# PikeOS POSIX Implementation Deep Audit

## Architecture Overview

PikeOS implements POSIX (PSE51 profile) via a **3-layer architecture**:

1. **PikeOS Microkernel** (`sources/ukernel-x86_amd64/`) — Raw syscall interface (119 syscalls), IPC, thread/task/memory management
2. **P4EXT / PSSW** (`sources/p4ext/`, `sources/ssw/`) — Process extension layer: heap, vmem, threads, stack management, ELF loading
3. **POSIX Personality Library** (`target/x86/amd64/posix/`) — PSE51-compliant POSIX API (pthread, signal, mq, sem, mmap, file I/O, time)

**Key Design:** PikeOS has NO fork/exec/wait/exit in the traditional Unix sense. POSIX processes are **PikeOS tasks** (statically partitioned at system configuration time). Threads are PikeOS threads. The POSIX personality is a library that wraps PikeOS kernel primitives.

---

## 1. PROCESS LIFECYCLE (fork/exec/wait/exit)

### ❌ NOT IMPLEMENTED (by design)
- `fork()`, `exec()`, `wait()`, `waitpid()`, `posix_spawn()` — **DO NOT EXIST** in PikeOS POSIX
- PikeOS is a **statically partitioned** RTOS. Processes (partitions) are defined at configuration time
- `_POSIX_SPAWN = -1` (explicitly disabled)
- `_POSIX_JOB_CONTROL = -1` (explicitly disabled)

### ✅ What exists instead:
- **Task activation**: `p4_task_activate()` → `P4_SYSCALL_TASK_ACTIVATE` (syscall #4)
- **Task start**: `p4_task_start()` → `P4_SYSCALL_TASK_START` (syscall #5)
- **Task terminate**: `p4_task_terminate()` → `P4_SYSCALL_TASK_TERMINATE` (syscall #6)
- **ELF loading**: `sources/ssw/src/app.c` — `app_load()` loads ELF executables from ROM FS
- **Process entry**: `sources/p4ext/src/entry.c` — `_p4_entry()` initializes: proc, diag, config, heap, vmem, stack, malloc, threads, args, then calls `main()`

### Files:
| File | Purpose |
|------|---------|
| `sources/ukernel-x86_amd64/include/kernel/p4task_user.h` | Task API (activate, start, terminate, donate) |
| `sources/p4ext/src/entry.c` | Process entry point (`_p4_entry()`) |
| `sources/ssw/src/app.c` | ELF loader (`app_load()`) |
| `target/x86/amd64/posix/src/posix_config.c` | POSIX process configuration |

---

## 2. THREADING (pthread)

### ✅ FULLY IMPLEMENTED
PikeOS POSIX provides complete PSE51 threading:

**Header:** `target/x86/amd64/posix/include/pthread.h`

**Functions declared:**
- `pthread_create()`, `pthread_join()`, `pthread_detach()`, `pthread_exit()`
- `pthread_self()`, `pthread_equal()`, `pthread_cancel()`
- `pthread_setcancelstate()`, `pthread_setcanceltype()`, `pthread_testcancel()`
- `pthread_cleanup_push()`, `pthread_cleanup_pop()`
- `pthread_atfork()` (stub — no fork support)

**Attributes:**
- `pthread_attr_init/destroy/get*/set*()` — detachstate, guardsize, inheritsched, schedparam, schedpolicy, scope, stack, stackaddr, stacksize
- `pthread_attr_getname_np()`, `pthread_attr_getschedquantum_np()` — PikeOS extensions

**Scheduling policies:**
- `SCHED_RR` (0), `SCHED_FIFO` (1), `SCHED_OTHER` (2)
- `PTHREAD_SCOPE_PROCESS` only (no `PTHREAD_SCOPE_SYSTEM`)

**Cancellation:**
- `PTHREAD_CANCEL_ENABLE/DISABLE`, `PTHREAD_CANCEL_DEFERRED/ASYNCHRONOUS`
- `PTHREAD_CANCELED` = `0x777`

