-**Summary:** AdrOS VMM is functional and well-designed (recursive mapping is elegant). Missing hardware NX (requires PAE migration) and free-area search for `mmap`.
+**Summary:** AdrOS VMM is functional and well-designed with CoW fork, recursive mapping, and SMEP. Missing hardware NX (requires PAE migration) and free-area search for `mmap`.
---
| Doubly-linked free list | Mentioned | ✅ `heap.c` with `HEAP_MAGIC` validation | None |
| Coalescing | Mentioned | ✅ Forward + backward coalesce (fixed in previous session) | None |
| Spinlock | ✅ Required | ✅ `heap_lock` spinlock present | None |
-| Slab allocator | ✅ `slab_cache_t` for fixed-size objects | ❌ Not implemented | Medium priority |
+| Slab allocator | ✅ `slab_cache_t` for fixed-size objects | ✅ `slab_cache_init`/`slab_alloc`/`slab_free` with spinlock | None |
+| Dynamic growth | Not discussed | ✅ Heap grows from 10MB up to 64MB on demand | **AdrOS is ahead** |
-**Summary:** Heap works correctly. Slab allocator would improve performance for frequent small allocations (process structs, file descriptors).
+**Summary:** Heap works correctly with dynamic growth and slab allocator for fixed-size objects.
---
| Aspect | Supplementary Suggestion | AdrOS Current State | Gap |
|--------|--------------------------|---------------------|-----|
| Process states | ✅ READY/RUNNING/SLEEPING/ZOMBIE | ✅ READY/RUNNING/ZOMBIE/BLOCKED/SLEEPING | AdrOS has more states |
-| Round-robin scheduling | Baseline | ✅ Implemented in `scheduler.c` | None |
-| O(1) scheduler (bitmap + active/expired) | â\9c\85 Full implementation | â\9d\8c Simple linked-list traversal | Enhancement |
-| Priority queues (MLFQ) | â\9c\85 32 priority levels | â\9d\8c No priority levels | Enhancement |
+| Round-robin scheduling | Baseline | ✅ Implemented as fallback | None |
+| O(1) scheduler (bitmap + active/expired) | â\9c\85 Full implementation | â\9c\85 Bitmap + active/expired swap, 32 priority levels | None |
+| Priority queues (MLFQ) | â\9c\85 32 priority levels | â\9c\85 32 priority levels via `SCHED_NUM_PRIOS` | None |
| Unix decay-based priority | ✅ `p_cpu` decay + `nice` | ❌ Not implemented | Enhancement |
| Per-CPU runqueues | ✅ `cpu_runqueue_t` per CPU | ❌ Single global queue | Needed for SMP |
-| Sleep/wakeup (wait queues) | ✅ `sleep(chan, lock)` / `wakeup(chan)` | ✅ Process blocking via `PROCESS_BLOCKED` state + manual wake | Partial — no generic wait queue abstraction |
+| Sleep/wakeup (wait queues) | ✅ `sleep(chan, lock)` / `wakeup(chan)` | ✅ Process blocking + `nanosleep` syscall | Partial — no generic wait queue abstraction |
| Context switch (assembly) | ✅ Save/restore callee-saved + CR3 | ✅ `context_switch.S` saves/restores regs + CR3 | None |
-| `fork()` | ✅ Slab + CoW + enqueue | ✅ `process_fork_create()` — full copy (no CoW) | CoW missing |
-| `execve()` | ✅ Load ELF, reset stack | ✅ `syscall_execve_impl()` — loads ELF, handles argv/envp | None |
+| `fork()` | ✅ Slab + CoW + enqueue | ✅ `vmm_as_clone_user_cow()` + page fault handler | None |
+| `execve()` | ✅ Load ELF, reset stack | ✅ `syscall_execve_impl()` — loads ELF, handles argv/envp, `O_CLOEXEC` | None |
| Spinlock protection | ✅ `sched_lock` | ✅ `sched_lock` present | None |
-**Summary:** AdrOS scheduler is functional with all essential operations. The supplementary material suggests O(1)/MLFQ upgrades which are performance enhancements, not correctness issues.
