kolibrios/programs/develop/libraries/newlib/pe/loader.c

#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <alloca.h>
#include <malloc.h>
#include <setjmp.h>
#include <envz.h>

#include <kos32sys.h>

#include "list.h"
#include "pe.h"

#define unlikely(x)     __builtin_expect(!!(x), 0)

//#define DBG(format,...) printf(format,##__VA_ARGS__)

#define DBG(format,...)


void      init_loader(void *libc_image);
void*     __fastcall create_image(void *raw);
int       __fastcall link_image(void *img_base);
int       __fastcall do_exec(uint32_t my_app, uint32_t *params);


extern char* __appenv;
extern int   __appenv_size;

typedef struct tag_module module_t;

struct app_hdr
{
    char  banner[8];
    int   version;
    int   start;
    int   iend;
    int   memsize;
    int   stacktop;
    char  *cmdline;
    char  *path;
    int    reserved;
    void  *__idata_start;
    void  *__idata_end;
    void  (*main)(int argc, char **argv, char **envp);
};

struct tag_module
{
    struct list_head list;

    char       *img_name;
    char       *img_path;

    uint32_t    refcount;

    void       *start;
    uint32_t    end;

    void       *entry;

    PIMAGE_NT_HEADERS32      img_hdr;
    PIMAGE_SECTION_HEADER    img_sec;
    PIMAGE_EXPORT_DIRECTORY  img_exp;
};

typedef struct
{
    struct list_head list;
    char *path;
    int   path_len;
}dll_path_t;

module_t* load_module(const char *name);

LIST_HEAD(path_list);

static module_t libc_dll;
static char libc_name[] = "libc.dll";
static char libc_path[] = "/KolibriOS/lib/libc.dll";

static inline int IsPowerOf2(uint32_t val)
{
    if(val == 0)
        return 0;
    return (val & (val - 1)) == 0;
}


int validate_pe(void *raw, size_t raw_size, int is_exec)
{
    PIMAGE_DOS_HEADER     dos;
    PIMAGE_NT_HEADERS32   nt;

    dos = (PIMAGE_DOS_HEADER)raw;

    if( !raw || raw_size < sizeof(IMAGE_DOS_HEADER) )
        return 0;

    if( dos->e_magic != IMAGE_DOS_SIGNATURE || dos->e_lfanew <= 0)
        return 0;

    nt =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);

    if( (uint32_t)nt < (uint32_t)raw)
        return 0;

    if(nt->Signature != IMAGE_NT_SIGNATURE)
        return 0;

    if(nt->FileHeader.Machine != IMAGE_FILE_MACHINE_I386)
        return 0;

    if(is_exec && (nt->FileHeader.Characteristics & IMAGE_FILE_DLL))
        return 0;

    if(nt->OptionalHeader.Magic != IMAGE_NT_OPTIONAL_HDR32_MAGIC)
        return 0;

    if( is_exec && nt->OptionalHeader.ImageBase != 0)
        return 0;

    if(nt->OptionalHeader.SectionAlignment < 4096)
    {
        if(nt->OptionalHeader.FileAlignment != nt->OptionalHeader.SectionAlignment)
            return 0;
    }
    else if(nt->OptionalHeader.SectionAlignment < nt->OptionalHeader.FileAlignment)
        return 0;

    if(!IsPowerOf2(nt->OptionalHeader.SectionAlignment) ||
       !IsPowerOf2(nt->OptionalHeader.FileAlignment))
        return 0;

    if(nt->FileHeader.NumberOfSections > 96)
        return 0;

    return 1;
}


void init_loader(void *libc_image)
{

    PIMAGE_DOS_HEADER        dos;
    PIMAGE_NT_HEADERS32      nt;
    PIMAGE_EXPORT_DIRECTORY  exp;

    struct   app_hdr *header;
#if 0
    dll_path_t *path;
    int len;
    char *p;

    if(__appenv_size)
    {
        char *env;
        env = envz_get(__appenv, __appenv_size, "PATH");
        if( env )
        {
            while( *env )
            {
                p = env;
                while(*p)
                {
                    if( *p == 0x0D)
                        break;
                    else if( *p == 0x0A)
                        break;
                    else if( *p == ':')
                        break;
                    p++;
                };
                len = p-env;
                if(len)
                {
                    char *p1;

