2008-06-27 Jan Kratochvil * NEWS (New commands): Mention "set disable-randomization". * configure.ac: Add check for HAVE_PERSONALITY and HAVE_DECL_ADDR_NO_RANDOMIZE. * configure, config.in: Regenerate. * linux-nat.c [HAVE_PERSONALITY]: New include . [HAVE_PERSONALITY] [!HAVE_DECL_ADDR_NO_RANDOMIZE]: Set ADDR_NO_RANDOMIZE. (disable_randomization, show_disable_randomization) (set_disable_randomization): New. (linux_nat_create_inferior) [HAVE_PERSONALITY]: New variables PERSONALITY_ORIG and PERSONALITY_SET. Disable randomization upon the variable DISABLE_RANDOMIZATION. (_initialize_linux_nat): Call ADD_SETSHOW_BOOLEAN_CMD for the variable DISABLE_RANDOMIZATION. 2008-06-27 Jan Kratochvil * gdb.texinfo (Starting): Document "set disable-randomization". 2008-06-27 Jan Kratochvil * gdb.base/randomize.exp, gdb.base/randomize.c: New files. --- gdb/NEWS 11 Jun 2008 12:56:36 -0000 1.277 +++ gdb/NEWS 27 Jun 2008 20:35:54 -0000 @@ -95,6 +95,12 @@ show arm force-mode the current CPSR value for instructions without symbols; previous versions of GDB behaved as if "set arm fallback-mode arm". +set disable-randomization +show disable-randomization + Standalone programs run with the virtual address space randomization enabled + by default on some platforms. This option keeps the addresses stable across + multiple debugging sessions. + * New targets x86 DICOS i[34567]86-*-dicos* --- gdb/config.in 26 Jun 2008 15:51:27 -0000 1.101 +++ gdb/config.in 27 Jun 2008 20:35:56 -0000 @@ -82,6 +82,10 @@ /* Define to 1 if you have the header file. */ #undef HAVE_CURSES_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 `free', and to 0 if you don't. */ #undef HAVE_DECL_FREE @@ -237,6 +241,9 @@ /* Define to 1 if you have the header file. */ #undef HAVE_NLIST_H +/* Define if you support the personality syscall. */ +#undef HAVE_PERSONALITY + /* Define to 1 if you have the `poll' function. */ #undef HAVE_POLL --- gdb/configure 26 Jun 2008 19:20:42 -0000 1.252 +++ gdb/configure 27 Jun 2008 20:36:06 -0000 @@ -23669,6 +23669,188 @@ _ACEOF fi +echo "$as_me:$LINENO: checking whether ADDR_NO_RANDOMIZE is declared" >&5 +echo $ECHO_N "checking whether ADDR_NO_RANDOMIZE is declared... $ECHO_C" >&6 +if test "${ac_cv_have_decl_ADDR_NO_RANDOMIZE+set}" = set; then + echo $ECHO_N "(cached) $ECHO_C" >&6 +else + cat >conftest.$ac_ext <<_ACEOF +/* confdefs.h. */ +_ACEOF +cat confdefs.h >>conftest.$ac_ext +cat >>conftest.$ac_ext <<_ACEOF +/* end confdefs.h. */ +#include + +int +main () +{ +#ifndef ADDR_NO_RANDOMIZE + char *p = (char *) ADDR_NO_RANDOMIZE; +#endif + + ; + return 0; +} +_ACEOF +rm -f conftest.$ac_objext +if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5 + (eval $ac_compile) 2>conftest.er1 + ac_status=$? + grep -v '^ *+' conftest.er1 >conftest.err + rm -f conftest.er1 + cat conftest.err >&5 + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); } && + { ac_try='test -z "$ac_c_werror_flag" + || test ! -s conftest.err' + { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5 + (eval $ac_try) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); }; } && + { ac_try='test -s conftest.$ac_objext' + { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5 + (eval $ac_try) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); }; }; then + ac_cv_have_decl_ADDR_NO_RANDOMIZE=yes +else + echo "$as_me: failed program was:" >&5 +sed 's/^/| /' conftest.$ac_ext >&5 + +ac_cv_have_decl_ADDR_NO_RANDOMIZE=no +fi +rm -f conftest.err conftest.$ac_objext conftest.$ac_ext +fi +echo "$as_me:$LINENO: result: $ac_cv_have_decl_ADDR_NO_RANDOMIZE" >&5 +echo "${ECHO_T}$ac_cv_have_decl_ADDR_NO_RANDOMIZE" >&6 +if test $ac_cv_have_decl_ADDR_NO_RANDOMIZE = yes; then + +cat >>confdefs.h <<_ACEOF +#define HAVE_DECL_ADDR_NO_RANDOMIZE 1 +_ACEOF + + +else + cat >>confdefs.h <<_ACEOF +#define HAVE_DECL_ADDR_NO_RANDOMIZE 0 +_ACEOF + + +fi + + + +if test "$cross_compiling" = yes; then + cat >conftest.$ac_ext <<_ACEOF +/* confdefs.h. */ +_ACEOF +cat confdefs.h >>conftest.$ac_ext +cat >>conftest.