install.texi: Build was tested with binutils 2.41 (just released)

[thirdparty/glibc.git] / elf / ldconfig.c

/* Copyright (C) 1999-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published
   by the Free Software Foundation; version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, see <https://www.gnu.org/licenses/>.  */

#define PROCINFO_CLASS static
#include <assert.h>
#include <alloca.h>
#include <argp.h>
#include <dirent.h>
#include <elf.h>
#include <error.h>
#include <errno.h>
#include <inttypes.h>
#include <libintl.h>
#include <locale.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <sys/fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <glob.h>
#include <libgen.h>

#include <ldconfig.h>
#include <dl-cache.h>
#include <dl-hwcaps.h>
#include <dl-is_dso.h>

#include <dl-procinfo.h>

#ifndef LD_SO_CONF
# define LD_SO_CONF SYSCONFDIR "/ld.so.conf"
#endif

/* Get libc version number.  */
#include <version.h>

#define PACKAGE _libc_intl_domainname

/* List of directories to handle.  */
struct dir_entry
{
  char *path;
  int flag;
  ino64_t ino;
  dev_t dev;
  const char *from_file;
  int from_line;

  /* Non-NULL for subdirectories under a glibc-hwcaps subdirectory.  */
  struct glibc_hwcaps_subdirectory *hwcaps;

  struct dir_entry *next;
};

/* The list is unsorted, contains no duplicates.  Entries are added at
   the end.  */
static struct dir_entry *dir_entries;

/* Flags for different options.  */
/* Print Cache.  */
static int opt_print_cache;

/* Be verbose.  */
int opt_verbose;

/* Format to support.  */
enum opt_format opt_format = opt_format_new;

/* Build cache.  */
static int opt_build_cache = 1;

/* Enable symbolic link processing.  If set, create or update symbolic
   links, and remove stale symbolic links.  */
static int opt_link = 1;

/* Only process directories specified on the command line.  */
static int opt_only_cline;

/* Path to root for chroot.  */
static char *opt_chroot;

/* Manually link given shared libraries.  */
static int opt_manual_link;

/* Should we ignore an old auxiliary cache file?  */
static int opt_ignore_aux_cache;

/* Cache file to use.  */
static char *cache_file;

/* Configuration file.  */
static const char *config_file;

/* Name and version of program.  */
static void print_version (FILE *stream, struct argp_state *state);
void (*argp_program_version_hook) (FILE *, struct argp_state *)
     = print_version;

/* Function to print some extra text in the help message.  */
static char *more_help (int key, const char *text, void *input);

/* Definitions of arguments for argp functions.  */
static const struct argp_option options[] =
{
  { "print-cache", 'p', NULL, 0, N_("Print cache"), 0},
  { "verbose", 'v', NULL, 0, N_("Generate verbose messages"), 0},
  { NULL, 'N', NULL, 0, N_("Don't build cache"), 0},
  { NULL, 'X', NULL, 0, N_("Don't update symbolic links"), 0},
  { NULL, 'r', N_("ROOT"), 0, N_("Change to and use ROOT as root directory"), 0},
  { NULL, 'C', N_("CACHE"), 0, N_("Use CACHE as cache file"), 0},
  { NULL, 'f', N_("CONF"), 0, N_("Use CONF as configuration file"), 0},
  { NULL, 'n', NULL, 0, N_("Only process directories specified on the command line.  Don't build cache."), 0},
  { NULL, 'l', NULL, 0, N_("Manually link individual libraries."), 0},
  { "format", 'c', N_("FORMAT"), 0, N_("Format to use: new (default), old, or compat"), 0},
  { "ignore-aux-cache", 'i', NULL, 0, N_("Ignore auxiliary cache file"), 0},
  { NULL, 0, NULL, 0, NULL, 0 }
};

#define PROCINFO_CLASS static
#include <dl-procinfo.c>

/* Short description of program.  */
static const char doc[] = N_("Configure Dynamic Linker Run Time Bindings.");

/* Prototype for option handler.  */
static error_t parse_opt (int key, char *arg, struct argp_state *state);

/* Data structure to communicate with argp functions.  */
static struct argp argp =
{
  options, parse_opt, NULL, doc, NULL, more_help, NULL
};