                    p1 = (char*)malloc(len+1);
                    memcpy(p1, env, len);
                    p1[len]=0;

                    path = (dll_path_t*)malloc(sizeof(dll_path_t));
                    INIT_LIST_HEAD(&path->list);
                    path->path = p1;
                    path->path_len = len;
                    DBG("add libraries path %s\n", path->path);
                    list_add_tail(&path->list, &path_list);
                };
                if(*p == ':')
                {
                    env = p+1;
                    continue;
                }
                else break;
            };
        };
    };

    header = (struct app_hdr*)NULL;

    len = strrchr(header->path, '/') - header->path+1;
    p = (char*)malloc(len+1);
    memcpy(p, header->path, len);
    p[len]=0;

    path = (dll_path_t*)malloc(sizeof(dll_path_t));
    INIT_LIST_HEAD(&path->list);
    path->path = p;
    path->path_len = len;
    DBG("add libraries path %s\n", path->path);
    list_add_tail(&path->list, &path_list);


#if 0
    path = (dll_path_t*)malloc(sizeof(dll_path_t));
    INIT_LIST_HEAD(&path->list);
    path->path = "/sys/lib/";
    path->path_len = 9;                           /* FIXME */
    DBG("add libraries path %s\n", path->path);
    list_add_tail(&path->list, &path_list);
#endif
#endif

    INIT_LIST_HEAD(&libc_dll.list);

    libc_dll.img_name = libc_name;
    libc_dll.img_path = libc_path;

    libc_dll.refcount = 1;

    dos =  (PIMAGE_DOS_HEADER)libc_image;
    nt  =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);
    exp =  MakePtr(PIMAGE_EXPORT_DIRECTORY, libc_image,
                   nt->OptionalHeader.DataDirectory[0].VirtualAddress);

    libc_dll.start = libc_image;
    libc_dll.end   = MakePtr(uint32_t,libc_image, nt->OptionalHeader.SizeOfImage);

    libc_dll.img_hdr  = nt;
    libc_dll.img_sec  = MakePtr(PIMAGE_SECTION_HEADER,nt, sizeof(IMAGE_NT_HEADERS32));
    libc_dll.img_exp  = MakePtr(PIMAGE_EXPORT_DIRECTORY,libc_image,
                        nt->OptionalHeader.DataDirectory[0].VirtualAddress);

};

const module_t* find_module(const char *name)
{
    module_t* mod = &libc_dll;

    do
    {
        if( !strncmp(name, mod->img_name, 16))
            return mod;
        mod = (module_t*)mod->list.next;
    }while(mod != &libc_dll);

    return load_module(name);
};

static inline void sec_copy(void *dst, void *src, size_t len)
{
    __asm__ __volatile__ (
    "shrl $2, %%ecx         \n\t"
    "rep movsl"
    :
    :"c"(len),"S"(src),"D"(dst)
    :"cc");
    __asm__ __volatile__ (
    ""
    :::"ecx","esi","edi");
};


void* __fastcall create_image(void *raw)
{
    PIMAGE_DOS_HEADER     dos;
    PIMAGE_NT_HEADERS32   nt;
    PIMAGE_SECTION_HEADER img_sec;

    void  *img_base;
    uint32_t  sec_align;
    int    i;

    dos = (PIMAGE_DOS_HEADER)raw;
    nt =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);

    img_base = user_alloc(nt->OptionalHeader.SizeOfImage);

    if(unlikely(img_base == NULL))
        return 0;

    sec_copy(img_base, raw, nt->OptionalHeader.SizeOfHeaders);

    img_sec = MakePtr(PIMAGE_SECTION_HEADER, nt, sizeof(IMAGE_NT_HEADERS32));

    sec_align = nt->OptionalHeader.SectionAlignment;

    for(i=0; i< nt->FileHeader.NumberOfSections; i++)
    {
        void *src_ptr;
        void *dest_ptr;
        size_t   sec_size;

        if ( img_sec->SizeOfRawData && img_sec->PointerToRawData )
        {
            src_ptr  = MakePtr(void*, raw, img_sec->PointerToRawData);
            dest_ptr = MakePtr(void*, img_base, img_sec->VirtualAddress);
            sec_copy(dest_ptr, src_ptr, img_sec->SizeOfRawData);
        };

