[linux] Trial & Error

Walk-Through

SECTION	SETUP
NEXT show hide	LINUX BOX show hide QEMU show hide

what is the shell?
ls -l /bin/sh
/bin/sh -> dash
/bin/sh -> bash
/bin/sh -> busybox

[linux] Set Everything Up

Walk-Through

SECTION	SETUP
PACKAGE show hide GIT show hide SOURCE show hide SYSTEM show hide CLEAN show hide CONFIG show hide MODULE show hide MAKE show hide RUN show hide TEST show hide NEXT show hide	LINUX BOX show hide QEMU show hide

(INSTALL) PACKAGE

$ apt-get update
$ apt-get upgrade
$ sudo apt install apt-file
$ sudo apt-file update
$ sudo apt-get install install-info
$ sudo apt install vim libncurses5-dev gcc make git git-all git-email gitk esmtp mutt exuberant-ctags libssl-dev bison flex libelf-dev bc build-essential kernel-package fakeroot ccache ncurses-dev alien cscope meld gitk libssl1.1 codespell python-ply qemu qemu-system gdb
$ pip install gitpython

(SETUP) GIT

$ git config --global user.name "John Doe"
$ git config --global user.email johndoe@gmail.com

Email:

• Create Google App Passwords

  $ vim ~/.muttrc

  Example:

  set realname = "John Doe" set from = "johndoe@gmail.com" set use_from = yes set envelope_from = yes set edit_headers=yes set smtp_url = "smtps://johndoe@gmail.com@smtp.gmail.com:465/" set smtp_pass = {SMPT_APP_PASSWORD} set imap_user = "johndoe@gmail.com" set imap_pass = {IMAP_APP_PASSWORD} set imap_keepalive = 900 set timeout = 10 set ssl_force_tls = yes set ssl_starttls = yes bind index G imap-fetch-mail set folder = "imaps://imap.gmail.com:993" set spoolfile = "imaps://imap.gmail.com/INBOX" set header_cache=~/.mutt/cache/headers set message_cachedir=~/.mutt/cache/bodies set certificate_file=~/.mutt/certificates set record = "" set postponed = "imaps://imap.gmail.com/[Gmail]/Draft" set editor = "vim" set charset = "utf-8"

• Create Yahoo App Passwords

  $ vim ~/.muttrc

  Example:

  set realname = "John Doe" set from = "johndoe@gmail.com" set use_from = yes set envelope_from = yes set edit_headers=yes set smtp_url = "smtps://johndoe@gmail.com@smtp.gmail.com:465/" set smtp_pass = {SMPT_APP_PASSWORD} set imap_user = "johndoe@gmail.com" set imap_pass = {IMAP_APP_PASSWORD} set imap_keepalive = 900 set timeout = 10 set ssl_force_tls = yes set ssl_starttls = yes set folder = "imaps://export.imap.mail.yahoo.com:993" set spoolfile="imaps://imap.mail.yahoo.com/INBOX" set header_cache=~/.mutt/cache/headers set message_cachedir=~/.mutt/cache/bodies set certificate_file=~/.mutt/certificates set record="imaps://imap.mail.yahoo.com/Sent" set postponed="imaps://imap.mail.yahoo.com/Drafts" set editor = "vim" set charset = "utf-8"

  $ mutt

  Say "no" to creating an inbox for now. Type 'm' to create a new message. Specify your own email address (or a secondary email) to send the test message to. Set the Subject however you want to. Type a message in the body, and then save and quit. Hit 'y' to send the message, hit 'e' to edit the message again, or hit 'q' to abort sending the message.
  
  Look in your email to double check you received a message. If you send the email to yourself, for some mail services like gmail, the message will not show up in your inbox, and you will have to look in your Sent Mail folder.

(INSTALL) SOURCE (CODE)

$ git clone -b staging-testing git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
$ git tag -l | less # list out the kernel versions
$ git checkout -b stable tag # Where tag is the latest vX.Y.Z tag you found.
$ git branch test # create branch named test, don't mess up the master branch (tree)
$ git checkout test # select test branch
$ git branch # check if currently at test branch

(FILE)SYSTEM

created rootfs.ext4 with buildroot

$ git clone git://git.buildroot.net/buildroot

$ cd buildroot

$ make menuconfig

Target Options → Target Architecture (x86_64) → (X) x86_64 # run it on x86_64 virtualized system with qemu.

Filesystem images → [*] ext2/3/4 root file system → ext2/3/4 variant (ext4) → (X) ext4 # ext4 file system to be mounted as default file system

$ make -j8 - Build ‘buildroot’ project

The rootfs.ext4 has been created

CLEAN( UP)

Cleaning is done on three levels.

$ make clean # Delete most generated files to build external modules
$ make mrproper # Delete the current configuration and all generated files
$ make distclean # Remove editor backup files, patch leftover files, etc

Delete old official kernels from boot loader

$ dpkg -l | grep linux-image- # list out (previous) installed kernels

...... rc linux-image-4.15.0-96-generic 4.15.0-96.97 amd64 Signed kernel image generic rc linux-image-4.15.0-99-generic 4.15.0-99.100 amd64 Signed kernel image generic ii linux-image-5.0.0-32-generic 5.0.0-32.34~18.04.2 amd64 Signed kernel image generic rc linux-image-5.0.0-37-generic 5.0.0-37.40~18.04.1 amd64 Signed kernel image generic ......