/* Handle program arguments.  */
static error_t
parse_opt (int key, char *arg, struct argp_state *state)
{
  switch (key)
    {
    case 'C':
      cache_file = arg;
      /* Ignore auxiliary cache since we use non-standard cache.  */
      opt_ignore_aux_cache = 1;
      break;
    case 'f':
      config_file = arg;
      break;
    case 'i':
      opt_ignore_aux_cache = 1;
      break;
    case 'l':
      opt_manual_link = 1;
      break;
    case 'N':
      opt_build_cache = 0;
      break;
    case 'n':
      opt_build_cache = 0;
      opt_only_cline = 1;
      break;
    case 'p':
      opt_print_cache = 1;
      break;
    case 'r':
      opt_chroot = arg;
      break;
    case 'v':
      opt_verbose = 1;
      break;
    case 'X':
      opt_link = 0;
      break;
    case 'c':
      if (strcmp (arg, "old") == 0)
        opt_format = opt_format_old;
      else if (strcmp (arg, "compat") == 0)
        opt_format = opt_format_compat;
      else if (strcmp (arg, "new") == 0)
        opt_format = opt_format_new;
      break;
    default:
      return ARGP_ERR_UNKNOWN;
    }

  return 0;
}

/* Print bug-reporting information in the help message.  */
static char *
more_help (int key, const char *text, void *input)
{
  char *tp = NULL;
  switch (key)
    {
    case ARGP_KEY_HELP_EXTRA:
      /* We print some extra information.  */
      if (asprintf (&tp, gettext ("\
For bug reporting instructions, please see:\n\
%s.\n"), REPORT_BUGS_TO) < 0)
        return NULL;
      return tp;
    default:
      break;
    }
  return (char *) text;
}

/* Print the version information.  */
static void
print_version (FILE *stream, struct argp_state *state)
{
  fprintf (stream, "ldconfig %s%s\n", PKGVERSION, VERSION);
  fprintf (stream, gettext ("\
Copyright (C) %s Free Software Foundation, Inc.\n\
This is free software; see the source for copying conditions.  There is NO\n\
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n\
"), "2023");
  fprintf (stream, gettext ("Written by %s.\n"),
           "Andreas Jaeger");
}

/* Allocate a new subdirectory with full path PATH under ENTRY, using
   inode data from *ST.  */
static struct dir_entry *
new_sub_entry (const struct dir_entry *entry, const char *path,
               const struct stat *st)
{
  struct dir_entry *new_entry = xmalloc (sizeof (struct dir_entry));
  new_entry->from_file = entry->from_file;
  new_entry->from_line = entry->from_line;
  new_entry->path = xstrdup (path);
  new_entry->flag = entry->flag;
  new_entry->hwcaps = NULL;
  new_entry->next = NULL;
  new_entry->ino = st->st_ino;
  new_entry->dev = st->st_dev;
  return new_entry;
}

/* Add a single directory entry.  Return true if the directory is
   actually added (because it is not a duplicate).  */
static bool
add_single_dir (struct dir_entry *entry, int verbose)
{
  struct dir_entry *ptr, *prev;
  bool added = true;

  ptr = dir_entries;
  prev = ptr;
  while (ptr != NULL)
    {
      /* Check for duplicates.  */
      if (ptr->ino == entry->ino && ptr->dev == entry->dev)
        {
          if (opt_verbose && verbose)
            {
              error (0, 0, _("Path `%s' given more than once"), entry->path);
              fprintf (stderr, _("(from %s:%d and %s:%d)\n"),
                       entry->from_file, entry->from_line,
                       ptr->from_file, ptr->from_line);
            }
          /* Use the newer information.  */
          ptr->flag = entry->flag;
          free (entry->path);
          free (entry);
          added = false;
          break;
        }
      prev = ptr;
      ptr = ptr->next;
    }
  /* Is this the first entry?  */
  if (ptr == NULL && dir_entries == NULL)
    dir_entries = entry;
  else if (ptr == NULL)
    prev->next = entry;
  return added;
}

/* Check if PATH contains a "glibc-hwcaps" subdirectory.  If so, queue
   its subdirectories for glibc-hwcaps processing.  */
static void
add_glibc_hwcaps_subdirectories (struct dir_entry *entry, const char *path)
{
  /* glibc-hwcaps subdirectories do not nest.  */
  assert (entry->hwcaps == NULL);

  char *glibc_hwcaps;
  if (asprintf (&glibc_hwcaps, "%s/" GLIBC_HWCAPS_SUBDIRECTORY, path) < 0)
    error (EXIT_FAILURE, errno, _("Could not form glibc-hwcaps path"));

  DIR *dir = opendir (glibc_hwcaps);
  if (dir != NULL)
    {
      while (true)
        {
          errno = 0;
          struct dirent64 *e = readdir64 (dir);
          if (e == NULL)
            {
              if (errno == 0)
                break;
              else
                error (EXIT_FAILURE, errno, _("Listing directory %s"), path);
            }

          /* Ignore hidden subdirectories, including "." and "..", and
             regular files.  File names containing a ':' cannot be
             looked up by the dynamic loader, so skip those as
             well.  */
          if (e->d_name[0] == '.' || e->d_type == DT_REG
              || strchr (e->d_name, ':') != NULL)
            continue;