$ac_ext <<_ACEOF +/* end confdefs.h. */ +#include +int +main () +{ + +# if !HAVE_DECL_ADDR_NO_RANDOMIZE +# define ADDR_NO_RANDOMIZE 0x0040000 +# endif + /* Test the flag could be set and stays set. */ + personality (personality (0xffffffff) | ADDR_NO_RANDOMIZE); + if (!(personality (personality (0xffffffff)) & ADDR_NO_RANDOMIZE)) + return 1 + ; + return 0; +} +_ACEOF +rm -f conftest.$ac_objext conftest$ac_exeext +if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5 + (eval $ac_link) 2>conftest.er1 + ac_status=$? + grep -v '^ *+' conftest.er1 >conftest.err + rm -f conftest.er1 + cat conftest.err >&5 + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); } && + { ac_try='test -z "$ac_c_werror_flag" + || test ! -s conftest.err' + { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5 + (eval $ac_try) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); }; } && + { ac_try='test -s conftest$ac_exeext' + { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5 + (eval $ac_try) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); }; }; then + have_personality=true +else + echo "$as_me: failed program was:" >&5 +sed 's/^/| /' conftest.$ac_ext >&5 + +have_personality=false +fi +rm -f conftest.err conftest.$ac_objext \ + conftest$ac_exeext conftest.$ac_ext +else + cat >conftest.$ac_ext <<_ACEOF +/* confdefs.h. */ +_ACEOF +cat confdefs.h >>conftest.$ac_ext +cat >>conftest.$ac_ext <<_ACEOF +/* end confdefs.h. */ +#include +int +main () +{ + +# if !HAVE_DECL_ADDR_NO_RANDOMIZE +# define ADDR_NO_RANDOMIZE 0x0040000 +# endif + /* Test the flag could be set and stays set. */ + personality (personality (0xffffffff) | ADDR_NO_RANDOMIZE); + if (!(personality (personality (0xffffffff)) & ADDR_NO_RANDOMIZE)) + return 1 + ; + return 0; +} +_ACEOF +rm -f conftest$ac_exeext +if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5 + (eval $ac_link) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); } && { ac_try='./conftest$ac_exeext' + { (eval echo "$as_me:$LINENO: \"$ac_try\"") >&5 + (eval $ac_try) 2>&5 + ac_status=$? + echo "$as_me:$LINENO: \$? = $ac_status" >&5 + (exit $ac_status); }; }; then + have_personality=true +else + echo "$as_me: program exited with status $ac_status" >&5 +echo "$as_me: failed program was:" >&5 +sed 's/^/| /' conftest.$ac_ext >&5 + +( exit $ac_status ) +have_personality=false +fi +rm -f core *.core gmon.out bb.out conftest$ac_exeext conftest.$ac_objext conftest.$ac_ext +fi +if $have_personality +then + +cat >>confdefs.h <<\_ACEOF +#define HAVE_PERSONALITY 1 +_ACEOF + +fi + # Check whether --with-sysroot or --without-sysroot was given. --- gdb/configure.ac 26 Jun 2008 19:20:42 -0000 1.72 +++ gdb/configure.ac 27 Jun 2008 20:36:07 -0000 @@ -1268,6 +1268,29 @@ if test "x$gdb_cv_sys_syscall_h_has_tkil AC_DEFINE(HAVE_TKILL_SYSCALL, 1, [Define if you support the tkill syscall.]) fi +dnl Check if we can disable the virtual address space randomization. +dnl The functionality of setarch -R. +AC_CHECK_DECLS([ADDR_NO_RANDOMIZE],,, [#include ]) +define([PERSONALITY_TEST], [AC_LANG_PROGRAM([#include ], [ +# 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], + [have_personality=true], + [have_personality=false], + [AC_LINK_IFELSE([PERSONALITY_TEST], + [have_personality=true], + [have_personality=false])]) +if $have_personality +then + AC_DEFINE([HAVE_PERSONALITY], 1, + [Define if you support the personality syscall.]) +fi + dnl Handle optional features that can be enabled. AC_ARG_WITH(sysroot, --- gdb/linux-nat.c 26 Jun 2008 17:40:23 -0000 1.87 +++ gdb/linux-nat.c 27 Jun 2008 20:36:12 -0000 @@ -50,6 +50,13 @@ #include "event-loop.h" #include "event-top.h" +#ifdef HAVE_PERSONALITY +# include +# if !HAVE_DECL_ADDR_NO_RANDOMIZE +# define ADDR_NO_RANDOMIZE 0x0040000 +# endif +#endif /* HAVE_PERSONALITY */ + /* This comment documents high-level logic of this file. Waiting for events in sync mode @@ -220,6 +227,33 @@ show_debug_linux_nat_async (struct ui_fi value); } +static int disable_randomization = 1; + +static void +show_disable_randomization (struct ui_file *file, int from_tty, + struct cmd_list_element *c, const char *value) +{ +#ifdef HAVE_PERSONALITY + fprintf_filtered (file, _("\ +Disabling randomization of debuggee's virtual address space is %s.