Kernel on Jayng9663

Build and Run on kernel using QEMU

Wed, 08 Apr 2026 16:10:31 -0700

Just for personal note, haven’t test on others.

Kernel Config

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make defconfig CC=clang

if want to include other module which is not enable be default in defconfig. run for e.g.

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./scripts/config --module CONFIG_MAC80211_HWSIM
./scripts/config --module CONFIG_IWLWIFI=y
./scripts/config --module CONFIG_IWLWIFI_LEDS=y
./scripts/config --module CONFIG_IWLDVM=m
./scripts/config --module CONFIG_IWLMVM=m

build-kernel.sh

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#!/bin/bash
set -e
 
make CC=clang -j$(nproc)
python3 scripts/clang-tools/gen_compile_commands.py
 
echo "Done — bzImage ready at arch/x86/boot/bzImage"

For subsequent small changes just run make CC=clang -j$(nproc) directly. Make only recompiles changed files, so a single .c change takes a few seconds.

Raw Kernel + Busybox Initramfs

QEMU loads the kernel and a cpio archive, the kernel unpacks it into a tmpfs, runs /init, and drops you into a busybox shell.

build-initramfs.sh

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#!/bin/bash
set -e
 
KBUILD=$(pwd)
 
rm -rf initramfs
mkdir -p initramfs/{bin,sbin,etc,proc,sys,dev,lib/modules}
 
cp /usr/bin/busybox initramfs/bin/
cd initramfs/bin
./busybox --install .
cd "$KBUILD"
 
cat > initramfs/init << 'EOF'
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys
mount -t devtmpfs none /dev 2>/dev/null || mdev -s
 
echo "Kernel $(uname -r) booted!"
exec /bin/sh
EOF
 
chmod +x initramfs/init
 
cd initramfs
find . | cpio -o -H newc | gzip > ../initramfs.cpio.gz
cd ..
 
echo "Done — initramfs.cpio.gz ready"

boot.sh

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#!/bin/bash
set -e
 
KBUILD=$(pwd)
 
qemu-system-x86_64 \
 -kernel "$KBUILD/arch/x86/boot/bzImage" \
 -initrd "$KBUILD/initramfs.cpio.gz" \
 -append "console=ttyS0,115200 earlyprintk=serial,ttyS0,115200 rdinit=/init nokaslr" \
 -nographic \
 -serial mon:stdio \
 -device e1000,netdev=net0 \
 -netdev user,id=net0,hostfwd=tcp::2222-:22 \
 -m 512M \
 -no-reboot

Rebuild

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bash build-kernel.sh
bash build-initramfs.sh
bash boot.sh

Exit QEMU with Ctrl-A X or run shutdown.

Full Arch Linux Rootfs

When you need pacman, ssh, or any real tooling, install Arch onto a qcow2 image and boot your custom kernel directly into it.

Create the Disk

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qemu-img create -f qcow2 rootfs.qcow2 10G

Install Arch from ISO

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qemu-system-x86_64 \
 -cdrom archlinux-x86_64.iso \
 -boot d \
 -drive file=rootfs.qcow2,format=qcow2 \
 -device e1000,netdev=net0 \
 -netdev user,id=net0,hostfwd=tcp::2222-:22 \
 -m 2G \
 -enable-kvm \
 -no-reboot \
 -vnc :0

Connect with vncviewer localhost:5900. Inside the installer:

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fdisk /dev/sda << 'EOF'
g
n
1
 
 
w
EOF
 
mkfs.ext4 /dev/sda1
mount /dev/sda1 /mnt
 
# base only, no need linux package
pacstrap /mnt base
genfstab -U /mnt >> /mnt/etc/fstab
arch-chroot /mnt
 
passwd root
 
# Network (optional)
cat > /etc/systemd/network/20-wired.network << 'NET'
[Match]
Name=ens3
 
[Network]
DHCP=yes
NET
 
systemctl enable systemd-networkd systemd-resolved
 
exit
umount -R /mnt
poweroff

boot.sh

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#!/bin/bash
set -e
 
KBUILD=$(pwd)
 
qemu-system-x86_64 \
 -kernel "$KBUILD/arch/x86/boot/bzImage" \
 -drive file="$KBUILD/rootfs.qcow2",format=qcow2 \
 -append "console=ttyS0,115200 earlyprintk=serial,ttyS0,115200 root=/dev/sda1 rw nokaslr" \
 -nographic \
 -serial mon:stdio \
 -device e1000,netdev=net0 \
 -netdev user,id=net0,hostfwd=tcp::2222-:22 \
 -m 2G \
 -enable-kvm \
 -no-reboot

SSH in with:

📝 Note

Need to install and start openssh, and set PermitRootLogin = yes in /etc/ssh/ssh_config.

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ssh -p 2222 root@127.0.0.1

Rebuild

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bash build-kernel.sh
bash build-initramfs.sh
bash boot.sh

Exit QEMU with Ctrl-A X or run shutdown.

/proc/[PID]/stat Field Reference

Sun, 29 Mar 2026 23:08:22 -0700

The /proc/[PID]/stat file exposes process status information. Each field is listed below in order of appearance.

Fields

ID	Field	Description
1	`pid`	Process ID
2	`tcomm`	Filename of the executable
3	`state`	Process state: `R` running, `S` sleeping, `D` uninterruptible sleep, `Z` zombie, `T` traced or stopped
4	`ppid`	Process ID of the parent process
5	`pgrp`	Process group ID
6	`sid`	Session ID
7	`tty_nr`	TTY the process uses
8	`tty_pgrp`	Process group ID of the TTY
9	`flags`	Task flags
10	`min_flt`	Number of minor faults
11	`cmin_flt`	Number of minor faults including children
12	`maj_flt`	Number of major faults
13	`cmaj_flt`	Number of major faults including children
14	`utime`	User mode jiffies
15	`stime`	Kernel mode jiffies
16	`cutime`	User mode jiffies including children
17	`cstime`	Kernel mode jiffies including children
18	`priority`	Priority level
19	`nice`	Nice level
20	`num_threads`	Number of threads
21	`it_real_value`	(Obsolete, always 0)
22	`start_time`	Time the process started after system boot
23	`vsize`	Virtual memory size
24	`rss`	Resident set memory size
25	`rsslim`	Current limit in bytes on the RSS
26	`start_code`	Address above which program text can run
27	`end_code`	Address below which program text can run
28	`start_stack`	Address of the start of the main process stack
29	`esp`	Current value of ESP
30	`eip`	Current value of EIP
31	`pending`	Bitmap of pending signals
32	`blocked`	Bitmap of blocked signals
33	`sigign`	Bitmap of ignored signals
34	`sigcatch`	Bitmap of caught signals
35	(placeholder)	(Was wchan address — use `/proc/[PID]/wchan` instead)
36	(placeholder)	(Reserved)
37	(placeholder)	(Reserved)
38	`exit_signal`	Signal sent to the parent thread on exit
39	`task_cpu`	CPU the task is scheduled on
40	`rt_priority`	Realtime priority
41	`policy`	Scheduling policy (see `man sched_setscheduler`)
42	`blkio_ticks`	Time spent waiting for block I/O
43	`gtime`	Guest time of the task in jiffies
44	`cgtime`	Guest time of child tasks in jiffies
45	`start_data`	Address above which program data+BSS is placed
46	`end_data`	Address below which program data+BSS is placed
47	`start_brk`	Address above which the heap can be expanded with `brk()`
48	`arg_start`	Address above which the command line is placed
49	`arg_end`	Address below which the command line is placed
50	`env_start`	Address above which the environment is placed
51	`env_end`	Address below which the environment is placed
52	`exit_code`	Thread exit code as reported by `waitpid`