          /* See if this entry eventually resolves to a directory.  */
          struct stat st;
          if (fstatat (dirfd (dir), e->d_name, &st, 0) < 0)
            /* Ignore unreadable entries.  */
            continue;

          if (S_ISDIR (st.st_mode))
            {
              /* This is a directory, so it needs to be scanned for
                 libraries, associated with the hwcaps implied by the
                 subdirectory name.  */
              char *new_path;
              if (asprintf (&new_path, "%s/" GLIBC_HWCAPS_SUBDIRECTORY "/%s",
                            /* Use non-canonicalized path here.  */
                            entry->path, e->d_name) < 0)
                error (EXIT_FAILURE, errno,
                       _("Could not form glibc-hwcaps path"));
              struct dir_entry *new_entry = new_sub_entry (entry, new_path,
                                                           &st);
              free (new_path);
              new_entry->hwcaps = new_glibc_hwcaps_subdirectory (e->d_name);
              add_single_dir (new_entry, 0);
            }
        }

      closedir (dir);
    }

  free (glibc_hwcaps);
}

/* Add one directory to the list of directories to process.  */
static void
add_dir_1 (const char *line, const char *from_file, int from_line)
{
  unsigned int i;
  struct dir_entry *entry = xmalloc (sizeof (struct dir_entry));
  entry->hwcaps = NULL;
  entry->next = NULL;

  entry->from_file = strdup (from_file);
  entry->from_line = from_line;

  entry->path = xstrdup (line);
  entry->flag = FLAG_ELF_LIBC6;

  /* Canonify path: for now only remove leading and trailing
     whitespace and the trailing slashes.  */
  i = strlen (entry->path);

  while (i > 0 && isspace (entry->path[i - 1]))
    entry->path[--i] = '\0';

  while (i > 0 && entry->path[i - 1] == '/')
    entry->path[--i] = '\0';

  if (i == 0)
    {
      free (entry->path);
      free (entry);
      return;
    }

  char *path = entry->path;
  if (opt_chroot != NULL)
    path = chroot_canon (opt_chroot, path);

  struct stat stat_buf;
  if (path == NULL || stat (path, &stat_buf))
    {
      if (opt_verbose)
        error (0, errno, _("Can't stat %s"), entry->path);
      free (entry->path);
      free (entry);
    }
  else
    {
      entry->ino = stat_buf.st_ino;
      entry->dev = stat_buf.st_dev;

      if (add_single_dir (entry, 1))
        /* Add glibc-hwcaps subdirectories if present.  */
        add_glibc_hwcaps_subdirectories (entry, path);
    }

  if (opt_chroot != NULL)
    free (path);
}

static void
add_dir (const char *line)
{
  add_dir_1 (line, "<builtin>", 0);
}

static int
chroot_stat (const char *real_path, const char *path, struct stat *st)
{
  int ret;
  char *canon_path;

  if (!opt_chroot)
    return stat (real_path, st);

  ret = lstat (real_path, st);
  if (ret || !S_ISLNK (st->st_mode))
    return ret;

  canon_path = chroot_canon (opt_chroot, path);
  if (canon_path == NULL)
    return -1;

  ret = stat (canon_path, st);
  free (canon_path);
  return ret;
}

/* Create a symbolic link from soname to libname in directory path.  */
static void
create_links (const char *real_path, const char *path, const char *libname,
              const char *soname)
{
  char *full_libname, *full_soname;
  char *real_full_libname, *real_full_soname;
  struct stat stat_lib, stat_so, lstat_so;
  int do_link = 1;
  int do_remove = 1;
  /* XXX: The logics in this function should be simplified.  */

  /* Get complete path.  */
  full_libname = alloca (strlen (path) + strlen (libname) + 2);
  full_soname = alloca (strlen (path) + strlen (soname) + 2);
  sprintf (full_libname, "%s/%s", path, libname);
  sprintf (full_soname, "%s/%s", path, soname);
  if (opt_chroot != NULL)
    {
      real_full_libname = alloca (strlen (real_path) + strlen (libname) + 2);
      real_full_soname = alloca (strlen (real_path) + strlen (soname) + 2);
      sprintf (real_full_libname, "%s/%s", real_path, libname);
      sprintf (real_full_soname, "%s/%s", real_path, soname);
    }
  else
    {
      real_full_libname = full_libname;
      real_full_soname = full_soname;
    }