+**Summary:** AdrOS scheduler is now O(1) with bitmap + active/expired arrays and 32 priority levels. Missing decay-based priority and per-CPU runqueues.
---
| PTY master/slave | Not discussed | ✅ Full PTY implementation with `/dev/ptmx` + `/dev/pts/0` | **AdrOS is ahead** |
| Job control (SIGTTIN/SIGTTOU) | Not discussed | ✅ `pty_jobctl_read_check()` / `pty_jobctl_write_check()` | **AdrOS is ahead** |
| `poll()` support | ✅ `tty_poll()` | ✅ `pty_master_can_read()` etc. integrated with `poll` | None |
-| Raw mode | Not discussed | ❌ Not implemented | Needed for editors/games |
+| Raw mode | Not discussed | ✅ `ICANON` clearable via `TCSETS` | None |
+| Signal characters | Not discussed | ✅ Ctrl+C→SIGINT, Ctrl+Z→SIGTSTP, Ctrl+D→EOF, Ctrl+\\→SIGQUIT | **AdrOS is ahead** |
+| Window size | Not discussed | ✅ `TIOCGWINSZ`/`TIOCSWINSZ` | **AdrOS is ahead** |
-**Summary:** AdrOS TTY/PTY is **significantly ahead** of the supplementary material. Full PTY with job control is a major achievement.
+**Summary:** AdrOS TTY/PTY is **significantly ahead** of the supplementary material. Full PTY with job control, raw mode, signal characters, and window size.
---
| IRQ save/restore | ✅ `pushcli`/`popcli` with nesting | ✅ `irq_save()`/`irq_restore()` via `pushf`/`popf` | None |
| `spin_lock_irqsave` | ✅ Combined lock + IRQ disable | ✅ `spin_lock_irqsave()` / `spin_unlock_irqrestore()` | None |
| Debug name field | ✅ `char *name` for panic messages | ❌ No name field | Minor |
-| CPU ID tracking | ✅ `lock->cpu_id` for deadlock detection | ❌ Not tracked | Needed for SMP |
-| Nesting counter (`ncli`) | ✅ Per-CPU nesting | ❌ Not implemented (flat save/restore) | Needed for SMP |
+| CPU ID tracking | ✅ `lock->cpu_id` for deadlock detection | ❌ Not tracked | Enhancement |
+| Nesting counter (`ncli`) | ✅ Per-CPU nesting | ❌ Not implemented (flat save/restore) | Enhancement |
-**Summary:** AdrOS spinlocks are correct for single-core. The supplementary material's SMP-aware features (CPU tracking, nesting) are needed only when AdrOS targets multi-core.
+**Summary:** AdrOS spinlocks are correct and used throughout the kernel (PMM, heap, slab, scheduler, TTY). SMP-aware features (CPU tracking, nesting) are enhancements.
---
|--------|--------------------------|---------------------|-----|
| `crt0.S` (entry point) | ✅ `_start` → `main` → `exit` | ✅ `user/crt0.S` with argc/argv setup | None |
| Syscall stub (int 0x80) | ✅ `_syscall_invoke` via registers | ✅ `_syscall` in `user/syscall.S` | None |
-| `SYSENTER` fast path | ✅ vDSO + MSR setup | ❌ Only `int 0x80` | Enhancement |
-| libc wrappers | ✅ `syscalls.c` with errno | ❌ Raw syscall wrappers only, no errno | **Key gap** |
+| libc wrappers | ✅ `syscalls.c` with errno | ✅ ulibc: `printf`, `malloc`/`free`/`calloc`/`realloc`, `string.h`, `errno.h` | None |
| `init.c` (early userspace) | ✅ mount + pivot_root + execve | ✅ `user/init.c` — comprehensive smoke tests | Different purpose |
| User linker script | ✅ `user.ld` at 0x08048000 | ✅ `user/user.ld` at 0x00400000 | Both valid |
+| `SYSENTER` fast path | ✅ vDSO + MSR setup | ✅ `sysenter_init.c` — MSR setup + handler | None |
-**Summary:** AdrOS has a working userspace with syscall stubs and a comprehensive test binary. Missing a proper libc and `SYSENTER` optimization.
