72b38bc994
## Root Cause Analysis (GPT5) **Physical Layout Constraints**: - Class 0: 8B = [1B header][7B payload] → offset 1 = 9B needed = ❌ IMPOSSIBLE - Class 1-6: >=16B = [1B header][15B+ payload] → offset 1 = ✅ POSSIBLE - Class 7: 1KB → offset 0 (compatibility) **Correct Specification**: - HAKMEM_TINY_HEADER_CLASSIDX != 0: - Class 0, 7: next at offset 0 (overwrites header when on freelist) - Class 1-6: next at offset 1 (after header) - HAKMEM_TINY_HEADER_CLASSIDX == 0: - All classes: next at offset 0 **Previous Bug**: - Attempted "ALL classes offset 1" unification - Class 0 with offset 1 caused immediate SEGV (9B > 8B block size) - Mixed 2-arg/3-arg API caused confusion ## Fixes Applied ### 1. Restored 3-Argument Box API (core/box/tiny_next_ptr_box.h) ```c // Correct signatures void tiny_next_write(int class_idx, void* base, void* next_value) void* tiny_next_read(int class_idx, const void* base) // Correct offset calculation size_t offset = (class_idx == 0 || class_idx == 7) ? 0 : 1; ``` ### 2. Updated 123+ Call Sites Across 34 Files - hakmem_tiny_hot_pop_v4.inc.h (4 locations) - hakmem_tiny_fastcache.inc.h (3 locations) - hakmem_tiny_tls_list.h (12 locations) - superslab_inline.h (5 locations) - tiny_fastcache.h (3 locations) - ptr_trace.h (macro definitions) - tls_sll_box.h (2 locations) - + 27 additional files Pattern: `tiny_next_read(base)` → `tiny_next_read(class_idx, base)` Pattern: `tiny_next_write(base, next)` → `tiny_next_write(class_idx, base, next)` ### 3. Added Sentinel Detection Guards - tiny_fast_push(): Block nodes with sentinel in ptr or ptr->next - tls_list_push(): Block nodes with sentinel in ptr or ptr->next - Defense-in-depth against remote free sentinel leakage ## Verification (GPT5 Report) **Test Command**: `./out/release/bench_random_mixed_hakmem --iterations=70000` **Results**: - ✅ Main loop completed successfully - ✅ Drain phase completed successfully - ✅ NO SEGV (previous crash at iteration 66151 is FIXED) - ℹ️ Final log: "tiny_alloc(1024) failed" is normal fallback to Mid/ACE layers **Analysis**: - Class 0 immediate SEGV: ✅ RESOLVED (correct offset 0 now used) - 66K iteration crash: ✅ RESOLVED (offset consistency fixed) - Box API conflicts: ✅ RESOLVED (unified 3-arg API) ## Technical Details ### Offset Logic Justification ``` Class 0: 8B block → next pointer (8B) fits ONLY at offset 0 Class 1: 16B block → next pointer (8B) fits at offset 1 (after 1B header) Class 2: 32B block → next pointer (8B) fits at offset 1 ... Class 6: 512B block → next pointer (8B) fits at offset 1 Class 7: 1024B block → offset 0 for legacy compatibility ``` ### Files Modified (Summary) - Core API: `box/tiny_next_ptr_box.h` - Hot paths: `hakmem_tiny_hot_pop*.inc.h`, `tiny_fastcache.h` - TLS layers: `hakmem_tiny_tls_list.h`, `hakmem_tiny_tls_ops.h` - SuperSlab: `superslab_inline.h`, `tiny_superslab_*.inc.h` - Refill: `hakmem_tiny_refill.inc.h`, `tiny_refill_opt.h` - Free paths: `tiny_free_magazine.inc.h`, `tiny_superslab_free.inc.h` - Documentation: Multiple Phase E3 reports ## Remaining Work None for Box API offset bugs - all structural issues resolved. Future enhancements (non-critical): - Periodic `grep -R '*(void**)' core/` to detect direct pointer access violations - Enforce Box API usage via static analysis - Document offset rationale in architecture docs 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
78 lines
2.4 KiB
C
78 lines
2.4 KiB
C
/**
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* @file ptr_conversion_box.h
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* @brief Box 3: Unified Pointer Conversion Layer
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*
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* MISSION: Fix BASE/USER pointer confusion across codebase
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*
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* DESIGN:
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* - BASE pointer: Points to start of block in storage (0-byte aligned)
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* - USER pointer: Points to usable memory (+1 byte for classes 0-6, +0 for class 7)
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* - Class 7 (2KB) is headerless (no +1 offset)
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* - Classes 0-6 have 1-byte header (need +1 offset)
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*
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* BOX BOUNDARIES:
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* - Box 1 (Front Gate) → Box 3 → Box 4 (User) [BASE to USER]
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* - Box 4 (User) → Box 3 → Box 1 (Front Gate) [USER to BASE]
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*/
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#ifndef HAKMEM_PTR_CONVERSION_BOX_H
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#define HAKMEM_PTR_CONVERSION_BOX_H
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#include <stdint.h>
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#include <stddef.h>
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#ifdef HAKMEM_PTR_CONVERSION_DEBUG
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#include <stdio.h>
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#define PTR_CONV_LOG(...) fprintf(stderr, "[PTR_CONV] " __VA_ARGS__)
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#else
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#define PTR_CONV_LOG(...) ((void)0)
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#endif
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/**
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* Convert BASE pointer (storage) to USER pointer (returned to caller)
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* Phase E1-CORRECT: ALL classes (0-7) have 1-byte headers
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*
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* @param base_ptr Pointer to block in storage (no offset)
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* @param class_idx Size class (0-7: +1 offset for all)
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* @return USER pointer (usable memory address)
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*/
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static inline void* ptr_base_to_user(void* base_ptr, uint8_t class_idx) {
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if (base_ptr == NULL) {
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return NULL;
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}
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/* Phase E1-CORRECT: All classes 0-7 have 1-byte header - skip it */
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void* user_ptr = (void*)((uint8_t*)base_ptr + 1);
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PTR_CONV_LOG("BASE→USER cls=%u base=%p → user=%p (+1 offset)\n",
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class_idx, base_ptr, user_ptr);
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return user_ptr;
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}
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/**
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* Convert USER pointer (from caller) to BASE pointer (storage)
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* Phase E1-CORRECT: ALL classes (0-7) have 1-byte headers
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*
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* @param user_ptr Pointer from user (may have +1 offset)
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* @param class_idx Size class (0-7: -1 offset for all)
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* @return BASE pointer (block start in storage)
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*/
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static inline void* ptr_user_to_base(void* user_ptr, uint8_t class_idx) {
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if (user_ptr == NULL) {
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return NULL;
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}
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/* Phase E1-CORRECT: All classes 0-7 have 1-byte header - rewind it */
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void* base_ptr = (void*)((uint8_t*)user_ptr - 1);
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PTR_CONV_LOG("USER→BASE cls=%u user=%p → base=%p (-1 offset)\n",
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class_idx, user_ptr, base_ptr);
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return base_ptr;
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}
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/**
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* Convenience macros for cleaner call sites
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*/
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#define PTR_BASE_TO_USER(base, cls) ptr_base_to_user((base), (cls))
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#define PTR_USER_TO_BASE(user, cls) ptr_user_to_base((user), (cls))
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#endif /* HAKMEM_PTR_CONVERSION_BOX_H */
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