On Thu, Jan 13, 2022 at 4:04 PM admin LI <admin@hifiphile.com> wrote:

 I'm developing a kernel module for an ARM machine, while debugging I found addresses
 printed are all randomized and useless for debugging.

 To prove I was not crazy I wrote this small program:


 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>

 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Somebody");
 MODULE_DESCRIPTION("A simple example Linux module.");
 MODULE_VERSION("0.01");

 static int __init example_init(void) {
     uint32_t a;
     uint32_t b;
     uint32_t c;
     uint8_t d[10];
     uint8_t *e;

     printk(KERN_INFO "Hello, World!\n");
     printk(KERN_INFO "&a %p\n",&a);
     printk(KERN_INFO "&b %p\n",&b);
     printk(KERN_INFO "&c %p\n",&c);
     printk(KERN_INFO "&d %p\n",d);
     printk(KERN_INFO "&d[0] %p\n",&d[0]);
     printk(KERN_INFO "&d[1] %p\n",&d[1]);

     e = kmalloc(10, GFP_KERNEL);
     printk(KERN_INFO "&e[0] %p\n",&e[0]);
     printk(KERN_INFO "&e[1] %p\n",&e[1]);

     kfree(e);

  return 0;
 }

 static void __exit example_exit(void) {
  printk(KERN_INFO "Goodbye, World!\n");
 }

 module_init(example_init);
 module_exit(example_exit);

 And it gave me this output:

 Hello, World!
 &a b3f9fa31
 &b 27e1c68a
 &c da50d287
 &d 9f9aec2b
 &d[0] 9f9aec2b
 &d[1] cc627580
 &e[0] 98b8c9eb
 &e[1] 45f248f8

 Then I tested on my debian host machine which gave me the same kind of randomized addresses.

 When I search randomization the only thing I found is KASLR which I don't think is the same thing.

I think something else may be going on, but I'll toss this out there
in case it helps.

In the past randomization was disabled by writing 0 to
/proc/sys/kernel/randomize_va_space. Something like:

    sysctl -w kernel.randomize_va_space=0

To make it permanent, change it in /etc/sysctl.conf.

Jeff