Hey there! Let's tackle this process enumeration problem for your Linux antivirus project—super cool that you've already nailed the math models and heuristic methods, by the way. Recursively scanning /proc is a common first approach, but as you've noticed, it misses short-lived processes that start and exit between directory scans. Here are two modern, clean C++ solutions to fix this:

1. Use libproc2 for Fast, Reliable One-Shot Scans #

libproc2 is the updated, maintained successor to the old libproc library, built for modern Linux kernels. It's efficient and avoids many pitfalls of manual /proc parsing.

Step-by-Step Implementation #

First, install the library (package names vary by distro: libproc2-dev on Debian/Ubuntu, procps-ng-devel on RHEL/CentOS).

Here's a concise C++ example that enumerates all processes, grabs their state, and writes to a file:

#include <iostream>
#include <fstream>
#include <cstring>
#include <proc/readproc.h>

int main() {
    // Open output file with RAII-style management
    std::ofstream out_file("process_snapshot.txt");
    if (!out_file.is_open()) {
        std::cerr << "Failed to open output file\n";
        return 1;
    }

    // Configure proc reader to fetch core process details + state
    proc_t proc_info{};
    PROCTAB* proc_tab = openproc(PROC_FILLSTAT | PROC_FILLSTATUS);

    if (!proc_tab) {
        std::cerr << "Failed to initialize proc table reader\n";
        return 1;
    }

    // Iterate through all process entries
    while (readproc(proc_tab, &proc_info) != nullptr) {
        out_file << "PID: " << proc_info.tgid 
                 << " | Name: " << proc_info.cmd 
                 << " | State: " << proc_info.state << "\n";
    }

    // Cleanup resources
    closeproc(proc_tab);
    out_file.close();

    return 0;
}

Compile with:

g++ -o proc_snapshot proc_snapshot.cpp -lps

This method is faster than manual /proc traversal and handles edge cases like zombie processes or kernel threads more reliably.

2. Combine with Netlink PROC_EVENT for Real-Time Process Tracking #

To catch short-lived processes that might escape a one-shot scan, use the Linux kernel's netlink PROC_EVENT interface. This lets your program receive real-time notifications when processes are created, exited, or modified.

C++ Example for Netlink Process Monitoring #

This code sets up a netlink socket to listen for process events and appends them to your output file:

#include <iostream>
#include <fstream>
#include <cstring>
#include <unistd.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/connector.h>
#include <linux/cn_proc.h>

#define BUFFER_SIZE 1024

void handle_proc_event(const struct proc_event* event, std::ofstream& out_file) {
    switch (event->what) {
        case PROC_EVENT_FORK:
            out_file << "[NEW PROCESS] Child PID: " << event->event_data.fork.child_tgid 
                     << " | Parent PID: " << event->event_data.fork.parent_tgid << "\n";
            break;
        case PROC_EVENT_EXIT:
            out_file << "[PROCESS EXIT] PID: " << event->event_data.exit.process_tgid 
                     << " | Exit Code: " << (event->event_data.exit.exit_code >> 8) << "\n";
            break;
        default:
            break;
    }
}

int main() {
    std::ofstream out_file("process_events.txt", std::ios::app);
    if (!out_file.is_open()) {
        std::cerr << "Failed to open events log file\n";
        return 1;
    }

    int sock_fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_CONNECTOR);
    if (sock_fd < 0) {
        std::cerr << "Failed to create netlink socket\n";
        return 1;
    }

    struct sockaddr_nl sa_nl{};
    sa_nl.nl_family = AF_NETLINK;
    sa_nl.nl_groups = CN_IDX_PROC;
    sa_nl.nl_pid = getpid();

    if (bind(sock_fd, (struct sockaddr*)&sa_nl, sizeof(sa_nl)) < 0) {
        std::cerr << "Failed to bind netlink socket\n";
        close(sock_fd);
        return 1;
    }

    // Send subscription request for process events
    struct cn_msg msg{};
    struct proc_event_mc mc{};
    msg.id.idx = CN_IDX_PROC;
    msg.id.val = CN_VAL_PROC;
    msg.len = sizeof(mc);
    mc.cmd = PROC_MC_LISTEN;

    if (send(sock_fd, &msg, sizeof(msg) + sizeof(mc), 0) < 0) {
        std::cerr << "Failed to subscribe to process events\n";
        close(sock_fd);
        return 1;
    }

    // Listen for incoming events
    char buffer[BUFFER_SIZE];
    while (true) {
        ssize_t recv_len = recv(sock_fd, buffer, BUFFER_SIZE, 0);
        if (recv_len < 0) {
            std::cerr << "Failed to receive netlink message\n";
            break;
        }

        struct nlmsghdr* nl_hdr = (struct nlmsghdr*)buffer;
        while (NLMSG_OK(nl_hdr, recv_len)) {
            struct cn_msg* cn_msg = (struct cn_msg*)NLMSG_DATA(nl_hdr);
            struct proc_event* event = (struct proc_event*)cn_msg->data;
            handle_proc_event(event, out_file);

            nl_hdr = NLMSG_NEXT(nl_hdr, recv_len);
        }
    }

    close(sock_fd);
    out_file.close();
    return 0;
}

Compile with:

g++ -o proc_monitor proc_monitor.cpp

Optimal Workflow for Your Antivirus #

For complete host fingerprinting:

1. Run the libproc2 snapshot first to capture all currently running processes.
2. Start the netlink monitor immediately after to track any new/exited processes, appending them to your file. This combination ensures you won't miss short-lived processes that start after your initial scan.

Both solutions use modern Linux APIs and clean C++ practices, avoiding outdated code patterns.

内容的提问来源于stack exchange，提问作者Mihai