### Kernel Integration:
- Thread creation: `p4ext_thr_create()` → `p4_thread_create_syscall()` → `P4_SYSCALL_THR_CREATE` (syscall #9)
- Thread deletion: `P4_SYSCALL_THR_DELETE` (syscall #10)
- Thread yield: `P4_SYSCALL_THR_YIELD` (syscall #11)
- Thread register exchange: `P4_SYSCALL_THR_EX_REGS` (syscall #12)
- Thread scheduling exchange: `P4_SYSCALL_THR_EX_SCHED` (syscall #14)
- Thread stop/resume: `P4_SYSCALL_THR_STOP/RESUME` (syscalls #17/#18)
- Thread affinity: `P4_SYSCALL_THR_EX_AFFINITY` (syscall #67)

### Implementation files:
| File | Purpose |
|------|---------|
| `sources/p4ext/src/thr_create.c` | `p4ext_thr_create()` — thread creation with stack allocation |
| `sources/p4ext/src/threads.c` | Thread descriptor management, TLS init |
| `sources/p4ext/src/thr_exit.c` | Thread exit |
| `sources/p4ext/src/thr_tls.c` | Thread-local storage |
| `sources/p4ext/src/thr_num.c` | Thread number allocation |
| `sources/p4ext/src/thr_reclaim.c` | Thread resource reclamation |
| `sources/p4ext/src/stack.c` / `stack_create.c` | Stack pool management |
| `sources/ukernel-x86_amd64/lib/stubs/p4_thread_create_syscall.S` | Syscall stub |

---

## 3. SYNCHRONIZATION (Mutex, Cond, Sem, RWLock)

### ✅ FULLY IMPLEMENTED

**Mutex** (`P4_MUTEX_*`):
- Kernel: `p4_mutex_init()`, `p4_mutex_lock()`, `p4_mutex_trylock()`, `p4_mutex_unlock()`
- Flags: `P4_MUTEX_SHARED`, `P4_MUTEX_RECURSIVE`, `P4_MUTEX_CANCELABLE`, `P4_MUTEX_ROBUST`
- Priority protocols: `PTHREAD_PRIO_NONE`, `PTHREAD_PRIO_INHERIT`, `PTHREAD_PRIO_PROTECT`
- Types: `PTHREAD_MUTEX_NORMAL`, `PTHREAD_MUTEX_ERRORCHECK`, `PTHREAD_MUTEX_RECURSIVE`
- Static init: `PTHREAD_MUTEX_INITIALIZER`, `PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP`

**Condition Variables** (`P4_COND_*`):
- Kernel: `p4_cond_init()`, `p4_cond_wait()`, `p4_cond_wake()`
- Flags: `P4_COND_SHARED`, `P4_COND_PRIO`, `P4_COND_WAKE_ALL`
- Static init: `PTHREAD_COND_INITIALIZER`

**Read-Write Locks:**
- `pthread_rwlock_init/destroy/rdlock/wrlock/tryrdlock/trywrlock/unlock()`
- Static init: `PTHREAD_RWLOCK_INITIALIZER`

**Semaphores** (`sem_*`):
- `sem_init()`, `sem_destroy()`, `sem_open()`, `sem_close()`, `sem_unlink()`
- `sem_wait()`, `sem_trywait()`, `sem_timedwait()`, `sem_post()`, `sem_getvalue()`
- Kernel: `P4_sem_t` with `p4_sem_init()`, `p4_sem_lock()`, `p4_sem_trylock()`, `p4_sem_unlock()`
- Max count: `P4_SEM_MAX_COUNT = 0x7fff`

**Wait Queues** (kernel-level):
- `p4_waitq_init()`, `p4_waitq_wait()`, `p4_waitq_wake()` — `P4_SYSCALL_WAITQ_*` (syscalls #105-108)

**ULock** (low-level):
- `P4_SYSCALL_ULOCK_WAIT` (#72), `P4_SYSCALL_ULOCK_WAKE` (#73) — futex-like primitives

### Kernel stubs:
| File | Syscall |
|------|---------|
| `sources/ukernel-x86_amd64/include/kernel/p4mutex_user.h` | Mutex API |
| `sources/ukernel-x86_amd64/include/kernel/p4cond_user.h` | Condvar API |
| `sources/ukernel-x86_amd64/include/kernel/p4sem_user.h` | Semaphore API |
| `sources/ukernel-x86_amd64/include/kernel/p4ulock_user.h` | ULock (futex) API |
| `sources/ukernel-x86_amd64/include/kernel/p4waitq_user.h` | Wait queue API |