        img_sec++;
    };

    if(nt->OptionalHeader.DataDirectory[5].Size)
    {
        PIMAGE_BASE_RELOCATION reloc;

        uint32_t delta = (uint32_t)img_base - nt->OptionalHeader.ImageBase;

        reloc = MakePtr(PIMAGE_BASE_RELOCATION, img_base,
                        nt->OptionalHeader.DataDirectory[5].VirtualAddress);

        while ( reloc->SizeOfBlock != 0 )
        {
            uint32_t  cnt;
            uint16_t *entry;
            uint16_t  reltype;
            uint32_t  offs;

            cnt = (reloc->SizeOfBlock - sizeof(*reloc))/sizeof(uint16_t);
            entry = MakePtr( uint16_t*, reloc, sizeof(*reloc) );

            for ( i=0; i < cnt; i++ )
            {
                uint16_t *p16;
                uint32_t *p32;

                reltype = (*entry & 0xF000) >> 12;
                offs = (*entry & 0x0FFF) + reloc->VirtualAddress;
                switch(reltype)
                {
                    case 1:
                        p16 = MakePtr(uint16_t*, img_base, offs);
                        *p16+= (uint16_t)(delta>>16);
                        break;
                    case 2:
                        p16 = MakePtr(uint16_t*, img_base, offs);
                        *p16+= (uint16_t)delta;
                        break;
                    case 3:
                        p32 = MakePtr(uint32_t*, img_base, offs);
                        *p32+= delta;
                }
                entry++;
            }
            reloc = MakePtr(PIMAGE_BASE_RELOCATION, reloc,reloc->SizeOfBlock);
        }
    };
    return img_base;
};

static jmp_buf loader_env;
static loader_recursion;

int __fastcall link_image(void *img_base)
{
    static jmp_buf loader_env;
    static recursion = -1;

    PIMAGE_DOS_HEADER     dos;
    PIMAGE_NT_HEADERS32   nt;
    int warn = 0;

    recursion++;
    if( !recursion )
    {
        if( unlikely(setjmp(loader_env) != 0))
        {
            recursion = -1;
            return 0;
        };
    };

    dos = (PIMAGE_DOS_HEADER)img_base;
    nt =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);

    if(nt->OptionalHeader.DataDirectory[1].Size)
    {
        PIMAGE_IMPORT_DESCRIPTOR imp;

        imp = MakePtr(PIMAGE_IMPORT_DESCRIPTOR, img_base,
                      nt->OptionalHeader.DataDirectory[1].VirtualAddress);

        while ( imp->Name )
        {
            PIMAGE_DOS_HEADER        expdos;
            PIMAGE_NT_HEADERS32      expnt;
            PIMAGE_EXPORT_DIRECTORY  exp;
            PIMAGE_THUNK_DATA32      thunk;

            void       **iat;
            char       *libname;
            uint32_t   *exp_functions;
            uint16_t   *exp_ordinals;
            char      **exp_names;

            const module_t *api;

            libname=MakePtr(char*,imp->Name, img_base);

            DBG("import from %s\n",libname);

            api = find_module(libname);
            if(unlikely(api == NULL))
            {
                printf("library %s not found\n", libname);
                longjmp(loader_env, 1);
            }

            iat = MakePtr(void**,imp->FirstThunk, img_base);

            if(imp->OriginalFirstThunk !=0 )
            {
                thunk = MakePtr(PIMAGE_THUNK_DATA32,imp->OriginalFirstThunk, img_base);
            }
            else
            {
                thunk = MakePtr(PIMAGE_THUNK_DATA32,imp->FirstThunk, img_base);
            };

            exp = api->img_exp;

            exp_functions = MakePtr(uint32_t*,exp->AddressOfFunctions,api->start);
            exp_ordinals = MakePtr(uint16_t*,  exp->AddressOfNameOrdinals,api->start);
            exp_names = MakePtr(char**, exp->AddressOfNames,api->start);

            while ( thunk->u1.AddressOfData != 0 )
            {
                PIMAGE_IMPORT_BY_NAME imp_name;

