dlfcn.c

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/*
 * dlfcn-win32
 * Copyright (c) 2007 Ramiro Polla
 * Copyright (c) 2015 Tiancheng "Timothy" Gu
 * Copyright (c) 2019 Pali Rohár <pali.rohar@gmail.com>
 * Copyright (c) 2020 Ralf Habacker <ralf.habacker@freenet.de>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
/*
 * From https://github.com/dlfcn-win32/dlfcn-win32
 * Filtered with dos2unix and clang-format.
 */
 
#ifdef _DEBUG
#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>
#endif
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
 
/* Older versions do not have this type */
#if _WIN32_WINNT < 0x0500
typedef ULONG ULONG_PTR;
#endif
 
/* Older SDK versions do not have these macros */
#ifndef GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS
#define GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS 0x4
#endif
#ifndef GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT
#define GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT 0x2
#endif
 
#ifdef _MSC_VER
/* https://docs.microsoft.com/en-us/cpp/intrinsics/returnaddress */
#pragma intrinsic(_ReturnAddress)
#else
/* https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html */
#ifndef _ReturnAddress
#define _ReturnAddress() (__builtin_extract_return_addr(__builtin_return_address(0)))
#endif
#endif
 
#ifdef DLFCN_WIN32_SHARED
#define DLFCN_WIN32_EXPORTS
#endif
#include "dlfcn.h"
 
#if defined(_MSC_VER) && _MSC_VER >= 1300
/* https://docs.microsoft.com/en-us/cpp/cpp/noinline */
#define DLFCN_NOINLINE __declspec(noinline)
#elif defined(__GNUC__) && ((__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1))
/* https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html */
#define DLFCN_NOINLINE __attribute__((noinline))
#else
#define DLFCN_NOINLINE
#endif
 
/* Note:
 * MSDN says these functions are not thread-safe. We make no efforts to have
 * any kind of thread safety.
 */
 
typedef struct local_object {
    HMODULE hModule;
    struct local_object* previous;
    struct local_object* next;
} local_object;
 
static local_object first_object;
 
/* These functions implement a double linked list for the local objects. */
static local_object* local_search(HMODULE hModule) {
    local_object* pobject;
 
    if (hModule == NULL)
        return NULL;
 
    for (pobject = &first_object; pobject; pobject = pobject->next)
        if (pobject->hModule == hModule)
            return pobject;
 
    return NULL;
}
 
static BOOL local_add(HMODULE hModule) {
    local_object* pobject;
    local_object* nobject;
 
    if (hModule == NULL)
        return TRUE;
 
    pobject = local_search(hModule);
 
    /* Do not add object again if it's already on the list */
    if (pobject != NULL)
        return TRUE;
 
    for (pobject = &first_object; pobject->next; pobject = pobject->next)
        ;
 
    nobject = (local_object*) malloc(sizeof(local_object));
 
    if (!nobject)
        return FALSE;
 
    pobject->next = nobject;
    nobject->next = NULL;
    nobject->previous = pobject;
    nobject->hModule = hModule;
 
    return TRUE;
}
 
static void local_rem(HMODULE hModule) {
    local_object* pobject;
 
    if (hModule == NULL)
        return;
 
    pobject = local_search(hModule);
 
    if (pobject == NULL)
        return;
 
    if (pobject->next)
        pobject->next->previous = pobject->previous;
    if (pobject->previous)
        pobject->previous->next = pobject->next;
 
    free(pobject);
}
 
/* POSIX says dlerror( ) doesn't have to be thread-safe, so we use one
 * static buffer.
 * MSDN says the buffer cannot be larger than 64K bytes, so we set it to
 * the limit.
 */
static char error_buffer[65535];
static BOOL error_occurred;
 
static void save_err_str(const char* str, DWORD dwMessageId) {
    DWORD ret;
    size_t pos, len;
 
    len = strlen(str);
    if (len > sizeof(error_buffer) - 5)
        len = sizeof(error_buffer) - 5;
 
    /* Format error message to:
     * "<argument to function that failed>": <Windows localized error message>
     */
    pos = 0;
    error_buffer[pos++] = '"';
    memcpy(error_buffer + pos, str, len);
    pos += len;
    error_buffer[pos++] = '"';
    error_buffer[pos++] = ':';
    error_buffer[pos++] = ' ';
 
    ret = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
                         NULL,
                         dwMessageId,
                         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                         error_buffer + pos,
                         (DWORD) (sizeof(error_buffer) - pos),
                         NULL);
    pos += ret;
 