+**Summary:** AdrOS has a working userspace with ulibc, SYSENTER fast path, and a comprehensive test binary. Missing a shell and core utilities.
---
-### 1.11 Drivers (Not Yet in AdrOS)
+### 1.11 Drivers
| Driver | Supplementary Suggestion | AdrOS Current State |
|--------|--------------------------|---------------------|
-| PCI enumeration | ✅ Full scan (bus/dev/func) | ❌ Not implemented |
+| PCI enumeration | ✅ Full scan (bus/dev/func) | ✅ Full scan with BAR + IRQ (`src/hal/x86/pci.c`) |
+| ATA DMA (Bus Master IDE) | Not discussed | ✅ Bounce buffer, PRDT, IRQ-coordinated (`src/hal/x86/ata_dma.c`) |
+| LAPIC + IOAPIC | Not discussed | ✅ Replaces legacy PIC; IRQ routing |
+| SMP (multi-CPU boot) | Not discussed | ✅ 4 CPUs via INIT-SIPI-SIPI, per-CPU data via GS |
+| ACPI (MADT parsing) | Not discussed | ✅ CPU topology + IOAPIC discovery |
+| VBE/Framebuffer | ✅ Map LFB + MTRR write-combining | ✅ Maps LFB, pixel drawing, font rendering (no MTRR WC) |
| Intel E1000 NIC | ✅ RX/TX descriptor rings + DMA | ❌ Not implemented |
-| VBE/Framebuffer | ✅ Map LFB + MTRR write-combining | ❌ VGA text mode only |
| Intel HDA Audio | ✅ DMA ring buffers | ❌ Not implemented |
| lwIP TCP/IP stack | ✅ `sys_arch.c` bridge | ❌ Not implemented |
---
-### 1.12 Advanced Features (Not Yet in AdrOS)
+### 1.12 Advanced Features
| Feature | Supplementary Suggestion | AdrOS Current State |
|---------|--------------------------|---------------------|
-| Copy-on-Write (CoW) fork | â\9c\85 Full implementation with ref-counting | â\9d\8c Full address space copy |
-| Slab allocator | â\9c\85 `slab_cache_t` with free-list-in-place | â\9d\8c Only `kmalloc`/`kfree` |
-| Shared memory (shmem/mmap) | â\9c\85 `sys_shmget` / `sys_shmat` | â\9d\8c Not implemented |
+| Copy-on-Write (CoW) fork | â\9c\85 Full implementation with ref-counting | â\9c\85 `vmm_as_clone_user_cow()` + `vmm_handle_cow_fault()` |
+| Slab allocator | â\9c\85 `slab_cache_t` with free-list-in-place | â\9c\85 `slab_cache_init`/`slab_alloc`/`slab_free` with spinlock |
+| Shared memory (shmem/mmap) | â\9c\85 `sys_shmget` / `sys_shmat` | â\9c\85 `shm_get`/`shm_at`/`shm_dt`/`shm_ctl` in `src/kernel/shm.c` |
| Zero-copy DMA I/O | ✅ Map DMA buffer into user VA | ❌ Not implemented |
| vDSO | ✅ Kernel-mapped page with syscall code | ❌ Not implemented |
## Part 2 — POSIX Compatibility Assessment
-### Overall Score: **~45% toward a practical Unix-like POSIX system**
+### Overall Score: **~70% toward a practical Unix-like POSIX system**
-This score reflects that AdrOS has the **core architectural skeleton** of a Unix system
-fully in place, but lacks several key POSIX interfaces and userland components needed
-for real-world use.
