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tclLoadAix.c

/* 
 * tclLoadAix.c --
 *
 *    This file implements the dlopen and dlsym APIs under the
 *    AIX operating system, to enable the Tcl "load" command to
 *    work.  This code was provided by Jens-Uwe Mager.
 *
 *    This file is subject to the following copyright notice, which is
 *    different from the notice used elsewhere in Tcl.  The file has
 *    been modified to incorporate the file dlfcn.h in-line.
 *
 *    Copyright (c) 1992,1993,1995,1996, Jens-Uwe Mager, Helios Software GmbH
 *    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.
 *
 * RCS: @(#) $Id: tclLoadAix.c,v 1.2 1998/09/14 18:40:16 stanton Exp $
 *
 * Note:  this file has been altered from the original in a few
 * ways in order to work properly with Tcl.
 */

/*
 * @(#)dlfcn.c    1.7 revision of 95/08/14  19:08:38
 * This is an unpublished work copyright (c) 1992 HELIOS Software GmbH
 * 30159 Hannover, Germany
 */

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

/*
 * 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;

/*
 * 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 */
      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;

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 (VOID *) mp;
            }
      if ((mp = (ModulePtr)calloc(1, sizeof(*mp))) == NULL) {
            errvalid++;
            strcpy(errbuf, "calloc: ");
            strcat(errbuf, strerror(errno));
            return (VOID *) NULL;
      }
      mp->name = malloc((unsigned) (strlen(path) + 1));
      strcpy(mp->name, path);
      /*
       * 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 (VOID *) 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 (VOID *) 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 (VOID *) NULL;
                  }
      }
      if (readExports(mp) == -1) {
            dlclose(mp);
            return (VOID *) 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")) {
            while (mp->cdtors->init) {
                  (*mp->cdtors->init)();
                  mp->cdtors++;
            }
      } else
            errvalid = 0;
      return (VOID *) 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:
            strcat(errbuf, "bad exec format in");
            strcat(errbuf, p);
            break;
      case L_ERROR_ERRNO:
            strcat(errbuf, strerror(atoi(++p)));
            break;
      default:
            strcat(errbuf, s);
            break;
      }
}

VOID *dlsym(void *handle, const char *symbol)
{
      register ModulePtr mp = (ModulePtr)handle;
      register ExportPtr ep;
      register int i;

      /*
       * Could speed up the search, but I assume that one assigns
       * the result to function pointers anyways.
       */
      for (ep = mp->exports, i = mp->nExports; i; i--, ep++)
            if (strcmp(ep->name, symbol) == 0)
                  return ep->addr;
      errvalid++;
      strcpy(errbuf, "dlsym: undefined symbol ");
      strcat(errbuf, symbol);
      return NULL;
}

char *dlerror(void)
{
      if (errvalid) {
            errvalid = 0;
            return errbuf;
      }
      return NULL;
}

int dlclose(void *handle)
{
      register ModulePtr mp = (ModulePtr)handle;
      int result;
      register ModulePtr mp1;

      if (--mp->refCnt > 0)
            return 0;
      if (mp->info && mp->info->fini)
            (*mp->info->fini)();
      if (mp->cdtors)
            while (mp->cdtors->term) {
                  (*mp->cdtors->term)();
                  mp->cdtors++;
            }
      result = unload(mp->entry);
      if (result == -1) {
            errvalid++;
            strcpy(errbuf, strerror(errno));
      }
      if (mp->exports) {
            register ExportPtr ep;
            register int i;
            for (ep = mp->exports, i = mp->nExports; i; i--, ep++)
                  if (ep->name)
                        free(ep->name);
            free(mp->exports);
      }
      if (mp == modList)
            modList = mp->next;
      else {
            for (mp1 = modList; mp1; mp1 = mp1->next)
                  if (mp1->next == mp) {
                        mp1->next = mp->next;
                        break;
                  }
      }
      free(mp->name);
      free(mp);
      return result;
}

static void terminate(void)
{
      while (modList)
            dlclose(modList);
}

/*
 * Build the export table from the XCOFF .loader section.
 */
static int readExports(ModulePtr mp)
{
      LDFILE *ldp = NULL;
      SCNHDR sh, shdata;
      LDHDR *lhp;
      char *ldbuf;
      LDSYM *ls;
      int i;
      ExportPtr ep;

