Linux Kernel Virtual memory space, Address Handling and Virtual Memory Confusion

I am trying to implement the Meltdown vulnerability on a linux intel x86 laptop for a class demo. In the machine I am using I have nokaslr and pti=off in the kernel parameters.

I have created a kernel module that creates a global static char array called secret_array_kernel and then printk the address of this array. In my terminal I then retrieve the address using dmesg. For example 0000000054b7a361

I then take this address and copy and paste it into a program called MeltdownAttack.c that tries to find the contents of each index of this string using Meltdown.

I run the program with the given address of the array in this case 0000000054b7a361 only to find out it does not work. I repeated running the program but was unable to get it to print out the correct value once.

My first step in debugging was to create a global static char array called test similar how I did in the Kernel module but now this array lives inside of MeltdownAttack.c. I passed the address of this new array and I was able to get the contents of this array using the same functions as I tried with address of secret_array_kernel.

From what I understand in terms of virtual memory the array test lives in the processes user virtual memory, while the array secret_array_kernel lives in the processes kernel virtual memory. I know some of the Kernel Virtual Memory is Identical for each process but some is different for each process..

My kernel module looks something this

//...
static char secret[8] = {'M','Y','S','E','C','R','E','T'};
//...
static __init int test_proc_init(void)
{
   // write message in kernel message buffer
   printk("secret data address:%p\n", &secret);      
   printk("secret data value  :%s\n", secret);      

   secret_buffer = (char*)vmalloc(8);

   // create data entry in /proc
   secret_entry = proc_create_data("secret_data", 
                  0444, NULL, &test_proc_fops, NULL);
   if (secret_entry) return 0;

   return -ENOMEM;
}
//...

To then get the address I do

$ sudo insmod MeltdownKernel.ko
$ dmesg | grep 'secret data address'

//prints
[  485.147336] secret data address:0000000054b7a361

I have the following questions

• I am unsure of the address given by dmesg is the address of the array in virtual memory or physical memory (I believe it to be virtual memory).
• If this address does live in virtual memory And lives in the kernel virtual memory. I am unsure if the address of the array secret_array_kernel that was printed out by dmesg lives in the part that is identical for each processor or lives in the part that is different for each process.See image here
• I am also unsure if its okay for me to use the exact same address that was given by the kernel module after I ran dmesg. To then be used inside MeltdownAttack.c. (Do I need to put some sort of offset?)

Clearing up this will help me deduce if I either try to fix my code again or just modify the address im using.

I am sorry if I have bad grammar in the post. English is not my first language.