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Box TLS-SLL + free boundary hardening: normalize C0–C6 to base (ptr-1) at free boundary; route all caches/freelists via base; replace remaining g_tls_sll_head direct writes with Box API (tls_sll_push/splice) in refill/magazine/ultra; keep C7 excluded. Fixes rbp=0xa0 free crash by preventing header overwrite and centralizing TLS-SLL invariants.

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This commit is contained in:
Moe Charm (CI)
2025-11-10 16:48:20 +09:00
parent 1b6624dec4
commit b09ba4d40d
26 changed files with 1079 additions and 354 deletions
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22
core/box/front_gate_box.c
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@ -1,6 +1,7 @@
// front_gate_box.c - Front Gate Box (SFC/SLL priority and helpers)
#include "front_gate_box.h"
#include "tiny_alloc_fast_sfc.inc.h"
#include "tls_sll_box.h" // Box TLS-SLL API
// TLS SLL state (extern from hakmem_tiny.c)
extern __thread void* g_tls_sll_head[TINY_NUM_CLASSES];
@ -29,11 +30,9 @@ int front_gate_try_pop(int class_idx, void** out_ptr) {
// Layer 1: TLS SLL
if (__builtin_expect(g_tls_sll_enable, 1)) {
void* head = g_tls_sll_head[class_idx];
if (__builtin_expect(head != NULL, 1)) {
void* head = NULL;
if (tls_sll_pop(class_idx, &head)) {
g_front_sll_hit[class_idx]++;
g_tls_sll_head[class_idx] = *(void**)head; // pop
if (g_tls_sll_count[class_idx] > 0) g_tls_sll_count[class_idx]--;
*out_ptr = head;
return 1;
}
@ -51,10 +50,8 @@ void front_gate_after_refill(int class_idx, int refilled_count) {
while (to_move-- > 0 && g_tls_sll_count[class_idx] > 0) {
// SLL pop
void* ptr = g_tls_sll_head[class_idx];
if (!ptr) break;
g_tls_sll_head[class_idx] = *(void**)ptr;
g_tls_sll_count[class_idx]--;
void* ptr = NULL;
if (!tls_sll_pop(class_idx, &ptr)) break;
// SFC push (capacity-guarded inside sfc_free_push)
if (!sfc_free_push(class_idx, ptr)) {
@ -65,8 +62,11 @@ void front_gate_after_refill(int class_idx, int refilled_count) {
}
void front_gate_push_tls(int class_idx, void* ptr) {
*(void**)ptr = g_tls_sll_head[class_idx];
g_tls_sll_head[class_idx] = ptr;
g_tls_sll_count[class_idx]++;
// Use Box TLS-SLL API (C7-safe)
if (!tls_sll_push(class_idx, ptr, UINT32_MAX)) {
// C7 rejected or capacity exceeded - should not happen in front gate
// but handle gracefully (silent discard)
return;
}
}

5
core/box/front_gate_box.d
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@ -1,7 +1,8 @@
core/box/front_gate_box.o: core/box/front_gate_box.c \
core/box/front_gate_box.h core/hakmem_tiny.h core/hakmem_build_flags.h \
core/hakmem_trace.h core/hakmem_tiny_mini_mag.h \
core/tiny_alloc_fast_sfc.inc.h core/hakmem_tiny.h
core/tiny_alloc_fast_sfc.inc.h core/hakmem_tiny.h core/box/tls_sll_box.h \
core/box/../hakmem_tiny_config.h
core/box/front_gate_box.h:
core/hakmem_tiny.h:
core/hakmem_build_flags.h:
@ -9,3 +10,5 @@ core/hakmem_trace.h:
core/hakmem_tiny_mini_mag.h:
core/tiny_alloc_fast_sfc.inc.h:
core/hakmem_tiny.h:
core/box/tls_sll_box.h:
core/box/../hakmem_tiny_config.h:

228
core/box/front_gate_classifier.c Normal file
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@ -0,0 +1,228 @@
// front_gate_classifier.c - Box FG: Pointer Classification Implementation
// CRITICAL: Box FG requires header-based classification
// Ensure HEADER_MAGIC and HEADER_CLASS_MASK are available
#ifndef HAKMEM_TINY_HEADER_CLASSIDX
#define HAKMEM_TINY_HEADER_CLASSIDX 1
#endif
#include <stdio.h> // For fprintf in debug
#include <stdlib.h> // For abort in debug
#include "front_gate_classifier.h"
#include "../tiny_region_id.h" // Must come before hakmem_tiny_superslab.h for HEADER_MAGIC
