common.c

/*
    Common helper and utility functions

    Copyright (C) 2018        Sebastian Parschauer  <s.parschauer(a)gmx.de>

    This file is part of libscanmem.

    This library is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published
    by the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this library.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>

#include "common.h"

/* states returned by check_process() */
enum pstate {
    PROC_RUNNING,
    PROC_ERR,  /* error during detection */
    PROC_DEAD,
    PROC_ZOMBIE
};

/*
 * We check if a process is running in /proc directly.
 * Also zombies are detected.
 *
 * Requirements: Linux kernel, mounted /proc
 * Assumption: (pid > 0)  --> Please check your PID before!
 */
static enum pstate check_process(pid_t pid)
{
    FILE *fp = NULL;
    char *line = NULL;
    size_t alloc_len = 0;
    char status = '\0';
    char path_str[128] = "/proc/";
    int pr_len, path_len = sizeof("/proc/") - 1;

    /* append $pid/status and check if file exists */
    pr_len = sprintf((path_str + path_len), "%d/status", pid);
    if (pr_len <= 0)
        goto err;
    path_len += pr_len;

    fp = fopen(path_str, "r");
    if (!fp) {
        if (errno != ENOENT)
            goto err;
        else
            return PROC_DEAD;
    }

    /* read process status */
    while (getline(&line, &alloc_len, fp) != -1) {
        if (alloc_len <= sizeof("State:\t"))
            continue;
        if (strncmp(line, "State:\t", sizeof("State:\t") - 1) == 0) {
            status = line[sizeof("State:\t") - 1];
            break;
        }
    }
    if (line)
        free(line);
    fclose(fp);

    if (status < 'A' || status > 'Z')
       goto err;

    /* zombies are not running - parent doesn't wait */
    if (status == 'Z' || status == 'X')
        return PROC_ZOMBIE;
    return PROC_RUNNING;
err:
    return PROC_ERR;
}

bool sm_process_is_dead(pid_t pid)
{
    return (check_process(pid) != PROC_RUNNING);
}