path: root/lib/relocatable.c

/* Provide relocatable packages.
   Copyright (C) 2003-2006, 2008-2024 Free Software Foundation, Inc.
   Written by Bruno Haible <bruno@clisp.org>, 2003.

   This file is free software: you can redistribute it and/or modify
   it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   This file 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 Lesser General Public License for more details.

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


/* Tell glibc's <stdio.h> to provide a prototype for getline().
   This must come before <config.h> because <config.h> may include
   <features.h>, and once <features.h> has been included, it's too late.  */
#ifndef _GNU_SOURCE
# define _GNU_SOURCE 1
#endif

#define _GL_USE_STDLIB_ALLOC 1
#include <config.h>

/* Specification.  */
#include "relocatable.h"

#if ENABLE_RELOCATABLE

#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef NO_XMALLOC
# define xmalloc malloc
#else
# include "xalloc.h"
#endif

#if defined _WIN32 && !defined __CYGWIN__
# define WIN32_LEAN_AND_MEAN
# include <windows.h>
#endif

#ifdef __EMX__
# define INCL_DOS
# include <os2.h>

# define strcmp  stricmp
# define strncmp strnicmp
#endif

#if DEPENDS_ON_LIBCHARSET
# include <libcharset.h>
#endif
#if DEPENDS_ON_LIBICONV && HAVE_ICONV
# include <iconv.h>
#endif
#if DEPENDS_ON_LIBINTL && ENABLE_NLS
# include <libintl.h>
#endif

#if defined _WIN32 && !defined __CYGWIN__
/* Don't assume that UNICODE is not defined.  */
# undef GetModuleFileName
# define GetModuleFileName GetModuleFileNameA
#endif

/* Faked cheap 'bool'.  */
#undef bool
#undef false
#undef true
#define bool int
#define false 0
#define true 1

/* Pathname support.
   ISSLASH(C)                tests whether C is a directory separator character.
   IS_FILE_NAME_WITH_DIR(P)  tests whether P contains a directory specification.
 */
#if (defined _WIN32 && !defined __CYGWIN__) || defined __EMX__ || defined __DJGPP__
  /* Native Windows, OS/2, DOS */
# define ISSLASH(C) ((C) == '/' || (C) == '\\')
# define HAS_DEVICE(P) \
    ((((P)[0] >= 'A' && (P)[0] <= 'Z') || ((P)[0] >= 'a' && (P)[0] <= 'z')) \
     && (P)[1] == ':')
# define IS_FILE_NAME_WITH_DIR(P) \
    (strchr (P, '/') != NULL || strchr (P, '\\') != NULL || HAS_DEVICE (P))
# define FILE_SYSTEM_PREFIX_LEN(P) (HAS_DEVICE (P) ? 2 : 0)
#else
  /* Unix */
# define ISSLASH(C) ((C) == '/')
# define IS_FILE_NAME_WITH_DIR(P) (strchr (P, '/') != NULL)
# define FILE_SYSTEM_PREFIX_LEN(P) 0
#endif

/* Whether to enable the more costly support for relocatable libraries.
   It allows libraries to be have been installed with a different original
   prefix than the program.  But it is quite costly, especially on Cygwin
   platforms, see below.  Therefore we enable it by default only on native
   Windows platforms.  */
#ifndef ENABLE_COSTLY_RELOCATABLE
# if defined _WIN32 && !defined __CYGWIN__
#  define ENABLE_COSTLY_RELOCATABLE 1
# else
#  define ENABLE_COSTLY_RELOCATABLE 0
# endif
#endif

/* Original installation prefix.  */
static char *orig_prefix;
static size_t orig_prefix_len;
/* Current installation prefix.  */
static char *curr_prefix;
static size_t curr_prefix_len;
/* These prefixes do not end in a slash.  Anything that will be concatenated
   to them must start with a slash.  */

