diff mbox

[rfc,gdbserver] Disable address space randomization

Message ID 201109212323.p8LNNTG1006616@d06av02.portsmouth.uk.ibm.com
State Superseded
Headers show

Commit Message

Ulrich Weigand Sept. 21, 2011, 4:23 p.m. UTC 
Hello,

this patch disables address space randomization on Linux in gdbserver.
The implementation is pretty much copied from GDB's linux-nat.c.

At this point this happens unconditionally, whenever the kernel
supports the personality system call.  If necessary, it would
be possible to make this configurable by adding a command line
argument to gdbserver ...

Tested on i386-linux.  Fixes a couple of test failures on Ubuntu.

Any thoughts or comments?

Bye,
Ulrich


ChangeLog:

	* configure.ac: Check support for personality routine.
	* configure: Regenerate.
	* config.in: Likewise.
	* linux-low.c (linux_create_inferior): Disable address space
	randomization when forking inferior.

Comments

Jan Kratochvil Sept. 29, 2011, 5:57 p.m. UTC | #1 
Hi Ulrich,

On Wed, 21 Sep 2011 18:23:34 +0200, Ulrich Weigand wrote:
> At this point this happens unconditionally, whenever the kernel
> supports the personality system call.  If necessary, it would
> be possible to make this configurable by adding a command line
> argument to gdbserver ...

I do not find too great it cannot be disabled.  This makes inferior problems
reproducibility worse.  There should be command-line option for legacy and/or
remote command for extended mode but that is obvious.

Still it is probably better even unconditionally.


> Tested on i386-linux.  Fixes a couple of test failures on Ubuntu.

I guess it has PIE by default?  I am aware some PIE corner cases need more
fixes (and Fedora contains some more PIE patches even formerly posted but
those patches are not well made).


Thanks,
Jan
diff mbox

Patch

Index: gdb/gdbserver/config.in
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/config.in,v
retrieving revision 1.32
diff -u -p -r1.32 config.in
--- gdb/gdbserver/config.in	21 Jul 2011 23:46:12 -0000	1.32
+++ gdb/gdbserver/config.in	21 Sep 2011 14:06:31 -0000
@@ -18,6 +18,10 @@ 
 /* Define to 1 if you have the <arpa/inet.h> header file. */
 #undef HAVE_ARPA_INET_H
 
+/* Define to 1 if you have the declaration of `ADDR_NO_RANDOMIZE', and to 0 if
+   you don't. */
+#undef HAVE_DECL_ADDR_NO_RANDOMIZE
+
 /* Define to 1 if you have the declaration of `memmem', and to 0 if you don't.
    */
 #undef HAVE_DECL_MEMMEM
@@ -96,6 +100,9 @@ 
 /* Define to 1 if you have the <netinet/tcp.h> header file. */
 #undef HAVE_NETINET_TCP_H
 
+/* Define if you support the personality syscall. */
+#undef HAVE_PERSONALITY
+
 /* Define to 1 if you have the `pread' function. */
 #undef HAVE_PREAD
 
Index: gdb/gdbserver/configure
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/configure,v
retrieving revision 1.60
diff -u -p -r1.60 configure
--- gdb/gdbserver/configure	21 Jul 2011 23:46:12 -0000	1.60
+++ gdb/gdbserver/configure	21 Sep 2011 14:06:32 -0000
@@ -5066,6 +5066,80 @@  fi
 rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
 CFLAGS="$saved_cflags"
 
+ac_fn_c_check_decl "$LINENO" "ADDR_NO_RANDOMIZE" "ac_cv_have_decl_ADDR_NO_RANDOMIZE" "#include <sys/personality.h>
+"
+if test "x$ac_cv_have_decl_ADDR_NO_RANDOMIZE" = x""yes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_ADDR_NO_RANDOMIZE $ac_have_decl
+_ACEOF
+
+
+if test "$cross_compiling" = yes; then :
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/personality.h>
+int
+main ()
+{
+
+#      if !HAVE_DECL_ADDR_NO_RANDOMIZE
+#       define ADDR_NO_RANDOMIZE 0x0040000
+#      endif
+       /* Test the flag could be set and stays set.  */
+       personality (personality (0xffffffff) | ADDR_NO_RANDOMIZE);
+       if (!(personality (personality (0xffffffff)) & ADDR_NO_RANDOMIZE))
+           return 1
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  gdbsrv_cv_have_personality=true
+else
+  gdbsrv_cv_have_personality=false
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <sys/personality.h>
+int
+main ()
+{
+
+#      if !HAVE_DECL_ADDR_NO_RANDOMIZE
+#       define ADDR_NO_RANDOMIZE 0x0040000
+#      endif
+       /* Test the flag could be set and stays set.  */
+       personality (personality (0xffffffff) | ADDR_NO_RANDOMIZE);
+       if (!(personality (personality (0xffffffff)) & ADDR_NO_RANDOMIZE))
+           return 1
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_run "$LINENO"; then :
+  gdbsrv_cv_have_personality=true
+else
+  gdbsrv_cv_have_personality=false
+fi
+rm -f core *.core core.conftest.* gmon.out bb.out conftest$ac_exeext \
+  conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+
+if $gdbsrv_cv_have_personality
+then
+
+$as_echo "#define HAVE_PERSONALITY 1" >>confdefs.h
+
+fi
+
 
