hakmem/debug_analysis_final_$(date +%Y%m%d_%H%M%S).md

Debug Analysis Final - TLS-SLL Guard Investigation

Date: 2025-11-10 Binary: out/debug/bench_fixed_size_hakmem (verbose debug build) Command: 200000 1024 128

1. Maximum Tracing Results

Key Findings:

[TLS_SLL_GUARD] splice_trav: misaligned base=0x7244b7e10009 cls=0 blk=8 off=1
[HAKMEM][EARLY SIGSEGV] backtrace (1 frames)
./out/debug/bench_fixed_size_hakmem(+0x6a5e)[0x5b4a8b13ea5e]

Critical Discovery:

• TLS-SLL GUARDが検出！ misaligned base=0x7244b7e10009
• SPLICE_TO_SLL直後のsplice_trav操作でアライメント違反
• これがSIGSEGVの直接原因！

Analysis of misaligned address:

• base=0x7244b7e10009 - 最後の9進数（0x9）が問題
• cls=0 blk=8 off=1 - class 0, block 8, offset 1
• 正しいはず: 0x7244b7e10000 + (8 * 256) + 1 = 0x7244b7e10081
• 実際: 0x7244b7e10009 - 計算が間違っている！

2. No Cache Results (Frontend Disabled)

Same Pattern:

[TLS_SLL_GUARD] splice_trav: misaligned base=0x7d9100410009 cls=0 blk=8 off=1
[HAKMEM][EARLY SIGSEGV] backtrace (1 frames)
./out/debug/bench_fixed_size_hakmem(+0x6a5e)[0x622ace44fa5e]

Confirmed:

• Frontend cacheを無効にしても問題は再現
• TLS-SLL境界の問題であることが確定

3. Root Cause Analysis

Problem Location:

• SPLICE_TO_SLL直後のTLS-SLL操作
• splice_trav（traverse splice）でポインタ計算が破壊されている

Calculation Error:

Expected: base + (blk * size) + off
Actual:   base + ??? = 0x7244b7e10009 (9 bytes from base)

Header Offset Confusion:

• Class 0 (128B): header offset should be 1 byte
• Block 8: should be at 8 * 128 = 1024 bytes from base
• Correct address: 0x7244b7e10000 + 1024 + 1 = 0x7244b7e10401
• Actual: 0x7244b7e10009 - 完全に間違った計算！

4. PTR_TRACE Analysis

Missing TLS Operations:

• PTR_TRACEにtls_push/tls_pop/tls_sp_trav/tls_sp_linkが記録されていない
• TLS-SLL GUARDが発火する段階で既にPTR_TRACEが動いていない
• PTR_TRACEマクロ自体が問題のコードパスを通っていない！

5. Recommendations

Immediate Fix:

1. TLS-SLL splice_travのポインタ計算を修正
   • base + (blk * size) + off の計算を確認
   • class 0 (128B) × block 8 = 1024 bytes offset

Debug Strategy:

1. PTR_TRACEマクロをTLS-SLL GUARDの前後に配置
2. splice_trav関数のアセンブリ出力を確認
3. TLS-SLL GUARDの条件判定を緩和して詳細ログ取得

Code Location to Fix:

• core/box/tls_sll_box.h - splice_trav implementation
• SPLICE_TO_SLL直後のTLS-SLL操作フロー

6. Verification Steps

After Fix:

1. Same test should show proper alignment
2. TLS-SLL GUARD should not fire
3. PTR_TRACE should show tls_push/tls_pop operations
4. SIGSEGV should be resolved

Test Commands:

HAKMEM_DEBUG_SEGV=1 HAKMEM_PTR_TRACE_DUMP=1 HAKMEM_FREE_WRAP_TRACE=1 ./out/debug/bench_fixed_size_hakmem 200000 1024 128

7. Summary

Root Cause: TLS-SLL splice_trav operation has critical pointer calculation error Location: SPLICE_TO_SLL immediate aftermath Impact: Misaligned memory access causes SIGSEGV Fix Priority: CRITICAL - core memory corruption issue

The TLS-SLL GUARD successfully identified the exact location of the problem!