/* Sets the original and the current installation prefix of this module.
   Relocation simply replaces a pathname starting with the original prefix
   by the corresponding pathname with the current prefix instead.  Both
   prefixes should be directory names without trailing slash (i.e. use ""
   instead of "/").  */
static void
set_this_relocation_prefix (const char *orig_prefix_arg,
                            const char *curr_prefix_arg)
{
  if (orig_prefix_arg != NULL && curr_prefix_arg != NULL
      /* Optimization: if orig_prefix and curr_prefix are equal, the
         relocation is a nop.  */
      && strcmp (orig_prefix_arg, curr_prefix_arg) != 0)
    {
      /* Duplicate the argument strings.  */
      char *memory;

      orig_prefix_len = strlen (orig_prefix_arg);
      curr_prefix_len = strlen (curr_prefix_arg);
      memory = (char *) xmalloc (orig_prefix_len + 1 + curr_prefix_len + 1);
#ifdef NO_XMALLOC
      if (memory != NULL)
#endif
        {
          memcpy (memory, orig_prefix_arg, orig_prefix_len + 1);
          orig_prefix = memory;
          memory += orig_prefix_len + 1;
          memcpy (memory, curr_prefix_arg, curr_prefix_len + 1);
          curr_prefix = memory;
          return;
        }
    }
  orig_prefix = NULL;
  curr_prefix = NULL;
  /* Don't worry about wasted memory here - this function is usually only
     called once.  */
}

/* Sets the original and the current installation prefix of the package.
   Relocation simply replaces a pathname starting with the original prefix
   by the corresponding pathname with the current prefix instead.  Both
   prefixes should be directory names without trailing slash (i.e. use ""
   instead of "/").  */
void
set_relocation_prefix (const char *orig_prefix_arg, const char *curr_prefix_arg)
{
  set_this_relocation_prefix (orig_prefix_arg, curr_prefix_arg);

  /* Now notify all dependent libraries.  */
#if DEPENDS_ON_LIBCHARSET
  libcharset_set_relocation_prefix (orig_prefix_arg, curr_prefix_arg);
#endif
#if DEPENDS_ON_LIBICONV && HAVE_ICONV && _LIBICONV_VERSION >= 0x0109
  libiconv_set_relocation_prefix (orig_prefix_arg, curr_prefix_arg);
#endif
#if DEPENDS_ON_LIBINTL && ENABLE_NLS && defined libintl_set_relocation_prefix
  libintl_set_relocation_prefix (orig_prefix_arg, curr_prefix_arg);
#endif
}

#if !defined IN_LIBRARY || (defined PIC && defined INSTALLDIR && ENABLE_COSTLY_RELOCATABLE)

/* Convenience function:
   Computes the current installation prefix, based on the original
   installation prefix, the original installation directory of a particular
   file, and the current pathname of this file.
   Returns it, freshly allocated.  Returns NULL upon failure.  */
#ifdef IN_LIBRARY
#define compute_curr_prefix local_compute_curr_prefix
static
#endif
char *
compute_curr_prefix (const char *orig_installprefix,
                     const char *orig_installdir,
                     const char *curr_pathname)
{
  char *curr_installdir;
  const char *rel_installdir;

  if (curr_pathname == NULL)
    return NULL;

  /* Determine the relative installation directory, relative to the prefix.
     This is simply the difference between orig_installprefix and
     orig_installdir.  */
  if (strncmp (orig_installprefix, orig_installdir, strlen (orig_installprefix))
      != 0)
    /* Shouldn't happen - nothing should be installed outside $(prefix).  */
    return NULL;
  rel_installdir = orig_installdir + strlen (orig_installprefix);