    /* When FormatMessageA() fails it returns zero and does not touch buffer
     * so add trailing null byte */
    if (ret == 0)
        error_buffer[pos] = '\0';
 
    if (pos > 1) {
        /* POSIX says the string must not have trailing <newline> */
        if (error_buffer[pos - 2] == '\r' && error_buffer[pos - 1] == '\n')
            error_buffer[pos - 2] = '\0';
    }
 
    error_occurred = TRUE;
}
 
static void save_err_ptr_str(const void* ptr, DWORD dwMessageId) {
    char ptr_buf[2 + 2 * sizeof(ptr) + 1];
    char num;
    size_t i;
 
    ptr_buf[0] = '0';
    ptr_buf[1] = 'x';
 
    for (i = 0; i < 2 * sizeof(ptr); i++) {
        num = (char) ((((ULONG_PTR) ptr) >> (8 * sizeof(ptr) - 4 * (i + 1))) & 0xF);
        ptr_buf[2 + i] = num + ((num < 0xA) ? '0' : ('A' - 0xA));
    }
 
    ptr_buf[2 + 2 * sizeof(ptr)] = 0;
 
    save_err_str(ptr_buf, dwMessageId);
}
 
static UINT MySetErrorMode(UINT uMode) {
    static BOOL(WINAPI * SetThreadErrorModePtr)(DWORD, DWORD*) = NULL;
    static BOOL failed = FALSE;
    HMODULE kernel32;
    DWORD oldMode;
 
    if (!failed && SetThreadErrorModePtr == NULL) {
        kernel32 = GetModuleHandleA("Kernel32.dll");
        if (kernel32 != NULL)
            SetThreadErrorModePtr = (BOOL(WINAPI*)(DWORD, DWORD*))(
                LPVOID) GetProcAddress(kernel32, "SetThreadErrorMode");
        if (SetThreadErrorModePtr == NULL)
            failed = TRUE;
    }
 
    if (!failed) {
        if (!SetThreadErrorModePtr(uMode, &oldMode))
            return 0;
        else
            return oldMode;
    } else {
        return SetErrorMode(uMode);
    }
}
 
static HMODULE MyGetModuleHandleFromAddress(const void* addr) {
    static BOOL(WINAPI * GetModuleHandleExAPtr)(DWORD, LPCSTR, HMODULE*) = NULL;
    static BOOL failed = FALSE;
    HMODULE kernel32;
    HMODULE hModule;
    MEMORY_BASIC_INFORMATION info;
    SIZE_T sLen;
 
    if (!failed && GetModuleHandleExAPtr == NULL) {
        kernel32 = GetModuleHandleA("Kernel32.dll");
        if (kernel32 != NULL)
            GetModuleHandleExAPtr = (BOOL(WINAPI*)(DWORD, LPCSTR, HMODULE*))(
                LPVOID) GetProcAddress(kernel32, "GetModuleHandleExA");
        if (GetModuleHandleExAPtr == NULL)
            failed = TRUE;
    }
 
    if (!failed) {
        /* If GetModuleHandleExA is available use it with GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS */
        if (!GetModuleHandleExAPtr(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
                                       GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
                                   addr,
                                   &hModule))
            return NULL;
    } else {
        /* To get HMODULE from address use undocumented hack from
         * https://stackoverflow.com/a/2396380 The HMODULE of a DLL is the same value as the
         * module's base address.
         */
        sLen = VirtualQuery(addr, &info, sizeof(info));
        if (sLen != sizeof(info))
            return NULL;
        hModule = (HMODULE) info.AllocationBase;
    }
 
    return hModule;
}
 
/* Load Psapi.dll at runtime, this avoids linking caveat */
static BOOL MyEnumProcessModules(HANDLE hProcess,
                                 HMODULE* lphModule,
                                 DWORD cb,
                                 LPDWORD lpcbNeeded) {
    static BOOL(WINAPI * EnumProcessModulesPtr)(HANDLE, HMODULE*, DWORD, LPDWORD) = NULL;
    static BOOL failed = FALSE;
    UINT uMode;
    HMODULE psapi;
 
    if (failed)
        return FALSE;
 
    if (EnumProcessModulesPtr == NULL) {
        /* Windows 7 and newer versions have K32EnumProcessModules in Kernel32.dll which is always
         * pre-loaded */
        psapi = GetModuleHandleA("Kernel32.dll");
        if (psapi != NULL)
            EnumProcessModulesPtr = (BOOL(WINAPI*)(HANDLE, HMODULE*, DWORD, LPDWORD))(
                LPVOID) GetProcAddress(psapi, "K32EnumProcessModules");
 
