gdb doesn't correctly places breakpoint at address

Question

I'm debugging the linux kernel using kgdb module and gdb. when trying to set a breakpoint at some address, gdb sets it at another, wrong address.

(gdb) b *0xffffffff81528690
Breakpoint 1 at 0x81528690

Anyone knows why?

Answer 1

I found what is the issue.

By default running gdb without specifying an executable will force 32-bit mode, that why address were truncated.

After running it on the kernel image, which was built for x86_64 architecture i could break on 64bit long addresses.