Linux Kernel Module Cheat

17.6.1.5. Panic trace show addresses instead of symbols

If CONFIG_KALLSYMS=n, then addresses are shown on traces instead of symbol plus offset.

In v4.16 it does not seem possible to configure that at runtime. GDB step debugging with:

./run --eval-after 'insmod dump_stack.ko' --gdb-wait --tmux-args dump_stack

shows that traces are printed at arch/x86/kernel/dumpstack.c:

static void printk_stack_address(unsigned long address, int reliable,
                 char *log_lvl)
{
    touch_nmi_watchdog();
    printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address);
}

and %pB is documented at Documentation/core-api/printk-formats.rst:

If KALLSYMS are disabled then the symbol address is printed instead.

I wasn’t able do disable CONFIG_KALLSYMS to test this this out however, it is being selected by some other option? But I then used make menuconfig to see which options select it, and they were all off…