        /* Windows Vista and older version have EnumProcessModules in Psapi.dll which needs to be
         * loaded */
        if (EnumProcessModulesPtr == NULL) {
            /* Do not let Windows display the critical-error-handler message box */
            uMode = MySetErrorMode(SEM_FAILCRITICALERRORS);
            psapi = LoadLibraryA("Psapi.dll");
            if (psapi != NULL) {
                EnumProcessModulesPtr = (BOOL(WINAPI*)(HANDLE, HMODULE*, DWORD, LPDWORD))(
                    LPVOID) GetProcAddress(psapi, "EnumProcessModules");
                if (EnumProcessModulesPtr == NULL)
                    FreeLibrary(psapi);
            }
            MySetErrorMode(uMode);
        }
 
        if (EnumProcessModulesPtr == NULL) {
            failed = TRUE;
            return FALSE;
        }
    }
 
    return EnumProcessModulesPtr(hProcess, lphModule, cb, lpcbNeeded);
}
 
DLFCN_EXPORT
void* dlopen(const char* file, int mode) {
    HMODULE hModule;
    UINT uMode;
 
    error_occurred = FALSE;
 
    /* Do not let Windows display the critical-error-handler message box */
    uMode = MySetErrorMode(SEM_FAILCRITICALERRORS);
 
    if (file == NULL) {
        /* POSIX says that if the value of file is NULL, a handle on a global
         * symbol object must be provided. That object must be able to access
         * all symbols from the original program file, and any objects loaded
         * with the RTLD_GLOBAL flag.
         * The return value from GetModuleHandle( ) allows us to retrieve
         * symbols only from the original program file. EnumProcessModules() is
         * used to access symbols from other libraries. For objects loaded
         * with the RTLD_LOCAL flag, we create our own list later on. They are
         * excluded from EnumProcessModules() iteration.
         */
        hModule = GetModuleHandle(NULL);
 
        if (!hModule)
            save_err_str("(null)", GetLastError());
    } else {
        HANDLE hCurrentProc;
        DWORD dwProcModsBefore, dwProcModsAfter;
        char lpFileName[MAX_PATH];
        size_t i, len;
 
        len = strlen(file);
 
        if (len >= sizeof(lpFileName)) {
            save_err_str(file, ERROR_FILENAME_EXCED_RANGE);
            hModule = NULL;
        } else {
            /* MSDN says backslashes *must* be used instead of forward slashes. */
            for (i = 0; i < len; i++) {
                if (file[i] == '/')
                    lpFileName[i] = '\\';
                else
                    lpFileName[i] = file[i];
            }
            lpFileName[len] = '\0';
 
            hCurrentProc = GetCurrentProcess();
 
            if (MyEnumProcessModules(hCurrentProc, NULL, 0, &dwProcModsBefore) == 0)
                dwProcModsBefore = 0;
 
            /* POSIX says the search path is implementation-defined.
             * LOAD_WITH_ALTERED_SEARCH_PATH is used to make it behave more closely
             * to UNIX's search paths (start with system folders instead of current
             * folder).
             */
            hModule = LoadLibraryExA(lpFileName, NULL, LOAD_WITH_ALTERED_SEARCH_PATH);
 
            if (!hModule) {
                save_err_str(lpFileName, GetLastError());
            } else {
                if (MyEnumProcessModules(hCurrentProc, NULL, 0, &dwProcModsAfter) == 0)
                    dwProcModsAfter = 0;
 
                /* If the object was loaded with RTLD_LOCAL, add it to list of local
                 * objects, so that its symbols cannot be retrieved even if the handle for
                 * the original program file is passed. POSIX says that if the same
                 * file is specified in multiple invocations, and any of them are
                 * RTLD_GLOBAL, even if any further invocations use RTLD_LOCAL, the
                 * symbols will remain global. If number of loaded modules was not
                 * changed after calling LoadLibraryEx(), it means that library was
                 * already loaded.
                 */
                if ((mode & RTLD_LOCAL) && dwProcModsBefore != dwProcModsAfter) {
                    if (!local_add(hModule)) {
                        save_err_str(lpFileName, ERROR_NOT_ENOUGH_MEMORY);
                        FreeLibrary(hModule);
                        hModule = NULL;
                    }
                } else if (!(mode & RTLD_LOCAL) && dwProcModsBefore == dwProcModsAfter) {
                    local_rem(hModule);
                }
            }
        }
    }
 