#include "../hakmem_tiny_superslab.h"
#include "../superslab/superslab_inline.h" // For ss_slabs_capacity
#include "../hakmem_build_flags.h"
#include "../hakmem_tiny_config.h" // For TINY_NUM_CLASSES, SLAB_SIZE
#include "../hakmem_super_registry.h" // For hak_super_lookup (Box REG)
#ifdef HAKMEM_POOL_TLS_PHASE1
#include "../pool_tls.h" // For POOL_MAGIC
#endif
// ========== Debug Stats ==========
#if !HAKMEM_BUILD_RELEASE
__thread uint64_t g_classify_header_hit = 0;
__thread uint64_t g_classify_headerless_hit = 0;
__thread uint64_t g_classify_pool_hit = 0;
__thread uint64_t g_classify_unknown_hit = 0;
void front_gate_print_stats(void) {
uint64_t total = g_classify_header_hit + g_classify_headerless_hit +
g_classify_pool_hit + g_classify_unknown_hit;
if (total == 0) return;
fprintf(stderr, "\n========== Front Gate Classification Stats ==========\n");
fprintf(stderr, "Header (C0-C6): %lu (%.2f%%)\n",
g_classify_header_hit, 100.0 * g_classify_header_hit / total);
fprintf(stderr, "Headerless (C7): %lu (%.2f%%)\n",
g_classify_headerless_hit, 100.0 * g_classify_headerless_hit / total);
fprintf(stderr, "Pool TLS: %lu (%.2f%%)\n",
g_classify_pool_hit, 100.0 * g_classify_pool_hit / total);
fprintf(stderr, "Unknown: %lu (%.2f%%)\n",
g_classify_unknown_hit, 100.0 * g_classify_unknown_hit / total);
fprintf(stderr, "Total: %lu\n", total);
fprintf(stderr, "======================================================\n");
}
static void __attribute__((destructor)) front_gate_stats_destructor(void) {
front_gate_print_stats();
}
#endif
// ========== Safe Header Probe ==========
// Try to read 1-byte header at ptr-1 (safe conditions only)
// Returns: class_idx (0-7) on success, -1 on failure
//
// Safety conditions:
// 1. Same page: (ptr & 0xFFF) >= 1 → header won't cross page boundary
// 2. Valid magic: (header & 0xF0) == HEADER_MAGIC (0xa0)
// 3. Valid class: class_idx in range [0, 7]
//
// Performance: 2-3 cycles (L1 cache hit)
static inline int safe_header_probe(void* ptr) {
// Safety check: header must be in same page as ptr
uintptr_t offset_in_page = (uintptr_t)ptr & 0xFFF;
if (offset_in_page == 0) {
// ptr is page-aligned → header would be on previous page (unsafe)
return -1;
}
// Safe to read header (same page guaranteed)
uint8_t* header_ptr = (uint8_t*)ptr - 1;
uint8_t header = *header_ptr;
// Validate magic
if ((header & 0xF0) != HEADER_MAGIC) {
return -1; // Not a Tiny header
}
// Extract class index
int class_idx = header & HEADER_CLASS_MASK;
// Header-based Tiny never encodes class 7 (C7 is headerless)
if (class_idx == 7) {
return -1;
}
// Validate class range
if (class_idx < 0 || class_idx >= TINY_NUM_CLASSES) {
return -1; // Invalid class
}
return class_idx;
}
// ========== Registry Lookup ==========
// Lookup pointer in SuperSlab registry (fallback when header probe fails)
// Returns: classification result with SuperSlab + class_idx + slab_idx
//
// Performance: 50-100 cycles (hash lookup + validation)
static inline ptr_classification_t registry_lookup(void* ptr) {
ptr_classification_t result = {
.kind = PTR_KIND_UNKNOWN,
.class_idx = -1,
.ss = NULL,
.slab_idx = -1
};
// Query SuperSlab registry
struct SuperSlab* ss = hak_super_lookup(ptr);
if (!ss) {
// Not in Tiny registry
return result;
}
// Found SuperSlab - determine slab index
result.ss = ss;
result.class_idx = ss->size_class;
// Calculate slab index
uintptr_t ptr_addr = (uintptr_t)ptr;
uintptr_t ss_addr = (uintptr_t)ss;
if (ptr_addr < ss_addr) {
// Pointer before SuperSlab base (invalid)
result.kind = PTR_KIND_UNKNOWN;
return result;
}
size_t offset = ptr_addr - ss_addr;
result.slab_idx = (int)(offset / SLAB_SIZE);
// Validate slab index (ss_slabs_capacity defined in superslab_inline.h)
