Virtualbox + kgdb: Can't see vmlinux symbols

[Kamran Khan]

This is happening only with kernel 4.8+.

When I compile kernel 4.4 with a stock Ubuntu Xenial .config, symbols
appear just fine.

When I compile kernel 4.8/4.10 with Yakkety/Zesty stock configs the
symbols disappear.

On Wed, Jun 14, 2017 at 4:58 PM, Kamran Khan <krkhan at inspirated.com> wrote:
> I have an Ubuntu 16.04 VM running in Virtualbox.
>
> I'm building kernel from git using make deb-pkg.
>
> After I install all the deb packages (including debug symbols) on the
> VM and restart it, I can see in uname -r output that the appropriate
> kernel was booted from.
>
> I'm passing the following parameters to the kernel:
>
>> kgdboc=ttyS0,115200 kgdbwait
>
> Once the kernel boots, I am able to connect to it via socat + gdb from host.
>
> I'm using the full uncompressed vmlinux file to start the gdb which
> contains all the debugging symbols.
>
> However, I can't see any of the symbols in backtrace etc.
>
>> $ du -sh vmlinux
>> 425M vmlinux
>> $ gdb vmlinux
>> GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.04) 7.11.1
>> Copyright (C) 2016 Free Software Foundation, Inc.
>> License GPLv3+: GNU GPL version 3 or later [gnu.org]
>> [...]
>> For help, type "help".
>> Type "apropos word" to search for commands related to "word"...
>> Reading symbols from vmlinux...done.
>> (gdb) target remote /dev/pts/2
>> Remote debugging using /dev/pts/2
>> 0xffffffffb113c5b4 in ?? ()
>> (gdb) bt
>> #0  0xffffffffb113c5b4 in ?? ()
>> #1  0xffffb035421c7dd0 in ?? ()
>> #2  0xffffffffb113c60c in ?? ()
>> #3  0xffffb035421c7e00 in ?? ()
>> #4  0xffffffffb153035a in ?? ()
>> #5  0x0000000000000002 in irq_stack_union ()
>> #6  0x00000000013a7408 in ?? ()
>> #7  0xffff8fb8bd0d3b00 in ?? ()
>> #8  0xffffb035421c7e18 in ?? ()
>> #9  0xffffffffb15307df in ?? ()
>> #10 0xffff8fb8b8779900 in ?? ()
>> #11 0xffffb035421c7e38 in ?? ()
>> #12 0xffffffffb12ab412 in ?? ()
>> #13 0xffff8fb8bd0d3b00 in ?? ()
>
>
> Any ideas what am I doing wrong?
>
> Thanks,
> Kamran.