  /* Determine the current installation directory.  */
  {
    const char *p_base = curr_pathname + FILE_SYSTEM_PREFIX_LEN (curr_pathname);
    const char *p = curr_pathname + strlen (curr_pathname);
    char *q;

    while (p > p_base)
      {
        p--;
        if (ISSLASH (*p))
          break;
      }

    q = (char *) xmalloc (p - curr_pathname + 1);
#ifdef NO_XMALLOC
    if (q == NULL)
      return NULL;
#endif
    memcpy (q, curr_pathname, p - curr_pathname);
    q[p - curr_pathname] = '\0';
    curr_installdir = q;
  }

  /* Compute the current installation prefix by removing the trailing
     rel_installdir from it.  */
  {
    const char *rp = rel_installdir + strlen (rel_installdir);
    const char *cp = curr_installdir + strlen (curr_installdir);
    const char *cp_base =
      curr_installdir + FILE_SYSTEM_PREFIX_LEN (curr_installdir);

    while (rp > rel_installdir && cp > cp_base)
      {
        bool same = false;
        const char *rpi = rp;
        const char *cpi = cp;

        while (rpi > rel_installdir && cpi > cp_base)
          {
            rpi--;
            cpi--;
            if (ISSLASH (*rpi) || ISSLASH (*cpi))
              {
                if (ISSLASH (*rpi) && ISSLASH (*cpi))
                  same = true;
                break;
              }
            /* Do case-insensitive comparison if the file system is always or
               often case-insensitive.  It's better to accept the comparison
               if the difference is only in case, rather than to fail.  */
#if defined _WIN32 || defined __CYGWIN__ || defined __EMX__ || defined __DJGPP__
            /* Native Windows, Cygwin, OS/2, DOS - case insignificant file system */
            if ((*rpi >= 'a' && *rpi <= 'z' ? *rpi - 'a' + 'A' : *rpi)
                != (*cpi >= 'a' && *cpi <= 'z' ? *cpi - 'a' + 'A' : *cpi))
              break;
#else
            if (*rpi != *cpi)
              break;
#endif
          }
        if (!same)
          break;
        /* The last pathname component was the same.  rpi and cpi now point
           to the slash before it.  */
        rp = rpi;
        cp = cpi;
      }

    if (rp > rel_installdir)
      {
        /* Unexpected: The curr_installdir does not end with rel_installdir.  */
        free (curr_installdir);
        return NULL;
      }

    {
      size_t computed_curr_prefix_len = cp - curr_installdir;
      char *computed_curr_prefix;

      computed_curr_prefix = (char *) xmalloc (computed_curr_prefix_len + 1);
#ifdef NO_XMALLOC
      if (computed_curr_prefix == NULL)
        {
          free (curr_installdir);
          return NULL;
        }
#endif
      memcpy (computed_curr_prefix, curr_installdir, computed_curr_prefix_len);
      computed_curr_prefix[computed_curr_prefix_len] = '\0';

      free (curr_installdir);

      return computed_curr_prefix;
    }
  }
}

#endif /* !IN_LIBRARY || PIC */

#if defined PIC && defined INSTALLDIR && ENABLE_COSTLY_RELOCATABLE

/* Full pathname of shared library, or NULL.  */
static char *shared_library_fullname;

#if defined _WIN32 && !defined __CYGWIN__
/* Native Windows only.
   On Cygwin, it is better to use the Cygwin provided /proc interface, than
   to use native Windows API and cygwin_conv_to_posix_path, because it
   supports longer file names
   (see <https://cygwin.com/ml/cygwin/2011-01/msg00410.html>).  */

/* Determine the full pathname of the shared library when it is loaded.