---

## 4. SIGNAL HANDLING

### ✅ IMPLEMENTED (PSE51 subset)

**Header:** `target/x86/amd64/posix/include/signal.h`

**Signals defined (32 standard + 32 realtime):**
- Standard: SIGHUP(1), SIGINT(2), SIGQUIT(3), SIGILL(4), SIGTRAP(5), SIGABRT(6), SIGBUS(7), SIGFPE(8), SIGKILL(9), SIGUSR1(10), SIGSEGV(11), SIGUSR2(12), SIGALRM(14), SIGTERM(15), SIGSYS(31)
- Extensions: SIGPIPE, SIGURG, SIGXCPU, SIGXFSZ, SIGVTALRM, SIGPROF, SIGIO, SIGPOLL (only when `__BSD_VISIBLE`)
- Realtime: `SIGRTMIN=33`, `SIGRTMAX=64`

**Functions declared:**
- `sigaction()`, `signal()` — signal handler installation
- `sigprocmask()`, `pthread_sigmask()` — signal mask manipulation (SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK)
- `sigpending()`, `sigsuspend()` — signal set operations
- `sigwait()`, `sigwaitinfo()`, `sigtimedwait()` — synchronous signal waiting
- `sigqueue()` — realtime signal queuing
- `kill()`, `pthread_kill()` — signal sending
- `sigemptyset()`, `sigfillset()`, `sigaddset()`, `sigdelset()`, `sigismember()` — signal set manipulation

**Signal info:**
- `SI_NOINFO` (0x10000), `SI_USER` (0x10001), `SI_QUEUE` (0x10002), `SI_TIMER` (0x10003), `SI_ASYNCIO` (0x10004), `SI_MESGQ` (0x10005)
- `siginfo_t`: si_signo, si_code, si_value, si_addr (extension)

**Configuration:**
- `max_sig_entries = 32` — max simultaneous signal handlers
- `sig_stack_size = 4 * PAGE_SIZE` — separate signal handler stack
- `sigqueue_max = 64` — max queued signals

---

## 5. MEMORY MANAGEMENT (mmap/munmap/mprotect/brk)

### ⚠️ PARTIALLY IMPLEMENTED

**Header:** `target/x86/amd64/posix/include/sys/mman.h`

**Implemented:**
- `mmap()` — maps shared memory from configured pools
- `munmap()` — unmaps memory
- `mlock()`, `munlock()`, `mlockall()`, `munlockall()` — **no-ops** (memory locked by design, no demand paging)
- `msync()` — **no-op**
- `shm_open()`, `shm_unlink()` — shared memory objects (statically configured)
- `PROT_NONE/READ/WRITE/EXEC`, `MAP_SHARED/FIXED`

**NOT Implemented:**
- `mprotect()` — `_POSIX_MEMORY_PROTECTION = 200112L` but "Function mprotect() not implemented"
- `MAP_PRIVATE` — "unsupported on PikeOS"
- `brk()`, `sbrk()` — replaced by heap pool management

**Kernel memory syscalls:**
- `P4_SYSCALL_MEM_MAP` (#32), `P4_SYSCALL_MEM_UNMAP` (#33), `P4_SYSCALL_MEM_SET_ATTR` (#34)
- `P4_SYSCALL_MEM_CREATE` (#36), `P4_SYSCALL_MEM_CLEAR` (#66)
- `P4_SYSCALL_ALLOC_PHYS` (#47), `P4_SYSCALL_ALLOC_ALIGNED` (#48)

**Heap management (P4EXT):**
- `sources/p4ext/src/heap.c` — `_heap_init()`, `sbrk()` implementation using SSW memory pools
- `sources/p4ext/src/vmem.c` — `_vmem_init()`, `p4ext_vmem_alloc()` — page-aligned virtual memory allocation
- `sources/p4ext/src/region.c` — Region allocator for virtual address space
- `sources/p4ext/src/malloc_impl.c` — malloc/free implementation on top of heap
- `sources/ssw/src/mem.c` — PSSW memory configuration and mapping

**Configuration (`posix_config.c`):**
- `stack_pool_addr/size` — thread stack memory pool
- `shm_pool_addr/size` — shared memory pool (for mmap)
- `heap_pool_addr/size` — heap memory pool (for malloc)
- `heap_pool_chunk` — allocation granularity