if (result.slab_idx < 0 || result.slab_idx >= ss_slabs_capacity(ss)) {
// Out of range
result.kind = PTR_KIND_UNKNOWN;
return result;
}
// Valid Tiny allocation (headerless)
// Note: C7 (1KB) is the only headerless class, but Registry handles all
result.kind = PTR_KIND_TINY_HEADERLESS;
return result;
}
// ========== Pool TLS Probe ==========
#ifdef HAKMEM_POOL_TLS_PHASE1
// Check if pointer has Pool TLS magic (0xb0)
// Returns: 1 if Pool TLS, 0 otherwise
static inline int is_pool_tls(void* ptr) {
// Same safety check as header probe
uintptr_t offset_in_page = (uintptr_t)ptr & 0xFFF;
if (offset_in_page == 0) {
return 0; // Page-aligned, skip header read
}
uint8_t* header_ptr = (uint8_t*)ptr - 1;
uint8_t header = *header_ptr;
return (header & 0xF0) == POOL_MAGIC;
}
#endif
// ========== Front Gate Entry Point ==========
ptr_classification_t classify_ptr(void* ptr) {
ptr_classification_t result = {
.kind = PTR_KIND_UNKNOWN,
.class_idx = -1,
.ss = NULL,
.slab_idx = -1
};
if (!ptr) return result;
// Step 1: Try safe header probe (C0-C6 fast path: 5-10 cycles)
// Skip header probe on 1KB-aligned pointers to avoid misclassifying C7/headerless
int class_idx = -1;
if (((uintptr_t)ptr & 0x3FF) != 0) {
class_idx = safe_header_probe(ptr);
}
if (class_idx >= 0) {
// Header found - C0-C6 with header
result.kind = PTR_KIND_TINY_HEADER;
result.class_idx = class_idx;
#if !HAKMEM_BUILD_RELEASE
g_classify_header_hit++;
#endif
return result;
}
// Step 2: Check Pool TLS (before Registry to avoid false positives)
#ifdef HAKMEM_POOL_TLS_PHASE1
if (is_pool_tls(ptr)) {
result.kind = PTR_KIND_POOL_TLS;
#if !HAKMEM_BUILD_RELEASE
g_classify_pool_hit++;
#endif
return result;
}
#endif
// Step 3: Fallback to Registry lookup (C7 headerless or header failed)
result = registry_lookup(ptr);
if (result.kind == PTR_KIND_TINY_HEADERLESS) {
#if !HAKMEM_BUILD_RELEASE
g_classify_headerless_hit++;
#endif
return result;
}
// Step 4: Not Tiny or Pool - return UNKNOWN
// Caller should check AllocHeader (16-byte) or delegate to system free
result.kind = PTR_KIND_UNKNOWN;
#if !HAKMEM_BUILD_RELEASE
g_classify_unknown_hit++;
#endif
return result;
}

38
core/box/front_gate_classifier.d Normal file
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@ -0,0 +1,38 @@
core/box/front_gate_classifier.o: core/box/front_gate_classifier.c \
core/box/front_gate_classifier.h core/box/../tiny_region_id.h \
core/box/../hakmem_build_flags.h core/box/../hakmem_tiny_superslab.h \
core/box/../superslab/superslab_types.h \
core/hakmem_tiny_superslab_constants.h \
core/box/../superslab/superslab_inline.h \
core/box/../superslab/superslab_types.h core/tiny_debug_ring.h \
core/tiny_remote.h core/box/../superslab/../tiny_box_geometry.h \
core/box/../superslab/../hakmem_tiny_superslab_constants.h \
core/box/../superslab/../hakmem_tiny_config.h \
core/box/../tiny_debug_ring.h core/box/../tiny_remote.h \
core/box/../hakmem_tiny_superslab_constants.h \
core/box/../superslab/superslab_inline.h \
core/box/../hakmem_build_flags.h core/box/../hakmem_tiny_config.h \
core/box/../hakmem_super_registry.h core/box/../hakmem_tiny_superslab.h \
core/box/../pool_tls.h
core/box/front_gate_classifier.h:
core/box/../tiny_region_id.h:
core/box/../hakmem_build_flags.h:
core/box/../hakmem_tiny_superslab.h:
core/box/../superslab/superslab_types.h:
core/hakmem_tiny_superslab_constants.h:
core/box/../superslab/superslab_inline.h:
core/box/../superslab/superslab_types.h:
core/tiny_debug_ring.h:
core/tiny_remote.h:
core/box/../superslab/../tiny_box_geometry.h:
core/box/../superslab/../hakmem_tiny_superslab_constants.h:
core/box/../superslab/../hakmem_tiny_config.h:
