/*

 * Copyright 2015-2024 the Pacemaker project contributors

 *

 * The version control history for this file may have further details.

 *

 * This source code is licensed under the GNU Lesser General Public License

 * version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.

 */

#include <crm_internal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <dirent.h>

#include <ctype.h>

/*!

 * \internal

 * \brief Get process ID and name associated with a /proc directory entry

 *

 * \param[in]  entry    Directory entry (must be result of readdir() on /proc)

 * \param[out] name     If not NULL, a char[16] to hold the process name

 * \param[out] pid      If not NULL, will be set to process ID of entry

 *

 * \return Standard Pacemaker return code

 * \note This should be called only on Linux systems, as not all systems that

 *       support /proc store process names and IDs in the same way. The kernel

 *       limits the process name to the first 15 characters (plus terminator).

 *       It would be nice if there were a public kernel API constant for that

 *       limit, but there isn't.

 */

static int

pcmk__procfs_process_info(const struct dirent *entry, char *name, pid_t *pid)

{

    int fd, local_pid;

    FILE *file;

    struct stat statbuf;

    char procpath[128] = { 0 };

    /* We're only interested in entries whose name is a PID,

     * so skip anything non-numeric or that is too long.

     *

     * 114 = 128 - strlen("/proc/") - strlen("/status") - 1

     */

    local_pid = atoi(entry->d_name);

    if ((local_pid <= 0) || (strlen(entry->d_name) > 114)) {

        return -1;

    }

    if (pid) {

        *pid = (pid_t) local_pid;

    }

    /* Get this entry's file information */

    strcpy(procpath, "/proc/");

    strcat(procpath, entry->d_name);

    fd = open(procpath, O_RDONLY);

    if (fd < 0 ) {

        return -1;

    }

    if (fstat(fd, &statbuf) < 0) {

        close(fd);

        return -1;

    }

    close(fd);

    /* We're only interested in subdirectories */

    if (!S_ISDIR(statbuf.st_mode)) {

        return -1;

    }

    /* Read the first entry ("Name:") from the process's status file.

     * We could handle the valgrind case if we parsed the cmdline file

     * instead, but that's more of a pain than it's worth.

     */

    if (name != NULL) {

        strcat(procpath, "/status");

        file = fopen(procpath, "r");

        if (!file) {

            return -1;

        }

        if (fscanf(file, "Name:\t%15[^\n]", name) != 1) {

            fclose(file);

            return -1;

        }

        name[15] = 0;

        fclose(file);

    }

    return 0;

}

/*!

 * \internal

 * \brief Return process ID of a named process

 *

 * \param[in] name  Process name (as used in /proc/.../status)

 *

 * \return Process ID of named process if running, 0 otherwise

 *

 * \note This will return 0 if the process is being run via valgrind.

 *       This should be called only on Linux systems.

 */

pid_t

pcmk__procfs_pid_of(const char *name)

{

    DIR *dp;

    struct dirent *entry;

    pid_t pid = 0;

    char entry_name[64] = { 0 };

    dp = opendir("/proc");

    if (dp == NULL) {

        crm_notice("Can not read /proc directory to track existing components");

        return 0;

    }

    while ((entry = readdir(dp)) != NULL) {

        if ((pcmk__procfs_process_info(entry, entry_name, &pid) == pcmk_rc_ok)

            && pcmk__str_eq(entry_name, name, pcmk__str_casei)

            && (pcmk__pid_active(pid, NULL) == pcmk_rc_ok)) {

            crm_info("Found %s active as process %lld", name, (long long) pid);

            break;

        }

        pid = 0;

    }

    closedir(dp);

    return pid;

}

/*!

 * \internal

 * \brief Calculate number of logical CPU cores from procfs

 *

 * \return Number of cores (or 1 if unable to determine)

 */

unsigned int

pcmk__procfs_num_cores(void)

{

    int cores = 0;

    FILE *stream = NULL;

    /* Parse /proc/stat instead of /proc/cpuinfo because it's smaller */

    stream = fopen("/proc/stat", "r");

    if (stream == NULL) {

        crm_perror(LOG_INFO, "Could not open /proc/stat");

    } else {

        char buffer[2048];

        while (fgets(buffer, sizeof(buffer), stream)) {

            if (pcmk__starts_with(buffer, "cpu") && isdigit(buffer[3])) {

                ++cores;

            }

        }

        fclose(stream);

    }

    return cores? cores : 1;

}

/*!

 * \internal

 * \brief Get the executable path corresponding to a process ID

 *

 * \param[in]  pid        Process ID to check

 * \param[out] path       Where to store executable path

 * \param[in]  path_size  Size of \p path in characters (ideally PATH_MAX)

 *

 * \return Standard Pacemaker error code (as possible errno values from

 *         readlink())

 */

int

pcmk__procfs_pid2path(pid_t pid, char path[], size_t path_size)

{

#if HAVE_LINUX_PROCFS

    char procfs_exe_path[PATH_MAX];

    ssize_t link_rc;

    if (snprintf(procfs_exe_path, PATH_MAX, "/proc/%lld/exe",

                 (long long) pid) >= PATH_MAX) {

        return ENAMETOOLONG; // Truncated (shouldn't be possible in practice)

    }

    link_rc = readlink(procfs_exe_path, path, path_size - 1);

    if (link_rc < 0) {

        return errno;

    } else if (link_rc >= (path_size - 1)) {

        return ENAMETOOLONG;

    }

    path[link_rc] = '\0';

    return pcmk_rc_ok;

#else

    return EOPNOTSUPP;

#endif // HAVE_LINUX_PROCFS

}

/*!

 * \internal

 * \brief Check whether process ID information is available from procfs

 *

 * \return true if process ID information is available, otherwise false

 */

bool

pcmk__procfs_has_pids(void)

{

#if HAVE_LINUX_PROCFS

    static bool have_pids = false;

    static bool checked = false;

    if (!checked) {

        char path[PATH_MAX];

        have_pids = pcmk__procfs_pid2path(getpid(), path, sizeof(path)) == pcmk_rc_ok;

        checked = true;

    }

    return have_pids;

#else

    return false;

#endif // HAVE_LINUX_PROCFS

}