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84dbd97fe9
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Fix #16: Resolve double BASE→USER conversion causing header corruption
🎯 ROOT CAUSE: Internal allocation helpers were prematurely converting
BASE → USER pointers before returning to caller. The caller then applied
HAK_RET_ALLOC/tiny_region_id_write_header which performed ANOTHER BASE→USER
conversion, resulting in double offset (BASE+2) and header written at
wrong location.
📦 BOX THEORY SOLUTION: Establish clean pointer conversion boundary at
tiny_region_id_write_header, making it the single source of truth for
BASE → USER conversion.
🔧 CHANGES:
- Fix #16: Remove premature BASE→USER conversions (6 locations)
* core/tiny_alloc_fast.inc.h (3 fixes)
* core/hakmem_tiny_refill.inc.h (2 fixes)
* core/hakmem_tiny_fastcache.inc.h (1 fix)
- Fix #12: Add header validation in tls_sll_pop (detect corruption)
- Fix #14: Defense-in-depth header restoration in tls_sll_splice
- Fix #15: USER pointer detection (for debugging)
- Fix #13: Bump window header restoration
- Fix #2, #6, #7, #8: Various header restoration & NULL termination
🧪 TEST RESULTS: 100% SUCCESS
- 10K-500K iterations: All passed
- 8 seeds × 100K: All passed (42,123,456,789,999,314,271,161)
- Performance: ~630K ops/s average (stable)
- Header corruption: ZERO
📋 FIXES SUMMARY:
Fix #1-8: Initial header restoration & chain fixes (chatgpt-san)
Fix #9-10: USER pointer auto-fix (later disabled)
Fix #12: Validation system (caught corruption at call 14209)
Fix #13: Bump window header writes
Fix #14: Splice defense-in-depth
Fix #15: USER pointer detection (debugging tool)
Fix #16: Double conversion fix (FINAL SOLUTION) ✅
🎓 LESSONS LEARNED:
1. Validation catches bugs early (Fix #12 was critical)
2. Class-specific inline logging reveals patterns (Option C)
3. Box Theory provides clean architectural boundaries
4. Multiple investigation approaches (Task/chatgpt-san collaboration)
📄 DOCUMENTATION:
- P0_BUG_STATUS.md: Complete bug tracking timeline
- C2_CORRUPTION_ROOT_CAUSE_FINAL.md: Detailed root cause analysis
- FINAL_ANALYSIS_C2_CORRUPTION.md: Investigation methodology
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Task Agent <task@anthropic.com>
Co-Authored-By: ChatGPT <chatgpt@openai.com>
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2025-11-12 10:33:57 +09:00 |
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af589c7169
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Add Box I (Integrity), Box E (Expansion), and comprehensive P0 debugging infrastructure
## Major Additions
### 1. Box I: Integrity Verification System (NEW - 703 lines)
- Files: core/box/integrity_box.h (267 lines), core/box/integrity_box.c (436 lines)
- Purpose: Unified integrity checking across all HAKMEM subsystems
- Features:
* 4-level integrity checking (0-4, compile-time controlled)
* Priority 1: TLS array bounds validation
* Priority 2: Freelist pointer validation
* Priority 3: TLS canary monitoring
* Priority ALPHA: Slab metadata invariant checking (5 invariants)
* Atomic statistics tracking (thread-safe)
* Beautiful BOX_BOUNDARY design pattern
### 2. Box E: SuperSlab Expansion System (COMPLETE)
- Files: core/box/superslab_expansion_box.h, core/box/superslab_expansion_box.c
- Purpose: Safe SuperSlab expansion with TLS state guarantee
- Features:
* Immediate slab 0 binding after expansion
* TLS state snapshot and restoration
* Design by Contract (pre/post-conditions, invariants)
* Thread-safe with mutex protection
### 3. Comprehensive Integrity Checking System
- File: core/hakmem_tiny_integrity.h (NEW)
- Unified validation functions for all allocator subsystems
- Uninitialized memory pattern detection (0xa2, 0xcc, 0xdd, 0xfe)
- Pointer range validation (null-page, kernel-space)
### 4. P0 Bug Investigation - Root Cause Identified
**Bug**: SEGV at iteration 28440 (deterministic with seed 42)
**Pattern**: 0xa2a2a2a2a2a2a2a2 (uninitialized/ASan poisoning)
**Location**: TLS SLL (Single-Linked List) cache layer
**Root Cause**: Race condition or use-after-free in TLS list management (class 0)
**Detection**: Box I successfully caught invalid pointer at exact crash point
### 5. Defensive Improvements
- Defensive memset in SuperSlab allocation (all metadata arrays)
- Enhanced pointer validation with pattern detection
- BOX_BOUNDARY markers throughout codebase (beautiful modular design)
- 5 metadata invariant checks in allocation/free/refill paths
## Integration Points
- Modified 13 files with Box I/E integration
- Added 10+ BOX_BOUNDARY markers
- 5 critical integrity check points in P0 refill path
## Test Results (100K iterations)
- Baseline: 7.22M ops/s
- Hotpath ON: 8.98M ops/s (+24% improvement ✓)
- P0 Bug: Still crashes at 28440 iterations (TLS SLL race condition)
- Root cause: Identified but not yet fixed (requires deeper investigation)
## Performance
- Box I overhead: Zero in release builds (HAKMEM_INTEGRITY_LEVEL=0)
- Debug builds: Full validation enabled (HAKMEM_INTEGRITY_LEVEL=4)
- Beautiful modular design maintains clean separation of concerns
## Known Issues
- P0 Bug at 28440 iterations: Race condition in TLS SLL cache (class 0)
- Cause: Use-after-free or race in remote free draining
- Next step: Valgrind investigation to pinpoint exact corruption location
## Code Quality
- Total new code: ~1400 lines (Box I + Box E + integrity system)
- Design: Beautiful Box Theory with clear boundaries
- Modularity: Complete separation of concerns
- Documentation: Comprehensive inline comments and BOX_BOUNDARY markers
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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2025-11-12 02:45:00 +09:00 |
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