$ sudo apt-get autoremove linux-image-5.3.0-51-generic # autoremove desired kernel
reboot
$ sudo apt-get autoclean & apt full-upgrade & apt-get dist-upgrade # upgrade everything again

Delete Custom Compiled Kernel from boot loader

$ sudo locate "*5.5.0-rc6*" | sudo xargs -p -ixxx rm -f 'xxx' # identify the files of kernels

Remove the following files:

$ sudo rm /boot/vmlinuz-5.5.0-rc6+
$ sudo rm /boot/initrd-5.5.0-rc6+
$ sudo rm /boot/System-5.5.0-rc6+
$ sudo rm /boot/config-5.5.0-rc6+
$ sudo rm /lib/modules-5.5.0-rc6+

and Finally,

$ sudo update-grub # boot loader as well

NOTE:

"E: gconf2: dependency problems - leaving triggers unprocessed"

try:

$ sudo dpkg --configure -a

CONFIG

$ cp /boot/config-`uname -r`* .config # [TRY THIS 1ST] duplicating your current config

$ make localmodconfig # utilized existing .config with modules installed

$ make menuconfig # Text-based with colored menus and radiolists.

$ make defconfig # This option creates a config file that uses default settings based on the current system's architecture.

$ make ${PLATFORM}_defconfig - Creates a config file using values from arch/$ARCH/configs/${PLATFORM}_defconfig.

$ make ARCH=x86_64 x86_64_defconfig # pick current kernel setting as base

$ make ARCH=x86_64 menuconfig # add debugging ability in TUI
Kernel hacking --->
Compile-time checks and compiler options --->
[*] Compile the kernel with debug info
[*] Provide GDB scripts for kernel debugging (New)
[ ] Reduce debugging information

(MODIFY )MODULE

$ lsmod # list out modules says, want to modify e1000e

says, want to modify e1000

...... e1000e 123456 0 ......

THEN EITHER,
$ git grep e1000e -- '*Makefile' # search the module path
OR
$ modinfo e1000e # find module path

filename: /lib/modules/X.X.X-XX-generic/kernel/drivers/net/ethernet/intel/e1000e/e1000e.ko version: 3.2.6-k license: GPL v2 description: Intel(R) PRO/1000 Network Driver ......

so, the path is drivers/net/ethernet/intel/e1000e
THEN,
$ vim drivers/net/ethernet/intel/e1000e/*.c # open all c files & find probe function

so, the path is drivers/net/ethernet/intel/e1000
THEN,
$ vim drivers/net/ethernet/intel/e1000/*.c # open all c files & find probe function

add a line to printk() to probe function for TESTing,

NOTE: ":n" to next file, ":N" return to last file, "/probe" to search keyword "probe"

struct e1000_hw *hw; # search for probe function by "/probe" in vi ..... static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent) {         struct net_device *netdev;         struct e1000_adapter *adapter;         struct e1000_hw *hw;         printk(KERN_DEBUG "DEBUG: Passed %s %d \n",__FUNCTION__,__LINE__);         const struct e1000_info *ei = e1000_info_tbl[ent->driver_data]; .....

MAKE (INSTALL)

$ make M=drivers/usb/serial -j8 # Build only a portion of the kernel with 4 core CPU
$ lscpu # check how many core the pc has
$ make -j8 # Build entire kernell with 4 core CPU
$ sudo make modules_install # Install the Linux kernel modules
$ sudo make install # sudo make install

Ubuntu (Default boot into latest kernel):
$ sudo update-grub2
Centos (Default boot into last kernel):
$ sudo grub2-set-default 0 # set to latest kernel
$ sudo grub2-mkconfig -o /boot/grub2/grub.cfg

$ sudo reboot

RUN

• Reboot
• Hold "Shift" at startup
• Select & Boot with installed kernel

• without debugger:

$ qemu-system-x86_64 -kernel arch/x86/boot/bzImage \
-boot c -m 2049M -hda ../buildroot/output/images/rootfs.ext4 \
-append "root=/dev/sda rw console=ttyS0,115200 acpi=off nokaslr" \
-serial stdio -display none

• with debugger:

$ qemu-system-x86_64 -s -kernel arch/x86/boot/bzImage \
-boot c -m 2049M -hda ../buildroot/output/images/rootfs.ext2 \
-append "root=/dev/sda rw console=ttyS0,115200 acpi=off nokaslr" \
-serial stdio -display none

Login as root (id = root, no passowrd)

# mkdir home # home directory not created by default
# adduser newuser # create normal user account
# exit
login as newuser

TEST

• $ dmesg | less
• type:

/DEBUG: Passed

[    2.093005] [ 2.114507] DEBUG: Passed e1000_probe 926 c

WHAT'S NEXT

NEXT