// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
/* Copyright (c) 2020 Facebook */
#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include <bpf/bpf_tracing.h>
#include "pid_iter.h"

/* keep in sync with the definition in main.h */
enum bpf_obj_type {
        BPF_OBJ_UNKNOWN,
        BPF_OBJ_PROG,
        BPF_OBJ_MAP,
        BPF_OBJ_LINK,
        BPF_OBJ_BTF,
};

struct bpf_perf_link___local {
        struct bpf_link link;
        struct file *perf_file;
} __attribute__((preserve_access_index));

struct perf_event___local {
        u64 bpf_cookie;
} __attribute__((preserve_access_index));

enum bpf_link_type___local {
        BPF_LINK_TYPE_PERF_EVENT___local = 7,
};

extern const void bpf_link_fops __ksym;
extern const void bpf_link_fops_poll __ksym __weak;
extern const void bpf_map_fops __ksym;
extern const void bpf_prog_fops __ksym;
extern const void btf_fops __ksym;

const volatile enum bpf_obj_type obj_type = BPF_OBJ_UNKNOWN;

static __always_inline __u32 get_obj_id(void *ent, enum bpf_obj_type type)
{
        switch (type) {
        case BPF_OBJ_PROG:
                return BPF_CORE_READ((struct bpf_prog *)ent, aux, id);
        case BPF_OBJ_MAP:
                return BPF_CORE_READ((struct bpf_map *)ent, id);
        case BPF_OBJ_BTF:
                return BPF_CORE_READ((struct btf *)ent, id);
        case BPF_OBJ_LINK:
                return BPF_CORE_READ((struct bpf_link *)ent, id);
        default:
                return 0;
        }
}

/* could be used only with BPF_LINK_TYPE_PERF_EVENT links */
static __u64 get_bpf_cookie(struct bpf_link *link)
{
        struct bpf_perf_link___local *perf_link;
        struct perf_event___local *event;

        perf_link = container_of(link, struct bpf_perf_link___local, link);
        event = BPF_CORE_READ(perf_link, perf_file, private_data);
        return BPF_CORE_READ(event, bpf_cookie);
}

SEC("iter/task_file")
int iter(struct bpf_iter__task_file *ctx)
{
        struct file *file = ctx->file;
        struct task_struct *task = ctx->task;
        struct pid_iter_entry e;
        const void *fops;

        if (!file || !task)
                return 0;

        switch (obj_type) {
        case BPF_OBJ_PROG:
                fops = &bpf_prog_fops;
                break;
        case BPF_OBJ_MAP:
                fops = &bpf_map_fops;
                break;
        case BPF_OBJ_BTF:
                fops = &btf_fops;
                break;
        case BPF_OBJ_LINK:
                if (&bpf_link_fops_poll &&
                    file->f_op == &bpf_link_fops_poll)
                        fops = &bpf_link_fops_poll;
                else
                        fops = &bpf_link_fops;
                break;
        default:
                return 0;
        }

        if (file->f_op != fops)
                return 0;

        __builtin_memset(&e, 0, sizeof(e));
        e.pid = task->tgid;
        e.id = get_obj_id(file->private_data, obj_type);

        if (obj_type == BPF_OBJ_LINK &&
            bpf_core_enum_value_exists(enum bpf_link_type___local,
                                       BPF_LINK_TYPE_PERF_EVENT___local)) {
                struct bpf_link *link = (struct bpf_link *) file->private_data;

                if (BPF_CORE_READ(link, type) == bpf_core_enum_value(enum bpf_link_type___local,
                                                                     BPF_LINK_TYPE_PERF_EVENT___local)) {
                        e.has_bpf_cookie = true;
                        e.bpf_cookie = get_bpf_cookie(link);
                }
        }

        bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm),
                                  task->group_leader->comm);
        bpf_seq_write(ctx->meta->seq, &e, sizeof(e));

        return 0;
}

char LICENSE[] SEC("license") = "Dual BSD/GPL";