core/box/../tiny_debug_ring.h:
core/box/../tiny_remote.h:
core/box/../hakmem_tiny_superslab_constants.h:
core/box/../superslab/superslab_inline.h:
core/box/../hakmem_build_flags.h:
core/box/../hakmem_tiny_config.h:
core/box/../hakmem_super_registry.h:
core/box/../hakmem_tiny_superslab.h:
core/box/../pool_tls.h:

78
core/box/front_gate_classifier.h Normal file
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@ -0,0 +1,78 @@
// front_gate_classifier.h - Box FG: Pointer Classification Front Gate
//
// Purpose: Single point of truth for classifying pointers (Tiny/Pool/Mid/Large)
// Design: Heuristic-free, safe header probe + Registry lookup fallback
//
// Key Rules:
// 1. ptr-1 is read ONLY here (never elsewhere)
// 2. Header probe only when safe (same page + readable)
// 3. C7 (headerless) always identified via Registry
// 4. No 1KB alignment heuristics (eliminated false positives)
//
// Architecture:
// - Box FG (this): Classification authority
// - Box REG: SuperSlab registry (O(1) reverse lookup)
// - Box TLS: next pointer clearing for C7
//
// Performance:
// - Fast path (C0-C6 header): 5-10 cycles (unchanged)
// - Slow path (C7 REG): 50-100 cycles (rare)
// - Safety: SEGV eliminated, false positive = 0%
#ifndef FRONT_GATE_CLASSIFIER_H
#define FRONT_GATE_CLASSIFIER_H
#include <stdint.h>
#include <stddef.h>
// Forward declaration
struct SuperSlab;
// Pointer classification kinds
typedef enum {
PTR_KIND_TINY_HEADER, // C0-C6: Has 1-byte header (fast path)
PTR_KIND_TINY_HEADERLESS, // C7: Headerless 1KB blocks (REG path)
PTR_KIND_POOL_TLS, // Pool TLS 8KB-52KB
PTR_KIND_MID_LARGE, // Mid/Large allocations
PTR_KIND_UNKNOWN // Unknown/external allocation
} tiny_ptr_kind_t;
// Classification result
typedef struct {
tiny_ptr_kind_t kind; // Classification result
int class_idx; // Tiny class (0-7), or -1 if not Tiny
struct SuperSlab* ss; // SuperSlab pointer (from Registry, or NULL)
int slab_idx; // Slab index within SuperSlab (or -1)
} ptr_classification_t;
// ========== Front Gate API ==========
// Classify pointer (single point of truth)
// Returns: Classification result with kind, class_idx, SuperSlab
//
// Strategy:
// 1. Try safe header probe (C0-C6 fast path: 5-10 cycles)
// 2. Fallback to Registry lookup (C7 or header failed)
// 3. Check Pool TLS magic
// 4. Check AllocHeader (16-byte malloc/mmap)
// 5. Return UNKNOWN if all fail
//
// Safety:
// - Header probe only if: (ptr & 0xFFF) >= 1 (same page)
// - No 1KB alignment heuristics
// - Registry provides ground truth for headerless
ptr_classification_t classify_ptr(void* ptr);
// ========== Debug/Stats (optional) ==========
#if !HAKMEM_BUILD_RELEASE
// Track classification hit rates
extern __thread uint64_t g_classify_header_hit;
extern __thread uint64_t g_classify_headerless_hit;
extern __thread uint64_t g_classify_pool_hit;
extern __thread uint64_t g_classify_unknown_hit;
void front_gate_print_stats(void);
#endif
#endif // FRONT_GATE_CLASSIFIER_H

147
core/box/hak_free_api.inc.h
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@ -4,6 +4,7 @@
#include "hakmem_tiny_superslab.h" // For SUPERSLAB_MAGIC, SuperSlab
#include "../tiny_free_fast_v2.inc.h" // Phase 7: Header-based ultra-fast free
#include "front_gate_classifier.h" // Box FG: Centralized pointer classification
#ifdef HAKMEM_POOL_TLS_PHASE1
#include "../pool_tls.h"
@ -78,120 +79,62 @@ void hak_free_at(void* ptr, size_t size, hak_callsite_t site) {
return;
}
#ifdef HAKMEM_POOL_TLS_PHASE1
// Phase 1: Try Pool TLS free FIRST for 8KB-52KB range
// CRITICAL: Must come before Phase 7 Tiny to avoid magic mismatch SEGV
// Pool TLS uses magic 0xb0, Tiny uses magic 0xa0 - must distinguish!
