os-aix-dso.c

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/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
**  os-aix-dso.c -- DSO system function emulation for AIX
 */

/*
**  Based on libdl (dlfcn.c/dlfcn.h) which is
**  Copyright (c) 1992,1993,1995,1996,1997,1988
**  Jens-Uwe Mager, Helios Software GmbH, Hannover, Germany.
**
**  Not derived from licensed software.
**
**  Permission is granted to freely use, copy, modify, and redistribute
**  this software, provided that the author is not construed to be liable
**  for any results of using the software, alterations are clearly marked
**  as such, and this notice is not modified.
**
**  Changes marked with `--jwe' were made on April 7 1996 by
**  John W. Eaton <[e-mail]> to support g++ 
**
**  Bundled, stripped and adjusted on April 1998 as one single source file 
**  for inclusion into the Apache HTTP server by 
**  Ralf S. Engelschall <[e-mail]>
*/

#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/ldr.h>
#include <a.out.h>

#undef FREAD
#undef FWRITE
#include <ldfcn.h>

/*
 * AIX 4.3 does remove some useful definitions from ldfcn.h. Define
 * these here to compensate for that lossage.
 */
#ifndef BEGINNING
#define BEGINNING SEEK_SET
#endif
#ifndef FSEEK
#define FSEEK(ldptr,o,p)   fseek(IOPTR(ldptr),(p==BEGINNING)?(OFFSET(ldptr) +o):o,p)
#endif
#ifndef FREAD
#define FREAD(p,s,n,ldptr) fread(p,s,n,IOPTR(ldptr))
#endif

/*
 * Mode flags for the dlopen routine.
 */
#undef  RTLD_LAZY
#define RTLD_LAZY	1	/* lazy function call binding */
#undef  RTLD_NOW
#define RTLD_NOW	2	/* immediate function call binding */
#undef  RTLD_GLOBAL
#define RTLD_GLOBAL	0x100	/* allow symbols to be global */

/*
 * To be able to initialize, a library may provide a dl_info structure
 * that contains functions to be called to initialize and terminate.
 */
struct dl_info {
    void (*init) (void);
    void (*fini) (void);
};


/*
 *  Forward declarations
 */
void *dlopen(const char *path, int mode);
void *dlsym(void *handle, const char *symbol);
const char *dlerror(void);
int dlclose(void *handle);

/*
 * We simulate dlopen() et al. through a call to load. Because AIX has
 * no call to find an exported symbol we read the loader section of the
 * loaded module and build a list of exported symbols and their virtual
 * address.
 */

typedef struct {
    char *name;			/* the symbols's name */
    void *addr;			/* its relocated virtual address */
} Export, *ExportPtr;

/*
 * xlC uses the following structure to list its constructors and
 * destructors. This is gleaned from the output of munch.
 */
typedef struct {
    void (*init) (void);	/* call static constructors */
    void (*term) (void);	/* call static destructors */
} Cdtor, *CdtorPtr;

typedef void (*GccCDtorPtr) (void);

/*
 * The void * handle returned from dlopen is actually a ModulePtr.
 */
typedef struct Module {
    struct Module *next;
    char *name;			/* module name for refcounting */
    int refCnt;			/* the number of references */
    void *entry;		/* entry point from load */
    struct dl_info *info;	/* optional init/terminate functions */
    CdtorPtr cdtors;		/* optional C++ constructors */
    GccCDtorPtr gcc_ctor;	/* g++ constructors  --jwe */
    GccCDtorPtr gcc_dtor;	/* g++ destructors  --jwe */
    int nExports;		/* the number of exports found */
    ExportPtr exports;		/* the array of exports */
} Module, *ModulePtr;

/*
 * We keep a list of all loaded modules to be able to call the fini
 * handlers and destructors at atexit() time.
 */
static ModulePtr modList;

/*
 * The last error from one of the dl* routines is kept in static
 * variables here. Each error is returned only once to the caller.
 */
static char errbuf[BUFSIZ];
static int errvalid;

/*
 * The `fixed' gcc header files on AIX 3.2.5 provide a prototype for
 * strdup().  --jwe
 */
extern char *strdup(const char *);
static void caterr(char *);
static int readExports(ModulePtr);
static void terminate(void);
static void *findMain(void);

void *dlopen(const char *path, int mode)
{
    register ModulePtr mp;
    static void *mainModule;

