minecraft-pi-docker/launcher/src/bootstrap.c

#define _FILE_OFFSET_BITS 64

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>
#include <errno.h>
#include <sys/stat.h>

#include <libreborn/libreborn.h>

#include "bootstrap.h"
#include "ldconfig.h"

// Set Environmental Variable
#define PRESERVE_ENVIRONMENTAL_VARIABLE(name) \
    { \
        char *original_env_value = getenv(name); \
        if (original_env_value != NULL) { \
            setenv("ORIGINAL_" name, original_env_value, 1); \
        } \
    }
static void trim(char **value) {
    // Remove Trailing Colon
    int length = strlen(*value);
    if ((*value)[length - 1] == ':') {
        (*value)[length - 1] = '\0';
    }
    if ((*value)[0] == ':') {
        *value = &(*value)[1];
    }
}
static void set_and_print_env(const char *name, char *value) {
    // Set Variable With No Trailing Colon
    trim(&value);

#ifdef DEBUG
    // Print New Value
    INFO("Set %s = %s", name, value);
#endif
    // Set The Value
    setenv(name, value, 1);
}

// Get Environmental Variable
static char *get_env_safe(const char *name) {
    // Get Variable Or Blank String If Not Set
    char *ret = getenv(name);
    return ret != NULL ? ret : "";
}

// Get All Mods In Folder
static void load(char **ld_preload, char *folder) {
    int folder_name_length = strlen(folder);
    // Retry Until Successful
    while (1) {
        // Open Folder
        DIR *dp = opendir(folder);
        if (dp != NULL) {
            // Loop Through Folder
            struct dirent *entry = NULL;
            errno = 0;
            while (1) {
                errno = 0;
                entry = readdir(dp);
                if (entry != NULL) {
                    // Check If File Is Regular
                    if (entry->d_type == DT_REG) {
                        // Get Full Name
                        int name_length = strlen(entry->d_name);
                        int total_length = folder_name_length + name_length;
                        char name[total_length + 1];

                        // Concatenate Folder Name And File Name
                        for (int i = 0; i < folder_name_length; i++) {
                            name[i] = folder[i];
                        }
                        for (int i = 0; i < name_length; i++) {
                            name[folder_name_length + i] = entry->d_name[i];
                        }
                        // Add Terminator
                        name[total_length] = '\0';

                        // Check If File Is Executable
                        int result = access(name, R_OK);
                        if (result == 0) {
                            // Add To LD_PRELOAD
                            string_append(ld_preload, ":%s", name);
                        } else if (result == -1 && errno != 0) {
                            // Fail
                            INFO("Unable To Acesss: %s: %s", name, strerror(errno));
                            errno = 0;
                        }
                    }
                } else if (errno != 0) {
                    // Error Reading Contents Of Folder
                    ERR("Error Reading Directory: %s: %s", folder, strerror(errno));
                } else {
                    // Done!
                    break;
                }
            }
            // Close Folder
            closedir(dp);

            // Exit Function
            return;
        } else if (errno == ENOENT) {
            // Folder Doesn't Exists, Attempt Creation
            int ret = mkdir(folder, S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH);
            if (ret != 0) {
                // Unable To Create Folder
                ERR("Error Creating Directory: %s: %s", folder, strerror(errno));
            }
            // Continue Retrying
        } else {
            // Unable To Open Folder
            ERR("Error Opening Directory: %s: %s", folder, strerror(errno));
        }
    }
}

#define MCPI_NAME "minecraft-pi"

// Bootstrap
void bootstrap(int argc, char *argv[]) {
    INFO("%s", "Configuring Game...");

    // Get Binary Directory
    char *binary_directory = get_binary_directory();

    // Configure LD_LIBRARY_PATH
    {
        PRESERVE_ENVIRONMENTAL_VARIABLE("LD_LIBRARY_PATH");
        // Add Library Directory
        char *new_ld_path;
        safe_asprintf(&new_ld_path, "%s/lib", binary_directory);
        // Add Existing LD_LIBRAR_PATH
        {
            char *value = get_env_safe("LD_LIBRARY_PATH");
            if (strlen(value) > 0) {
                string_append(&new_ld_path, ":%s", value);
            }
        }
        // Load ARM Libraries
#ifdef __ARM_ARCH
        string_append(&new_ld_path, "%s", ":/usr/lib/arm-linux-gnueabihf:/usr/arm-linux-gnueabihf/lib");
#endif
        // Add Full Library Search Path
        {
            char *value = get_full_library_search_path();
            if (strlen(value) > 0) {
                string_append(&new_ld_path, ":%s", value);
            }
            free(value);
        }
        // Add Fallback Library Directory
        string_append(&new_ld_path, ":%s/fallback-lib", binary_directory);
        // Set And Free
        set_and_print_env("LD_LIBRARY_PATH", new_ld_path);
        free(new_ld_path);
    }

    // Configure LD_PRELOAD
    {
        PRESERVE_ENVIRONMENTAL_VARIABLE("LD_PRELOAD");
        char *new_ld_preload = NULL;
        safe_asprintf(&new_ld_preload, "%s", get_env_safe("LD_PRELOAD"));

        // Get Mods Folder
        char *mods_folder = NULL;
        safe_asprintf(&mods_folder, "%s/mods/", binary_directory);
        // Load Mods From ./mods
        load(&new_ld_preload, mods_folder);
        // Free Mods Folder
        free(mods_folder);

        // Set LD_PRELOAD
        set_and_print_env("LD_PRELOAD", new_ld_preload);
        free(new_ld_preload);
    }

    // Start Game
    INFO("%s", "Starting Game...");

    // Use Correct LibC
#ifndef __ARM_ARCH
    setenv("QEMU_LD_PREFIX", "/usr/arm-linux-gnueabihf", 1);
#endif

    // Create Full Path
    char *full_path = NULL;
    safe_asprintf(&full_path, "%s/" MCPI_NAME, binary_directory);

    // Free Binary Directory
    free(binary_directory);

#ifdef __ARM_ARCH
    // Mark argc As Used
    (void) argc;
    // Run
    safe_execvpe(full_path, argv, environ);
#else
    // Use Static QEMU So It Isn't Affected By LD_* Variables
#define EXE_INTERPRETER "qemu-arm-static"
    // Create Arguments List
    char *new_argv[argc + 2];
    for (int i = 1; i <= argc; i++) {
        new_argv[i + 1] = argv[i];
    }
    new_argv[0] = NULL; // Updated By safe_execvpe()
    new_argv[1] = full_path; // Path To MCPI
    // Run
    safe_execvpe(EXE_INTERPRETER, new_argv, environ);
#endif
}