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Re: [PATCH][BZ 17251] Calculate RPATH $ORIGIN from absolute path


ping

On Mon, Nov 3, 2014 at 3:31 PM, Brennan Shacklett <bpshacklett@gmail.com> wrote:
> ping
>
> On Sun, Oct 26, 2014 at 12:43 PM, Brennan Shacklett
> <bpshacklett@gmail.com> wrote:
>> ping
>>
>> On Mon, Oct 6, 2014 at 9:18 AM, Brennan Shacklett <bpshacklett@gmail.com> wrote:
>>> ping
>>>
>>> On Wed, Oct 1, 2014 at 12:28 AM, Brennan Shacklett
>>> <bpshacklett@gmail.com> wrote:
>>>> ping
>>>>
>>>> On Tue, Sep 23, 2014 at 8:09 PM, Brennan Shacklett
>>>> <bpshacklett@gmail.com> wrote:
>>>>> On Tue, Aug 12, 2014 at 9:16 AM, Brennan Shacklett
>>>>> <bpshacklett@gmail.com> wrote:
>>>>>> Bug 17251 deals with (what I believe is) the incorrect calculation of $ORIGIN
>>>>>> for shared libraries. Currently $ORIGIN is calculated correctly for executables
>>>>>> on linux, because readlink is called on /proc/self/exe, which means the
>>>>>> resulting path is absolute and has no symlinks.
>>>>>> Shared libraries with relative paths on the other hand are based
>>>>>> off of appending the name / path of the library to the current working
>>>>>> directory, which means if the library is a symlink, it is not followed, which
>>>>>> breaks RPATH $ORIGIN in the following scenario:
>>>>>>
>>>>>> libone.so and libtwo.so are both in ~/lib
>>>>>> libone.so needs libtwo.so, so libone.so has an RPATH of $ORIGIN.
>>>>>> If I run ldd on ~/lib/libone.so, libtwo.so is found and all is good.
>>>>>> If I create a symlink named ~/libone.so to ~/lib/libone.so, and run ldd on it
>>>>>> libtwo is not found, because $ORIGIN for the library is calculated as ~
>>>>>> instead of ~/lib.
>>>>>>
>>>>>> If I was to repeat the above test but instead of libone.so use an executable,
>>>>>> everything would work as expected, which is why I think the shared library
>>>>>> behavior is a bug.
>>>>>>
>>>>>> I ran into this in the real world when attempting to dynamically load a .so
>>>>>> for python SWIG bindings, because the .so which python was loading was
>>>>>> symlinked to the actual library directory where all of the .so's dependencies
>>>>>> were located.
>>>>>>
>>>>>> The attached patch fixes this behavior by having realname evaluated with
>>>>>> __realpath in _dl_map_object_from_fd, before _dl_new_object is called (which is
>>>>>> where l_origin is assigned). This also somewhat simplifies the code in
>>>>>> elf/dl-object.c, because realname is guaranteed to be an absolute path
>>>>>> generated by realpath, so I was able to remove the code dealing with relative
>>>>>> paths.
>>>>>> I used the implementation of dl_realpath from sysdeps/tile/dl-runtime.c as the
>>>>>> generic implementation, and extended it with lstat and readlink in the linux
>>>>>> version. This means the bug is still present on other systems than linux (the
>>>>>> generic implementation only returns an absolute path, it doesn't do anything
>>>>>> with symlinks), but if there is a way to get the generic version to follow
>>>>>> symlinks on all systems please let me know.
>>>>>>
>>>>>> I tested and ran the elf test suite on Gentoo Linux x86-64. If this change is
>>>>>> wanted, I will happily write a test to go along with it.
>>>>>> I don't have any sort of copyright attribution set up with the FSF, let me know
>>>>>> if it is necessary for this change.
>>>>>>
>>>>>> Thanks,
>>>>>> Brennan Shacklett
>>>>>>
>>>>>> 2014-08-12  Brennan Shacklett  <bpshacklett@gmail.com>
>>>>>>
>>>>>>         [BZ #17251]
>>>>>>         * elf/Makefile (rtld-routines): Add dl-realpath.
>>>>>>         * elf/dl-load.c (_dl_map_object_from_fd):
>>>>>>         Calculate realname with __realpath.
>>>>>>         * elf/dl-object.c (_dl_new_object): Remove relative path handling.
>>>>>>         * elf/dl-realpath.c: New file. Generic implementation of __realpath.