---

## 6. IPC MECHANISMS

### 6a. Message Queues ✅ IMPLEMENTED

**Header:** `target/x86/amd64/posix/include/mqueue.h`

**Functions:** `mq_open()`, `mq_close()`, `mq_unlink()`, `mq_send()`, `mq_receive()`, `mq_timedsend()`, `mq_timedreceive()`, `mq_getattr()`, `mq_setattr()`, `mq_notify()`

**Configuration:** `mq_max_msgs=32`, `mq_max_msg_len=256`, `num_mq=8` (static allocation)

**File type:** `LCL_MQ` (in `dev_type_t` enum)

### 6b. Shared Memory ✅ IMPLEMENTED (static)

- `shm_open()`, `shm_unlink()` — declared in `sys/mman.h`
- `_POSIX_SHARED_MEMORY_OBJECTS = 200112L`
- "Shared memory objects can not be dynamically created or destroyed"
- File type: `RMT_SHM` (remote shared memory segments)

### 6c. Pipes ✅ IMPLEMENTED (local)

- File type: `LCL_PIPE` in `dev_type_t`
- `pipe()` function available
- Used internally for console I/O buffering

### 6d. PikeOS Native IPC (kernel-level)

**Header:** `sources/ukernel-x86_amd64/include/kernel/p4ipc_user.h`

- `p4_ipc()` — combined send/receive IPC (`P4_SYSCALL_IPC` #23)
- Supports: copied data (`buf`/`buf_size`) + memory mappings (`map`/`map_size`)
- `P4_SYSCALL_COMM_GRANT` (#20) — grant communication rights
- `P4_SYSCALL_COMM_LINK` (#21) — link communication
- `P4_SYSCALL_IPC_MASK` (#22) — set IPC mask
- `P4_SYSCALL_EV_WAIT/SIGNAL/MASK` (#25-26, #24) — event notification

### 6e. Semaphores — See Section 3

---

## 7. FILE OPERATIONS

### ✅ IMPLEMENTED (via VFS layer)

**File description structure:** `sources/ssw/include/vm_se_file.h` / `target/x86/amd64/posix/include/sys/fs_file.h`

**`struct _file`** — open file description with:
- `f_ops` (method table), `f_provider`, `f_pos`, `f_flags`, `f_type`, `f_count`
- Reference counting via `_fs_fref()`, `_fs_frele()`
- File types: `NULL_DEV`, `LCL_DEV`, `LCL_FILE`, `LCL_PIPE`, `LCL_SOCKET`, `LCL_MQ`, `LCL_SEM`, `RMT_DEV`, `RMT_FILE`, `RMT_SOCKET`, `RMT_PROP`, `RMT_SHM`

**Kernel device syscalls (KDEV):**
- `P4_SYSCALL_KDEV_OPEN` (#80), `P4_SYSCALL_KDEV_CLOSE` (#86)
- `P4_SYSCALL_KDEV_READ` (#88), `P4_SYSCALL_KDEV_WRITE` (#89)
- `P4_SYSCALL_KDEV_LSEEK` (#111), `P4_SYSCALL_KDEV_STATVFS` (#116)
- `P4_SYSCALL_KDEV_UNLINK` (#112), `P4_SYSCALL_KDEV_RENAME` (#113)
- `P4_SYSCALL_KDEV_DIR_CREATE` (#114), `P4_SYSCALL_KDEV_DIR_READ` (#115)
- `P4_SYSCALL_KDEV_DUP` (#79), `P4_SYSCALL_KDEV_CONTROL` (#91) (ioctl)
- `P4_SYSCALL_KDEV_PSTAT` (#87), `P4_SYSCALL_KDEV_PSYNC` (#93)

**PSSW file operations:** `sources/ssw/libvm/`
- `vm_open.c`, `vm_open_at.c`, `vm_close.c`, `vm_read.c`, `vm_read_at.c`
- `vm_lseek.c`, `vm_fstat.c`, `vm_fsync.c`, `vm_ftruncate.c`
- `vm_ioctl.c`, `vm_rename.c`, `vm_unlink.c`, `vm_stat.c`, `vm_statvfs.c`
- `vm_dir_open.c`, `vm_dir_close.c`, `vm_dir_read_at.c`, `vm_dir_create.c`, `vm_dir_rewind.c`, `vm_dir_sync.c`

