Re: [patch] Disable child VMA randomizations

[Daniel Jacobowitz <drow at false dot org>]

Please also add the new commands to NEWS.

On Sun, Jun 08, 2008 at 06:43:31PM +0200, Jan Kratochvil wrote:
> @@ -149,6 +156,19 @@ show_debug_linux_nat_async (struct ui_fi
>  		    value);
>  }
>  
> +#ifdef HAVE_PERSONALITY
> +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)
> +{
> +  fprintf_filtered (file, _("\
> +Disabling randomization of debuggee's virtual address space is %s.\n"),
> +		    value);
> +}
> +#endif /* HAVE_PERSONALITY */
> +
>  static int linux_parent_pid;
>  
>  struct simple_pid_list

I think it would be better to register the command unconditionally,
but only call personality if it is available.  I'd like to keep
conditionally compiled code to a minimum.

> +	warning (_("Error setting the enabled disable-randomization: %s"),

Error disabling address space randomization:

> +		 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 (_("Problem restoring the disable-randomization state: %s"),

Error restoring address space randomization:

> +When this mode is on (which is the default), the randomization of\n\
> +the virtual address space is disabled.  Standalone programs run with the\n\
> +randomization enabled by default on some platforms."),

You don't need "the" before randomization in this case (two places).

> +misusing it.  Still even a prelinked shared library can get loaded a a new

at a

> +    gdb_test_multiple "continue" $testname {
> +	-re "address = (0x\[0-9a-f\]*).*Program exited normally..*$gdb_prompt $" {
> +	    pass $testname
> +	    return $expect_out(1,string)
> +	}

Please set a breakpoint and use GDB to print out the variable, instead
of relying on printf; some test configurations don't work with stdio.
They probably won't work with this test anyway, but no reason to
complicate things.

> +gdb_test "set 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} {
> +    fail $test
> +} else {
> +    pass $test
> +}

This test will only pass if the system supports address randomization
and has it enabled.  I don't know about you, but the first thing I do
on a new developer system is turn it off...

-- 
Daniel Jacobowitz
CodeSourcery