why does kgdb not show function symbols when debugging vmlinux?

Question

I have compiled my kernel with the following kernel option enabled. That should be enough.

CONFIG_KGDB=y
CONFIG_KGDB_SERIAL_CONSOLE=y
CONFIG_DEBUG_INFO=y

I want to implement a tcp socket server under kernel space. However when I debug my kernel, gdb seems can't recognize function symbol. Question marks are shown.

#0  0xffffffffb92ef58a in ?? ()
#1  0xffffffffb92ef6dd in ?? ()
#2  0xffffb4a640c73c38 in ?? ()
#3  0xffff9b0c275587c0 in ?? ()
#4  0xffff9b0c5c9fbc00 in ?? ()
#5  0xffff9b0c7c3ec480 in ?? ()
#6  0xffffffffc063d000 in ?? ()
#7  0xffffffffc063b22e in myserver ()
    at /home/river/Desktop/kernel-sock/server.c:75
#8  0xffffffffc063b285 in server_init ()
    at /home/river/Desktop/kernel-sock/server.c:88
#9  0xffffffffb8e0218e in ?? ()
#10 0xffff9b0c7ffeb5c0 in ?? ()
#11 0x000000000000001f in ?? ()
#12 0x85ce74a569aec8a5 in ?? ()

The current kernel version is 4.9.82.

Answer 1

I disabled CONFIG_DEBUG_RODATA and CONFIG_RANDOMIZE_BASE. CONFIG_RANDOMIZE_MEMORY randomizes the virtual addresses of memory sections, including physical memory mappings, vmalloc, and vemmap. I think memory address randomizing is the key.