  /* Does soname already exist and point to the right library?  */
  if (chroot_stat (real_full_soname, full_soname, &stat_so) == 0)
    {
      if (chroot_stat (real_full_libname, full_libname, &stat_lib))
        {
          error (0, 0, _("Can't stat %s\n"), full_libname);
          return;
        }
      if (stat_lib.st_dev == stat_so.st_dev
          && stat_lib.st_ino == stat_so.st_ino)
        /* Link is already correct.  */
        do_link = 0;
      else if (lstat (full_soname, &lstat_so) == 0
               && !S_ISLNK (lstat_so.st_mode))
        {
          error (0, 0, _("%s is not a symbolic link\n"), full_soname);
          do_link = 0;
          do_remove = 0;
        }
    }
  else if (lstat (real_full_soname, &lstat_so) != 0
           || !S_ISLNK (lstat_so.st_mode))
    /* Unless it is a stale symlink, there is no need to remove.  */
    do_remove = 0;

  if (opt_verbose)
    printf ("\t%s -> %s", soname, libname);

  if (do_link && opt_link)
    {
      /* Remove old link.  */
      if (do_remove)
        if (unlink (real_full_soname))
          {
            error (0, 0, _("Can't unlink %s"), full_soname);
            do_link = 0;
          }
      /* Create symbolic link.  */
      if (do_link && symlink (libname, real_full_soname))
        {
          error (0, 0, _("Can't link %s to %s"), full_soname, libname);
          do_link = 0;
        }
      if (opt_verbose)
        {
          if (do_link)
            fputs (_(" (changed)\n"), stdout);
          else
            fputs (_(" (SKIPPED)\n"), stdout);
        }
    }
  else if (opt_verbose)
    fputs ("\n", stdout);
}

/* Manually link the given library.  */
static void
manual_link (char *library)
{
  char *path;
  char *real_path;
  char *real_library;
  char *libname;
  char *soname;
  struct stat stat_buf;
  int flag;
  unsigned int isa_level;

  /* Prepare arguments for create_links call.  Split library name in
     directory and filename first.  Since path is allocated, we've got
     to be careful to free at the end.  */
  path = xstrdup (library);
  libname = strrchr (path, '/');

  if (libname)
    {
      /* Successfully split names.  Check if path is just "/" to avoid
         an empty path.  */
      if (libname == path)
        {
          libname = library + 1;
          path = xrealloc (path, 2);
          strcpy (path, "/");
        }
      else
        {
          *libname = '\0';
          ++libname;
        }
    }
  else
    {
      /* There's no path, construct one. */
      libname = library;
      path = xrealloc (path, 2);
      strcpy (path, ".");
    }

  if (opt_chroot != NULL)
    {
      real_path = chroot_canon (opt_chroot, path);
      if (real_path == NULL)
        {
          error (0, errno, _("Can't find %s"), path);
          free (path);
          return;
        }
      real_library = alloca (strlen (real_path) + strlen (libname) + 2);
      sprintf (real_library, "%s/%s", real_path, libname);
    }
  else
    {
      real_path = path;
      real_library = library;
    }

  /* Do some sanity checks first.  */
  if (lstat (real_library, &stat_buf))
    {
      error (0, errno, _("Cannot lstat %s"), library);
      goto out;
    }
  /* We don't want links here!  */
  else if (!S_ISREG (stat_buf.st_mode))
    {
      error (0, 0, _("Ignored file %s since it is not a regular file."),
             library);
      goto out;
    }

  if (process_file (real_library, library, libname, &flag, &isa_level, &soname,
                    0, &stat_buf))
    {
      error (0, 0, _("No link created since soname could not be found for %s"),
             library);
      goto out;
    }
  if (soname == NULL)
    soname = xstrdup (libname);
  create_links (real_path, path, libname, soname);
  free (soname);
out:
  if (path != real_path)
    free (real_path);
  free (path);
}


/* Read a whole directory and search for libraries.
   The purpose is two-fold:
   - search for libraries which will be added to the cache
   - create symbolic links to the soname for each library

   This has to be done separately for each directory.

   To keep track of which libraries to add to the cache and which
   links to create, we save a list of all libraries.

   The algorithm is basically:
   for all libraries in the directory do
     get soname of library
     if soname is already in list
       if new library is newer, replace entry
       otherwise ignore this library
     otherwise add library to list

   For example, if the two libraries libxy.so.1.1 and libxy.so.1.2
   exist and both have the same soname, e.g. libxy.so, a symbolic link
   is created from libxy.so.1.2 (the newer one) to libxy.so.
   libxy.so.1.2 and libxy.so are added to the cache - but not
   libxy.so.1.1.  */

/* Information for one library.  */
struct dlib_entry
{
  char *name;
  char *soname;
  int flag;
  int is_link;
  unsigned int isa_level;
  struct dlib_entry *next;
};


static void
search_dir (const struct dir_entry *entry)
{
  if (opt_verbose)
    {
      if (entry->hwcaps == NULL)
        printf ("%s:", entry->path);
      else
        printf ("%s: (hwcap: \"%s\")", entry->path,
                glibc_hwcaps_subdirectory_name (entry->hwcaps));
      printf (_(" (from %s:%d)\n"), entry->from_file, entry->from_line);
    }

  char *dir_name;
  char *real_file_name;
  char *file_name;
  if (opt_chroot != NULL)
    dir_name = chroot_canon (opt_chroot, entry->path);
  else
    dir_name = entry->path;