---

## 8. TIME FUNCTIONS

### ✅ IMPLEMENTED

**Header:** `target/x86/amd64/posix/include/time.h`

**Clocks:**
- `CLOCK_REALTIME` (0) — supported
- `CLOCK_THREAD_CPUTIME_ID` (0x80000000) — "does not support timers"
- `CLOCK_PROCESS_CPUTIME_ID` (0x40000000) — "does not support timers"

**Functions declared:**
- `clock_gettime()`, `clock_settime()`, `clock_getres()`
- `timer_create()`, `timer_delete()`, `timer_settime()`, `timer_gettime()`, `timer_getoverrun()`
- `nanosleep()`, `clock_nanosleep()`
- `clock()` — `CLOCKS_PER_SEC = 1000000`
- `time()`, `difftime()`, `mktime()`, `asctime()`, `ctime()`, `gmtime()`, `localtime()`, `strftime()`

**Timer configuration:** `num_of_timers = 64`

**Kernel time syscall:**
- `P4_SYSCALL_GET_TIME` (#55)
- `P4_SYSCALL_GET_TS` (#74)
- `P4_SYSCALL_SLEEP` (#2)
- `P4_SYSCALL_THR_ALARM` (#77)

---

## 9. SCHEDULING

### ✅ IMPLEMENTED

**Header:** `target/x86/amd64/posix/include/sched.h`

**Policies:** `SCHED_RR` (0), `SCHED_FIFO` (1), `SCHED_OTHER` (2)

**Functions:** `sched_yield()`, `sched_get_priority_max()`, `sched_get_priority_min()`, `sched_rr_get_interval()`

**Configuration:**
- `sched_rr_quantum_ticks = 1`, `sched_tick_duration = 20ms`
- `sched_other_quantum_ticks = 1`
- `base_prio = 1`, `base_prio_mcp_off = 32`
- `_POSIX_PRIORITY_SCHEDULING = 200112L`

---

## 10. POSIX CONFIGURATION (`_configurables` structure)

**File:** `target/x86/amd64/posix/include/sys/posix_config.h` + `target/x86/amd64/posix/src/posix_config.c`

**Key parameters:**
| Parameter | Default | Purpose |
|-----------|---------|---------|
| `pthread_default_priority` | 10 | Default thread priority |
| `pthread_default_stack_size` | 4*PAGE_SIZE | Default stack size |
| `pthread_default_guard_size` | PAGE_SIZE | Stack guard size |
| `pthread_stack_min` | PAGE_SIZE | Minimum stack size |
| `sched_tick_duration` | 20ms | Scheduler tick |
| `mq_max_msgs` | 32 | Default MQ messages |
| `mq_max_msg_len` | 256 | Default MQ message size |
| `num_of_timers` | 64 | Max timers |
| `num_of_semaphores` | 256 | Max semaphores |
| `max_sig_entries` | 32 | Max simultaneous signal handlers |
| `sig_stack_size` | 4*PAGE_SIZE | Signal handler stack |
| `sigqueue_max` | 64 | Max queued signals |
| `proc_nfiles` | 64 | Max open files |
| `num_mq` | 8 | Max message queues |
| `num_fs_io_threads` | 4 | FS I/O threads |

---

## 11. SYSCALL TABLE (Complete)

**File:** `sources/ukernel-x86_amd64/arch/common/include/syscalls.h`

119 syscalls total (P4_SYSCALL_NUM = 119):

