svn commit: r328610 - head/sys/amd64/amd64

[John Baldwin]

On Tuesday, January 30, 2018 11:29:27 PM John Baldwin wrote:
> Author: jhb
> Date: Tue Jan 30 23:29:27 2018
> New Revision: 328610
> URL: https://svnweb.freebsd.org/changeset/base/328610
> 
> Log:
>   Ensure 'name' is not NULL before passing to strcmp().
>   
>   This avoids a nested page fault when obtaining a stack trace in DDB if
>   the address from the first frame does not resolve to a known symbol.
>   
>   MFC after:	1 week
>   Sponsored by:	Chelsio Communications

This appears to be fallout from lld?  After fixing this, the stack trace
for my next panic shows no symbols for functions in the kernel, only
functions in kernel modules:

KDB: stack backtrace:                                                           
??() at 0xffffffff803c372b/frame 0xfffffe0093632750                             
??() at 0xffffffff80a07539/frame 0xfffffe0093632800                             
??() at 0xffffffff809cc14c/frame 0xfffffe0093632860                             
??() at 0xffffffff809cc203/frame 0xfffffe00936328c0                             
do_rx_tls_cmp() at do_rx_tls_cmp+0x1d3/frame 0xfffffe0093632910                 
service_iq() at service_iq+0x380/frame 0xfffffe00936329b0                       
t4_intr() at t4_intr+0x2e/frame 0xfffffe00936329d0                              
??() at 0xffffffff80993f1f/frame 0xfffffe0093632a10                             
??() at 0xffffffff80994716/frame 0xfffffe0093632a30                             
??() at 0xffffffff809945cb/frame 0xfffffe0093632a70                             
??() at 0xffffffff809912f3/frame 0xfffffe0093632ab0                             
??() at 0xffffffff80e1de8e                                                      
KDB: enter: panic                                                               

I don't spot anything obvious comparing readelf of an older kernel
with the LLD kernel, but I also haven't tried debugging this further.

-- 
John Baldwin