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Re: dpkg bug

At 19:41 +0200 1998-05-21, Anders Hammarquist wrote:
>Ok. I have some thoghts on a proper fix which you may want to include
>in the bug report. The problem is in two parts (or may be anyway, I
>haven't actually looked at libc to verify this). First, applications
>(such as tar) which expect lchown behaviour should call lchown and not
>chown (tar call chown as it is now). Second, libc needs to figure out
>if the particular kernel has a lchown syscall or not and divert calls
>to lchown to the appropriate syscall.

glibc 2.1 snapshots and test releases have code to handle Linux kernels
with both old and new chown/lchown behavior (the code is only officially in
for x86 (this may have changed in the CVS tree), but the patch I have for
powerpc is a verbatim copy of sysdeps/unix/sysv/linux/i386/chown.c copied
into sysdeps/unix/sysv/linux/powerpc/chown.c, and a tiny diff to
sysdeps/unix/sysv/linux/powerpc/syscalls.list). I don't know how easily
this could be backported to glibc 2.0 for alpha. For reference, here's the
patch for powerpc:

--- old/glibc-2.0.93/sysdeps/unix/sysv/linux/powerpc/chown.c	Wed Dec 31
16:00:00 1969
+++ glibc-2.0.93/sysdeps/unix/sysv/linux/powerpc/chown.c	Fri May  8
18:54:45 1998
@@ -0,0 +1,101 @@
+/* Copyright (C) 1998 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 Library General Public License as
+   published by the Free Software Foundation; either version 2 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
+   Library General Public License for more details.
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+#include <errno.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+  In Linux 2.1.x the chown functions have been changed.  A new function lchown
+  was introduced.  The new chown now follows symlinks - the old chown and the
+  new lchown do not follow symlinks.
+  The new lchown function has the same number as the old chown had and the
+  new chown has a new number.  When compiling with headers from Linux > 2.1.8x
+  it's impossible to run this libc with older kernels.  In these cases libc
+  has therefore to route calls to chown to the old chown function.
+extern int __syscall_chown (const char *__file,
+			    uid_t __owner, gid_t __group);
+#ifdef __NR_lchown
+/* running under Linux 2.0 or < 2.1.8x */
+static int __libc_old_chown;
+__real_chown (const char *file, uid_t owner, gid_t group)
+  int result;
+  if (!__libc_old_chown)
+    {
+      int saved_errno = errno;
+      result = __syscall_chown (file, owner, group);
+      if (result >= 0 || errno != ENOSYS)
+	return result;
+      __set_errno (saved_errno);
+      __libc_old_chown = 1;
+    }
+  return __lchown (file, owner, group);
+#ifndef __NR_lchown
+/* Compiling under older kernels.  */
+__chown_is_lchown (const char *file, uid_t owner, gid_t group)
+  return __syscall_chown (file, owner, group);
+#elif defined HAVE_ELF && defined PIC && defined DO_VERSIONING
+/* Compiling for compatibiity.  */
+__chown_is_lchown (const char *file, uid_t owner, gid_t group)
+  return __lchown (file, owner, group);
+#if defined HAVE_ELF && defined PIC && defined DO_VERSIONING
+strong_alias (__chown_is_lchown, _chown_is_lchown)
+symbol_version (__chown_is_lchown, __chown, GLIBC_2.0);
+symbol_version (_chown_is_lchown, chown, GLIBC_2.0);
+# ifdef __NR_lchown
+strong_alias (__real_chown, _real_chown)
+default_symbol_version (__real_chown, __chown, GLIBC_2.1);
+default_symbol_version (_real_chown, chown, GLIBC_2.1);
+# else
+strong_alias (__chown_is_lchown, __chown_is_lchown21)
+strong_alias (__chown_is_lchown, _chown_is_lchown21)
+default_symbol_version (__chown_is_lchown21, __chown, GLIBC_2.1);
+default_symbol_version (_chown_is_lchown21, chown, GLIBC_2.1);
+# endif
+# ifdef __NR_lchown
+strong_alias (__real_chown, __chown)
+weak_alias (__real_chown, chown)
+# else
+strong_alias (__chown_is_lchown, __chown)
+weak_alias (__chown_is_lchown, chown)
+# endif

--- old/glibc-2.0.93/sysdeps/unix/sysv/linux/powerpc/syscalls.list	Thu
Mar 12 09:16:02 1998
+++ glibc-2.0.93/sysdeps/unix/sysv/linux/powerpc/syscalls.list	Fri May  8
18:54:23 1998
@@ -4,3 +4,5 @@

 getresuid	-	getresuid	3	getresuid
 getresgid	-	getresgid	3	getresgid
+s_chown		chown	chown		3	__syscall_chown

Joel "Espy" Klecker    <mailto:jk@espy.org>    <http://web.espy.org/>
Debian GNU/Linux Developer...................<http://www.debian.org/>

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