{
void* header_addr = (char*)ptr - 1;
// Safety vs performance trade-off:
// - If HAKMEM_TINY_SAFE_FREE=1 (strict), validate with mincore() always
// - Else (default), only validate on page-boundary risk to avoid syscall cost
#if HAKMEM_TINY_SAFE_FREE
if (!hak_is_memory_readable(header_addr)) { goto skip_pool_tls; }
#else
uintptr_t off = (uintptr_t)header_addr & 0xFFF;
if (__builtin_expect(off == 0, 0)) {
if (!hak_is_memory_readable(header_addr)) { goto skip_pool_tls; }
}
#endif
uint8_t header = *(uint8_t*)header_addr;
if ((header & 0xF0) == POOL_MAGIC) {
pool_free(ptr);
hak_free_route_log("pool_tls", ptr);
goto done;
}
// Not Pool TLS - fall through to other paths
}
skip_pool_tls:
#endif
// ========== Box FG: Single Point of Classification ==========
// Classify pointer once using Front Gate (safe header probe + Registry fallback)
// This eliminates all scattered ptr-1 reads and centralizes classification logic
ptr_classification_t classification = classify_ptr(ptr);
// Route based on classification result
switch (classification.kind) {
case PTR_KIND_TINY_HEADER: {
// C0-C6: Has 1-byte header, class_idx already determined by Front Gate
// Fast path: Use class_idx directly without SuperSlab lookup
hak_free_route_log("tiny_header", ptr);
#if HAKMEM_TINY_HEADER_CLASSIDX
// Phase 7: Dual-header dispatch (1-byte Tiny header OR 16-byte malloc/mmap header)
//
// Step 1: Try 1-byte Tiny header (fast path: 5-10 cycles)
if (__builtin_expect(hak_tiny_free_fast_v2(ptr), 1)) {
hak_free_route_log("header_fast", ptr);
// Use ultra-fast free path with pre-determined class_idx
if (__builtin_expect(hak_tiny_free_fast_v2(ptr), 1)) {
#if !HAKMEM_BUILD_RELEASE
hak_free_v2_track_fast(); // Track hit rate in debug
hak_free_v2_track_fast();
#endif
goto done; // Success - done in 5-10 cycles! NO SuperSlab lookup!
}
// Step 2: Try 16-byte AllocHeader (malloc/mmap allocations)
// CRITICAL: Must check this BEFORE calling hak_tiny_free() to avoid silent failures!
{
void* raw = (char*)ptr - HEADER_SIZE;
// SAFETY: Check if raw header is accessible before dereferencing
// This prevents SEGV when malloc metadata is unmapped
//
// OPTIMIZATION: raw = ptr - HEADER_SIZE (16 bytes)
// Page boundary case: if ptr is in first 16 bytes of page, raw crosses page boundary
// Check: (ptr & 0xFFF) < HEADER_SIZE → raw might be on previous (unmapped) page
uintptr_t offset_in_page = (uintptr_t)ptr & 0xFFF;
if (__builtin_expect(offset_in_page < HEADER_SIZE, 0)) {
// Potential page boundary crossing - do safety check
if (!hak_is_memory_readable(raw)) {
goto slow_path_after_step2;
}
}
// Normal case (99.6%): raw is on same page as ptr (no mincore call!)