 IPA_DEPFILES=""
 extra_libraries=""
Index: gdb/gdbserver/configure.ac
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/configure.ac,v
retrieving revision 1.47
diff -u -p -r1.47 configure.ac
--- gdb/gdbserver/configure.ac	21 Jul 2011 23:46:12 -0000	1.47
+++ gdb/gdbserver/configure.ac	21 Sep 2011 14:06:32 -0000
@@ -358,6 +358,29 @@  AC_COMPILE_IFELSE(AC_LANG_PROGRAM([]),
 	        	[gdbsrv_cv_have_visibility_hidden=no])
 CFLAGS="$saved_cflags"
 
+dnl Check if we can disable the virtual address space randomization.
+dnl The functionality of setarch -R.
+AC_CHECK_DECLS([ADDR_NO_RANDOMIZE],,, [#include <sys/personality.h>])
+define([PERSONALITY_TEST], [AC_LANG_PROGRAM([#include <sys/personality.h>], [
+#      if !HAVE_DECL_ADDR_NO_RANDOMIZE
+#       define ADDR_NO_RANDOMIZE 0x0040000
+#      endif
+       /* Test the flag could be set and stays set.  */
+       personality (personality (0xffffffff) | ADDR_NO_RANDOMIZE);
+       if (!(personality (personality (0xffffffff)) & ADDR_NO_RANDOMIZE))
+           return 1])])
+AC_RUN_IFELSE([PERSONALITY_TEST],
+              [gdbsrv_cv_have_personality=true],
+              [gdbsrv_cv_have_personality=false],
+              [AC_LINK_IFELSE([PERSONALITY_TEST],
+                              [gdbsrv_cv_have_personality=true],
+                              [gdbsrv_cv_have_personality=false])])
+if $gdbsrv_cv_have_personality
+then
+    AC_DEFINE([HAVE_PERSONALITY], 1,
+              [Define if you support the personality syscall.])
+fi
+
 
 IPA_DEPFILES=""
 extra_libraries=""
Index: gdb/gdbserver/linux-low.c
===================================================================
RCS file: /cvs/src/src/gdb/gdbserver/linux-low.c,v
retrieving revision 1.176
diff -u -p -r1.176 linux-low.c
--- gdb/gdbserver/linux-low.c	24 Aug 2011 12:17:39 -0000	1.176
+++ gdb/gdbserver/linux-low.c	21 Sep 2011 14:06:33 -0000
@@ -55,6 +55,13 @@ 
 #define SPUFS_MAGIC 0x23c9b64e
 #endif
 
+#ifdef HAVE_PERSONALITY
+# include <sys/personality.h>
+# if !HAVE_DECL_ADDR_NO_RANDOMIZE
+#  define ADDR_NO_RANDOMIZE 0x0040000
+# endif
+#endif
+
 #ifndef O_LARGEFILE
 #define O_LARGEFILE 0
 #endif
@@ -520,10 +527,27 @@  add_lwp (ptid_t ptid)
 static int
 linux_create_inferior (char *program, char **allargs)
 {
+#ifdef HAVE_PERSONALITY
+  int personality_orig = 0, personality_set = 0;
+#endif
   struct lwp_info *new_lwp;
   int pid;
   ptid_t ptid;
 
+#ifdef HAVE_PERSONALITY
+  errno = 0;
+  personality_orig = personality (0xffffffff);
+  if (errno == 0 && !(personality_orig & ADDR_NO_RANDOMIZE))
+    {
+      personality_set = 1;
+      personality (personality_orig | ADDR_NO_RANDOMIZE);
+    }
+  if (errno != 0 || (personality_set
+		     && !(personality (0xffffffff) & ADDR_NO_RANDOMIZE)))
+    warning ("Error disabling address space randomization: %s",
+	     strerror (errno));
+#endif
+
 #if defined(__UCLIBC__) && defined(HAS_NOMMU)
   pid = vfork ();
 #else
@@ -552,6 +576,17 @@  linux_create_inferior (char *program, ch
       _exit (0177);
     }
 
+#ifdef HAVE_PERSONALITY
+  if (personality_set)
+    {
+      errno = 0;
+      personality (personality_orig);
+      if (errno != 0)
+	warning ("Error restoring address space randomization: %s",
+		 strerror (errno));
+    }
+#endif
+
   linux_add_process (pid, 0);
 
   ptid = ptid_build (pid, pid, 0);