<?php

$bpf_text = <<<EOT
#include <uapi/linux/ptrace.h>
#include <linux/blk-mq.h>

BPF_HISTOGRAM(dist);
BPF_HISTOGRAM(dist_linear);

int trace_req_done(struct pt_regs *ctx, struct request *req)
{
    dist.increment(bpf_log2l(req->__data_len / 1024));
    dist_linear.increment(req->__data_len / 1024);
    return 0;
}
EOT;

$b = new Bpf(["text" => $bpf_text]);

// Attach kprobe based on kernel version
if ($b->get_kprobe_functions('__blk_account_io_done')) {
    // __blk_account_io_done is available before kernel v6.4
    $b->attach_kprobe('__blk_account_io_done', 'trace_req_done');
} elseif ($b->get_kprobe_functions('blk_account_io_done')) {
    // blk_account_io_done is traceable (not inline) before v5.16
    $b->attach_kprobe('blk_account_io_done', 'trace_req_done');
} else {
    $b->attach_kprobe('blk_mq_end_request', 'trace_req_done');
}

echo "Tracing... Hit Ctrl-C to end.\n";

// Set up signal handler for Ctrl-C
pcntl_signal(SIGINT, "signalHandler");
pcntl_async_signals(true);

// Keep running until interrupted
while (true) {
    sleep(99999999);
}

function signalHandler($signo)
{
    global $b;
    switch ($signo) {
        case SIGINT:
            echo "\n";
            echo "log2 histogram\n";
            echo "~~~~~~~~~~~~~~\n";
            $b->dist->print_log2_hist("kbytes");

            echo "\nlinear histogram\n";
            echo "~~~~~~~~~~~~~~~~\n";
            $b->dist_linear->print_linear_hist("kbytes");
            exit(0);
    }
}