+This score reflects that AdrOS has a **mature kernel** with most core subsystems
+implemented and working. The main remaining gaps are userland tooling (shell, core
+utilities) and some POSIX interfaces (`mmap`, permissions, links).
### What AdrOS Already Has (Strengths)
-1. **Process model** — `fork`, `execve`, `waitpid`, `exit`, `getpid`, `getppid`, `setsid`, `setpgid`, `getpgrp` — all working
-2. **File I/O** — `open`, `read`, `write`, `close`, `lseek`, `stat`, `fstat`, `dup`, `dup2`, `dup3`, `pipe`, `pipe2`, `fcntl`, `getdents` — comprehensive
-3. **Signals** — `sigaction`, `sigprocmask`, `kill`, `sigreturn` with full trampoline — robust
-4. **VFS** — 5 filesystem types, mount table, path resolution, per-process cwd — excellent
-5. **TTY/PTY** — Line discipline, job control, blocking I/O, `ioctl` — very good
-6. **Select/Poll** — Working for pipes and TTY devices
-7. **Memory isolation** — Per-process address spaces, user/kernel separation, `uaccess` validation
-8. **ELF loading** — Secure loader with W^X enforcement
-9. **Spinlocks** — Correct `xchg`-based implementation with IRQ save/restore
+1. **Process model** — `fork` (CoW), `execve`, `waitpid`, `exit`, `getpid`, `getppid`, `setsid`, `setpgid`, `getpgrp`, `brk` — all working
+2. **File I/O** — `open`, `read`, `write`, `close`, `lseek`, `stat`, `fstat`, `dup`, `dup2`, `dup3`, `pipe`, `pipe2`, `fcntl`, `getdents`, `O_CLOEXEC`, `FD_CLOEXEC` — comprehensive
+3. **Signals** — `sigaction`, `sigprocmask`, `kill`, `sigreturn` with full trampoline, Ctrl+C/Z/D signal chars — robust
+4. **VFS** — 6 filesystem types (tmpfs, devfs, overlayfs, diskfs, persistfs, procfs), mount table, path resolution — excellent
+5. **TTY/PTY** — Line discipline, raw mode, job control, signal chars, `TIOCGWINSZ`, PTY — very good
+6. **Select/Poll** — Working for pipes, TTY, PTY, `/dev/null`
+7. **Memory management** — PMM (spinlock + refcount), VMM (CoW, recursive PD), heap (dynamic 64MB), slab allocator, SMEP, shared memory
+8. **Hardware** — PCI, ATA DMA, LAPIC/IOAPIC, SMP (4 CPUs), ACPI, VBE framebuffer, SYSENTER, CPUID
+9. **Userland** — ulibc (`printf`, `malloc`, `string.h`, `errno.h`), ELF loader with W^X
+10. **Testing** — 47 host unit tests, 19 smoke tests, cppcheck, GDB scripted checks
+11. **Security** — SMEP, user_range_ok hardened, sigreturn eflags sanitized, atomic file refcounts
### What's Missing for Practical POSIX (Gaps by Priority)
#### Tier 1 — Blocks basic usability
| Gap | Impact | Effort |
|-----|--------|--------|
-| **Minimal libc** (`printf`, `malloc`, `string.h`, `stdio.h`) | Can't build real userland programs | Medium |
+| ~~Minimal libc~~ | ✅ ulibc implemented | Done |
| **Shell** (`sh`-compatible) | No interactive use without it | Medium |
-| **Signal characters** (Ctrl+C → SIGINT, Ctrl+D → EOF) | Can't interrupt/control processes | Small |
-| **`brk`/`sbrk`** (user heap) | No `malloc` in userspace | Small-Medium |
+| ~~Signal characters~~ | ✅ Ctrl+C/Z/D implemented | Done |
+| ~~`brk`/`sbrk`~~ | ✅ Implemented | Done |
| **Core utilities** (`ls`, `cat`, `echo`, `mkdir`, `rm`) | No file management | Medium |