    /* Return to previous state of the error-mode bit flags. */
    MySetErrorMode(uMode);
 
    return (void*) hModule;
}
 
DLFCN_EXPORT
int dlclose(void* handle) {
    HMODULE hModule = (HMODULE) handle;
    BOOL ret;
 
    error_occurred = FALSE;
 
    ret = FreeLibrary(hModule);
 
    /* If the object was loaded with RTLD_LOCAL, remove it from list of local
     * objects.
     */
    if (ret)
        local_rem(hModule);
    else
        save_err_ptr_str(handle, GetLastError());
 
    /* dlclose's return value in inverted in relation to FreeLibrary's. */
    ret = !ret;
 
    return (int) ret;
}
 
DLFCN_NOINLINE /* Needed for _ReturnAddress() */
    DLFCN_EXPORT void*
    dlsym(void* handle, const char* name) {
    FARPROC symbol;
    HMODULE hCaller;
    HMODULE hModule;
    DWORD dwMessageId;
 
    error_occurred = FALSE;
 
    symbol = NULL;
    hCaller = NULL;
    hModule = GetModuleHandle(NULL);
    dwMessageId = 0;
 
    if (handle == RTLD_DEFAULT) {
        /* The symbol lookup happens in the normal global scope; that is,
         * a search for a symbol using this handle would find the same
         * definition as a direct use of this symbol in the program code.
         * So use same lookup procedure as when filename is NULL.
         */
        handle = hModule;
    } else if (handle == RTLD_NEXT) {
        /* Specifies the next object after this one that defines name.
         * This one refers to the object containing the invocation of dlsym().
         * The next object is the one found upon the application of a load
         * order symbol resolution algorithm. To get caller function of dlsym()
         * use _ReturnAddress() intrinsic. To get HMODULE of caller function
         * use MyGetModuleHandleFromAddress() which calls either standard
         * GetModuleHandleExA() function or hack via VirtualQuery().
         */
        hCaller = MyGetModuleHandleFromAddress(_ReturnAddress());
 
        if (hCaller == NULL) {
            dwMessageId = ERROR_INVALID_PARAMETER;
            goto end;
        }
    }
 
    if (handle != RTLD_NEXT) {
        symbol = GetProcAddress((HMODULE) handle, name);
 
        if (symbol != NULL)
            goto end;
    }
 
    /* If the handle for the original program file is passed, also search
     * in all globally loaded objects.
     */
 
    if (hModule == handle || handle == RTLD_NEXT) {
        HANDLE hCurrentProc;
        HMODULE* modules;
        DWORD cbNeeded;
        DWORD dwSize;
        size_t i;
 
        hCurrentProc = GetCurrentProcess();
 
        /* GetModuleHandle( NULL ) only returns the current program file. So
         * if we want to get ALL loaded module including those in linked DLLs,
         * we have to use EnumProcessModules( ).
         */
        if (MyEnumProcessModules(hCurrentProc, NULL, 0, &dwSize) != 0) {
            modules = malloc(dwSize);
            if (modules) {
                if (MyEnumProcessModules(hCurrentProc, modules, dwSize, &cbNeeded) != 0 &&
                    dwSize == cbNeeded) {
                    for (i = 0; i < dwSize / sizeof(HMODULE); i++) {
                        if (handle == RTLD_NEXT && hCaller) {
                            /* Next modules can be used for RTLD_NEXT */
                            if (hCaller == modules[i])
                                hCaller = NULL;
                            continue;
                        }
                        if (local_search(modules[i]))
                            continue;
                        symbol = GetProcAddress(modules[i], name);
                        if (symbol != NULL) {
                            free(modules);
                            goto end;
                        }
                    }
                }
                free(modules);
            } else {
                dwMessageId = ERROR_NOT_ENOUGH_MEMORY;
                goto end;
            }
        }
    }
 
end:
    if (symbol == NULL) {
        if (!dwMessageId)
            dwMessageId = ERROR_PROC_NOT_FOUND;
        save_err_str(name, dwMessageId);
    }
 
    return *(void**) (&symbol);
}
 
DLFCN_EXPORT
char* dlerror(void) {
    /* If this is the second consecutive call to dlerror, return NULL */
    if (!error_occurred)
        return NULL;
 