\n"), + value); +#else /* !HAVE_PERSONALITY */ + fputs_filtered (_("\ +Disabling randomization of debuggee's virtual address space is unsupported on\n\ +this platform.\n"), file); +#endif /* !HAVE_PERSONALITY */ +} + +static void +set_disable_randomization (char *args, int from_tty, struct cmd_list_element *c) +{ +#ifndef HAVE_PERSONALITY + error (_("\ +Disabling randomization of debuggee's virtual address space is unsupported on\n\ +this platform.")); +#endif /* !HAVE_PERSONALITY */ +} + static int linux_parent_pid; struct simple_pid_list @@ -1266,6 +1300,9 @@ linux_nat_create_inferior (char *exec_fi int from_tty) { int saved_async = 0; +#ifdef HAVE_PERSONALITY + int personality_orig = 0, personality_set = 0; +#endif /* HAVE_PERSONALITY */ /* The fork_child mechanism is synchronous and calls target_wait, so we have to mask the async mode. */ @@ -1281,8 +1318,36 @@ linux_nat_create_inferior (char *exec_fi sigdelset (&suspend_mask, SIGCHLD); } +#ifdef HAVE_PERSONALITY + if (disable_randomization) + { + 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"), + safe_strerror (errno)); + } +#endif /* HAVE_PERSONALITY */ + linux_ops->to_create_inferior (exec_file, allargs, env, from_tty); +#ifdef HAVE_PERSONALITY + if (personality_set) + { + errno = 0; + personality (personality_orig); + if (errno != 0) + warning (_("Error restoring address space randomization: %s"), + safe_strerror (errno)); + } +#endif /* HAVE_PERSONALITY */ + if (saved_async) linux_nat_async_mask (saved_async); } @@ -4326,6 +4391,17 @@ Tells gdb whether to control the GNU/Lin /* Install the default mode. */ linux_nat_set_async_mode (linux_async_permitted); + + add_setshow_boolean_cmd ("disable-randomization", class_support, + &disable_randomization, _("\ +Set disabling of debuggee's virtual address space randomization."), _("\ +Show disabling of debuggee's virtual address space randomization."), _("\ +When this mode is on (which is the default), randomization of the virtual\n\ +address space is disabled. Standalone programs run with the randomization\n\ +enabled by default on some platforms."), + &set_disable_randomization, + &show_disable_randomization, + &setlist, &showlist); } --- gdb/doc/gdb.texinfo 10 Jun 2008 10:23:53 -0000 1.504 +++ gdb/doc/gdb.texinfo 27 Jun 2008 20:37:27 -0000 @@ -1999,6 +1999,57 @@ environment: This command is available when debugging locally on most targets, excluding @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino. +@kindex set disable-randomization +@item set disable-randomization +@itemx set disable-randomization on +This option (enabled by default in @value{GDBN}) will turn off the native +randomization of the virtual address space of the started program. This option +is useful for multiple debugging sessions to make the execution better +reproducible and memory addresses reusable across debugging sessions. + +This feature is implemented only on @sc{gnu}/Linux. You can get the same +behavior using + +@smallexample +(@value{GDBP}) set exec-wrapper setarch `uname -m` -R +@end smallexample + +@item set disable-randomization off +Leave the behavior of the started executable unchanged. Some bugs rear their +ugly heads only when the program is loaded at certain addresses. If your bug +disappears when you run the program under @value{GDBN}, that might be because +@value{GDBN} by default disables the address randomization on platforms, such +as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set +disable-randomization off} to try to reproduce such elusive bugs. + +The virtual address space randomization is implemented only on @sc{gnu}/Linux. +It protects the programs against some kinds of security attacks. In these +cases the attacker needs to know the exact location of a concrete executable +code. Randomizing its location makes it impossible to inject jumps misusing +a code at its expected addresses. + +Prelinking shared libraries provides a startup performance advantage but it +makes