+| **`/dev/zero`** | Missing common device node | Small |
+| **Multiple PTY pairs** | Only 1 pair limits multi-process use | Small |
#### Tier 2 — Required for POSIX compliance
| Gap | Impact | Effort |
|-----|--------|--------|
-| **`mmap`/`munmap`** | No memory-mapped files, no shared memory | Medium-Large |
-| **`O_CLOEXEC`** | FD leaks across `execve` | Small |
+| **`mmap`/`munmap`** | No memory-mapped files | Medium-Large |
+| ~~`O_CLOEXEC`~~ | ✅ Implemented | Done |
| **Permissions** (`uid`/`gid`/mode/`chmod`/`chown`) | No multi-user security | Medium |
| **Hard/symbolic links** | Incomplete filesystem semantics | Medium |
-| **`/proc` filesystem** | No process introspection | Medium |
-| **`nanosleep`/`clock_gettime`** | No time management | Small |
-| **Raw TTY mode** | Can't run editors or games | Small |
+| **`/proc` per-process** | Only `/proc/meminfo`, no `/proc/[pid]` | Medium |
+| ~~`nanosleep`/`clock_gettime`~~ | ✅ Implemented | Done |
+| ~~Raw TTY mode~~ | ✅ Implemented | Done |
+| **VMIN/VTIME** | Non-canonical timing not supported | Small |
#### Tier 3 — Full Unix experience
| Gap | Impact | Effort |
|-----|--------|--------|
-| **CoW fork** | Memory waste on fork-heavy workloads | Large |
+| ~~CoW fork~~ | ✅ Implemented | Done |
| **PAE + NX bit** | No hardware W^X enforcement | Large |
-| **Slab allocator** | Performance for frequent small allocs | Medium |
+| ~~Slab allocator~~ | ✅ Implemented | Done |
| **Networking** (socket API + TCP/IP) | No network connectivity | Very Large |
| **Threads** (`clone`/`pthread`) | No multi-threaded programs | Large |
| **Dynamic linking** (`ld.so`) | Can't use shared libraries | Very Large |
-| **VBE framebuffer** | No graphical output | Medium |
-| **PCI + device drivers** | No hardware discovery | Large |
+| ~~VBE framebuffer~~ | ✅ Implemented | Done |
+| ~~PCI + device drivers~~ | ✅ PCI + ATA DMA implemented | Done |
---
## Part 3 — Architectural Comparison Summary
| Dimension | Supplementary Material | AdrOS Current | Verdict |
-|-----------|----------------------|---------------|---------|
+|-----------|----------------------|---------------|----------|
| **Boot flow** | GRUB → Stub (LZ4) → Kernel → USTAR InitRD | GRUB → Kernel → Custom InitRD → OverlayFS | Both valid; AdrOS is simpler |
-| **Memory architecture** | PMM + Slab + CoW + Zero-Copy DMA | PMM + Heap (linked list) | Supplementary is more advanced |
-| **Scheduler** | O(1) with bitmap + active/expired arrays | Round-robin with linked list | Supplementary is more advanced |
-| **VFS** | USTAR + FAT (planned) | tmpfs + devfs + overlayfs + diskfs + persistfs | **AdrOS is more advanced** |
-| **Syscall interface** | int 0x80 + SYSENTER + vDSO | int 0x80 only | Supplementary has more optimization |
-| **Signal handling** | Basic trampoline concept | Full SA_SIGINFO + sigreturn + sigframe | **AdrOS is more advanced** |
-| **TTY/PTY** | Basic circular buffer | Full PTY with job control | **AdrOS is more advanced** |
-| **Synchronization** | SMP-aware spinlocks with CPU tracking | Single-core spinlocks with IRQ save | Supplementary targets SMP |
