Compiling Kernel Debugging and Know-Hows.

GoNeFast_01 · May 7, 2023

I was having the known problem with Text Console using CTRL + ALT + F1-F8 bug of tearing / square pixelated screens.
I am currently still trying/testing with some options in /boot/loader.conf file to see if I can fix this issue of the tearing with Nvidia drivers 510.60.2.

Similar to:

Solved - Can't get to text console using Alt+Ctrl+F1-F8

I can use the graphical session on ALT+CTRL+F9 When I try to switch back to any other virtual terminal (using ALT+CTRL]+F), I get colored squares. It seems to be exactly this bug: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=213912 Is this something that cannot be circumvented? I wonder...

forums.freebsd.org

Artifacts / tearing in text terminal with tty1-tty7

system FreeBSD localhost 12.1-RELEASE FreeBSD 12.1-RELEASE r354233 GENERIC amd64, graph shell gdm 3, driver nvidia-driver-440.100_1 OpenGL rendering video card gtx 1070, monique full hd 32 ' ------------ /etc/rc.conf the following is written kld_list = "linux nvidia" gnome_enable = "YES"...

forums.freebsd.org

And one of the solution is to re-compile the kernel the GENERIC

⚙ D33141 Remove options VESA from x86 GENERIC

reviews.freebsd.org

=====================================================

I created a Bhyve VM of FBSD 13p2 and decided to build kernel and install kernel for testing purposes.

Code:

git clone https://git.freebsd.org/src.git /usr/src
&& \
vi /sys/amd64/conf/GENERIC
206 #options         #VESA                    #Add support for VESA BIOS Extensions (VBE)
&& \
cp -v /sys/amd64/conf/GENERIC /sys/amd64/conf/CUSTOM-TEST1
&& \
cd /sys/amd64/conf
&& \
make buildkernel KERNCONF=CUSTOM-TEST1
#make buildkernel KERNCONF=GENERIC
make installkernel KERNCONF=CUSTOM-TEST1
#make installkernel KERNCONF=GENERIC
&& \
shutdown -r now
ls -lah /boot/kernel
ls -lah /boot/kernel.old

After reviewing the /boot/kernel folder I am still seeing the vesa.ko file inside the /boot/kernel, did I do something wrong?

How can I debug if vesa.ko is truly not compiled in kernel?

How do more experienced developers debug kernel issues or if the kernel compiled correctly?

Any advice what to do / not do while compiling kernel?

Alain De Vos · May 7, 2023

For console i use sc instead of vt.

Alex Seitsinger · May 7, 2023

Alain De Vos said:
For console i use sc instead of vt.

Is there any reason why?

GoNeFast_01 · May 7, 2023

alexseitsinger said:
Is there any reason why?

It fixes the tearing / square pixelated issue I am facing.

One of the solutions is ....
edit

/boot/loader.conf
kern.vty="sc"

Was simply looking to find a solution with default
kern.vty="vt"

Hence kernel build.

astyle · May 9, 2023

GoNeFast_01 said:
After reviewing the /boot/kernel folder I am still seeing the vesa.ko file inside the /boot/kernel, did I do something wrong?

How can I debug if vesa.ko is truly not compiled in kernel?

How do more experienced developers debug kernel issues or if the kernel compiled correctly?

Any advice what to do / not do while compiling kernel?

Usually, there are sysctls that can be tweaked without rebuilding the kernel.

If the kernel boots, then your compilation can be considered a success, or at least a 'Pheeew, at least I did not mess up!'.

Not every .ko file in /boot/kernel/ gets loaded by kldload - just check using kldstat...

IIRC, a debugger takes a single file, and reverse-compiles it... so that you 'see' how the program progresses... that's one way to debug that I remember from college, but on these Forums, there are ppl who know much better than me about the debugging process...

When I tried to compile / recompile my own kernel, I just followed the relevant chapters in the Handbook. Of course, it's important to actually have sources in /usr/src...

George · May 9, 2023

I wonder whether install-kernel just copies files to /boot/kernel or whether it deletes the files in that folder beforehand.. The vesa.ko might be from previous kernel. There are these make options: delete-old delete-old-dirs delete-old-files delete-old-libs
I will check the makefiles..

astyle · May 9, 2023

George said:
I wonder whether install-kernel just copies files to /boot/kernel or whether it deletes the files in that folder beforehand..

The command install-kernel doesn't just copy files to /boot/kernel/ - it also reworks symlinks to all kinds of libs. And no, older kernels don't get deleted. Evidence of that is in the boot menu... Did you read this section of the Handbook (https://docs.freebsd.org/en/books/handbook/cutting-edge/#makeworld), esp. Section 25.6.4?