      if ((ldp = ldopen(mp->name, ldp)) == NULL) {
            struct ld_info *lp;
            char *buf;
            int size = 4*1024;
            if (errno != ENOENT) {
                  errvalid++;
                  strcpy(errbuf, "readExports: ");
                  strcat(errbuf, strerror(errno));
                  return -1;
            }
            /*
             * The module might be loaded due to the LIBPATH
             * environment variable. Search for the loaded
             * module using L_GETINFO.
             */
            if ((buf = malloc(size)) == NULL) {
                  errvalid++;
                  strcpy(errbuf, "readExports: ");
                  strcat(errbuf, strerror(errno));
                  return -1;
            }
            while ((i = loadquery(L_GETINFO, buf, size)) == -1 && errno == ENOMEM) {
                  free(buf);
                  size += 4*1024;
                  if ((buf = malloc(size)) == NULL) {
                        errvalid++;
                        strcpy(errbuf, "readExports: ");
                        strcat(errbuf, strerror(errno));
                        return -1;
                  }
            }
            if (i == -1) {
                  errvalid++;
                  strcpy(errbuf, "readExports: ");
                  strcat(errbuf, strerror(errno));
                  free(buf);
                  return -1;
            }
            /*
             * Traverse the list of loaded modules. The entry point
             * returned by load() does actually point to the data
             * segment origin.
             */
            lp = (struct ld_info *)buf;
            while (lp) {
                  if (lp->ldinfo_dataorg == mp->entry) {
                        ldp = ldopen(lp->ldinfo_filename, ldp);
                        break;
                  }
                  if (lp->ldinfo_next == 0)
                        lp = NULL;
                  else
                        lp = (struct ld_info *)((char *)lp + lp->ldinfo_next);
            }
            free(buf);
            if (!ldp) {
                  errvalid++;
                  strcpy(errbuf, "readExports: ");
                  strcat(errbuf, strerror(errno));
                  return -1;
            }
      }
      if (TYPE(ldp) != U802TOCMAGIC) {
            errvalid++;
            strcpy(errbuf, "readExports: bad magic");
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      /*
       * Get the padding for the data section. This is needed for
       * AIX 4.1 compilers. This is used when building the final
       * function pointer to the exported symbol.
       */
      if (ldnshread(ldp, _DATA, &shdata) != SUCCESS) {
            errvalid++;
            strcpy(errbuf, "readExports: cannot read data section header");
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      if (ldnshread(ldp, _LOADER, &sh) != SUCCESS) {
            errvalid++;
            strcpy(errbuf, "readExports: cannot read loader section header");
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      /*
       * We read the complete loader section in one chunk, this makes
       * finding long symbol names residing in the string table easier.
       */
      if ((ldbuf = (char *)malloc(sh.s_size)) == NULL) {
            errvalid++;
            strcpy(errbuf, "readExports: ");
            strcat(errbuf, strerror(errno));
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      if (FSEEK(ldp, sh.s_scnptr, BEGINNING) != OKFSEEK) {
            errvalid++;
            strcpy(errbuf, "readExports: cannot seek to loader section");
            free(ldbuf);
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      if (FREAD(ldbuf, sh.s_size, 1, ldp) != 1) {
            errvalid++;
            strcpy(errbuf, "readExports: cannot read loader section");
            free(ldbuf);
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      lhp = (LDHDR *)ldbuf;
      ls = (LDSYM *)(ldbuf+LDHDRSZ);
      /*
       * Count the number of exports to include in our export table.
       */
      for (i = lhp->l_nsyms; i; i--, ls++) {
            if (!LDR_EXPORT(*ls))
                  continue;
            mp->nExports++;
      }
      if ((mp->exports = (ExportPtr)calloc(mp->nExports, sizeof(*mp->exports))) == NULL) {
            errvalid++;
            strcpy(errbuf, "readExports: ");
            strcat(errbuf, strerror(errno));
            free(ldbuf);
            while(ldclose(ldp) == FAILURE)
                  ;
            return -1;
      }
      /*
       * Fill in the export table. All entries are relative to
       * the entry point we got from load.
       */
      ep = mp->exports;
      ls = (LDSYM *)(ldbuf+LDHDRSZ);
      for (i = lhp->l_nsyms; i; i--, ls++) {
            char *symname;
            char tmpsym[SYMNMLEN+1];
            if (!LDR_EXPORT(*ls))
                  continue;
            if (ls->l_zeroes == 0)
                  symname = ls->l_offset+lhp->l_stoff+ldbuf;
            else {
                  /*
                   * The l_name member is not zero terminated, we
                   * must copy the first SYMNMLEN chars and make
                   * sure we have a zero byte at the end.
                   */
                  strncpy(tmpsym, ls->l_name, SYMNMLEN);
                  tmpsym[SYMNMLEN] = '\0';
                  symname = tmpsym;
            }
            ep->name = malloc((unsigned) (strlen(symname) + 1));
            strcpy(ep->name, symname);
            ep->addr = (void *)((unsigned long)mp->entry +
                              ls->l_value - shdata.s_vaddr);
            ep++;
      }
      free(ldbuf);
      while(ldclose(ldp) == FAILURE)
            ;
      return 0;
}

/*
 * Find the main modules entry point. This is used as export pointer
 * for loadbind() to be able to resolve references to the main part.
 */
static void * findMain(void)
{
      struct ld_info *lp;
      char *buf;
      int size = 4*1024;
      int i;
      void *ret;

      if ((buf = malloc(size)) == NULL) {
            errvalid++;
            strcpy(errbuf, "findMain: ");
            strcat(errbuf, strerror(errno));
            return NULL;
      }
      while ((i = loadquery(L_GETINFO, buf, size)) == -1 && errno == ENOMEM) {
            free(buf);
            size += 4*1024;
            if ((buf = malloc(size)) == NULL) {
                  errvalid++;
                  strcpy(errbuf, "findMain: ");
                  strcat(errbuf, strerror(errno));
                  return NULL;
            }
      }
      if (i == -1) {
            errvalid++;
            strcpy(errbuf, "findMain: ");
            strcat(errbuf, strerror(errno));
            free(buf);
            return NULL;
      }
      /*
       * The first entry is the main module. The entry point
       * returned by load() does actually point to the data
       * segment origin.
       */
      lp = (struct ld_info *)buf;
      ret = lp->ldinfo_dataorg;
      free(buf);
      return ret;
}


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