hakmem/core/box/ss_pt_register_box.h

#ifndef SS_PT_REGISTER_BOX_H
#define SS_PT_REGISTER_BOX_H

#include "ss_pt_types_box.h"
#include <sys/mman.h>

// Register single 512KB chunk (cold path)
static inline void ss_pt_register_chunk(void* chunk_base, struct SuperSlab* ss) {
    uintptr_t p = (uintptr_t)chunk_base;

    // Out-of-range check
    if (p >> 48) return;

    uint32_t l1_idx = SS_PT_L1_INDEX(chunk_base);
    uint32_t l2_idx = SS_PT_L2_INDEX(chunk_base);

    // Ensure L2 exists
    SsPtL2* l2 = atomic_load_explicit(&g_ss_pt.l2[l1_idx], memory_order_acquire);
    if (l2 == NULL) {
        SsPtL2* new_l2 = (SsPtL2*)mmap(NULL, sizeof(SsPtL2),
                                        PROT_READ | PROT_WRITE,
                                        MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        if (new_l2 == MAP_FAILED) return;

        SsPtL2* expected = NULL;
        if (!atomic_compare_exchange_strong_explicit(&g_ss_pt.l2[l1_idx],
                &expected, new_l2, memory_order_acq_rel, memory_order_acquire)) {
            munmap(new_l2, sizeof(SsPtL2));
            l2 = expected;
        } else {
            l2 = new_l2;
        }
    }

    // Store SuperSlab pointer (release)
    atomic_store_explicit(&l2->entries[l2_idx], ss, memory_order_release);
}

// Unregister single chunk (NULL store, L2 never freed)
static inline void ss_pt_unregister_chunk(void* chunk_base) {
    uintptr_t p = (uintptr_t)chunk_base;
    if (p >> 48) return;

    uint32_t l1_idx = SS_PT_L1_INDEX(chunk_base);
    uint32_t l2_idx = SS_PT_L2_INDEX(chunk_base);

    SsPtL2* l2 = atomic_load_explicit(&g_ss_pt.l2[l1_idx], memory_order_acquire);
    if (l2) {
        atomic_store_explicit(&l2->entries[l2_idx], NULL, memory_order_release);
    }
}

// Register all chunks of a SuperSlab (1MB=2 chunks, 2MB=4 chunks)
static inline void ss_pt_register(struct SuperSlab* ss, void* base, int lg_size) {
    size_t size = (size_t)1 << lg_size;
    size_t chunk_size = (size_t)1 << SS_PT_CHUNK_LG;  // 512KB
    size_t n_chunks = size / chunk_size;

    for (size_t i = 0; i < n_chunks; i++) {
        ss_pt_register_chunk((char*)base + i * chunk_size, ss);
    }
}

static inline void ss_pt_unregister(void* base, int lg_size) {
    size_t size = (size_t)1 << lg_size;
    size_t chunk_size = (size_t)1 << SS_PT_CHUNK_LG;
    size_t n_chunks = size / chunk_size;

    for (size_t i = 0; i < n_chunks; i++) {
        ss_pt_unregister_chunk((char*)base + i * chunk_size);
    }
}

#endif