[PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[Jakub Jelinek]

Hi!

LD_ASSUME_KERNEL doesn't work for static binaries, the following patch makes
it work even for them (so you can influence what libraries it will use
during NSS lookups or ICONV).

2002-12-09  Jakub Jelinek  <jakub@redhat.com>

	* elf/dl-support.c (_dl_non_dynamic_init): Add DL_OSVERSION_INIT if
	defined.
	* sysdeps/unix/sysv/linux/dl-librecon.h (_dl_osversion_init): New
	function.
	(EXTRA_LD_ENVVARS): Use it.
	(DL_OSVERSION_INIT): Define.
	* sysdeps/unix/sysv/linux/i386/dl-librecon.h: Include linux
	dl-librecon.h.
	(EXTRA_LD_ENVVARS): Undef before defining.  Use _dl_osversion_init.

--- libc/elf/dl-support.c.jj	2002-12-06 12:27:23.000000000 +0100
+++ libc/elf/dl-support.c	2002-12-09 16:57:58.000000000 +0100
@@ -214,6 +214,10 @@ _dl_non_dynamic_init (void)
   DL_PLATFORM_INIT;
 #endif
 
+#ifdef DL_OSVERSION_INIT
+  DL_OSVERSION_INIT;
+#endif
+
   /* Now determine the length of the platform string.  */
   if (_dl_platform != NULL)
     _dl_platformlen = strlen (_dl_platform);
--- libc/sysdeps/unix/sysv/linux/i386/dl-librecon.h.jj	2002-01-31 04:39:22.000000000 +0100
+++ libc/sysdeps/unix/sysv/linux/i386/dl-librecon.h	2002-12-09 17:15:06.000000000 +0100
@@ -19,7 +19,8 @@
    02111-1307 USA.  */
 
 #ifndef _DL_LIBRECON_H
-#define _DL_LIBRECON_H	1
+
+#include <sysdeps/unix/sysv/linux/dl-librecon.h>
 
 #define DISTINGUISH_LIB_VERSIONS \
   do									      \
@@ -47,27 +48,12 @@
   while (0)
 
 /* Recognizing extra environment variables.  */
+#undef EXTRA_LD_ENVVARS
 #define EXTRA_LD_ENVVARS \
   case 13:								      \
     if (memcmp (envline, "ASSUME_KERNEL", 13) == 0)			      \
       {									      \
-	unsigned long int i, j, osversion = 0;				      \
-	char *p = &envline[14], *q;					      \
-									      \
-	for (i = 0; i < 3; i++, p = q + 1)				      \
-	  {								      \
-	    j = __strtoul_internal (p, &q, 0, 0);			      \
-	    if (j >= 255 || p == q || (i < 2 && *q && *q != '.'))	      \
-	      {								      \
-		osversion = 0;						      \
-		break;							      \
-	      }								      \
-	    osversion |= j << (16 - 8 * i);				      \
-	    if (!*q)							      \
-	      break;							      \
-	  }								      \
-	if (osversion)							      \
-	  GL(dl_osversion) = osversion;					      \
+	_dl_osversion_init (&envline[14]);				      \
 	break;								      \
       }									      \
 									      \
--- libc/sysdeps/unix/sysv/linux/dl-librecon.h.jj	2002-01-31 04:39:22.000000000 +0100
+++ libc/sysdeps/unix/sysv/linux/dl-librecon.h	2002-12-09 17:20:45.000000000 +0100
@@ -1,5 +1,5 @@
 /* Optional code to distinguish library flavours.
-   Copyright (C) 2001 Free Software Foundation, Inc.
+   Copyright (C) 2001, 2002 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Jakub Jelinek <jakub@redhat.com>, 2001.
 
@@ -21,29 +21,42 @@
 #ifndef _DL_LIBRECON_H
 #define _DL_LIBRECON_H	1
 
+static inline void __attribute__ ((unused, always_inline))
+_dl_osversion_init (char *assume_kernel)
+{
+  unsigned long int i, j, osversion = 0;
+  char *p = assume_kernel, *q;
+
+  for (i = 0; i < 3; i++, p = q + 1)
+    {
+      j = __strtoul_internal (p, &q, 0, 0);
+      if (j >= 255 || p == q || (i < 2 && *q && *q != '.'))
+	{
+	  osversion = 0;
+	  break;
+	}
+      osversion |= j << (16 - 8 * i);
+      if (!*q)
+	break;
+    }
+  if (osversion)
+    GL(dl_osversion) = osversion;
+}
+
 /* Recognizing extra environment variables.  */
 #define EXTRA_LD_ENVVARS \
   case 13:								      \
     if (memcmp (envline, "ASSUME_KERNEL", 13) == 0)			      \
       {									      \
-	unsigned long int i, j, osversion = 0;				      \
-	char *p = &envline[14], *q;					      \
-									      \
-	for (i = 0; i < 3; i++, p = q + 1)				      \
-	  {								      \
-	    j = __strtoul_internal (p, &q, 0, 0);			      \
-	    if (j >= 255 || p == q || (i < 2 && *q && *q != '.'))	      \
-	      {								      \
-		osversion = 0;						      \
-		break;							      \
-	      }								      \
-	    osversion |= j << (16 - 8 * i);				      \
-	    if (!*q)							      \
-	      break;							      \
-	  }								      \
-	if (osversion)							      \
-	  GL(dl_osversion) = osversion;					      \
+	_dl_osversion_init (&envline[14]);				      \
 	break;								      \
       }
 
+#define DL_OSVERSION_INIT \
+  do {									      \
+    char *assume_kernel = getenv ("LD_ASSUME_KERNEL");			      \
+    if (assume_kernel)							      \
+      _dl_osversion_init (assume_kernel);				      \
+  } while (0)
+
 #endif /* dl-librecon.h */

	Jakub

Re: [PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[Roland McGrath]

> LD_ASSUME_KERNEL doesn't work for static binaries, the following patch makes
> it work even for them (so you can influence what libraries it will use
> during NSS lookups or ICONV).

Ok, we need that.  I think it needs to be __secure_getenv, though.
I also wonder why this stuff is in linux/i386 instead of linux/.

Re: [PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[Ulrich Drepper]

Jakub Jelinek wrote:

> I'm not sure either way. LD_ASSUME_KERNEL in ld.so ATM is not limited to
> non-suid.

I don't think it is necessary to use __secure_getenv.  It doesn't let
the user directly make decisions about what DSO is used.  And if the
DSOs with support are vulnerable to something the new DSOs are not there
are other ways to get to this.

-- 
--------------.                        ,-.            444 Castro Street
Ulrich Drepper \    ,-----------------'   \ Mountain View, CA 94041 USA
Red Hat         `--' drepper at redhat.com `---------------------------

Re: [PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[Roland McGrath]

> I don't think it is necessary to use __secure_getenv.  It doesn't let
> the user directly make decisions about what DSO is used.  And if the
> DSOs with support are vulnerable to something the new DSOs are not there
> are other ways to get to this.

Ok, that makes sense.

Re: [PATCH] Make LD_ASSUME_KERNEL working even for static binaries

[Roland McGrath]

Thanks, I've put this in and cleaned up the duplication of the macro contents.