It contains Linux kernel modules.
- Buildroot:
2021.08.1 - Kernel:
linux-5.10.72 - Compiler:
gcc-arm-10.3-2021.07-x86_64-aarch64-none-linux-gnu - Qemu:
v6.1.0(aarch64-softmmu @ cortex-a57)
- How to do setup of workspace, follow this.
- For Docker
cd /path/to/repo/.devcontainer
docker build --tag aarch64-qemu:latest .
docker run -it aarch64-qemu:latest /bin/bashSimple kernel module
# insmod helloworld.ko
[ 8604.716927] Helloworld_module: init
#
# rmmod helloworld.ko
[ 8610.234228] Helloworld_module: exit
#A kernel module which can accept parameters.
-
Insert module with no parameter
#
# insmod helloworld_param.ko
[ 8773.412883] Helloworld_module: init
[ 8773.413270] Helloworld_parameters:
[ 8773.413524] - param_integer # 500
[ 8773.413785] - param_array # [ 500][ 501][ 502]
[ 8773.414045] - param_string # helloworld
#
# rmmod helloworld_param.ko
[ 8780.668106] Helloworld_module: exit
[ 8780.668684] Helloworld_parameters:
[ 8780.668980] - param_integer # 500
[ 8780.669249] - param_array # [ 500][ 501][ 502]
[ 8780.669564] - param_string # helloworld
#- Insert module with user defined parameter
# insmod helloworld_param.ko param_integer=600 param_string="testing" param_array=1,2,3
[ 8869.944889] Helloworld_module: init
[ 8869.945650] Helloworld_parameters:
[ 8869.945948] - param_integer # 600
[ 8869.949919] - param_array # [ 1][ 2][ 3]
[ 8869.952371] - param_string # testing
#
# rmmod helloworld_param.ko
[ 8893.422618] Helloworld_module: exit
[ 8893.423951] Helloworld_parameters:
[ 8893.424284] - param_integer # 600
[ 8893.424550] - param_array # [ 1][ 2][ 3]
[ 8893.424878] - param_string # testing
#A kernel module with probe and remove by having entry in DTS file.
An example of how to use container_of.
# modinfo container_of.ko
filename: /root/container_of.ko
author: aakbar5 <[email protected]>
license: GPL
description: co: container_of example
version: 0.0.1
srcversion: 39B80B8E047FA102727B810
depends:
name: container_of
vermagic: 5.4.0-00001-gade746754348-dirty SMP preempt mod_unload aarch64
parm: param_count:Number of groups to be created -- (Read only) (int)
parm: param_idx:Index of the group to be shown -- (Read/write only) (int)# insmod container_of.ko
[11503.238689] co: init
[11503.240342] Group @ index based
[11503.240556] - Id # 32
[11503.240742] - Obj1 # 21 -- obj1=1
[11503.240949] - Obj2 # 11 -- obj2=1
[11503.241165] Group @ container_of @ id
[11503.241349] - Id # 32
[11503.241517] - Obj1 # 21 -- obj1=1
[11503.241698] - Obj2 # 11 -- obj2=1
[11503.241893] Group @ container_of @ obj1
[11503.242079] - Id # 32
[11503.242246] - Obj1 # 21 -- obj1=1
[11503.242435] - Obj2 # 11 -- obj2=1
#
# rmmod container_of.ko
[11523.668908] co: exit
## insmod container_of.ko param_idx=2
[ 46.364041] container_of: loading out-of-tree module taints kernel.
[ 46.397061] co: init
[ 46.400697] Group @ index based
[ 46.400988] - Id # 34
[ 46.401183] - Obj1 # 22 -- obj1=2
[ 46.401410] - Obj2 # 12 -- obj2=2
[ 46.401628] Group @ container_of @ id
[ 46.406580] - Id # 34
[ 46.406878] - Obj1 # 22 -- obj1=2
[ 46.407131] - Obj2 # 12 -- obj2=2
[ 46.407360] Group @ container_of @ obj1
[ 46.407643] - Id # 34
[ 46.407889] - Obj1 # 22 -- obj1=2
[ 46.408230] - Obj2 # 12 -- obj2=2An example of how to kernel linked list interface.
