You can also do this programmatically from C source before a UNIX exec.
If you take a look at the sources for setarch (here's one source):
http://code.metager.de/source/xref/linux/utils/util-linux/sys-utils/setarch.c
You can see if boils down to a system call (syscall) or a function call (depending on what your system defines). From setarch.c:
#ifndef HAVE_PERSONALITY
# include <syscall.h>
# define personality(pers) ((long)syscall(SYS_personality, pers))
#endif
On my CentOS 6 64-bit system, it looks like it uses a function (which probably calls the self-same syscall above). Take a look at this snippet from the include file in /usr/include/sys/personality.h (as referenced as <sys/personality.h> in the setarch source code):
/* Set different ABIs (personalities). */
extern int personality (unsigned long int __persona) __THROW;
What it boils down to, is that you can, from C code, call and set the personality to use ADDR_NO_RANDOMIZE and then exec (just like setarch does).
#include <sys/personality.com>
#ifndef HAVE_PERSONALITY
# include <syscall.h>
# define personality(pers) ((long)syscall(SYS_personality, pers))
#endif
...
void mycode()
{
// If requested, turn off the address rand feature right before execing
if (MyGlobalVar_Turn_Address_Randomization_Off) {
personality(ADDR_NO_RANDOMIZE);
}
execvp(argv[0], argv); // ... from set-arch.
}
It's pretty obvious you can't turn address randomization off in the process you are in (grin: unless maybe dynamic loading), so this only affects forks and execs later. I believe the Address Randomization flags are inherited by child sub-processes?
Anyway, that's how you can programmatically turn off the address randomization in C source code. This may be your only solution if you don't want the force a user to intervene manually and start-up with setarch or one of the other solutions listed earlier.
Before you complain about security issues in turning this off, some shared memory libraries/tools (such as PickingTools shared memory and some IBM databases) need to be able to turn off randomization of memory addresses.
