enabling kernel dump options in GENERIC

[Mark Millard]

Mark Johnston markj at FreeBSD.org wrote on
Thu May 17 17:24:19 UTC 2018 :

> Over the past couple of years, a number of kernel dump features have
> been added: encryption, compression and dumping to a remote host
> (netdump). These features are currently all omitted from GENERIC.
> 
> . . .
> Therefore, I'd like to propose enabling these features by default
> on i386, amd64, arm64, powerpc(64) and sparc64 so that they're available
> out of the box in 12.0.
> . . .

Bugzilla 214598 (from late 2016) was about
dump for TARGET_ARCH=powerpc64 builds getting
failures like:

KDB: enter: manual escape to debugger
[ thread pid 12 tid 10018 ]
Stopped at       .kdb_enter+0x70:       ori r0, r0, 0x0
db> dump
Dumping 9 MB (3 chunks)
  chunk 0: 10MB (2510 pages) ... ok
  chunk 1: 1MB (24 pages) ... ok
  chunk 2: 1MB (2 pages)panic: vm_fault: fault on nofault entry, addr: c000000000022000

(A 32-bit powerpc build on the same machine worked
fine for dumping.)

I just tried it with head -r333594 and I got something
similar. (Old and new mention routines with _bus_dma_map_
in the names near the trap in the call stack. I've not
done a detailed comparison.)

So, at least for the old PowerMac G5 so-called "Quad
Core" powerpc64 context that was in use, there may be
problems putting the changes to use --or  in any use
of dump.

As for config for the kernel configuration involved:

# more /usr/src/sys/powerpc/conf/GENERIC64vtsc-NODBG
#
# GENERIC -- Custom configuration for the powerpc/powerpc64
#

include "GENERIC64"

ident   GENERIC64vtsc-NODBG

makeoptions     DEBUG=-g                # Build kernel with gdb(1) debug symbols

nooptions       PS3                     # Sony Playstation 3               HACK!!! to allow sc

options         KDB                     # Enable kernel debugger support

options         ALT_BREAK_TO_DEBUGGER
options         BREAK_TO_DEBUGGER

# For minimum debugger support (stable branch) use:
options         KDB_TRACE               # Print a stack trace for a panic
options         DDB                     # Enable the kernel debugger
options         GDB                     # HACK!!! ...

# Extra stuff:
#options        VERBOSE_SYSINIT         # Enable verbose sysinit messages
#options        BOOTVERBOSE=1
#options        BOOTHOWTO=RB_VERBOSE
#options        KTR
#options        KTR_MASK=KTR_TRAP
##options       KTR_CPUMASK=0xF
#options        KTR_VERBOSE

# HACK!!! to allow sc for 2560x1440 display on Radeon X1950 that vt historically mishandled during booting
device          sc
#device                 kbdmux          # HACK: already listed by vt
options         SC_OFWFB        # OFW frame buffer
options         SC_DFLT_FONT    # compile font in
makeoptions     SC_DFLT_FONT=cp437


# Disable any extra checking for. . .
nooptions       DEADLKRES               # Enable the deadlock resolver
nooptions       INVARIANTS              # Enable calls of extra sanity checking
nooptions       INVARIANT_SUPPORT       # Extra sanity checks of internal structures, required by INVARIANTS
nooptions       WITNESS                 # Enable checks to detect deadlocks and cycles
nooptions       WITNESS_SKIPSPIN        # Don't run witness on spinlocks for speed
nooptions       DIAGNOSTIC
nooptions       MALLOC_DEBUG_MAXZONES   # Separate malloc(9) zones

device          filemon
device          geom_label

===
Mark Millard
marklmi26-fbsd at yahoo.com
( dsl-only.net went
away in early 2018-Mar)