>>>>>>         * elf/tile/dl-runtime.c (_dl_after_load): Remove dl_realpath and
>>>>>>         change call to __realpath.
>>>>>>         * sysdeps/unix/sysv/linux/Makefile (sysdep-rtld-routines):
>>>>>>         Add dl-lxstat64.
>>>>>>         * sysdeps/unix/sysv/linux/dl-lxstat64.c: New file.
>>>>>>         * sysdeps/unix/sysv/linux/dl-realpath.c: New file. Handle symlinks
>>>>>>         unlike generic implementation.
>>>>>> ---
>>>>>>  elf/Makefile                          |   3 +-
>>>>>>  elf/dl-load.c                         |  18 +++++
>>>>>>  elf/dl-object.c                       |  54 ++-------------
>>>>>>  elf/dl-realpath.c                     |  85 ++++++++++++++++++++++++
>>>>>>  sysdeps/tile/dl-runtime.c             |  66 +------------------
>>>>>>  sysdeps/unix/sysv/linux/Makefile      |   2 +-
>>>>>>  sysdeps/unix/sysv/linux/dl-lxstat64.c |   1 +
>>>>>>  sysdeps/unix/sysv/linux/dl-realpath.c | 121 ++++++++++++++++++++++++++++++++++
>>>>>>  8 files changed, 236 insertions(+), 114 deletions(-)
>>>>>>  create mode 100644 elf/dl-realpath.c
>>>>>>  create mode 100644 sysdeps/unix/sysv/linux/dl-lxstat64.c
>>>>>>  create mode 100644 sysdeps/unix/sysv/linux/dl-realpath.c
>>>>>>
>>>>>> diff --git a/elf/Makefile b/elf/Makefile
>>>>>> index 25012cc..c130f21 100644
>>>>>> --- a/elf/Makefile
>>>>>> +++ b/elf/Makefile
>>>>>> @@ -43,7 +43,8 @@ shared-only-routines += dl-caller
>>>>>>
>>>>>>  # ld.so uses those routines, plus some special stuff for being the program
>>>>>>  # interpreter and operating independent of libc.
>>>>>> -rtld-routines  := rtld $(dl-routines) dl-sysdep dl-environ dl-minimal
>>>>>> +rtld-routines  := rtld $(dl-routines) dl-sysdep dl-environ dl-minimal \
>>>>>> +                  dl-realpath
>>>>>>  all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines)
>>>>>>
>>>>>>  CFLAGS-dl-runtime.c = -fexceptions -fasynchronous-unwind-tables
>>>>>> diff --git a/elf/dl-load.c b/elf/dl-load.c
>>>>>> index 016a99c..7353837 100644
>>>>>> --- a/elf/dl-load.c
>>>>>> +++ b/elf/dl-load.c
>>>>>> @@ -891,6 +891,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
>>>>>>    int errval = 0;
>>>>>>    struct r_debug *r = _dl_debug_initialize (0, nsid);
>>>>>>    bool make_consistent = false;
>>>>>> +  char *absolutename = NULL;
>>>>>>
>>>>>>    /* Get file information.  */
>>>>>>    if (__glibc_unlikely (__fxstat64 (_STAT_VER, fd, &st) < 0))
>>>>>> @@ -902,6 +903,23 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
>>>>>>        lose (errval, fd, name, realname, l, errstring,
>>>>>>             make_consistent ? r : NULL, nsid);
>>>>>>      }
>>>>>> +  /* Find absolute pathname for object */
>>>>>> +  absolutename = (char *) malloc (PATH_MAX);
>>>>>> +  if (!absolutename)
>>>>>> +    {
>>>>>> +      errstring = N_("cannot allocate memory for absolute path");
>>>>>> +      goto call_lose_errno;
>>>>>> +    }
>>>>>> +
>>>>>> +  if (!__realpath (realname, absolutename))
>>>>>> +    {
>>>>>> +      free (absolutename);
>>>>>> +      errstring = N_("cannot find absolute path of shared object");
>>>>>> +      goto call_lose_errno;
>>>>>> +    }
>>>>>> +
>>>>>> +  free (realname);
>>>>>> +  realname = absolutename;
>>>>>>
>>>>>>    /* Look again to see if the real name matched another already loaded.  */
>>>>>>    for (l = GL(dl_ns)[nsid]._ns_loaded; l; l = l->l_next)
>>>>>> diff --git a/elf/dl-object.c b/elf/dl-object.c
>>>>>> index afd80a6..d93935b 100644
>>>>>> --- a/elf/dl-object.c
>>>>>> +++ b/elf/dl-object.c
>>>>>> @@ -158,55 +158,15 @@ _dl_new_object (char *realname, const char *libname, int type,
>>>>>>        char *origin;
>>>>>>        char *cp;
>>>>>>
>>>>>> -      if (realname[0] == '/')
>>>>>> +      /* It is an absolute path, calculated by realpath. Use it.