   Documentation:
   <https://docs.microsoft.com/en-us/windows/win32/dlls/dllmain>  */

BOOL WINAPI
DllMain (HINSTANCE module_handle, DWORD event, LPVOID reserved)
{
  (void) reserved;

  if (event == DLL_PROCESS_ATTACH)
    {
      /* The DLL is being loaded into an application's address range.  */
      static char location[MAX_PATH];

      if (!GetModuleFileName (module_handle, location, sizeof (location)))
        /* Shouldn't happen.  */
        return FALSE;

      if (!IS_FILE_NAME_WITH_DIR (location))
        /* Shouldn't happen.  */
        return FALSE;

      /* Avoid a memory leak when the same DLL get attached, detached,
         attached, detached, and so on.  This happens e.g. when a spell
         checker DLL is used repeatedly by a mail program.  */
      if (!(shared_library_fullname != NULL
            && strcmp (shared_library_fullname, location) == 0))
        /* Remember the full pathname of the shared library.  */
        shared_library_fullname = strdup (location);
    }

  return TRUE;
}

#elif defined __EMX__

extern int  _CRT_init (void);
extern void _CRT_term (void);
extern void __ctordtorInit (void);
extern void __ctordtorTerm (void);

unsigned long _System
_DLL_InitTerm (unsigned long hModule, unsigned long ulFlag)
{
  static char location[CCHMAXPATH];

  switch (ulFlag)
    {
      case 0:
        if (_CRT_init () == -1)
          return 0;

        __ctordtorInit();

        /* See http://cyberkinetica.homeunix.net/os2tk45/cp1/1247_L2H_DosQueryModuleNameSy.html
           for specification of DosQueryModuleName(). */
        if (DosQueryModuleName (hModule, sizeof (location), location))
          return 0;

        _fnslashify (location);
        shared_library_fullname = strdup (location);
        break;

      case 1:
        __ctordtorTerm();

        _CRT_term ();
        break;
    }

  return 1;
}

#else /* Unix */

static void
find_shared_library_fullname ()
{
#if (defined __linux__ && (__GLIBC__ >= 2 || defined __UCLIBC__)) || defined __CYGWIN__
  /* Linux has /proc/self/maps. glibc 2 and uClibc have the getline()
     function.
     Cygwin >= 1.5 has /proc/self/maps and the getline() function too.
     But it is costly: ca. 0.3 ms on Linux, 3 ms on Cygwin 1.5, and 5 ms on
     Cygwin 1.7.  */
  FILE *fp;

  /* Open the current process' maps file.  It describes one VMA per line.  */
  fp = fopen ("/proc/self/maps", "r");
  if (fp)
    {
      unsigned long address = (unsigned long) &find_shared_library_fullname;
      for (;;)
        {
          unsigned long start, end;
          int c;

          if (fscanf (fp, "%lx-%lx", &start, &end) != 2)
            break;
          if (address >= start && address <= end - 1)
            {
              /* Found it.  Now see if this line contains a filename.  */
              while (c = getc (fp), c != EOF && c != '\n' && c != '/')
                continue;
              if (c == '/')
                {
                  size_t size;
                  int len;

                  ungetc (c, fp);
                  shared_library_fullname = NULL; size = 0;
                  len = getline (&shared_library_fullname, &size, fp);
                  if (len >= 0)
                    {
                      /* Success: filled shared_library_fullname.  */
                      if (len > 0 && shared_library_fullname[len - 1] == '\n')
                        shared_library_fullname[len - 1] = '\0';
                    }
                }
              break;
            }
          while (c = getc (fp), c != EOF && c != '\n')
            continue;
        }
      fclose (fp);
    }
#endif
}

#endif /* Native Windows / EMX / Unix */

/* Return the full pathname of the current shared library.
   Return NULL if unknown.
   Guaranteed to work only on Linux, EMX, Cygwin, and native Windows.  */
static char *
get_shared_library_fullname ()
{
#if !(defined _WIN32 && !defined __CYGWIN__) && !defined __EMX__
  static bool tried_find_shared_library_fullname;
  if (!tried_find_shared_library_fullname)
    {
      find_shared_library_fullname ();
      tried_find_shared_library_fullname = true;
    }
#endif
  return shared_library_fullname;
}