                if (thunk->u1.Ordinal & IMAGE_ORDINAL_FLAG)
                {
//                    ordinal = (*func_list) & 0x7fffffff;
//                   *ImportAddressList = LdrGetExportByOrdinal(ImportedModule->DllBase, Ordinal);
//                    if ((*ImportAddressList) == NULL)
//                    {
//                        DPRINT1("Failed to import #%ld from %wZ\n", Ordinal, &ImportedModule->FullDllName);
//                        RtlpRaiseImportNotFound(NULL, Ordinal, &ImportedModule->FullDllName);
//                        return STATUS_ENTRYPOINT_NOT_FOUND;
//                    }
                }
                else
                {
                    char *export_name;
                    uint16_t   ordinal;
                    void      *function;
                    uint32_t   minn;
                    uint32_t   maxn;

                    imp_name = MakePtr(PIMAGE_IMPORT_BY_NAME,
                                  thunk->u1.AddressOfData, img_base);
                    *iat = NULL;

                    DBG("import %s", imp_name->Name);

                    if(imp_name->Hint < exp->NumberOfNames)
                    {
                        export_name = MakePtr(char*,exp_names[imp_name->Hint],
                                              api->start);
                        if(strcmp(imp_name->Name, export_name) == 0)
                        {
                            ordinal = exp_ordinals[imp_name->Hint];
                            function = MakePtr(void*,exp_functions[ordinal], api->start);
                            if((uint32_t)function >= (uint32_t)exp)
                            {
                                printf("forward %s\n", function);
                                warn=1;
                            }
                            else
                            {
                                DBG(" \t\tat %x\n", function);
                                *iat = function;
                            };
                            thunk++;  // Advance to next thunk
                            iat++;
                            continue;
                        };
                    };


                    minn = 0;
                    maxn = exp->NumberOfNames - 1;
                    while (minn <= maxn)
                    {
                        int mid;
                        int res;

                        mid = (minn + maxn) / 2;

                        export_name = MakePtr(char*,exp_names[mid],api->start);

                        res = strcmp(export_name, imp_name->Name);
                        if (res == 0)
                        {
                            ordinal  = exp_ordinals[mid];
                            function = MakePtr(void*,exp_functions[ordinal], api->start);

                            if((uint32_t)function >= (uint32_t)exp)
                            {
                                printf("forward %s\n", function);
                                warn=1;
                            }
                            else
                            {
                                DBG(" \t\tat %x\n", function);
                                *iat = function;
                            };
                            break;
                        }
                        else if (minn == maxn)
                        {
                            printf(" unresolved %s\n",imp_name->Name);
                            warn=1;
                            break;
                        }
                        else if (res > 0)
                        {
                            maxn = mid - 1;
                        }
                        else
                        {
                            minn = mid + 1;
                        }
                    };
                };
                thunk++;            // Advance to next thunk
                iat++;
            }
            imp++;  // advance to next IMAGE_IMPORT_DESCRIPTOR
        };
    };

    recursion--;

    if ( !warn )
        return 1;
    else
        return 0;
}

int link_app()
{
    PIMAGE_IMPORT_DESCRIPTOR imp;

    struct app_hdr *header = NULL;

    int warn = 0;

    if( unlikely(setjmp(loader_env) != 0))
    {
        loader_recursion = 0;
        return 0;
    };

    imp = (PIMAGE_IMPORT_DESCRIPTOR)header->__idata_start;

    while ( imp->Name )
    {
        PIMAGE_DOS_HEADER        expdos;
        PIMAGE_NT_HEADERS32      expnt;
        PIMAGE_EXPORT_DIRECTORY  exp;
        PIMAGE_THUNK_DATA32      thunk;

        void       **iat;
        char       *libname;
        uint32_t   *exp_functions;
        uint16_t   *exp_ordinals;
        char      **exp_names;

        const module_t *api;

        libname=MakePtr(char*,imp->Name, NULL);