>>>>>> +       * But we have to make a copy since we strip out the trailing slash. */
>>>>>> +      assert (realname[0] == '/');
>>>>>> +      cp = origin = (char *) malloc (realname_len);
>>>>>> +      if (origin == NULL)
>>>>>>         {
>>>>>> -         /* It is an absolute path.  Use it.  But we have to make a
>>>>>> -            copy since we strip out the trailing slash.  */
>>>>>> -         cp = origin = (char *) malloc (realname_len);
>>>>>> -         if (origin == NULL)
>>>>>> -           {
>>>>>> -             origin = (char *) -1;
>>>>>> -             goto out;
>>>>>> -           }
>>>>>> +         origin = (char *) -1;
>>>>>> +         goto out;
>>>>>>         }
>>>>>> -      else
>>>>>> -       {
>>>>>> -         size_t len = realname_len;
>>>>>> -         char *result = NULL;
>>>>>> -
>>>>>> -         /* Get the current directory name.  */
>>>>>> -         origin = NULL;
>>>>>> -         do
>>>>>> -           {
>>>>>> -             char *new_origin;
>>>>>> -
>>>>>> -             len += 128;
>>>>>> -             new_origin = (char *) realloc (origin, len);
>>>>>> -             if (new_origin == NULL)
>>>>>> -               /* We exit the loop.  Note that result == NULL.  */
>>>>>> -               break;
>>>>>> -             origin = new_origin;
>>>>>> -           }
>>>>>> -         while ((result = __getcwd (origin, len - realname_len)) == NULL
>>>>>> -                && errno == ERANGE);
>>>>>> -
>>>>>> -         if (result == NULL)
>>>>>> -           {
>>>>>> -             /* We were not able to determine the current directory.
>>>>>> -                Note that free(origin) is OK if origin == NULL.  */
>>>>>> -             free (origin);
>>>>>> -             origin = (char *) -1;
>>>>>> -             goto out;
>>>>>> -           }
>>>>>> -
>>>>>> -         /* Find the end of the path and see whether we have to add a
>>>>>> -            slash.  We could use rawmemchr but this need not be
>>>>>> -            fast.  */
>>>>>> -         cp = (strchr) (origin, '\0');
>>>>>> -         if (cp[-1] != '/')
>>>>>> -           *cp++ = '/';
>>>>>> -       }
>>>>>> -
>>>>>>        /* Add the real file name.  */
>>>>>>        cp = __mempcpy (cp, realname, realname_len);
>>>>>>
>>>>>> diff --git a/elf/dl-realpath.c b/elf/dl-realpath.c
>>>>>> new file mode 100644
>>>>>> index 0000000..2549bb3
>>>>>> --- /dev/null
>>>>>> +++ b/elf/dl-realpath.c
>>>>>> @@ -0,0 +1,85 @@
>>>>>> +/* Dynamic loader version of realpath.
>>>>>> +   Copyright (C) 2014 Free Software Foundation, Inc.
>>>>>> +   This file is part of the GNU C Library.
>>>>>> +
>>>>>> +   The GNU C Library 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.