Example

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871869 (VN-Presence) S 12198 871869 12198 34830 871869 4194560 1205 0 173 0 46734 8492 0 0 20 0 2 0 10523393 176685056 2837 18446744073709551615 94266814361600 94266814993397 140734575381584 0 0 0 0 0 16386 0 0 0 17 16 0 0 0 0 0 94266815325280 94266815330208 94267110821888 140734575389833 140734575389847 140734575389847 140734575394794 0

Parsed field by field:

ID	Field	Value	Notes
1	`pid`	`871869`	Process ID
2	`tcomm`	`(VN-Presence)`	Executable name
3	`state`	`S`	Sleeping (interruptible)
4	`ppid`	`12198`	Parent PID
5	`pgrp`	`871869`	Process group ID
6	`sid`	`12198`	Session ID
7	`tty_nr`	`34830`	TTY device number
8	`tty_pgrp`	`871869`	Foreground process group of TTY
9	`flags`	`4194560`	Task flags
10	`min_flt`	`1205`	Minor page faults
11	`cmin_flt`	`0`	Minor faults including children
12	`maj_flt`	`173`	Major page faults
13	`cmaj_flt`	`0`	Major faults including children
14	`utime`	`46734`	User-mode CPU time (jiffies) — ~467s at 100 Hz
15	`stime`	`8492`	Kernel-mode CPU time (jiffies) — ~84s at 100 Hz
16	`cutime`	`0`	Children user-mode jiffies
17	`cstime`	`0`	Children kernel-mode jiffies
18	`priority`	`20`	Kernel priority
19	`nice`	`0`	Nice value (0 = default)
20	`num_threads`	`2`	Thread count
21	`it_real_value`	`0`	Obsolete, always 0
22	`start_time`	`10523393`	Jiffies after boot when process started
23	`vsize`	`176685056`	Virtual memory size (168 MiB)
24	`rss`	`2837`	Resident set size (pages) — 2837 × 4 KiB ≈ 11 MiB
25	`rsslim`	`18446744073709551615`	RSS limit (0xFFFFFFFFFFFFFFFF = unlimited)
26	`start_code`	`94266814361600`	Start of executable text segment
27	`end_code`	`94266814993397`	End of executable text segment
28	`start_stack`	`140734575381584`	Stack start address
29	`esp`	`0`	Current stack pointer
30	`eip`	`0`	Current instruction pointer
31	`pending`	`0`	Pending signals bitmap
32	`blocked`	`0`	Blocked signals bitmap
33	`sigign`	`16386`	Ignored signals bitmap
34	`sigcatch`	`0`	Caught signals bitmap
35	(placeholder)	`0`	(Was wchan)
36	(placeholder)	`0`	(Reserved)
37	(placeholder)	`0`	(Reserved)
38	`exit_signal`	`17`	Signal sent to parent on exit (17 = SIGCHLD)
39	`task_cpu`	`16`	Last CPU the task ran on
40	`rt_priority`	`0`	Realtime priority (0 = not realtime)
41	`policy`	`0`	Scheduling policy (0 = SCHED_NORMAL)
42	`blkio_ticks`	`0`	Block I/O wait ticks
43	`gtime`	`0`	Guest time (jiffies)
44	`cgtime`	`0`	Children guest time (jiffies)
45	`start_data`	`94266815325280`	Start of data+BSS segment
46	`end_data`	`94266815330208`	End of data+BSS segment
47	`start_brk`	`94267110821888`	Start of heap
48	`arg_start`	`140734575389833`	Start of command-line args
49	`arg_end`	`140734575389847`	End of command-line args
50	`env_start`	`140734575389847`	Start of environment
51	`env_end`	`140734575394794`	End of environment
52	`exit_code`	`0`	Exit code

Notes

Fields are space-separated and appear in the order listed above.
Time values (utime, stime, etc.) are measured in jiffies (clock ticks). Divide by sysconf(_SC_CLK_TCK) to convert to seconds.

References

The /proc Filesystem linux kernel doc
Linux kernel source: fs/proc/array.c