        DBG("import from %s\n",libname);

        api = find_module(libname);
        if(unlikely(api == NULL))
        {
            printf("library %s not found\n", libname);
            longjmp(loader_env, 1);
        }

        iat = MakePtr(void**,imp->FirstThunk, NULL);

        if(imp->OriginalFirstThunk !=0 )
        {
            thunk = MakePtr(PIMAGE_THUNK_DATA32,imp->OriginalFirstThunk, NULL);
        }
        else
        {
            thunk = MakePtr(PIMAGE_THUNK_DATA32,imp->FirstThunk, NULL);
        };

        exp = api->img_exp;

        exp_functions = MakePtr(uint32_t*,exp->AddressOfFunctions,api->start);
        exp_ordinals = MakePtr(uint16_t*,  exp->AddressOfNameOrdinals,api->start);
        exp_names = MakePtr(char**, exp->AddressOfNames,api->start);

        while ( thunk->u1.AddressOfData != 0 )
        {
            PIMAGE_IMPORT_BY_NAME imp_name;

            if (thunk->u1.Ordinal & IMAGE_ORDINAL_FLAG)
            {
//                ordinal = (*func_list) & 0x7fffffff;
//               *ImportAddressList = LdrGetExportByOrdinal(ImportedModule->DllBase, Ordinal);
//                if ((*ImportAddressList) == NULL)
//                {
//                    DPRINT1("Failed to import #%ld from %wZ\n", Ordinal, &ImportedModule->FullDllName);
//                    RtlpRaiseImportNotFound(NULL, Ordinal, &ImportedModule->FullDllName);
//                    return STATUS_ENTRYPOINT_NOT_FOUND;
//                }
            }
            else
            {
                char *export_name;
                uint16_t   ordinal;
                void      *function;
                uint32_t   minn;
                uint32_t   maxn;

                imp_name = MakePtr(PIMAGE_IMPORT_BY_NAME,
                              thunk->u1.AddressOfData, NULL);
                *iat = NULL;

                DBG("import %s", imp_name->Name);

                if(imp_name->Hint < exp->NumberOfNames)
                {
                    export_name = MakePtr(char*,exp_names[imp_name->Hint],
                                          api->start);
                    if(strcmp(imp_name->Name, export_name) == 0)
                    {
                        ordinal = exp_ordinals[imp_name->Hint];
                        function = MakePtr(void*,exp_functions[ordinal], api->start);
                        if((uint32_t)function >= (uint32_t)exp)
                        {
                            printf("forward %s\n", function);
                            warn=1;
                        }
                        else
                        {
                            DBG(" \t\tat %x\n", function);
                            *iat = function;
                        };
                        thunk++;  // Advance to next thunk
                        iat++;
                        continue;
                    };
                };


                minn = 0;
                maxn = exp->NumberOfNames - 1;
                while (minn <= maxn)
                {
                    int mid;
                    int res;

                    mid = (minn + maxn) / 2;

                    export_name = MakePtr(char*,exp_names[mid],api->start);

                    res = strcmp(export_name, imp_name->Name);
                    if (res == 0)
                    {
                        ordinal  = exp_ordinals[mid];
                        function = MakePtr(void*,exp_functions[ordinal], api->start);

                        if((uint32_t)function >= (uint32_t)exp)
                        {
                            DBG("forward %s\n", function);
                            warn=1;
                        }
                        else
                        {
                            DBG(" \t\tat %x\n", function);
                            *iat = function;
                        };
                        break;
                    }
                    else if (minn == maxn)
                    {
                        printf(" unresolved %s\n",imp_name->Name);
                        warn=1;
                        break;
                    }
                    else if (res > 0)
                    {
                        maxn = mid - 1;
                    }
                    else
                    {
                        minn = mid + 1;
                    }
                };
            };
            thunk++;            // Advance to next thunk
            iat++;
        }
        imp++;  // advance to next IMAGE_IMPORT_DESCRIPTOR
    };

    if ( !warn )
        return 1;
    else
        return 0;
}



void* get_entry_point(void *raw)
{
    PIMAGE_DOS_HEADER     dos;
    PIMAGE_NT_HEADERS32   nt;

    dos = (PIMAGE_DOS_HEADER)raw;
    nt =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);

    return  MakePtr(void*, raw, nt->OptionalHeader.AddressOfEntryPoint);
};


void *get_proc_address(module_t *module, char *proc_name)
{

    PIMAGE_DOS_HEADER        expdos;
    PIMAGE_NT_HEADERS32      expnt;
    PIMAGE_EXPORT_DIRECTORY  exp;