    /* POSIX says that invoking dlerror( ) a second time, immediately following
     * a prior invocation, shall result in NULL being returned.
     */
    error_occurred = FALSE;
 
    return error_buffer;
}
 
/* See
 * https://docs.microsoft.com/en-us/archive/msdn-magazine/2002/march/inside-windows-an-in-depth-look-into-the-win32-portable-executable-file-format-part-2
 * for details */
 
/* Get specific image section */
static BOOL get_image_section(HMODULE module, int index, void** ptr, DWORD* size) {
    IMAGE_DOS_HEADER* dosHeader;
    IMAGE_NT_HEADERS* ntHeaders;
    IMAGE_OPTIONAL_HEADER* optionalHeader;
 
    dosHeader = (IMAGE_DOS_HEADER*) module;
 
    if (dosHeader->e_magic != IMAGE_DOS_SIGNATURE)
        return FALSE;
 
    ntHeaders = (IMAGE_NT_HEADERS*) ((BYTE*) dosHeader + dosHeader->e_lfanew);
 
    if (ntHeaders->Signature != IMAGE_NT_SIGNATURE)
        return FALSE;
 
    optionalHeader = &ntHeaders->OptionalHeader;
 
    if (optionalHeader->Magic != IMAGE_NT_OPTIONAL_HDR_MAGIC)
        return FALSE;
 
    if (index < 0 || index > IMAGE_DIRECTORY_ENTRY_COM_DESCRIPTOR)
        return FALSE;
 
    if (optionalHeader->DataDirectory[index].Size == 0 ||
        optionalHeader->DataDirectory[index].VirtualAddress == 0)
        return FALSE;
 
    if (size != NULL)
        *size = optionalHeader->DataDirectory[index].Size;
 
    *ptr = (void*) ((BYTE*) module + optionalHeader->DataDirectory[index].VirtualAddress);
 
    return TRUE;
}
 
/* Return symbol name for a given address from export table */
static const char* get_export_symbol_name(HMODULE module,
                                          IMAGE_EXPORT_DIRECTORY* ied,
                                          const void* addr,
                                          void** func_address) {
    DWORD i;
    void* candidateAddr = NULL;
    int candidateIndex = -1;
    BYTE* base = (BYTE*) module;
    DWORD* functionAddressesOffsets = (DWORD*) (base + ied->AddressOfFunctions);
    DWORD* functionNamesOffsets = (DWORD*) (base + ied->AddressOfNames);
    USHORT* functionNameOrdinalsIndexes = (USHORT*) (base + ied->AddressOfNameOrdinals);
 
    for (i = 0; i < ied->NumberOfFunctions; i++) {
        if ((void*) (base + functionAddressesOffsets[i]) > addr ||
            candidateAddr >= (void*) (base + functionAddressesOffsets[i]))
            continue;
 
        candidateAddr = (void*) (base + functionAddressesOffsets[i]);
        candidateIndex = i;
    }
 
    if (candidateIndex == -1)
        return NULL;
 
    *func_address = candidateAddr;
 
    for (i = 0; i < ied->NumberOfNames; i++) {
        if (functionNameOrdinalsIndexes[i] == candidateIndex)
            return (const char*) (base + functionNamesOffsets[i]);
    }
 
    return NULL;
}
 
static BOOL is_valid_address(const void* addr) {
    MEMORY_BASIC_INFORMATION info;
    SIZE_T result;
 
    if (addr == NULL)
        return FALSE;
 
    /* check valid pointer */
    result = VirtualQuery(addr, &info, sizeof(info));
 
    if (result == 0 || info.AllocationBase == NULL || info.AllocationProtect == 0 ||
        info.AllocationProtect == PAGE_NOACCESS)
        return FALSE;
 
    return TRUE;
}
 
/* Return state if address points to an import thunk
 *
 * An import thunk is setup with a 'jmp' instruction followed by an
 * absolute address (32bit) or relative offset (64bit) pointing into
 * the import address table (iat), which is partially maintained by
 * the runtime linker.
 */
static BOOL is_import_thunk(const void* addr) {
    return *(short*) addr == 0x25ff ? TRUE : FALSE;
}
 
