// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */

#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
#include "test_user_ringbuf.h"

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

struct {
        __uint(type, BPF_MAP_TYPE_USER_RINGBUF);
} user_ringbuf SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_RINGBUF);
} kernel_ringbuf SEC(".maps");

/* inputs */
int pid, err, val;

int read = 0;

/* Counter used for end-to-end protocol test */
__u64 kern_mutated = 0;
__u64 user_mutated = 0;
__u64 expected_user_mutated = 0;

static int
is_test_process(void)
{
        int cur_pid = bpf_get_current_pid_tgid() >> 32;

        return cur_pid == pid;
}

static long
record_sample(struct bpf_dynptr *dynptr, void *context)
{
        const struct sample *sample = NULL;
        struct sample stack_sample;
        int status;
        static int num_calls;

        if (num_calls++ % 2 == 0) {
                status = bpf_dynptr_read(&stack_sample, sizeof(stack_sample), dynptr, 0, 0);
                if (status) {
                        bpf_printk("bpf_dynptr_read() failed: %d\n", status);
                        err = 1;
                        return 1;
                }
        } else {
                sample = bpf_dynptr_data(dynptr, 0, sizeof(*sample));
                if (!sample) {
                        bpf_printk("Unexpectedly failed to get sample\n");
                        err = 2;
                        return 1;
                }
                stack_sample = *sample;
        }

        __sync_fetch_and_add(&read, 1);
        return 0;
}

static void
handle_sample_msg(const struct test_msg *msg)
{
        switch (msg->msg_op) {
        case TEST_MSG_OP_INC64:
                kern_mutated += msg->operand_64;
                break;
        case TEST_MSG_OP_INC32:
                kern_mutated += msg->operand_32;
                break;
        case TEST_MSG_OP_MUL64:
                kern_mutated *= msg->operand_64;
                break;
        case TEST_MSG_OP_MUL32:
                kern_mutated *= msg->operand_32;
                break;
        default:
                bpf_printk("Unrecognized op %d\n", msg->msg_op);
                err = 2;
        }
}

static long
read_protocol_msg(struct bpf_dynptr *dynptr, void *context)
{
        const struct test_msg *msg = NULL;

        msg = bpf_dynptr_data(dynptr, 0, sizeof(*msg));
        if (!msg) {
                err = 1;
                bpf_printk("Unexpectedly failed to get msg\n");
                return 0;
        }

        handle_sample_msg(msg);

        return 0;
}

static int publish_next_kern_msg(__u32 index, void *context)
{
        struct test_msg *msg = NULL;
        int operand_64 = TEST_OP_64;
        int operand_32 = TEST_OP_32;

        msg = bpf_ringbuf_reserve(&kernel_ringbuf, sizeof(*msg), 0);
        if (!msg) {
                err = 4;
                return 1;
        }

        switch (index % TEST_MSG_OP_NUM_OPS) {
        case TEST_MSG_OP_INC64:
                msg->operand_64 = operand_64;
                msg->msg_op = TEST_MSG_OP_INC64;
                expected_user_mutated += operand_64;
                break;
        case TEST_MSG_OP_INC32:
                msg->operand_32 = operand_32;
                msg->msg_op = TEST_MSG_OP_INC32;
                expected_user_mutated += operand_32;
                break;
        case TEST_MSG_OP_MUL64:
                msg->operand_64 = operand_64;
                msg->msg_op = TEST_MSG_OP_MUL64;
                expected_user_mutated *= operand_64;
                break;
        case TEST_MSG_OP_MUL32:
                msg->operand_32 = operand_32;
                msg->msg_op = TEST_MSG_OP_MUL32;
                expected_user_mutated *= operand_32;
                break;
        default:
                bpf_ringbuf_discard(msg, 0);
                err = 5;
                return 1;
        }

        bpf_ringbuf_submit(msg, 0);

        return 0;
}

static void
publish_kern_messages(void)
{
        if (expected_user_mutated != user_mutated) {
                bpf_printk("%lu != %lu\n", expected_user_mutated, user_mutated);
                err = 3;
                return;
        }

        bpf_loop(8, publish_next_kern_msg, NULL, 0);
}

SEC("fentry/" SYS_PREFIX "sys_prctl")
int test_user_ringbuf_protocol(void *ctx)
{
        long status = 0;

        if (!is_test_process())
                return 0;

        status = bpf_user_ringbuf_drain(&user_ringbuf, read_protocol_msg, NULL, 0);
        if (status < 0) {
                bpf_printk("Drain returned: %ld\n", status);
                err = 1;
                return 0;
        }

        publish_kern_messages();

        return 0;
}

SEC("fentry/" SYS_PREFIX "sys_getpgid")
int test_user_ringbuf(void *ctx)
{
        if (!is_test_process())
                return 0;

        err = bpf_user_ringbuf_drain(&user_ringbuf, record_sample, NULL, 0);

        return 0;
}

static long
do_nothing_cb(struct bpf_dynptr *dynptr, void *context)
{
        __sync_fetch_and_add(&read, 1);
        return 0;
}

SEC("fentry/" SYS_PREFIX "sys_prlimit64")
int test_user_ringbuf_epoll(void *ctx)
{
        long num_samples;

        if (!is_test_process())
                return 0;

        num_samples = bpf_user_ringbuf_drain(&user_ringbuf, do_nothing_cb, NULL, 0);
        if (num_samples <= 0)
                err = 1;

        return 0;
}