// SPDX-License-Identifier: GPL-2.0
/* Copyright (C) 2023 Chuyi Zhou <zhouchuyi@bytedance.com> */

#include "vmlinux.h"
#include <errno.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include "bpf_misc.h"
#include "bpf_experimental.h"

char _license[] SEC("license") = "GPL";

struct cgroup *bpf_cgroup_acquire(struct cgroup *p) __ksym;
struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
void bpf_cgroup_release(struct cgroup *p) __ksym;

pid_t target_pid;
int css_task_cnt;
u64 cg_id;

SEC("lsm/file_mprotect")
int BPF_PROG(iter_css_task_for_each, struct vm_area_struct *vma,
            unsigned long reqprot, unsigned long prot, int ret)
{
        struct task_struct *cur_task = bpf_get_current_task_btf();
        struct cgroup_subsys_state *css;
        struct task_struct *task;
        struct cgroup *cgrp;

        if (cur_task->pid != target_pid)
                return ret;

        cgrp = bpf_cgroup_from_id(cg_id);

        if (!cgrp)
                return -EPERM;

        css = &cgrp->self;
        css_task_cnt = 0;

        bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS)
                if (task->pid == target_pid)
                        css_task_cnt++;

        bpf_cgroup_release(cgrp);

        return -EPERM;
}

static inline u64 cgroup_id(struct cgroup *cgrp)
{
        return cgrp->kn->id;
}

SEC("?iter/cgroup")
int cgroup_id_printer(struct bpf_iter__cgroup *ctx)
{
        struct seq_file *seq = ctx->meta->seq;
        struct cgroup *cgrp = ctx->cgroup;
        struct cgroup_subsys_state *css;
        struct task_struct *task;

        /* epilogue */
        if (cgrp == NULL) {
                BPF_SEQ_PRINTF(seq, "epilogue\n");
                return 0;
        }

        /* prologue */
        if (ctx->meta->seq_num == 0)
                BPF_SEQ_PRINTF(seq, "prologue\n");

        BPF_SEQ_PRINTF(seq, "%8llu\n", cgroup_id(cgrp));

        css = &cgrp->self;
        css_task_cnt = 0;
        bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {
                if (task->pid == target_pid)
                        css_task_cnt++;
        }

        return 0;
}

SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
int BPF_PROG(iter_css_task_for_each_sleep)
{
        u64 cgrp_id = bpf_get_current_cgroup_id();
        struct cgroup *cgrp = bpf_cgroup_from_id(cgrp_id);
        struct cgroup_subsys_state *css;
        struct task_struct *task;

        if (cgrp == NULL)
                return 0;
        css = &cgrp->self;

        bpf_for_each(css_task, task, css, CSS_TASK_ITER_PROCS) {

        }
        bpf_cgroup_release(cgrp);
        return 0;
}