    /*
     * Upon the first call register a terminate handler that will
     * close all libraries. Also get a reference to the main module
     * for use with loadbind.
     */
    if (!mainModule) {
	if ((mainModule = findMain()) == NULL)
	    return NULL;
	atexit(terminate);
    }
    /*
     * Scan the list of modules if we have the module already loaded.
     */
    for (mp = modList; mp; mp = mp->next)
	if (strcmp(mp->name, path) == 0) {
	    mp->refCnt++;
	    return mp;
	}
    if ((mp = (ModulePtr) calloc(1, sizeof(*mp))) == NULL) {
	errvalid++;
	strcpy(errbuf, "calloc: ");
	strcat(errbuf, strerror(errno));
	return NULL;
    }
    if ((mp->name = strdup(path)) == NULL) {
	errvalid++;
	strcpy(errbuf, "strdup: ");
	strcat(errbuf, strerror(errno));
	free(mp);
	return NULL;
    }
    /*
     * load should be declared load(const char *...). Thus we
     * cast the path to a normal char *. Ugly.
     */
    if ((mp->entry = (void *) load((char *) path, L_NOAUTODEFER, NULL)) == NULL) {
	free(mp->name);
	free(mp);
	errvalid++;
	strcpy(errbuf, "dlopen: ");
	strcat(errbuf, path);
	strcat(errbuf, ": ");
	/*
	 * If AIX says the file is not executable, the error
	 * can be further described by querying the loader about
	 * the last error.
	 */
	if (errno == ENOEXEC) {
	    char *tmp[BUFSIZ / sizeof(char *)];
	    if (loadquery(L_GETMESSAGES, tmp, sizeof(tmp)) == -1)
		strcpy(errbuf, strerror(errno));
	    else {
		char **p;
		for (p = tmp; *p; p++)
		    caterr(*p);
	    }
	}
	else
	    strcat(errbuf, strerror(errno));
	return NULL;
    }
    mp->refCnt = 1;
    mp->next = modList;
    modList = mp;
    if (loadbind(0, mainModule, mp->entry) == -1) {
	dlclose(mp);
	errvalid++;
	strcpy(errbuf, "loadbind: ");
	strcat(errbuf, strerror(errno));
	return NULL;
    }
    /*
     * If the user wants global binding, loadbind against all other
     * loaded modules.
     */
    if (mode & RTLD_GLOBAL) {
	register ModulePtr mp1;
	for (mp1 = mp->next; mp1; mp1 = mp1->next)
	    if (loadbind(0, mp1->entry, mp->entry) == -1) {
		dlclose(mp);
		errvalid++;
		strcpy(errbuf, "loadbind: ");
		strcat(errbuf, strerror(errno));
		return NULL;
	    }
    }
    if (readExports(mp) == -1) {
	dlclose(mp);
	return NULL;
    }
    /*
     * If there is a dl_info structure, call the init function.
     */
    if (mp->info = (struct dl_info *) dlsym(mp, "dl_info")) {
	if (mp->info->init)
	    (*mp->info->init) ();
    }
    else
	errvalid = 0;
    /*
     * If the shared object was compiled using xlC we will need
     * to call static constructors (and later on dlclose destructors).
     */
    if (mp->cdtors = (CdtorPtr) dlsym(mp, "__cdtors")) {
	CdtorPtr cp = mp->cdtors;
	while (cp->init || cp->term) {
	    if (cp->init && cp->init != (void (*)(void)) 0xffffffff)
		(*cp->init) ();
	    cp++;
	}
	/*
	 * If the shared object was compiled using g++, we will need
	 * to call global constructors using the _GLOBAL__DI function,
	 * and later, global destructors using the _GLOBAL_DD
	 * funciton.  --jwe
	 */
    }
    else if (mp->gcc_ctor = (GccCDtorPtr) dlsym(mp, "_GLOBAL__DI")) {
	(*mp->gcc_ctor) ();
	mp->gcc_dtor = (GccCDtorPtr) dlsym(mp, "_GLOBAL__DD");
    }
    else
	errvalid = 0;
    return mp;
}

/*
 * Attempt to decipher an AIX loader error message and append it
 * to our static error message buffer.
 */
static void caterr(char *s)
{
    register char *p = s;

    while (*p >= '0' && *p <= '9')
	p++;
    switch (atoi(s)) {
    case L_ERROR_TOOMANY:
	strcat(errbuf, "to many errors");
	break;
    case L_ERROR_NOLIB:
	strcat(errbuf, "can't load library");
	strcat(errbuf, p);
	break;
    case L_ERROR_UNDEF:
	strcat(errbuf, "can't find symbol");
	strcat(errbuf, p);
	break;
    case L_ERROR_RLDBAD:
	strcat(errbuf, "bad RLD");
	strcat(errbuf, p);
	break;
    case L_ERROR_FORMAT: