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ryanbreen merged 1 commit into from
Feb 4, 2026
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docs(arm64): restructure parity tracking by tests unblocked #150

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163 changes: 153 additions & 10 deletions arm64-parity.md
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**Tracking Document for ARM64 vs x86-64 Feature Parity**

## Last Updated: 2026-02-02
## Last Updated: 2026-02-04

---

## Executive Summary

**Goal**: Achieve ARM64 test parity with x86-64

### Test Inventory Comparison

| Category | x86-64 | ARM64 | Gap |
|----------|--------|-------|-----|
| Kernel Test Framework | 91 | 91* | 0* |
| Userspace Test Binaries | 122 | 100 | **-22** |
| Rust Integration Tests | 72 | 2 | **-70** |
| **Total Potential Tests** | **285** | **193** | **-92** |

*\*Kernel test framework exists on ARM64 but many tests may be arch-gated*

### Current ARM64 Userspace Results

| Metric | Baseline | Current | Target |
|--------|----------|---------|--------|
| ARM64 Pass Rate | 41.25% (33/80) | **62.5% (50/80)** | ~90% |
| x86-64 Pass Rate | - | ~90% | - |
| Kernel Feature Parity | - | ~100% | - |
| Userspace Pass Rate | 41.25% (33/80) | **62.5% (50/80)** | ~90% |
| Tests in Suite | 80 | 80 | 100+ |

**Progress**: +21.25% improvement from baseline, +17 new tests passing

**Key Fixes Applied**:
### Key Fixes Applied ✅
1. ~~exec() spinlock deadlock~~ **FIXED** - added explicit lock release before ERET
2. ~~sys_read for RegularFile~~ **FIXED** - implemented ext2 file read support
3. Test infrastructure now uses writable ext2 disk copy
3. ~~Network ENETUNREACH~~ **FIXED** - added virtio-net to QEMU scripts
4. ~~Filesystem readonly~~ **FIXED** - removed readonly=on from QEMU disk
5. ~~argc/argv setup~~ **FIXED** - implemented create_process_with_argv()
6. ~~COW syscalls~~ **ALREADY IMPLEMENTED** - no changes needed

---

## Priority Queue: Ordered by Tests Unblocked

**Principle**: Each priority level is chosen because it unblocks the largest number of tests for the effort required.

### PRIORITY 1: Port Rust Integration Tests to ARM64 [+70 tests]
**Status**: NOT STARTED
**Effort**: High (infrastructure + test porting)
**Tests Unblocked**: 70

The Rust integration tests (`tests/*.rs`) provide 72 tests on x86-64 but only 2 on ARM64. This is the single largest gap in test coverage.

**What's needed**:
1. Create ARM64 QEMU test harness (like `shared_qemu.rs` but for ARM64)
2. Port architecture-specific test setup code
3. Verify each test file works on ARM64:

| Test File | x86-64 Tests | ARM64 Status |
|-----------|--------------|--------------|
| syscall_tests.rs | 1 | Not ported |
| memory_tests.rs | 3 | Not ported |
| system_tests.rs | 4 | Not ported |
| exception_tests.rs | ~8 | Not ported |
| guard_page_tests.rs | ~5 | Not ported |
| interrupt_tests.rs | ~6 | Not ported |
| timer_tests.rs | ~4 | Not ported |
| keyboard_tests.rs | ~3 | Not ported |
| logging_tests.rs | ~2 | Not ported |
| stack_bounds_tests.rs | ~4 | Not ported |
| async_executor_tests.rs | ~5 | Not ported |
| boot_post_test.rs | 1 | **Ported** |
| arm64_boot_post_test.rs | 1 | **ARM64 native** |
| shared_qemu.rs | - | x86-64 only |
| shared_qemu_aarch64.rs | - | **Exists** |
| simple_kernel_test.rs | ~2 | Not ported |
| kernel_build_test.rs | ~1 | Not ported |
| ring3_smoke_test.rs | ~3 | Not ported |
| ring3_enosys_test.rs | ~2 | Not ported |

---

### PRIORITY 2: Port x86-64 Assembly Tests to libbreenix [+12 tests]
**Status**: NOT STARTED
**Effort**: Medium (rewrite tests to use libbreenix syscall wrappers)
**Tests Unblocked**: 12

These tests are excluded from ARM64 because they use x86-64 inline assembly (`int 0x80`, register manipulation). They need to be rewritten to use libbreenix syscall wrappers.

| Test | Current Issue | Porting Approach |
|------|---------------|------------------|
| `pipe_test` | Uses `int 0x80` for syscalls | Use `libbreenix::io::pipe()` |
| `pipe_refcount_test` | Uses `int 0x80` | Use `libbreenix::io::pipe()` |
| `poll_test` | Uses `int 0x80` | Use `libbreenix::io::poll()` |
| `select_test` | Uses `int 0x80` | Use `libbreenix::io::select()` |
| `brk_test` | Uses `int 0x80` | Use `libbreenix::memory::brk()` |
| `stdin_test` | Uses `int 0x80` | Use `libbreenix::io::read()` |
| `timer_test` | Uses `int 0x80` | Use `libbreenix::time` |
| `register_init_test` | x86-64 register checks | Rewrite for ARM64 regs (x0-x30) |
| `syscall_diagnostic_test` | Uses `int 0x80` | Use libbreenix syscalls |
| `syscall_enosys` | Uses `int 0x80` | Use libbreenix syscalls |
| `signal_regs_test` | Uses r12-r15 (x86-64) | Rewrite for x19-x28 (ARM64) |
| `sigaltstack_test` | Uses RSP access | Rewrite for SP access (ARM64) |

---

### PRIORITY 3: Fix Signal Delivery [+5 tests]
**Status**: NOT STARTED
**Effort**: Medium (kernel debugging)
**Tests Unblocked**: 5 (of the 30 currently failing)

Signal delivery via `kill()` is not working on ARM64. SIGCHLD works (sigchld_test passes), so some signal paths are functional.

**Debugging approach**:
1. Trace `kill()` syscall on ARM64
2. Compare with x86-64 signal delivery path
3. Fix the delivery mechanism

**Tests that will pass once fixed**:
| Test | What it tests |
|------|---------------|
| `signal_test` | `kill(pid, SIGTERM)` to child |
| `ctrl_c_test` | `kill(pid, SIGINT)` to child |
| `alarm_test` | SIGALRM after timer expires |
| `itimer_test` | setitimer/getitimer + SIGALRM |
| `kill_process_group_test` | `kill(0, sig)`, `kill(-pgid, sig)` |

---

### PRIORITY 4: Remaining Userspace Test Failures [~25 tests]
**Status**: INVESTIGATION NEEDED
**Effort**: Variable
**Tests Unblocked**: ~25

After P1-P3, approximately 25 tests may still be failing. These need individual investigation:

| Category | Est. Count | Notes |
|----------|------------|-------|
| Filesystem write bugs | ~6 | May already be fixed by readonly fix |
| Process/fork edge cases | ~5 | Need investigation |
| Network edge cases | ~4 | May need virtio-net driver fixes |
| TTY/PTY issues | ~3 | Need investigation |
| Other | ~7 | Need investigation |

---

### PRIORITY 5: Kernel Test Framework on ARM64 [+91 tests potentially]
**Status**: NOT STARTED
**Effort**: Medium-High
**Tests Unblocked**: Up to 91 (if not already running)

Verify the kernel test framework runs on ARM64 boot and all arch-agnostic tests pass.

**What's needed**:
1. Verify test framework initializes on ARM64
2. Identify which tests are x86-64 only vs arch-agnostic
3. Run and fix arch-agnostic tests
4. Port x86-64-specific tests where valuable

---

## Test Gap Summary

| Priority | Work Item | Tests Unblocked | Effort | Cumulative |
|----------|-----------|-----------------|--------|------------|
| P1 | Port Rust integration tests | +70 | High | 70 |
| P2 | Port x86-64 asm tests | +12 | Medium | 82 |
| P3 | Fix signal delivery | +5 | Medium | 87 |
| P4 | Fix remaining failures | +25 | Variable | 112 |
| P5 | Kernel test framework | +91 | Medium-High | 203 |

**Remaining Gaps**:
1. Network configuration (ENETUNREACH) - ~6 tests
2. argc/argv setup for initial process - ~4 tests
3. Various syscall issues - ~20 tests
**Total potential improvement**: From current 50 passing to 203+ tests

---

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