>>>>>> +
>>>>>> +   The GNU C Library 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 the GNU C Library; if not, see
>>>>>> +   <http://www.gnu.org/licenses/>.  */
>>>>>> +
>>>>>> +#include <stdlib.h>
>>>>>> +#include <unistd.h>
>>>>>> +#include <limits.h>
>>>>>> +#include <ldsodefs.h>
>>>>>> +
>>>>>> +/* Simplified implementation of realpath(): no dynamic memory use, no lstat(),
>>>>>> +   no set_errno(), no valid "rpath" on error, etc.  This simplifies cases
>>>>>> +   involving relative paths, specifically where $ORIGIN needs to be
>>>>>> +   calculated. For this relatively rare case, one could also imagine using
>>>>>> +   link_map.l_origin to avoid the getcwd() here, but the simpler code
>>>>>> +   here seems like a better solution.  */
>>>>>> +char * internal_function
>>>>>> +__realpath (const char *name, char *rpath)
>>>>>> +{
>>>>>> +  char *dest;
>>>>>> +  const char *start, *end;
>>>>>> +
>>>>>> +  if (name[0] != '/')
>>>>>> +    {
>>>>>> +      if (!__getcwd (rpath, PATH_MAX))
>>>>>> +       return NULL;
>>>>>> +      dest = __rawmemchr (rpath, '\0');
>>>>>> +    }
>>>>>> +  else
>>>>>> +    {
>>>>>> +      rpath[0] = '/';
>>>>>> +      dest = rpath + 1;
>>>>>> +    }
>>>>>> +
>>>>>> +  for (start = end = name; *start; start = end)
>>>>>> +    {
>>>>>> +      /* Skip sequence of multiple path-separators.  */
>>>>>> +      while (*start == '/')
>>>>>> +       ++start;
>>>>>> +
>>>>>> +      /* Find end of path component.  */
>>>>>> +      for (end = start; *end && *end != '/'; ++end)
>>>>>> +       /* Nothing.  */;
>>>>>> +
>>>>>> +      if (end - start == 0)
>>>>>> +       break;
>>>>>> +      else if (end - start == 1 && start[0] == '.')
>>>>>> +       /* nothing */;
>>>>>> +      else if (end - start == 2 && start[0] == '.' && start[1] == '.')
>>>>>> +       {
>>>>>> +         /* Back up to previous component, ignore if at root already.  */
>>>>>> +         if (dest > rpath + 1)
>>>>>> +           while ((--dest)[-1] != '/');
>>>>>> +       }
>>>>>> +      else
>>>>>> +       {
>>>>>> +         if (dest[-1] != '/')
>>>>>> +           *dest++ = '/';
>>>>>> +
>>>>>> +         if (dest + (end - start) >= rpath + PATH_MAX)
>>>>>> +           return NULL;
>>>>>> +
>>>>>> +         dest = __mempcpy (dest, start, end - start);
>>>>>> +         *dest = '\0';
>>>>>> +       }
>>>>>> +    }
>>>>>> +  if (dest > rpath + 1 && dest[-1] == '/')
>>>>>> +    --dest;
>>>>>> +  *dest = '\0';
>>>>>> +
>>>>>> +  return rpath;
>>>>>> +}
>>>>>> diff --git a/sysdeps/tile/dl-runtime.c b/sysdeps/tile/dl-runtime.c
>>>>>> index bcc00bc..45251d0 100644
>>>>>> --- a/sysdeps/tile/dl-runtime.c
>>>>>> +++ b/sysdeps/tile/dl-runtime.c
>>>>>> @@ -29,70 +29,6 @@
>>>>>>  #include <arch/sim.h>
>>>>>>  #include <dl-unmap-segments.h>
>>>>>>
>>>>>> -/* Like realpath(), but simplified: no dynamic memory use, no lstat(),
>>>>>> -   no set_errno(), no valid "rpath" on error, etc.  This handles some
>>>>>> -   simple cases where the simulator might not have a valid entry for
>>>>>> -   a loaded Elf object, in particular dlopen() with a relative path.
>>>>>> -   For this relatively rare case, one could also imagine using
>>>>>> -   link_map.l_origin to avoid the getcwd() here, but the simpler code
>>>>>> -   here seems like a better solution.  */
>>>>>> -static char *
>>>>>> -dl_realpath (const char *name, char *rpath)
>>>>>> -{
>>>>>> -  char *dest;
>>>>>> -  const char *start, *end;
>>>>>> -
>>>>>> -  if (name[0] != '/')
>>>>>> -    {
>>>>>> -      if (!__getcwd (rpath, PATH_MAX))
>>>>>> -        return NULL;
>>>>>> -      dest = __rawmemchr (rpath, '\0');
>>>>>> -    }
>>>>>> -  else
>>>>>> -    {
>>>>>> -      rpath[0] = '/';
>>>>>> -      dest = rpath + 1;
>>>>>> -    }
>>>>>> -
>>>>>> -  for (start = end = name; *start; start = end)
>>>>>> -    {
>>>>>> -      /* Skip sequence of multiple path-separators.  */
>>>>>> -      while (*start == '/')
>>>>>> -       ++start;
>>>>>> -
>>>>>> -      /* Find end of path component.  */
>>>>>> -      for (end = start; *end && *end != '/'; ++end)
>>>>>> -       /* Nothing.  */;
>>>>>> -
>>>>>> -      if (end - start == 0)
>>>>>> -       break;
>>>>>> -      else if (end - start == 1 && start[0] == '.')
