GDB：对于不同硬件平台上的每个程序，function 地址是固定的还是动态的？

Question

If we write a C code like printf("%p\n", __builtin_return_address(0)); and suppose we get the result 0xabcd from customer's platform . And then, we run the same program with gdb on our platform , and we find out that 0xabcd maps to sample_function() , is this same function on customer's platform when he is running that program? Or in other word, is stack address fixed or dynamic for same program but different hardware platform?

Answer 1

In order to prevent some attacks, such as buffer overflow, operating systems use Address Space Layout Randomization (ASLR). ASLR ensures that each time you run a program, the addresses will be placed randomly on virtual address space. On Linux, it is enabled by default. You can disable it by running

echo 0 | sudo tee /proc/sys/kernel/randomize_va_space

And then, if you want to enable it again, just run

echo 2 | sudo tee /proc/sys/kernel/randomize_va_space

For more information you can check this article How Effective is ASLR on Linux Systems?

On the other hand, ASLR is disabled in gdb by default to ease debugging. You can enable/disable it with these commands

set disable-randomization off
set disable-randomization on