/boot/System.map*中的符号地址与/ proc / kallsyms中的符号地址不同

Question

There is a fixed gap between /boot/System.map and /proc/kallsyms . And the gap changes on every reboot.

Is there something like layout randomization?

For example,

> cat /boot/System.map
ffffffff81d2b5f0 T x86_64_start_kernel
ffffffff81d2bb33 T start_kernel
ffffffff81d2ee1b T xen_start_kernel

> cat /proc/kallsyms | grep start_kernel
ffffffffa4d2b5f0 T x86_64_start_kernel
ffffffffa4d2bb33 T start_kernel
ffffffffa4d2ee1b T xen_start_kernel

Answer 1

Yes, the Linux kernel can use ASLR (address space layout randomization), at least on x86. Actually, only the base address can be randomized at the moment.

See the description of CONFIG_RANDOMIZE_BASE in arch/x86/Kconfig in the kernel sources for details.

It is hard to guess what is going on on your system without knowledge of what kind on Linux that is and how the kernel is configured.

See if CONFIG_RANDOMIZE_BASE is set in the config file for that kernel (usually - /boot/config-<something> ).