How to properly import the configuration of the Buster kernel into own development ?

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

are people here who make their own kernels and know how to import the
configuration of the originally installed kernel ?

I got lured by
  https://kernel-team.pages.debian.net/kernel-handbook/ch-common-tasks.html
into following
  "generate a configuration based on the running kernel and the currently
   loaded modules (make localmodconfig)"
which was obviously a poor decision.

What should i do in order to bring the configuration of the original Buster
kernel 4.19.0 to my experimental kernel which stems from the Buster package
"linux-source-4.19" ?
(There seem to be some new configuration options in the source kernel.)

-------------------------------------------------------------------------
Long story:

After happily hacking on the CDROM bugs i now look at ISO 9660 (year 2038
is near). At that occasion i am faced with no loop devices for mounting
my test ISO 9660 images.

Some googling brought me to diffing the configuration reports at boot
time of the original Buster kernel 4.19.0 and my hack which stems from
the Buster package "linux-source-4.19":
  diff -puN /boot/config-4.19.0-9-amd64 /boot/config-4.19.118-ts

That diff is huge and reveils a massacre with CONFIG_BLK_DEV options.
  -CONFIG_BLK_DEV_LOOP=m
  ...
  -CONFIG_BLK_DEV_RAM=m
  ...
  +# CONFIG_BLK_DEV_LOOP is not set
  +...
  +# CONFIG_BLK_DEV_RAM is not set
and many more.

I hope to have now enabled the old CONFIG_BLK_DEV settings.
But the reason why they were unset is obscure to me and i don't know
which of the many other differences will bite me when this kernel goes
into real use.


Well, at least i can mount my ISO images now.
This here is in need to be fixed:

  $ xorriso -outdev test.iso \
            -blank as_needed \
            -map /bin/true /victim \
            -alter_date m 'Oct 01 22:06:12 2040' /victim --

  # mount /home/thomas/test.iso /mnt/iso

  $ ls -l /mnt/iso/victim
  -rwxr-xr-x 1 root root 35424 Aug 26  1904 /mnt/iso/victim

(The error to map everything above 2028 to 1970 was fixed since kernel 3.16.
 But the function iso_date() still returns int, which rolls over in 2038.
   https://github.com/torvalds/linux/blob/master/fs/isofs/util.c
 line 19.
)

-------------------------------------------------------------------------

Have a nice day :)

Thomas