/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "secport.h"

#include "nspr.h"

#ifdef XP_UNIX

#include <unistd.h>

#define BL_MAXSYMLINKS 20

/*

 * If 'link' is a symbolic link, this function follows the symbolic links

 * and returns the pathname of the ultimate source of the symbolic links.

 * If 'link' is not a symbolic link, this function returns NULL.

 * The caller should call PR_Free to free the string returned by this

 * function.

 */

static char*

loader_GetOriginalPathname(const char* link)

{

    char* resolved = NULL;

    char* input = NULL;

    PRUint32 iterations = 0;

    PRInt32 len = 0, retlen = 0;

    if (!link) {

        PR_SetError(PR_INVALID_ARGUMENT_ERROR, 0);

        return NULL;

    }

    len = PR_MAX(1024, strlen(link) + 1);

    resolved = PR_Malloc(len);

    input = PR_Malloc(len);

    if (!resolved || !input) {

        if (resolved) {

            PR_Free(resolved);

        }

        if (input) {

            PR_Free(input);

        }

        return NULL;

    }

    strcpy(input, link);

    while ((iterations++ < BL_MAXSYMLINKS) &&

           ((retlen = readlink(input, resolved, len - 1)) > 0)) {

        char* tmp = input;

        resolved[retlen] = '\0'; /* NULL termination */

        input = resolved;

        resolved = tmp;

    }

    PR_Free(resolved);

    if (iterations == 1 && retlen < 0) {

        PR_Free(input);

        input = NULL;

    }

    return input;

}

#endif /* XP_UNIX */

/*

 * Load the library with the file name 'name' residing in the same

 * directory as the reference library, whose pathname is 'referencePath'.

 */

static PRLibrary*

loader_LoadLibInReferenceDir(const char* referencePath, const char* name)

{

    PRLibrary* dlh = NULL;

    char* fullName = NULL;

    char* c;

    PRLibSpec libSpec;

    /* Remove the trailing filename from referencePath and add the new one */

    c = strrchr(referencePath, PR_GetDirectorySeparator());

    if (c) {

        size_t referencePathSize = 1 + c - referencePath;

        fullName = (char*)PORT_Alloc(strlen(name) + referencePathSize + 1);

        if (fullName) {

            memcpy(fullName, referencePath, referencePathSize);

            strcpy(fullName + referencePathSize, name);

#ifdef DEBUG_LOADER

            PR_fprintf(PR_STDOUT, "\nAttempting to load fully-qualified %s\n",

                       fullName);

#endif

            libSpec.type = PR_LibSpec_Pathname;

            libSpec.value.pathname = fullName;

            dlh = PR_LoadLibraryWithFlags(libSpec, PR_LD_NOW | PR_LD_LOCAL

#ifdef PR_LD_ALT_SEARCH_PATH

                                                       /* allow library's dependencies to be found in the same directory

                                                        * on Windows even if PATH is not set. Requires NSPR 4.8.1 . */

                                                       | PR_LD_ALT_SEARCH_PATH

#endif

                                          );

            PORT_Free(fullName);

        }

    }

    return dlh;

}

/*

 * Load a shared library called "newShLibName" in the same directory as

 * a shared library that is already loaded, called existingShLibName.

 * A pointer to a static function in that shared library,

 * staticShLibFunc, is required.

 *

 * existingShLibName:

 *   The file name of the shared library that shall be used as the

 *   "reference library". The loader will attempt to load the requested

 *   library from the same directory as the reference library.

 *

 * staticShLibFunc:

 *   Pointer to a static function in the "reference library".

 *

 * newShLibName:

 *   The simple file name of the new shared library to be loaded.

 *

 * We use PR_GetLibraryFilePathname to get the pathname of the loaded

 * shared lib that contains this function, and then do a

 * PR_LoadLibraryWithFlags with an absolute pathname for the shared

 * library to be loaded.

 *

 * On Windows, the "alternate search path" strategy is employed, if available.

 * On Unix, if existingShLibName is a symbolic link, and no link exists for the

 * new library, the original link will be resolved, and the new library loaded

 * from the resolved location.

 *

 * If the new shared library is not found in the same location as the reference

 * library, it will then be loaded from the normal system library path.

 *

 */

PRLibrary*

PORT_LoadLibraryFromOrigin(const char* existingShLibName,

                           PRFuncPtr staticShLibFunc,

                           const char* newShLibName)

{

    PRLibrary* lib = NULL;

    char* fullPath = NULL;

    PRLibSpec libSpec;

    /* Get the pathname for existingShLibName, e.g. /usr/lib/libnss3.so

     * PR_GetLibraryFilePathname works with either the base library name or a

     * function pointer, depending on the platform.

     * We require the address of a function in the "reference library",

     * provided by the caller. To avoid getting the address of the stub/thunk

     * of an exported function by accident, use the address of a static

     * function rather than an exported function.

     */

    fullPath = PR_GetLibraryFilePathname(existingShLibName,

                                         staticShLibFunc);

    if (fullPath) {

        lib = loader_LoadLibInReferenceDir(fullPath, newShLibName);

#ifdef XP_UNIX

        if (!lib) {

            /*

             * If fullPath is a symbolic link, resolve the symbolic

             * link and try again.

             */

            char* originalfullPath = loader_GetOriginalPathname(fullPath);

            if (originalfullPath) {

                PR_Free(fullPath);

                fullPath = originalfullPath;

                lib = loader_LoadLibInReferenceDir(fullPath, newShLibName);

            }

        }

#endif

        PR_Free(fullPath);

    }

    if (!lib) {

#ifdef DEBUG_LOADER

        PR_fprintf(PR_STDOUT, "\nAttempting to load %s\n", newShLibName);

#endif

        libSpec.type = PR_LibSpec_Pathname;

        libSpec.value.pathname = newShLibName;

        lib = PR_LoadLibraryWithFlags(libSpec, PR_LD_NOW | PR_LD_LOCAL);

    }

    if (NULL == lib) {

#ifdef DEBUG_LOADER

        PR_fprintf(PR_STDOUT, "\nLoading failed : %s.\n", newShLibName);

#endif

    }

    return lib;

}