/* Return adress from the import address table (iat),
 * if the original address points to a thunk table entry.
 */
static void* get_address_from_import_address_table(void* iat, DWORD iat_size, const void* addr) {
    BYTE* thkp = (BYTE*) addr;
    /* Get offset from thunk table (after instruction 0xff 0x25)
     *   4018c8 <_VirtualQuery>: ff 25 4a 8a 00 00
     */
    ULONG offset = *(ULONG*) (thkp + 2);
#ifdef _WIN64
    /* On 64 bit the offset is relative
     *      4018c8:   ff 25 4a 8a 00 00    jmpq    *0x8a4a(%rip)    # 40a318 <__imp_VirtualQuery>
     * And can be also negative (MSVC in WDK)
     *   100002f20:   ff 25 3a e1 ff ff    jmpq   *-0x1ec6(%rip)    # 0x100001060
     * So cast to signed LONG type
     */
    BYTE* ptr = (BYTE*) (thkp + 6 + (LONG) offset);
#else
    /* On 32 bit the offset is absolute
     *   4019b4:    ff 25 90 71 40 00    jmp    *0x40719
     */
    BYTE* ptr = (BYTE*) offset;
#endif
 
    if (!is_valid_address(ptr) || ptr < (BYTE*) iat || ptr > (BYTE*) iat + iat_size)
        return NULL;
 
    return *(void**) ptr;
}
 
/* Holds module filename */
static char module_filename[2 * MAX_PATH];
 
static BOOL fill_info(const void* addr, Dl_info* info) {
    HMODULE hModule;
    DWORD dwSize;
    IMAGE_EXPORT_DIRECTORY* ied;
    void* funcAddress = NULL;
 
    /* Get module of the specified address */
    hModule = MyGetModuleHandleFromAddress(addr);
 
    if (hModule == NULL)
        return FALSE;
 
    dwSize = GetModuleFileNameA(hModule, module_filename, sizeof(module_filename));
 
    if (dwSize == 0 || dwSize == sizeof(module_filename))
        return FALSE;
 
    info->dli_fname = module_filename;
    info->dli_fbase = (void*) hModule;
 
    /* Find function name and function address in module's export table */
    if (get_image_section(hModule, IMAGE_DIRECTORY_ENTRY_EXPORT, (void**) &ied, NULL))
        info->dli_sname = get_export_symbol_name(hModule, ied, addr, &funcAddress);
    else
        info->dli_sname = NULL;
 
    info->dli_saddr = info->dli_sname == NULL ? NULL
                      : funcAddress != NULL   ? funcAddress
                                              : (void*) addr;
 
    return TRUE;
}
 
DLFCN_EXPORT
int dladdr(const void* addr, Dl_info* info) {
    if (info == NULL)
        return 0;
 
    if (!is_valid_address(addr))
        return 0;
 
    if (is_import_thunk(addr)) {
        void* iat;
        DWORD iatSize;
        HMODULE hModule;
 
        /* Get module of the import thunk address */
        hModule = MyGetModuleHandleFromAddress(addr);
 
        if (hModule == NULL)
            return 0;
 
        if (!get_image_section(hModule, IMAGE_DIRECTORY_ENTRY_IAT, &iat, &iatSize)) {
            /* Fallback for cases where the iat is not defined,
             * for example i586-mingw32msvc-gcc */
            IMAGE_IMPORT_DESCRIPTOR* iid;
            DWORD iidSize;
 
            if (!get_image_section(hModule, IMAGE_DIRECTORY_ENTRY_IMPORT, (void**) &iid, &iidSize))
                return 0;
 
            if (iid == NULL || iid->Characteristics == 0 || iid->FirstThunk == 0)
                return 0;
 
            iat = (void*) ((BYTE*) hModule + iid->FirstThunk);
            /* We assume that in this case iid and iat's are in linear order */
            iatSize = iidSize - (DWORD) ((BYTE*) iat - (BYTE*) iid);
        }
 
        addr = get_address_from_import_address_table(iat, iatSize, addr);
 
        if (!is_valid_address(addr))
            return 0;
    }
 
    if (!fill_info(addr, info))
        return 0;
 
    return 1;
}
 
#ifdef DLFCN_WIN32_SHARED
BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
    (void) hinstDLL;
    (void) fdwReason;
    (void) lpvReserved;
    return TRUE;
}
#endif