  DIR *dir;
  if (dir_name == NULL || (dir = opendir (dir_name)) == NULL)
    {
      if (opt_verbose)
        error (0, errno, _("Can't open directory %s"), entry->path);
      if (opt_chroot != NULL)
        free (dir_name);
      return;
    }

  struct dirent64 *direntry;
  struct dlib_entry *dlibs = NULL;
  while ((direntry = readdir64 (dir)) != NULL)
    {
      int flag;
      /* We only look at links and regular files.  */
      if (direntry->d_type != DT_UNKNOWN
          && direntry->d_type != DT_LNK
          && direntry->d_type != DT_REG
          && direntry->d_type != DT_DIR)
        continue;
      /* Does this file look like a shared library?  The dynamic linker
         is also considered as shared library.  */
      if (!_dl_is_dso (direntry->d_name)
          && (direntry->d_type == DT_REG || entry->hwcaps == NULL))
        continue;

      size_t len = strlen (direntry->d_name);
      /* Skip temporary files created by the prelink program.  Files with
         names like these are never really DSOs we want to look at.  */
      if (len >= sizeof (".#prelink#") - 1)
        {
          if (strcmp (direntry->d_name + len - sizeof (".#prelink#") + 1,
                      ".#prelink#") == 0)
            continue;
          if (len >= sizeof (".#prelink#.XXXXXX") - 1
              && memcmp (direntry->d_name + len - sizeof (".#prelink#.XXXXXX")
                         + 1, ".#prelink#.", sizeof (".#prelink#.") - 1) == 0)
            continue;
        }
      if (asprintf (&file_name, "%s/%s", entry->path, direntry->d_name) < 0)
        error (EXIT_FAILURE, errno, _("Could not form library path"));
      if (opt_chroot != NULL)
        {
          if (asprintf (&real_file_name, "%s/%s",
                        dir_name, direntry->d_name) < 0)
            error (EXIT_FAILURE, errno, _("Could not form library path"));
        }
      else
        real_file_name = xstrdup (file_name);

      struct stat lstat_buf;
      /* We optimize and try to do the lstat call only if needed.  */
      if (direntry->d_type != DT_UNKNOWN)
        lstat_buf.st_mode = DTTOIF (direntry->d_type);
      else
        if (__glibc_unlikely (lstat (real_file_name, &lstat_buf)))
          {
            error (0, errno, _("Cannot lstat %s"), file_name);
            goto next;
          }

      struct stat stat_buf;
      int is_link = S_ISLNK (lstat_buf.st_mode);
      if (is_link)
        {
          /* In case of symlink, we check if the symlink refers to
             a directory. */
          char *target_name = real_file_name;
          if (opt_chroot != NULL)
            {
              target_name = chroot_canon (opt_chroot, file_name);
              if (target_name == NULL)
                {
                  if (strstr (file_name, ".so") == NULL)
                    error (0, 0, _("Input file %s not found.\n"), file_name);
                  goto next;
                }
            }
          if (__glibc_unlikely (stat (target_name, &stat_buf)))
            {
              if (opt_verbose)
                error (0, errno, _("Cannot stat %s"), file_name);

              /* Remove stale symlinks.  */
              if (opt_link && strstr (direntry->d_name, ".so."))
                unlink (real_file_name);

              if (opt_chroot != NULL)
                free (target_name);

              goto next;
            }

          if (opt_chroot != NULL)
            free (target_name);

          /* lstat_buf is later stored, update contents.  */
          lstat_buf.st_dev = stat_buf.st_dev;
          lstat_buf.st_ino = stat_buf.st_ino;
          lstat_buf.st_size = stat_buf.st_size;
          lstat_buf.st_ctime = stat_buf.st_ctime;
        }
      else if (!S_ISREG (lstat_buf.st_mode))
        goto next;

      char *real_name;
      if (opt_chroot != NULL && is_link)
        {
          real_name = chroot_canon (opt_chroot, file_name);
          if (real_name == NULL)
            {
              if (strstr (file_name, ".so") == NULL)
                error (0, 0, _("Input file %s not found.\n"), file_name);
              goto next;
            }
        }
      else
        real_name = real_file_name;

      /* Call lstat if not done yet.  */
      if (!is_link
          && direntry->d_type != DT_UNKNOWN
          && __builtin_expect (lstat (real_file_name, &lstat_buf), 0))
        {
          error (0, errno, _("Cannot lstat %s"), file_name);
          goto next;
        }

