Linux Kernel in a nutshell

Although I've been working with Linux kernel for ages, I decided to browse through Linux Kernel in a nutshell, an excellent book on the practical things regarding working with the kernel. There certainly were things that I was not aware of. Here are my notes on these things.


Using a read-only source tree with O=/path/to/build/output

Some basic static analysis with

  • sparse with C=1 or C=2.
  • checkstack
  • namespacecheck

Localversion-prefixed files in object and source trees.


Finding all kernel modules required by the running system, using modaliases in the /sys tree and modprobe with --show-depends. Or get-driver.sh helper script.


Kernel argument max_addr to force a upper bound on physical addresses used. Probably a good for validating a software image for a low cost board version. I've used mem=XX for this before, but I believe max_addr could yield even more realistic results.


The book included nice "demos" for tools like

  • quilt for managing a set of patches against an upstream source tree
  • ketchup as a frontend to upstream kernel archives.


These were not described in detail, but are interesting and I need to remember to read more about them later.

  • RCU's
  • format of modaliases
  • seccomp for sandboxing processes
  • kernel SPI support
  • inotify mechanism
  • oprofile tooling
  • kernel security models.


Comments

Post a Comment

Popular posts from this blog

iMovie event library on a network drive, NAS

I was shocked to find that iMovie '09 would not allow storing event libraries on networked disks. The AFP volume would show up, but remain non-functional with a yellow exclamation sign. There are plenty of instructions for hacking around the limitation with clumsy symbolic links. I discovered a much simpler approach, using an undocumented (?) setting built right into iMovie:"Allow Network Volumes". Use at your own risk, try the following command in Terminal defaults write -app iMovie allowNV -bool true
Read more

Proxmox PCIe passthrough on HP gen8 - failed to set iommu for container

Problem Setting up PCIe passthrough from host to a VM was supposed to be easy. However, being an HP server, there was a bit more to it than usual. The VM simply refused to start when configured use Nvidia GPU from the host: vfio error: 0000:04:00.0: failed to setup container for group 21: failed to set iommu for container: Operation not permitted In dmesg there was a bit more background on what was wrong: fio-pci 0000:04:00.1: Device is ineligible for IOMMU domain attach due to platform RMRR requirement.  Contact your platform vendor. Luckily, HP had issued a customer advisory on this. It describes a convoluted method to disable this RMRR per slot basis. It seems to work for me, so I thought I'd write down some notes if I ever run into this again. Basic setup Proxmox has decent instructions for preparing the host for passthrough setup in general, in summary: -  add  intel_iommu=on to   GRUB_CMDLINE_LINUX_DEFAULT  in the file  /etc/default/grub - add vfio modules to  /etc/modules
Read more

Backup and restore observium

Note to self, how to backup and restore an Observium installation such as Turn Key Linux . backup mysqldump --all--databases >sql.txt tar zcvf rrd.tgz /opt/observium/rrd restore log in at https://observium:12322/ as adminer import the sql.txt tar zxvf  rrd.tgz -C /
Read more