#endif /* PIC */

/* Returns the pathname, relocated according to the current installation
   directory.
   The returned string is either PATHNAME unmodified or a freshly allocated
   string that you can free with free() after casting it to 'char *'.  */
const char *
relocate (const char *pathname)
{
#if defined PIC && defined INSTALLDIR && ENABLE_COSTLY_RELOCATABLE
  static int initialized;

  /* Initialization code for a shared library.  */
  if (!initialized)
    {
      /* At this point, orig_prefix and curr_prefix likely have already been
         set through the main program's set_program_name_and_installdir
         function.  This is sufficient in the case that the library has
         initially been installed in the same orig_prefix.  But we can do
         better, to also cover the cases that 1. it has been installed
         in a different prefix before being moved to orig_prefix and (later)
         to curr_prefix, 2. unlike the program, it has not moved away from
         orig_prefix.  */
      const char *orig_installprefix = INSTALLPREFIX;
      const char *orig_installdir = INSTALLDIR;
      char *curr_prefix_better;

      curr_prefix_better =
        compute_curr_prefix (orig_installprefix, orig_installdir,
                             get_shared_library_fullname ());

      set_relocation_prefix (orig_installprefix,
                             curr_prefix_better != NULL
                             ? curr_prefix_better
                             : curr_prefix);

      if (curr_prefix_better != NULL)
        free (curr_prefix_better);

      initialized = 1;
    }
#endif

  /* Note: It is not necessary to perform case insensitive comparison here,
     even for DOS-like file systems, because the pathname argument was
     typically created from the same Makefile variable as orig_prefix came
     from.  */
  if (orig_prefix != NULL && curr_prefix != NULL
      && strncmp (pathname, orig_prefix, orig_prefix_len) == 0)
    {
      if (pathname[orig_prefix_len] == '\0')
        {
          /* pathname equals orig_prefix.  */
          char *result = (char *) xmalloc (strlen (curr_prefix) + 1);

#ifdef NO_XMALLOC
          if (result != NULL)
#endif
            {
              strcpy (result, curr_prefix);
              return result;
            }
        }
      else if (ISSLASH (pathname[orig_prefix_len]))
        {
          /* pathname starts with orig_prefix.  */
          const char *pathname_tail = &pathname[orig_prefix_len];
          char *result =
            (char *) xmalloc (curr_prefix_len + strlen (pathname_tail) + 1);

#ifdef NO_XMALLOC
          if (result != NULL)
#endif
            {
              memcpy (result, curr_prefix, curr_prefix_len);
              strcpy (result + curr_prefix_len, pathname_tail);
              return result;
            }
        }
    }

#ifdef __EMX__
# ifdef __KLIBC__
#  undef strncmp

  if (strncmp (pathname, "/@unixroot", 10) == 0
      && (pathname[10] == '\0' || ISSLASH (pathname[10])))
    {
      /* kLIBC itself processes /@unixroot prefix */
      return pathname;
    }
  else
# endif
  if (ISSLASH (pathname[0]))
    {
      const char *unixroot = getenv ("UNIXROOT");

      if (unixroot && HAS_DEVICE (unixroot) && unixroot[2] == '\0')
        {
          char *result = (char *) xmalloc (2 + strlen (pathname) + 1);
#ifdef NO_XMALLOC
          if (result != NULL)
#endif
            {
              memcpy (result, unixroot, 2);
              strcpy (result + 2, pathname);
              return result;
            }
        }
    }
#endif

  /* Nothing to relocate.  */
  return pathname;
}

/* Returns the pathname, relocated according to the current installation
   directory.
   This function sets *ALLOCATEDP to the allocated memory, or to NULL if
   no memory allocation occurs.  So that, after you're done with the return
   value, to reclaim allocated memory, you can do: free (*ALLOCATEDP).  */
const char *
relocate2 (const char *pathname, char **allocatedp)
{
  const char *result = relocate (pathname);
  *allocatedp = (result != pathname ? (char *) result : NULL);
  return result;
}

#endif