addresses in these libraries predictable for privileged processes by +having just unprivileged access at the target system. Reading the shared +library binary gives enough information for assembling the malicious code +misusing it. Still even a prelinked shared library can get loaded at a new +random address just requiring the regular relocation process during the +startup. Shared libraries not already prelinked are always loaded at +a randomly chosen address. + +Position independent executables (PIE) contain position independent code +similar to the shared libraries and therefore such executables get loaded at +a randomly chosen address upon startup. PIE executables always load even +already prelinked shared libraries at a random address. You can build such +executable using @command{gcc -fPIE -pie}. + +Heap (malloc storage), stack and custom mmap areas are always placed randomly +(as long as the randomization is enabled). + +@item show disable-randomization +Show the current setting of the explicit disable of the native randomization of +the virtual address space of the started program. + @end table @node Arguments --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ gdb/testsuite/gdb.base/randomize.c 27 Jun 2008 20:37:28 -0000 @@ -0,0 +1,31 @@ +/* This testcase is part of GDB, the GNU debugger. + + Copyright 2008 Free Software Foundation, Inc. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . + + Please email any bugs, comments, and/or additions to this file to: + bug-gdb@prep.ai.mit.edu */ + +#include +#include + +int main() +{ + void *p; + + p = malloc (1); + + return 0; /* print p */ +} --- /dev/null 1 Jan 1970 00:00:00 -0000 +++ gdb/testsuite/gdb.base/randomize.exp 27 Jun 2008 20:37:28 -0000 @@ -0,0 +1,87 @@ +# Copyright 2008 Free Software Foundation, Inc. + +# This program is free software; you can redistribute it and/or modify +# it under the terms of the GNU General Public License as published by +# the Free Software Foundation; either version 3 of the License, or +# (at your option) any later version. +# +# This program 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 General Public License for more details. +# +# You should have received a copy of the GNU General Public License +# along with this program. If not, see . + +set testfile randomize +set srcfile ${testfile}.c +set binfile ${objdir}/${subdir}/${testfile} +if { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } { + untested "Couldn't compile test program" + return -1 +} + +# Get things started. + +gdb_exit +gdb_start +gdb_reinitialize_dir $srcdir/$subdir +gdb_load ${binfile} + +proc address_get { testname } { + global gdb_prompt + + if {![runto_main]} { + return -1 + } + + # Do not rely on printf; some test configurations don't work with stdio. + + gdb_breakpoint [gdb_get_line_number "print p"] + gdb_continue_to_breakpoint "$testname - address set" + + gdb_test_multiple "print/x p" $testname { + -re "\\$\[0-9\]+ = (0x\[0-9a-f\]*)\r?\n$gdb_prompt $" { + pass $testname + return $expect_out(1,string) + } + } +} + +set test "set disable-randomization off" +gdb_test_multiple "${test}" "${test}" { + -re "Disabling randomization .* unsupported .*$gdb_prompt $" { + untested "No randomization supported by this GDB" + return -1 + } + -re "$gdb_prompt $" { + pass $test + } +} +gdb_test "show disable-randomization" \ + "Disabling randomization .* is off." \ + "show disable-randomization off" + +set addr1 [address_get "randomized first address"] +set addr2 [address_get "randomized second address"] +set test "randomized addresses should not match" +if {$addr1 eq $addr2} { + untested "No randomization detected on this system" + return -1 +} else { + pass $test +} + +gdb_test "set disable-randomization on" +gdb_test "show disable-randomization" \ + "Disabling randomization .* is on." \ + "show disable-randomization on" + +set addr1 [address_get "fixed first address"] +set addr2 [address_get "fixed second address"] +set test "fixed addresses should match" +if {$addr1 eq $addr2} { + pass $test +} else { + fail $test +}