      /* First search whether the auxiliary cache contains this
         library already and it's not changed.  */
      char *soname;
      unsigned int isa_level;
      if (!search_aux_cache (&lstat_buf, &flag, &isa_level, &soname))
        {
          if (process_file (real_name, file_name, direntry->d_name, &flag,
                            &isa_level, &soname, is_link, &lstat_buf))
            {
              if (real_name != real_file_name)
                free (real_name);
              goto next;
            }
          else if (opt_build_cache)
            add_to_aux_cache (&lstat_buf, flag, isa_level, soname);
        }

      if (soname == NULL)
        soname = xstrdup (direntry->d_name);

      /* A link may just point to itself.  */
      if (is_link)
        {
          /* If the path the link points to isn't its soname or it is not
             the .so symlink for ld(1), we treat it as a normal file.

             You should always do this:

                libfoo.so -> SONAME -> Arbitrary package-chosen name.

             e.g. libfoo.so -> libfoo.so.1 -> libfooimp.so.9.99.
             Given a SONAME of libfoo.so.1.

             You should *never* do this:

                libfoo.so -> libfooimp.so.9.99

             If you do, and your SONAME is libfoo.so.1, then libfoo.so
             fails to point at the SONAME. In that case ldconfig may consider
             libfoo.so as another implementation of SONAME and will create
             symlinks against it causing problems when you try to upgrade
             or downgrade. The problems will arise because ldconfig will,
             depending on directory ordering, creat symlinks against libfoo.so
             e.g. libfoo.so.1.2 -> libfoo.so, but when libfoo.so is removed
             (typically by the removal of a development package not required
             for the runtime) it will break the libfoo.so.1.2 symlink and the
             application will fail to start.  */
          const char *real_base_name = basename (real_file_name);

          if (strcmp (real_base_name, soname) != 0)
            {
              len = strlen (real_base_name);
              if (len < strlen (".so")
                  || strcmp (real_base_name + len - strlen (".so"), ".so") != 0
                  || strncmp (real_base_name, soname, len) != 0)
                is_link = 0;
            }
        }

      if (real_name != real_file_name)
        free (real_name);

      if (is_link)
        {
          free (soname);
          soname = xstrdup (direntry->d_name);
        }

      /* Some sanity checks to print warnings.  */
      if (opt_verbose)
        {
          if (flag == FLAG_ELF_LIBC6 && entry->flag != FLAG_ELF_LIBC6)
            error (0, 0, _("libc6 library %s in wrong directory"), file_name);
        }

      /* Add library to list.  */
      struct dlib_entry *dlib_ptr;
      for (dlib_ptr = dlibs; dlib_ptr != NULL; dlib_ptr = dlib_ptr->next)
        {
          /* Is soname already in list?  */
          if (strcmp (dlib_ptr->soname, soname) == 0)
            {
              /* Prefer a file to a link, otherwise check which one
                 is newer.  */
              if ((!is_link && dlib_ptr->is_link)
                  || (is_link == dlib_ptr->is_link
                      && _dl_cache_libcmp (dlib_ptr->name, direntry->d_name) < 0))
                {
                  /* It's newer - add it.  */
                  /* Flag should be the same - sanity check.  */
                  if (dlib_ptr->flag != flag)
                    error (0, 0, _("libraries %s and %s in directory %s have same soname but different type."),
                           dlib_ptr->name, direntry->d_name, entry->path);
                  free (dlib_ptr->name);
                  dlib_ptr->name = xstrdup (direntry->d_name);
                  dlib_ptr->is_link = is_link;
                  dlib_ptr->isa_level = isa_level;
                }
              /* Don't add this library, abort loop.  */
              /* Also free soname, since it's dynamically allocated.  */
              free (soname);
              break;
            }
        }
      /* Add the library if it's not already in.  */
      if (dlib_ptr == NULL)
        {
          dlib_ptr = (struct dlib_entry *)xmalloc (sizeof (struct dlib_entry));
          dlib_ptr->name = xstrdup (direntry->d_name);
          dlib_ptr->soname = soname;
          dlib_ptr->flag = flag;
          dlib_ptr->is_link = is_link;
          dlib_ptr->isa_level = isa_level;
          /* Add at head of list.  */
          dlib_ptr->next = dlibs;
          dlibs = dlib_ptr;
        }

    next:
      free (file_name);
      free (real_file_name);
    }

  closedir (dir);