// Safe to dereference now
AllocHeader* hdr = (AllocHeader*)raw;
if (hdr->magic == HAKMEM_MAGIC) {
// Valid 16-byte header found (malloc/mmap allocation)
hak_free_route_log("header_16byte", ptr);
if (hdr->method == ALLOC_METHOD_MALLOC) {
// CRITICAL: raw was allocated with __libc_malloc, so free with __libc_free
extern void __libc_free(void*);
__libc_free(raw);
goto done;
}
// Handle other methods (mmap, etc) - continue to slow path below
}
slow_path_after_step2:;
}
// Fallback: Invalid header (non-tiny) or TLS cache full
// Fallback to slow path if TLS cache full
#if !HAKMEM_BUILD_RELEASE
hak_free_v2_track_slow();
hak_free_v2_track_slow();
#endif
#endif
hak_tiny_free(ptr);
goto done;
}
case PTR_KIND_TINY_HEADERLESS: {
// C7: Headerless 1KB blocks, SuperSlab + slab_idx provided by Registry
// Medium path: Use Registry result, no header read needed
hak_free_route_log("tiny_headerless", ptr);
hak_tiny_free(ptr);
goto done;
}
#ifdef HAKMEM_POOL_TLS_PHASE1
case PTR_KIND_POOL_TLS: {
// Pool TLS: 8KB-52KB allocations with 0xb0 magic
hak_free_route_log("pool_tls", ptr);
pool_free(ptr);
goto done;
}
#endif
// SS-first free（既定ON）
#if !HAKMEM_TINY_HEADER_CLASSIDX
// Only run SS-first if Phase 7 header-based free is not enabled
// (Phase 7 already does the SS lookup and handles SS allocations)
{
static int s_free_to_ss = -2;
if (s_free_to_ss == -2) {
const char* e = getenv("HAKMEM_TINY_FREE_TO_SS");
s_free_to_ss = (e && *e) ? ((*e!='0')?1:0) : 1;
}
if (s_free_to_ss) {
extern int g_use_superslab;
if (__builtin_expect(g_use_superslab != 0, 1)) {
SuperSlab* ss = hak_super_lookup(ptr);
if (ss && ss->magic == SUPERSLAB_MAGIC) {
int sidx = slab_index_for(ss, ptr);
int cap = ss_slabs_capacity(ss);
if (__builtin_expect(sidx >= 0 && sidx < cap, 1)) { hak_free_route_log("ss_hit", ptr); hak_tiny_free(ptr); goto done; }
}
// FIX: Removed dangerous "guess loop" (lines 92-95)
// The loop dereferenced unmapped memory causing SEGV
// If registry lookup fails, allocation is not from SuperSlab
}
case PTR_KIND_UNKNOWN:
default: {
// Not Tiny or Pool - check 16-byte AllocHeader (Mid/Large/malloc/mmap)
// This is the slow path for large allocations
break; // Fall through to header dispatch below
}
}
#endif
// ========== Slow Path: 16-byte AllocHeader Dispatch ==========
// Handle Mid/Large allocations (malloc/mmap/Pool/L25)
// Note: All Tiny allocations (C0-C7) already handled by Front Gate above
// Mid/L25 headerless経路
{

164
core/box/tls_sll_box.h Normal file
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@ -0,0 +1,164 @@
// tls_sll_box.h - Box TLS-SLL: Single-Linked List API (C7-safe)
//
// Purpose: Centralized TLS SLL management with C7 protection
// Design: Zero-overhead static inline API, C7 always rejected
//
// Key Rules:
// 1. C7 (1KB headerless) is ALWAYS rejected (returns false/0)
// 2. All SLL direct writes MUST go through this API
// 3. Pop returns with first 8 bytes cleared for C7 (safety)
// 4. Capacity checks prevent overflow
//
// Architecture:
// - Box TLS-SLL (this): Push/Pop/Splice authority
// - Caller: Provides capacity limits, handles fallback on failure
//
// Performance:
// - Static inline → zero function call overhead
// - C7 check: 1 comparison + predict-not-taken (< 1 cycle)
// - Same performance as direct SLL access for C0-C6
#ifndef TLS_SLL_BOX_H
#define TLS_SLL_BOX_H
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h> // For fprintf in debug
#include <stdlib.h> // For abort in debug
#include "../hakmem_tiny_config.h" // For TINY_NUM_CLASSES
// External TLS SLL state (defined elsewhere)
extern __thread void* g_tls_sll_head[TINY_NUM_CLASSES];
extern __thread uint32_t g_tls_sll_count[TINY_NUM_CLASSES];