-| **Userland** | libc stubs + init + shell concept | Raw syscall wrappers + test binary | Both early-stage |
-| **Drivers** | PCI + E1000 + VBE + HDA (conceptual) | UART + VGA text + PS/2 + ATA PIO | Supplementary has more scope |
+| **Memory architecture** | PMM + Slab + CoW + Zero-Copy DMA | PMM (spinlock+refcount) + Slab + CoW + Heap (64MB dynamic) + SMEP + Shmem | **Comparable** (AdrOS missing zero-copy DMA) |
+| **Scheduler** | O(1) with bitmap + active/expired arrays | O(1) with bitmap + active/expired, 32 priority levels | **Comparable** (AdrOS missing decay + per-CPU) |
+| **VFS** | USTAR + FAT (planned) | tmpfs + devfs + overlayfs + diskfs + persistfs + procfs | **AdrOS is more advanced** |
+| **Syscall interface** | int 0x80 + SYSENTER + vDSO | int 0x80 + SYSENTER | **Comparable** (AdrOS missing vDSO) |
+| **Signal handling** | Basic trampoline concept | Full SA_SIGINFO + sigreturn + sigframe + signal chars | **AdrOS is more advanced** |
+| **TTY/PTY** | Basic circular buffer | Full PTY + raw mode + job control + signal chars + TIOCGWINSZ | **AdrOS is more advanced** |
+| **Synchronization** | SMP-aware spinlocks with CPU tracking | Spinlocks with IRQ save, used throughout (PMM, heap, slab, sched) | **Comparable** (AdrOS missing CPU tracking) |
+| **Userland** | libc stubs + init + shell concept | ulibc (printf, malloc, string.h) + init + echo | **Comparable** (AdrOS missing shell) |
+| **Drivers** | PCI + E1000 + VBE + HDA (conceptual) | PCI + ATA DMA + VBE + LAPIC/IOAPIC + SMP + ACPI | **AdrOS is more advanced** |
---
## Part 4 — Recommendations
-### Immediate Actions (use supplementary material as inspiration)
+### Completed (since initial analysis)
-1. **Add signal characters to TTY** — Ctrl+C/Ctrl+Z/Ctrl+D handling in `tty_input_char()`. Small change, huge usability gain.
+1. ~~Add signal characters to TTY~~ ✅ Ctrl+C/Z/D/\\ implemented
+2. ~~Implement `brk`/`sbrk` syscall~~ ✅ `syscall_brk_impl()`
+3. ~~Build minimal libc~~ ✅ ulibc with printf, malloc, string.h, errno.h
+4. ~~PMM ref-counting~~ ✅ `pmm_incref`/`pmm_decref`/`pmm_get_refcount`
+5. ~~CoW fork~~ ✅ `vmm_as_clone_user_cow()` + `vmm_handle_cow_fault()`
+6. ~~O(1) scheduler~~ ✅ Bitmap + active/expired arrays, 32 priority levels
+7. ~~Slab allocator~~ ✅ `slab_cache_init`/`slab_alloc`/`slab_free`
+8. ~~PCI enumeration~~ ✅ Full bus/slot/func scan
+9. ~~CPUID~~ ✅ Leaf 0/1/7/extended, SMEP enabled
-2. **Implement `brk`/`sbrk` syscall** — Track a per-process heap break pointer. Essential for userland `malloc`.
+### Immediate Actions (next priorities)
-3. **Build minimal libc** — Start with `write`-based `printf`, `brk`-based `malloc`, `string.h`. The supplementary `syscalls.c.txt` and `unistd.c.txt` show the pattern.
+1. **Build a shell** — All required syscalls are implemented. This is the single biggest usability unlock.
-4. **Build a shell** — All required syscalls (`fork`+`execve`+`waitpid`+`pipe`+`dup2`+`chdir`) are already implemented.
+2. **Core utilities** — `ls`, `cat`, `echo`, `mkdir`, `rm`. All required VFS operations exist.