  /* Now dlibs contains a list of all libs - add those to the cache
     and created all symbolic links.  */
  struct dlib_entry *dlib_ptr;
  for (dlib_ptr = dlibs; dlib_ptr != NULL; dlib_ptr = dlib_ptr->next)
    {
      /* The cached file name is the soname for non-glibc-hwcaps
         subdirectories (relying on symbolic links; this helps with
         library updates that change the file name), and the actual
         file for glibc-hwcaps subdirectories.  */
      const char *filename;
      if (entry->hwcaps == NULL)
        {
          /* Don't create links to links.  */
          if (dlib_ptr->is_link == 0)
            create_links (dir_name, entry->path, dlib_ptr->name,
                          dlib_ptr->soname);
          filename = dlib_ptr->soname;
        }
      else
        {
          /* Do not create links in glibc-hwcaps subdirectories, but
             still log the cache addition.  */
          if (opt_verbose)
            printf ("\t%s -> %s\n", dlib_ptr->soname, dlib_ptr->name);
          filename = dlib_ptr->name;
        }
      if (opt_build_cache)
        add_to_cache (entry->path, filename, dlib_ptr->soname,
                      dlib_ptr->flag, dlib_ptr->isa_level, entry->hwcaps);
    }

  /* Free all resources.  */
  while (dlibs)
    {
      dlib_ptr = dlibs;
      free (dlib_ptr->soname);
      free (dlib_ptr->name);
      dlibs = dlibs->next;
      free (dlib_ptr);
    }

  if (opt_chroot != NULL && dir_name != NULL)
    free (dir_name);
}

/* Search through all libraries.  */
static void
search_dirs (void)
{
  struct dir_entry *entry;

  for (entry = dir_entries; entry != NULL; entry = entry->next)
    search_dir (entry);

  /* Free all allocated memory.  */
  while (dir_entries)
    {
      entry = dir_entries;
      dir_entries = dir_entries->next;
      free (entry->path);
      free (entry);
    }
}


static void parse_conf_include (const char *config_file, unsigned int lineno,
                                bool do_chroot, const char *pattern);

/* Parse configuration file.  */
static void
parse_conf (const char *filename, bool do_chroot)
{
  FILE *file = NULL;
  char *line = NULL;
  const char *canon;
  size_t len = 0;
  unsigned int lineno;

  if (do_chroot && opt_chroot)
    {
      canon = chroot_canon (opt_chroot, filename);
      if (canon)
        file = fopen (canon, "r");
      else
        canon = filename;
    }
  else
    {
      canon = filename;
      file = fopen (filename, "r");
    }

  if (file == NULL)
    {
      if (errno != ENOENT)
        error (0, errno, _("\
Warning: ignoring configuration file that cannot be opened: %s"),
               canon);
      if (canon != filename)
        free ((char *) canon);
      return;
    }

  /* No threads use this stream.  */
  __fsetlocking (file, FSETLOCKING_BYCALLER);

  if (canon != filename)
    free ((char *) canon);

  lineno = 0;
  do
    {
      ssize_t n = getline (&line, &len, file);
      if (n < 0)
        break;

      ++lineno;
      if (line[n - 1] == '\n')
        line[n - 1] = '\0';

      /* Because the file format does not know any form of quoting we
         can search forward for the next '#' character and if found
         make it terminating the line.  */
      *strchrnul (line, '#') = '\0';

      /* Remove leading whitespace.  NUL is no whitespace character.  */
      char *cp = line;
      while (isspace (*cp))
        ++cp;

      /* If the line is blank it is ignored.  */
      if (cp[0] == '\0')
        continue;

      if (!strncmp (cp, "include", 7) && isblank (cp[7]))
        {
          char *dir;
          cp += 8;
          while ((dir = strsep (&cp, " \t")) != NULL)
            if (dir[0] != '\0')
              parse_conf_include (filename, lineno, do_chroot, dir);
        }
      else if (!strncasecmp (cp, "hwcap", 5) && isblank (cp[5]))
        error (0, 0, _("%s:%u: hwcap directive ignored"), filename, lineno);
      else
        add_dir_1 (cp, filename, lineno);
    }
  while (!feof_unlocked (file));

  /* Free buffer and close file.  */
  free (line);
  fclose (file);
}

/* Handle one word in an `include' line, a glob pattern of additional
   config files to read.  */
static void
parse_conf_include (const char *config_file, unsigned int lineno,
                    bool do_chroot, const char *pattern)
{
  if (opt_chroot != NULL && pattern[0] != '/')
    error (EXIT_FAILURE, 0,
           _("need absolute file name for configuration file when using -r"));

  char *copy = NULL;
  if (pattern[0] != '/' && strchr (config_file, '/') != NULL)
    {
      if (asprintf (&copy, "%s/%s", dirname (strdupa (config_file)),
                    pattern) < 0)
        error (EXIT_FAILURE, 0, _("memory exhausted"));
      pattern = copy;
    }

  glob64_t gl;
  int result;
  if (do_chroot && opt_chroot)
    {
      char *canon = chroot_canon (opt_chroot, pattern);
      if (canon == NULL)
        return;
      result = glob64 (canon, 0, NULL, &gl);
      free (canon);
    }
  else
    result = glob64 (pattern, 0, NULL, &gl);