// ========== Push ==========
// Push pointer to TLS SLL
// Returns: true on success, false if C7 or capacity exceeded
//
// Safety:
// - C7 always rejected (headerless, first 8 bytes = user data)
// - Capacity check prevents overflow
// - Caller must handle fallback (e.g., meta->freelist)
//
// Performance: 2-3 cycles (C0-C6), < 1 cycle (C7 fast rejection)
static inline bool tls_sll_push(int class_idx, void* ptr, uint32_t capacity) {
// CRITICAL: C7 (1KB) is headerless - MUST NOT use TLS SLL
// Reason: SLL stores next pointer in first 8 bytes (user data for C7)
if (__builtin_expect(class_idx == 7, 0)) {
return false; // C7 rejected
}
// Capacity check
if (g_tls_sll_count[class_idx] >= capacity) {
return false; // SLL full
}
// Push to SLL (standard linked list push)
*(void**)ptr = g_tls_sll_head[class_idx];
g_tls_sll_head[class_idx] = ptr;
g_tls_sll_count[class_idx]++;
return true;
}
// ========== Pop ==========
// Pop pointer from TLS SLL
// Returns: true on success (writes to *out), false if empty
//
// Safety:
// - C7 protection: clears first 8 bytes on pop (prevents next pointer leak)
// - NULL check before deref
//
// Performance: 3-4 cycles
static inline bool tls_sll_pop(int class_idx, void** out) {
void* head = g_tls_sll_head[class_idx];
if (!head) {
return false; // SLL empty
}
// Pop from SLL
void* next = *(void**)head;
g_tls_sll_head[class_idx] = next;
if (g_tls_sll_count[class_idx] > 0) {
g_tls_sll_count[class_idx]--;
}
// CRITICAL: C7 (1KB) returns with first 8 bytes cleared
// Reason: C7 is headerless, first 8 bytes are user data area
// Without this: user sees stale SLL next pointer → corruption
// Cost: 1 store instruction (~1 cycle), only for C7 (~1% of allocations)
//
// Note: C0-C6 have 1-byte header, so first 8 bytes are safe (header hides next)
if (__builtin_expect(class_idx == 7, 0)) {
*(void**)head = NULL;
}
*out = head;
return true;
}
// ========== Splice ==========
// Splice chain of pointers to TLS SLL (batch push)
// Returns: actual count moved (0 for C7 or if capacity exceeded)
//
// Safety:
// - C7 always returns 0 (no splice)
// - Capacity check limits splice size
// - Chain traversal with safety (breaks on NULL)
//
// Performance: ~5 cycles + O(count) for chain traversal
static inline uint32_t tls_sll_splice(int class_idx, void* chain_head, uint32_t count, uint32_t capacity) {
// CRITICAL: C7 (1KB) is headerless - MUST NOT splice to TLS SLL
if (__builtin_expect(class_idx == 7, 0)) {
return 0; // C7 rejected
}
// Calculate available capacity
uint32_t available = (capacity > g_tls_sll_count[class_idx])
? (capacity - g_tls_sll_count[class_idx]) : 0;
if (available == 0 || count == 0 || !chain_head) {
return 0; // No space or empty chain
}
// Limit splice size to available capacity
uint32_t to_move = (count < available) ? count : available;
// Find chain tail (traverse to_move - 1 nodes)
void* tail = chain_head;
for (uint32_t i = 1; i < to_move; i++) {
void* next = *(void**)tail;
if (!next) {
// Chain shorter than expected, adjust to_move
to_move = i;
break;
}
tail = next;
}
// Splice chain to SLL head
*(void**)tail = g_tls_sll_head[class_idx];
g_tls_sll_head[class_idx] = chain_head;
g_tls_sll_count[class_idx] += to_move;
return to_move;
}
// ========== Debug/Stats (optional) ==========
#if !HAKMEM_BUILD_RELEASE
// Verify C7 is not in SLL (debug only, call at safe points)
static inline void tls_sll_verify_no_c7(void) {
void* head = g_tls_sll_head[7];
if (head != NULL) {
fprintf(stderr, "[TLS_SLL_BUG] C7 found in TLS SLL! head=%p count=%u\n",
head, g_tls_sll_count[7]);
fprintf(stderr, "[TLS_SLL_BUG] This should NEVER happen - C7 is headerless!\n");
abort();
}
}
#endif
#endif // TLS_SLL_BOX_H