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Re: 32bit UID support for glibc 2.1.3


>>>>> Ulrich Drepper writes:

Uli> Andreas Jaeger <aj@suse.de> writes:
>> The normal stat call only returns a 16bit uid.  To get 32bit uids we
>> have to use stat64 and convert struct stat64 to struct stat with
>> checking for overflow (some entries in struct stat and struct stat64
>> have different sizes).  
>> 
>> Anybody with another idea how to solve the problem?

Uli> Look at the reality.  I think that even though those fields have
Uli> larger types the values are not really larger and we can get along
Uli> with a simple assignment.  The field type for stat64 are chosen after
Uli> the glibc version of stat64 not (only) because of changed kernel
Uli> requirements.

I'm appending a "clean" patch to implement my proposal.  I check for
overflow in just two places: st_size and st_blocks.  Both can be
larger than 32bit - in reality.

I'm just appending a patch for xstat for i386.  If you agree that this
is the right solution, I'll do the rest.  Please give me your feedback.

Thanks,
Andreas

2000-01-12  Andreas Jaeger  <aj@suse.de>

	* sysdeps/unix/sysv/linux/xstatconv.c (xstat32_conv): New
	function; needed for 32bit uid support.	

	* sysdeps/unix/sysv/linux/i386/xstat.c: New file, handles 32bit
	uids correctly.

============================================================
Index: sysdeps/unix/sysv/linux/xstatconv.c
--- sysdeps/unix/sysv/linux/xstatconv.c	1999/02/11 11:56:29	1.5
+++ sysdeps/unix/sysv/linux/xstatconv.c	2000/01/12 14:52:35
@@ -1,5 +1,5 @@
 /* Convert between the kernel's `struct stat' format, and libc's.
-   Copyright (C) 1991, 1995, 1996, 1997 Free Software Foundation, Inc.
+   Copyright (C) 1991, 1995, 1996, 1997, 2000 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
@@ -142,4 +142,72 @@
 
   return 0;
 #endif
+}
+
+static inline int
+xstat32_conv (int vers, struct stat64 *kbuf, struct stat *buf)
+{
+  switch (vers)
+    {
+    case _STAT_VER_LINUX:
+      {
+	/* Convert current kernel version of `struct stat64' to `struct stat'.  */
+	buf->st_dev = kbuf->st_dev;
+#ifdef _HAVE___PAD1
+	buf->__pad1 = 0;
+#endif
+	buf->st_ino = kbuf->st_ino;
+	buf->st_mode = kbuf->st_mode;
+	buf->st_nlink = kbuf->st_nlink;
+	buf->st_uid = kbuf->st_uid;
+	buf->st_gid = kbuf->st_gid;
+	buf->st_rdev = kbuf->st_rdev;
+#ifdef _HAVE___PAD2
+	buf->__pad2 = 0;
+#endif
+	buf->st_size = kbuf->st_size;
+	/* Check for overflow.  */
+	if (buf->st_size != kbuf->st_size)
+	  {
+	    __set_errno (EOVERFLOW);
+	    return -1;
+	  }
+	buf->st_blksize = kbuf->st_blksize;
+	buf->st_blocks = kbuf->st_blocks;
+	/* Check for overflow.  */
+	if (buf->st_blocks != kbuf->st_blocks)
+	  {
+	    __set_errno (EOVERFLOW);
+	    return -1;
+	  }
+	buf->st_atime = kbuf->st_atime;
+#ifdef _HAVE___UNUSED1
+	buf->__unused1 = 0;
+#endif
+	buf->st_mtime = kbuf->st_mtime;
+#ifdef _HAVE___UNUSED2
+	buf->__unused2 = 0;
+#endif
+	buf->st_ctime = kbuf->st_ctime;
+#ifdef _HAVE___UNUSED3
+	buf->__unused3 = 0;
+#endif
+#ifdef _HAVE___UNUSED4
+	buf->__unused4 = 0;
+#endif
+#ifdef _HAVE___UNUSED5
+	buf->__unused5 = 0;
+#endif
+      }
+      break;
+
+      /* If struct stat64 is different from struct stat then
+	 _STAT_VER_KERNEL does not make sense.  */
+    case _STAT_VER_KERNEL:
+    default:
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  return 0;
 }
============================================================
Index: sysdeps/unix/sysv/linux/i386/xstat.c
--- sysdeps/unix/sysv/linux/i386/xstat.c	created
+++ sysdeps/unix/sysv/linux/i386/xstat.c	Wed Jan 12 15:50:26 2000	1.1
@@ -0,0 +1,97 @@
+/* xstat using old-style Unix stat system call.
+   Copyright (C) 1991,95,96,97,98,2000 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
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   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.  */
+
+/* Ho hum, if xstat == xstat64 we must get rid of the prototype or gcc
+   will complain since they don't strictly match.  */
+#define __xstat64 __xstat64_disable
+
+#include <errno.h>
+#include <stddef.h>
+#include <sys/stat.h>
+#include <kernel_stat.h>
+
+#include <sysdep.h>
+#include <sys/syscall.h>
+
+#include <xstatconv.c>
+
+extern int __syscall_stat (const char *, struct kernel_stat *);
+
+#ifdef __NR_stat64
+extern int __syscall_stat64 (const char *, struct stat64 *);
+# if  __ASSUME_STAT64_SYSCALL == 0
+/* The variable is shared between all wrappers around *stat64 calls.  */
+extern int __have_no_stat64;
+# endif
+#endif
+
+
+/* Get information about the file NAME in BUF.  */
+int
+__xstat (int vers, const char *name, struct stat *buf)
+{
+#if __ASSUME_STAT64_SYSCALL > 0
+  struct kernel_stat kbuf;
+  int result;
+
+  result = INLINE_SYSCALL (stat64, 2, name, &buf64);
+  if (result == 0)
+    result = xstat32_conv (vers, &buf64, buf);
+  return result;
+#else
+  struct kernel_stat kbuf;
+  int result;
+
+  if (vers == _STAT_VER_KERNEL)
+    {
+      return INLINE_SYSCALL (stat, 2, name, (struct kernel_stat *) buf);
+    }
+# if defined __NR_stat64
+  /* To support 32 bit UIDs, we have to use stat64.  The normal stat call only returns
+     16 bit UIDs.  */
+  if (! __have_no_stat64)
+    {
+      struct stat64 buf64;
+      
+      int saved_errno = errno;
+      result = INLINE_SYSCALL (stat64, 2, name, &buf64);
+
+      if (result == 0)
+	result = xstat32_conv (vers, &buf64, buf);
+      
+      if (result != -1 || errno != ENOSYS)
+	return result;
+
+      __set_errno (saved_errno);
+      __have_no_stat64 = 1;
+    }
+# endif  
+  result = INLINE_SYSCALL (stat, 2, name, &kbuf);
+  if (result == 0)
+    result = xstat_conv (vers, &kbuf, buf);
+
+  return result;
+#endif  /* __ASSUME_STAT64_SYSCALL  */
+}
+
+weak_alias (__xstat, _xstat);
+#ifdef XSTAT_IS_XSTAT64
+#undef __xstat64
+strong_alias (__xstat, __xstat64);
+#endif

-- 
 Andreas Jaeger
  SuSE Labs aj@suse.de
   private aj@arthur.rhein-neckar.de

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