>>>>>> -       /* nothing */;
>>>>>> -      else if (end - start == 2 && start[0] == '.' && start[1] == '.')
>>>>>> -       {
>>>>>> -         /* Back up to previous component, ignore if at root already.  */
>>>>>> -         if (dest > rpath + 1)
>>>>>> -           while ((--dest)[-1] != '/');
>>>>>> -       }
>>>>>> -      else
>>>>>> -       {
>>>>>> -         if (dest[-1] != '/')
>>>>>> -           *dest++ = '/';
>>>>>> -
>>>>>> -         if (dest + (end - start) >= rpath + PATH_MAX)
>>>>>> -            return NULL;
>>>>>> -
>>>>>> -         dest = __mempcpy (dest, start, end - start);
>>>>>> -         *dest = '\0';
>>>>>> -       }
>>>>>> -    }
>>>>>> -  if (dest > rpath + 1 && dest[-1] == '/')
>>>>>> -    --dest;
>>>>>> -  *dest = '\0';
>>>>>> -
>>>>>> -  return rpath;
>>>>>> -}
>>>>>> -
>>>>>>  /* Support notifying the simulator about new objects.  */
>>>>>>  void internal_function
>>>>>>  _dl_after_load (struct link_map *l)
>>>>>> @@ -117,7 +53,7 @@ _dl_after_load (struct link_map *l)
>>>>>>    DLPUTC (':');
>>>>>>
>>>>>>    /* Write the library path, including the terminating '\0'.  */
>>>>>> -  path = dl_realpath (l->l_name, pathbuf) ?: l->l_name;
>>>>>> +  path = __realpath (l->l_name, pathbuf) ?: l->l_name;
>>>>>>    for (size_t i = 0;; i++)
>>>>>>      {
>>>>>>        DLPUTC (path[i]);
>>>>>> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
>>>>>> index 9ad6d22..4525429 100644
>>>>>> --- a/sysdeps/unix/sysv/linux/Makefile
>>>>>> +++ b/sysdeps/unix/sysv/linux/Makefile
>>>>>> @@ -176,7 +176,7 @@ endif
>>>>>>
>>>>>>  ifeq ($(subdir),elf)
>>>>>>  sysdep-rtld-routines += dl-brk dl-sbrk dl-getcwd dl-openat64 dl-opendir \
>>>>>> -                       dl-fxstatat64
>>>>>> +                       dl-fxstatat64 dl-lxstat64
>>>>>>
>>>>>>  CPPFLAGS-lddlibc4 += -DNOT_IN_libc
>>>>>>
>>>>>> diff --git a/sysdeps/unix/sysv/linux/dl-lxstat64.c b/sysdeps/unix/sysv/linux/dl-lxstat64.c
>>>>>> new file mode 100644
>>>>>> index 0000000..63e6800
>>>>>> --- /dev/null
>>>>>> +++ b/sysdeps/unix/sysv/linux/dl-lxstat64.c
>>>>>> @@ -0,0 +1 @@
>>>>>> +#include <lxstat64.c>
>>>>>> diff --git a/sysdeps/unix/sysv/linux/dl-realpath.c b/sysdeps/unix/sysv/linux/dl-realpath.c
>>>>>> new file mode 100644
>>>>>> index 0000000..91652dc
>>>>>> --- /dev/null
>>>>>> +++ b/sysdeps/unix/sysv/linux/dl-realpath.c
>>>>>> @@ -0,0 +1,121 @@
>>>>>> +/* Dynamic loader version of realpath for linux.
>>>>>> +   Copyright (C) 2014 Free Software Foundation, Inc.
>>>>>> +   This file is part of the GNU C Library.
>>>>>> +
>>>>>> +   The GNU C Library 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.