    uint32_t   *exp_functions;
    uint16_t   *exp_ordinals;
    char      **exp_names;

    int minn, maxn;
    char *export_name;
    uint16_t   ordinal;
    void *function=NULL;

    exp = module->img_exp;

    exp_functions = MakePtr(uint32_t*,exp->AddressOfFunctions,module->start);
    exp_ordinals = MakePtr(uint16_t*,  exp->AddressOfNameOrdinals,module->start);
    exp_names = MakePtr(char**, exp->AddressOfNames,module->start);

    minn = 0;
    maxn = exp->NumberOfNames - 1;
    while (minn <= maxn)
    {
        int mid;
        int res;

        mid = (minn + maxn) / 2;

        export_name = MakePtr(char*,exp_names[mid],module->start);

        res = strcmp(export_name, proc_name);
        if (res == 0)
        {
            ordinal  = exp_ordinals[mid];
            function = MakePtr(void*,exp_functions[ordinal], module->start);

            if((uint32_t)function >= (uint32_t)exp)
            {
                printf("forward %s\n", function);
            }
            else
            {
                DBG(" \t\tat %x\n", function);
            };
            break;
        }
        else if (minn == maxn)
        {
            DBG(" unresolved %s\n",proc_name);
            break;
        }
        else if (res > 0)
        {
            maxn = mid - 1;
        }
        else
        {
            minn = mid + 1;
        }
    };

    return function;
};


module_t* load_module(const char *name)
{
    char *path;
    int   len;

    len = strlen(name);

    dll_path_t *dllpath;

    list_for_each_entry(dllpath, &path_list, list)
    {
        PIMAGE_DOS_HEADER        dos;
        PIMAGE_NT_HEADERS32      nt;
        PIMAGE_EXPORT_DIRECTORY  exp;

        module_t *module;
        void     *raw_img;
        size_t    raw_size;
        void     *img_base;

        path = alloca(len+dllpath->path_len+1);
        memcpy(path, dllpath->path, dllpath->path_len);

        memcpy(path+dllpath->path_len, name, len);
        path[len+dllpath->path_len]=0;

//        raw_img = load_file(path, &raw_size);
        if(raw_img == NULL)
            continue;

        if( validate_pe(raw_img, raw_size, 0) == 0)
        {
            printf("invalide module %s\n", path);
            user_free(raw_img);
            continue;
        };

        img_base = create_image(raw_img);
        user_free(raw_img);

        if( unlikely(img_base == NULL) )
        {
            printf("cannot create image %s\n",path);
            continue;
        };

        module = (module_t*)malloc(sizeof(module_t));

        if(unlikely(module == NULL))
        {
            printf("%s epic fail: no enough memory\n",__FUNCTION__);
            user_free(img_base);
            return 0;
        }

        INIT_LIST_HEAD(&module->list);

        module->img_name = strdup(name);
        module->img_path = strdup(path);
        module->start    = img_base;
        module->entry    = get_entry_point(img_base);
        module->refcount = 1;

        dos =  (PIMAGE_DOS_HEADER)img_base;
        nt  =  MakePtr( PIMAGE_NT_HEADERS32, dos, dos->e_lfanew);
        exp =  MakePtr(PIMAGE_EXPORT_DIRECTORY, img_base,
                   nt->OptionalHeader.DataDirectory[0].VirtualAddress);

        module->end   = MakePtr(uint32_t,img_base, nt->OptionalHeader.SizeOfImage);

        module->img_hdr  = nt;
        module->img_sec  = MakePtr(PIMAGE_SECTION_HEADER,nt, sizeof(IMAGE_NT_HEADERS32));
        module->img_exp  = MakePtr(PIMAGE_EXPORT_DIRECTORY, img_base,
                           nt->OptionalHeader.DataDirectory[0].VirtualAddress);

        list_add_tail(&module->list, &libc_dll.list);

        if( link_image(img_base))
        {
            int (*dll_startup)(module_t *mod, uint32_t reason);

            dll_startup = get_proc_address(module, "DllStartup");
            if( dll_startup )
            {
                if( 0 == dll_startup(module, 1))
                    return 0;
            }
            return module;
        };

        return NULL;
    };

    return NULL;
};