  switch (result)
    {
    case 0:
      for (size_t i = 0; i < gl.gl_pathc; ++i)
        parse_conf (gl.gl_pathv[i], false);
      globfree64 (&gl);
      break;

    case GLOB_NOMATCH:
      break;

    case GLOB_NOSPACE:
      errno = ENOMEM;
      /* Fall through.  */
    case GLOB_ABORTED:
      if (opt_verbose)
        error (0, errno, _("%s:%u: cannot read directory %s"),
               config_file, lineno, pattern);
      break;

    default:
      abort ();
      break;
    }

  free (copy);
}


int
main (int argc, char **argv)
{
  /* Set locale via LC_ALL.  */
  setlocale (LC_ALL, "");

  /* But keep the C collation.  That way `include' directives using
     globbing patterns are processed in a locale-independent order.  */
  setlocale (LC_COLLATE, "C");

  /* Set the text message domain.  */
  textdomain (_libc_intl_domainname);

  /* Parse and process arguments.  */
  int remaining;
  argp_parse (&argp, argc, argv, 0, &remaining, NULL);

  /* Remaining arguments are additional directories if opt_manual_link
     is not set.  */
  if (remaining != argc && !opt_manual_link)
    {
      int i;
      for (i = remaining; i < argc; ++i)
        if (opt_build_cache && argv[i][0] != '/')
          error (EXIT_FAILURE, 0,
                 _("relative path `%s' used to build cache"),
                 argv[i]);
        else
          add_dir_1 (argv[i], "<cmdline>", 0);
    }

  if (opt_chroot != NULL)
    {
      /* Normalize the path a bit, we might need it for printing later.  */
      char *endp = strchr (opt_chroot, '\0');
      while (endp > opt_chroot && endp[-1] == '/')
        --endp;
      *endp = '\0';
      if (endp == opt_chroot)
        opt_chroot = NULL;

      if (opt_chroot != NULL)
        {
          /* It is faster to use chroot if we can.  */
          if (!chroot (opt_chroot))
            {
              if (chdir ("/"))
                error (EXIT_FAILURE, errno, _("Can't chdir to /"));
              opt_chroot = NULL;
            }
        }
    }

  if (cache_file == NULL)
    {
      cache_file = alloca (strlen (LD_SO_CACHE) + 1);
      strcpy (cache_file, LD_SO_CACHE);
    }

  if (config_file == NULL)
    config_file = LD_SO_CONF;

  if (opt_print_cache)
    {
      if (opt_chroot != NULL)
        {
          char *p = chroot_canon (opt_chroot, cache_file);
          if (p == NULL)
            error (EXIT_FAILURE, errno, _("Can't open cache file %s\n"),
                   cache_file);
          cache_file = p;
        }
      print_cache (cache_file);
      if (opt_chroot != NULL)
        free (cache_file);
      exit (0);
    }

  if (opt_chroot != NULL)
    {
      /* Canonicalize the directory name of cache_file, not cache_file,
         because we'll rename a temporary cache file to it.  */
      char *p = strrchr (cache_file, '/');
      char *canon = chroot_canon (opt_chroot,
                                  p ? (*p = '\0', cache_file) : "/");

      if (canon == NULL)
        error (EXIT_FAILURE, errno,
               _("Can't open cache file directory %s\n"),
               p ? cache_file : "/");

      if (p)
        ++p;
      else
        p = cache_file;

      cache_file = alloca (strlen (canon) + strlen (p) + 2);
      sprintf (cache_file, "%s/%s", canon, p);
      free (canon);
    }

  if (opt_manual_link)
    {
      /* Link all given libraries manually.  */
      int i;

      for (i = remaining; i < argc; ++i)
        manual_link (argv[i]);

      exit (0);
    }


  if (opt_build_cache)
    init_cache ();

  if (!opt_only_cline)
    {
      parse_conf (config_file, true);

      /* Always add the standard search paths.  */
      add_system_dir (SLIBDIR);
      if (strcmp (SLIBDIR, LIBDIR))
        add_system_dir (LIBDIR);
    }

  const char *aux_cache_file = _PATH_LDCONFIG_AUX_CACHE;
  if (opt_chroot != NULL)
    aux_cache_file = chroot_canon (opt_chroot, aux_cache_file);

  if (! opt_ignore_aux_cache && aux_cache_file)
    load_aux_cache (aux_cache_file);
  else
    init_aux_cache ();

  search_dirs ();

  if (opt_build_cache)
    {
      save_cache (cache_file);
      if (aux_cache_file)
        save_aux_cache (aux_cache_file);
    }

  return 0;
}