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Re: [PATCH][BZ 17251] Calculate RPATH $ORIGIN from absolute path
- From: Brennan Shacklett <bpshacklett at gmail dot com>
- To: libc-alpha at sourceware dot org
- Date: Mon, 3 Nov 2014 15:31:21 -0800
- Subject: Re: [PATCH][BZ 17251] Calculate RPATH $ORIGIN from absolute path
- Authentication-results: sourceware.org; auth=none
- References: <1407860209-21797-1-git-send-email-bpshacklett at gmail dot com> <CAL8Wma9QBp9o7p2iipTUHDb38pNJxzopq8WHrgrU+pQTsqT1Ug at mail dot gmail dot com> <CAL8Wma-GKCeT=3qFdQC3Db_PVZZD2TpDbaxphko+PL7e2SYfSg at mail dot gmail dot com> <CAL8Wma_7uqxWhw4TKLZnXbUwwGXZ71Mc0mGakeLZ91u-wmtASg at mail dot gmail dot com> <CAL8Wma9Ev6FjPhcDZ8pbPEmF2QVYQQ1DYTB74tbwnYmGHaJhzQ at mail dot gmail dot com>
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.