-### Medium-Term (architectural improvements from supplementary material)
+3. **`/dev/zero`** + **`/dev/random`** — Simple device nodes, small effort.
-5. **PMM ref-counting** — Add `uint16_t` ref-count array alongside bitmap. Prerequisite for CoW.
+4. **Multiple PTY pairs** — Currently only 1 pair. Needed for multi-process terminal use.
-6. **CoW fork** — Use PTE bit 9 as CoW marker, handle in page fault. The supplementary material's `vmm_copy_for_fork()` pattern is clean.
+### Medium-Term
-7. **W^X policy function** — Add `vmm_apply_wx_policy()` as a centralized check. Currently AdrOS achieves W^X ad-hoc in the ELF loader.
+5. **`mmap`/`munmap`** — Requires `vmm_find_free_area()`. Critical for POSIX.
-8. **`mmap`/`munmap`** — Requires `vmm_find_free_area()` from supplementary material. Critical for POSIX.
+6. **Permissions model** — `uid`/`gid`/mode bits, `chmod`, `chown`, `access`, `umask`.
-### Long-Term (from supplementary material roadmap)
+7. **`/proc` per-process** — `/proc/[pid]/status`, `/proc/[pid]/maps`.
-9. **CPUID + PAE + NX** — Follow the `cpu_get_features()` / `cpu_enable_nx()` pattern for hardware W^X.
+8. **Hard/symbolic links** — `link`, `symlink`, `readlink`.
-10. **O(1) scheduler** — The active/expired bitmap swap pattern is elegant and well-suited for AdrOS.
+### Long-Term
-11. **Slab allocator** — The supplementary material's free-list-in-place design is simple and effective.
+9. **PAE + NX** — Hardware W^X enforcement.
-12. **PCI + networking** — Follow the PCI scan → BAR mapping → E1000 DMA ring → lwIP bridge pattern.
+10. **Networking** — E1000 DMA ring → lwIP bridge → socket API.
+
+11. **Threads** — `clone`/`pthread`.
+
+12. **Dynamic linking** — `ld.so`.
---
## Conclusion
-AdrOS is a **well-architected hobby OS** that has already implemented many of the hardest
-parts of a Unix-like system: process management with signals, a multi-filesystem VFS,
-PTY with job control, and a secure ELF loader. It is approximately **45% of the way**
-to a practical POSIX-compatible system.
+AdrOS is a **mature hobby OS** that has implemented most of the hard parts of a Unix-like
+system: CoW fork, O(1) scheduler, slab allocator, SMP boot, PCI/DMA drivers, full signal
+handling, a multi-filesystem VFS, PTY with job control, and a secure ELF loader. It is
+approximately **70% of the way** to a practical POSIX-compatible system.
-The supplementary material provides excellent **architectural blueprints** for the next
-evolution: CoW memory, O(1) scheduling, hardware NX, and networking. However, AdrOS is
-already **ahead** of the supplementary material in several areas (VFS diversity, signal
-handling, PTY/job control).
+The supplementary material's architectural blueprints have been largely **realized**:
+CoW memory, O(1) scheduling, slab allocator, PCI enumeration, and CPUID detection are
+all implemented. AdrOS is **ahead** of the supplementary material in several areas
+(VFS diversity, signal handling, TTY/PTY, driver support, SMP).
-The most impactful next steps are **not** the advanced features from the supplementary
-material, but rather the **userland enablers**: a minimal libc, a shell, and `brk`/`sbrk`.
-These would transform AdrOS from a kernel with smoke tests into an interactive Unix system.
+The most impactful next steps are **userland tooling**: a shell and core utilities.
+With ulibc already providing `printf`/`malloc`/`string.h`, and all required syscalls
+implemented, building a functional shell is now straightforward. This would transform
+AdrOS from a kernel with smoke tests into an **interactive Unix system**.
projects / AdrOS.git / commitdiff