>>>>>> +
>>>>>> +   The GNU C Library 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 the GNU C Library; if not, see
>>>>>> +   <http://www.gnu.org/licenses/>.  */
>>>>>> +
>>>>>> +#include <stdlib.h>
>>>>>> +#include <unistd.h>
>>>>>> +#include <limits.h>
>>>>>> +#include <ldsodefs.h>
>>>>>> +#include <sys/stat.h>
>>>>>> +#include <kernel-features.h>
>>>>>> +#include <sysdep.h>
>>>>>> +
>>>>>> +/* Simplified version of realpath which extends elf/dl-realpath.c to use
>>>>>> + * linux syscalls for handling symlinks */
>>>>>> +char * internal_function
>>>>>> +__realpath (const char *name, char *rpath)
>>>>>> +{
>>>>>> +  char *dest;
>>>>>> +  char extra_buf[PATH_MAX];
>>>>>> +  const char *start, *end;
>>>>>> +  int num_links = 0;
>>>>>> +
>>>>>> +  if (name[0] != '/')
>>>>>> +    {
>>>>>> +      if (!__getcwd (rpath, PATH_MAX))
>>>>>> +       return NULL;
>>>>>> +      dest = __rawmemchr (rpath, '\0');
>>>>>> +    }
>>>>>> +  else
>>>>>> +    {
>>>>>> +      rpath[0] = '/';
>>>>>> +      dest = rpath + 1;
>>>>>> +    }
>>>>>> +
>>>>>> +  for (start = end = name; *start; start = end)
>>>>>> +    {
>>>>>> +      struct stat64 st;
>>>>>> +      int n;
>>>>>> +      /* Skip sequence of multiple path-separators.  */
>>>>>> +      while (*start == '/')
>>>>>> +       ++start;
>>>>>> +
>>>>>> +      /* Find end of path component.  */
>>>>>> +      for (end = start; *end && *end != '/'; ++end)
>>>>>> +       /* Nothing.  */;
>>>>>> +
>>>>>> +      if (end - start == 0)
>>>>>> +       break;
>>>>>> +      else if (end - start == 1 && start[0] == '.')
>>>>>> +       /* nothing */;
>>>>>> +      else if (end - start == 2 && start[0] == '.' && start[1] == '.')
>>>>>> +       {
>>>>>> +         /* Back up to previous component, ignore if at root already.  */
>>>>>> +         if (dest > rpath + 1)
>>>>>> +           while ((--dest)[-1] != '/');
>>>>>> +       }
>>>>>> +      else
>>>>>> +       {
>>>>>> +         if (dest[-1] != '/')
>>>>>> +           *dest++ = '/';
>>>>>> +
>>>>>> +         if (dest + (end - start) >= rpath + PATH_MAX)
>>>>>> +           return NULL;
>>>>>> +
>>>>>> +         dest = __mempcpy (dest, start, end - start);
>>>>>> +         *dest = '\0';
>>>>>> +         if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
>>>>>> +           return NULL;
>>>>>> +
>>>>>> +         if (S_ISLNK (st.st_mode))
>>>>>> +           {
>>>>>> +             char buf[PATH_MAX];
>>>>>> +             size_t len;
>>>>>> +
>>>>>> +             INTERNAL_SYSCALL_DECL (err);
>>>>>> +
>>>>>> +             n = INTERNAL_SYSCALL (readlink, err, 3, rpath, buf,
>>>>>> +                                   PATH_MAX - 1);
>>>>>> +
>>>>>> +             if (n <= 0 || buf[0] == '[')
>>>>>> +               return NULL;
>>>>>> +             buf[n] = '\0';
>>>>>> +
>>>>>> +             len = strlen (end);
>>>>>> +             if ((long int) (n + len) >= PATH_MAX)
>>>>>> +               return NULL;
>>>>>> +
>>>>>> +             /* Careful here, end may be a pointer into extra_buf... */
>>>>>> +             memmove (&extra_buf[n], end, len + 1);
>>>>>> +             name = end = memcpy (extra_buf, buf, n);
>>>>>> +
>>>>>> +             if (buf[0] == '/')
>>>>>> +               dest = rpath + 1;     /* Absolute symlink */
>>>>>> +             else
>>>>>> +               /* Back up to previous component, ignore if at root already: */
>>>>>> +               if (dest > rpath + 1)
>>>>>> +                 while ((--dest)[-1] != '/');
>>>>>> +           }
>>>>>> +       }
>>>>>> +    }
>>>>>> +  if (dest > rpath + 1 && dest[-1] == '/')
>>>>>> +    --dest;
>>>>>> +  *dest = '\0';
>>>>>> +
>>>>>> +  return rpath;
>>>>>> +
>>>>>> +}
>>>>>> --
>>>>>> 2.0.4
>>>>>>
>>>>>
>>>>> ping.


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