/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */
#pragma once
#include "bpf_arena_common.h"

#ifndef __round_mask
#define __round_mask(x, y) ((__typeof__(x))((y)-1))
#endif
#ifndef round_up
#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
#endif

#ifdef __BPF__
#define NR_CPUS (sizeof(struct cpumask) * 8)

static void __arena * __arena page_frag_cur_page[NR_CPUS];
static int __arena page_frag_cur_offset[NR_CPUS];

/* Simple page_frag allocator */
static inline void __arena* bpf_alloc(unsigned int size)
{
        __u64 __arena *obj_cnt;
        __u32 cpu = bpf_get_smp_processor_id();
        void __arena *page = page_frag_cur_page[cpu];
        int __arena *cur_offset = &page_frag_cur_offset[cpu];
        int offset;

        size = round_up(size, 8);
        if (size >= PAGE_SIZE - 8)
                return NULL;
        if (!page) {
refill:
                page = bpf_arena_alloc_pages(&arena, NULL, 1, NUMA_NO_NODE, 0);
                if (!page)
                        return NULL;
                cast_kern(page);
                page_frag_cur_page[cpu] = page;
                *cur_offset = PAGE_SIZE - 8;
                obj_cnt = page + PAGE_SIZE - 8;
                *obj_cnt = 0;
        } else {
                cast_kern(page);
                obj_cnt = page + PAGE_SIZE - 8;
        }

        offset = *cur_offset - size;
        if (offset < 0)
                goto refill;

        (*obj_cnt)++;
        *cur_offset = offset;
        return page + offset;
}

static inline void bpf_free(void __arena *addr)
{
        __u64 __arena *obj_cnt;

        addr = (void __arena *)(((long)addr) & ~(PAGE_SIZE - 1));
        obj_cnt = addr + PAGE_SIZE - 8;
        if (--(*obj_cnt) == 0)
                bpf_arena_free_pages(&arena, addr, 1);
}
#else
static inline void __arena* bpf_alloc(unsigned int size) { return NULL; }
static inline void bpf_free(void __arena *addr) {}
#endif