| # | Name | Category |
|---|------|----------|
| 0 | FAST_GET_UID | Identity |
| 1 | KERNEL_CONTROL | System |
| 2 | SLEEP | Time |
| 3 | FAST_GET_CPUID | Identity |
| 4-8 | TASK_* | Task management |
| 9-19 | THR_* | Thread management |
| 20-22 | COMM_*/IPC_MASK | Communication rights |
| 23 | IPC | Inter-process communication |
| 24-26 | EV_* | Events |
| 27-29 | INT_* | Interrupts |
| 30-31 | FAST_GET/SET_PRIO | Priority |
| 32-36 | MEM_* | Memory management |
| 37-39 | IOPORT_* | I/O ports |
| 40-46 | TRACE_* | Tracing |
| 47-48 | ALLOC_* | Physical memory |
| 49 | MON_MEM_LIST | Monitor |
| 50-53 | TP_* | Time partitions |
| 54 | THR_GET_REGS | Thread registers |
| 55 | GET_TIME | Time |
| 56-57 | MEM_READ/WRITE | Memory access |
| 58-59 | DEV_* | Devices |
| 60-65 | MON_* | Monitoring |
| 66 | MEM_CLEAR | Memory |
| 67 | THR_EX_AFFINITY | Thread affinity |
| 68 | TP_WIN_GET_ATTR | Time partition |
| 69 | SYSEMU_ENTER | System emulation |
| 70 | THR_PREEMPT | Thread preemption |
| 71 | TLS_REGISTER | TLS |
| 72-73 | ULOCK_WAIT/WAKE | User locks (futex) |
| 74 | GET_TS | Timestamp |
| 75-76 | RESPART_* | Resource partitions |
| 77 | THR_ALARM | Thread alarm |
| 78-96 | KDEV_* | Kernel device I/O |
| 97 | TLS_SYNC_PRIO | TLS priority sync |
| 98-104 | HM_* | Health monitoring |
| 105-108 | WAITQ_* | Wait queues |
| 109 | CACHE | Cache control |
| 110 | FAST_GET_TIMEPART | Time partition |
| 111-116 | KDEV_* | More device I/O |
| 117 | KDEV_DISCOVER_GATE | Device discovery |
| 118 | MON_MEMREG_GET_ATTR | Memory region monitor |

**Syscall mechanism (x86_64):**
```asm
mov     $SYSCALL_NUM, %eax
syscall                    ; x86-64 SYSCALL instruction
ret
```

---

## 12. POSIX COMPLIANCE MATRIX (PSE51)

| Feature | Status | Notes |
|---------|--------|-------|
| Threads | ✅ Full | pthread_create/join/detach/cancel |
| Mutexes | ✅ Full | Including priority inheritance/ceiling |
| Condition Variables | ✅ Full | Including timedwait |
| RW Locks | ✅ Full | |
| Semaphores | ✅ Full | Named + unnamed |
| Message Queues | ✅ Full | mq_open/send/receive/timed |
| Signals | ✅ Full | Including realtime signals, sigqueue |
| Timers | ✅ Full | timer_create/settime, clock_gettime |
| Clocks | ✅ Partial | CLOCK_REALTIME only |
| File I/O | ✅ Full | open/read/write/close/lseek/fstat |
| mmap | ⚠️ Partial | MAP_SHARED only, no mprotect |
| Shared Memory | ⚠️ Static | shm_open, no dynamic creation |
| Pipes | ✅ Full | Local pipes |
| Scheduling | ✅ Full | SCHED_FIFO/RR/OTHER |
| fork/exec | ❌ N/A | Not in PSE51 scope |
| Process spawn | ❌ Disabled | _POSIX_SPAWN = -1 |
| Job control | ❌ Disabled | _POSIX_JOB_CONTROL = -1 |
| Barriers | ❌ Disabled | _POSIX_BARRIERS = -1 |
| Spin locks | ❌ Disabled | _POSIX_SPIN_LOCKS = -1 |
| Async I/O | ❌ Disabled | _POSIX_ASYNCHRONOUS_IO = -1 |
| Process-shared sync | ❌ Disabled | _POSIX_THREAD_PROCESS_SHARED = -1 |

---

## 13. KEY DESIGN PATTERNS FOR UNIVERSALISOS PARITY

### Pattern 1: POSIX → PikeOS Kernel Bridge
```
POSIX API (pthread_create) 
  → POSIX library (internal implementation)
    → p4ext (thread creation: stack alloc, TLS init)
      → p4_thread_create_syscall (ASM stub)
        → SYSCALL instruction → PikeOS kernel
```

### Pattern 2: File System Provider Model
```
struct _file → f_ops → _fileops (read/write/close/ioctl/lseek/fstat)
                     ↓
             _fs_provider (LCL_DEV, LCL_FILE, LCL_PIPE, LCL_MQ, etc.)
```

### Pattern 3: Memory Pool Architecture
- Stack pool: fixed virtual region for thread stacks
- SHM pool: fixed virtual region for mmap/shm_open
- Heap pool: fixed virtual region for malloc/sbrk
- All backed by PSSW memory requirements configured at partition time

### Pattern 4: Configuration-Driven
- `struct _configurables` defines ALL tunable parameters
- Can be overridden via application property section
- Version-controlled structure for backward compatibility