# insmod linked_list.ko
[ 796.369350] ll: init
[ 796.370399] Add nodes to the list...
[ 796.371385] List is not empty
[ 796.371567] Traverse the list...
[ 796.371774] #1: obj=0
[ 796.371944] #2: obj=1
[ 796.372098] #3: obj=2
[ 796.372249] #4: obj=3
[ 796.372400] #5: obj=4
[ 796.372554] Delete all nodes from the list...
[ 796.373165] List is empty
[ 796.373361] Traverse the list...
#
# rmmod linked_list.ko
[ 812.966234] ll: exit
#An example of usage of for_each_process.
# insmod proc_info.ko
[37227.566385] proinfo_module: init
[37227.575743] PID NAME STATE TIME
[37227.576613] 1 init Stopped[In] 00:00:00
[37227.576974] 2 kthreadd Stopped[In] 00:00:00
[37227.577241] 3 rcu_gp Stopped[UnNo] 00:00:00
[37227.577522] 4 rcu_par_gp Stopped[UnNo] 00:00:00
[37227.577779] 6 kworker/0:0H Stopped[UnNo] 00:00:00
[37227.578037] 8 mm_percpu_wq Stopped[UnNo] 00:00:00
[37227.578319] 9 ksoftirqd/0 Stopped[In] 00:00:00
[37227.578587] 10 rcu_preempt Stopped[UnNo] 00:00:00
[37227.578865] 11 migration/0 Stopped[In] 00:00:00
[37227.579131] 12 cpuhp/0 Stopped[In] 00:00:00
[37227.579401] 13 cpuhp/1 Stopped[In] 00:00:00
[37227.579677] 14 migration/1 Stopped[In] 00:00:00
[37227.579971] 15 ksoftirqd/1 Stopped[In] 00:00:00
[37227.580296] 16 kworker/1:0 Stopped[UnNo] 00:00:00
[37227.580729] 17 kworker/1:0H Stopped[UnNo] 00:00:00
[37227.581011] 18 kdevtmpfs Stopped[In] 00:00:00
[37227.581280] 19 netns Stopped[UnNo] 00:00:00
[37227.581555] 20 rcu_tasks_kthre Stopped[In] 00:00:00
[37227.581847] 21 kworker/0:1 Stopped[UnNo] 00:00:00
[37227.582355] 22 kworker/1:1 Stopped[UnNo] 00:00:00
[37227.583305] 23 kauditd Stopped[In] 00:00:00
[37227.583620] 24 oom_reaper Stopped[In] 00:00:00
[37227.583998] 25 writeback Stopped[UnNo] 00:00:00
[37227.584653] 26 kcompactd0 Stopped[In] 00:00:00
[37227.584988] 27 ksmd Stopped[In] 00:00:00
[37227.585294] 28 khugepaged Stopped[In] 00:00:00
[37227.585603] 46 cryptd Stopped[UnNo] 00:00:00
[37227.585935] 77 kintegrityd Stopped[UnNo] 00:00:01
[37227.586283] 78 kblockd Stopped[UnNo] 00:00:01
[37227.586657] 79 blkcg_punt_bio Stopped[UnNo] 00:00:01
[37227.586986] 80 tpm_dev_wq Stopped[UnNo] 00:00:01
[37227.587359] 81 ata_sff Stopped[UnNo] 00:00:01
[37227.587705] 82 edac-poller Stopped[UnNo] 00:00:01
[37227.588303] 83 devfreq_wq Stopped[UnNo] 00:00:01
[37227.588645] 84 watchdogd Stopped[In] 00:00:01
[37227.588950] 85 rpciod Stopped[UnNo] 00:00:01
[37227.589260] 86 kworker/u5:0 Stopped[UnNo] 00:00:01
[37227.589598] 87 xprtiod Stopped[UnNo] 00:00:01
[37227.589930] 146 kswapd0 Stopped[In] 00:00:02
[37227.590287] 147 nfsiod Stopped[UnNo] 00:00:02
[37227.590615] 151 kworker/1:1H Stopped[UnNo] 00:00:04
[37227.590950] 152 vfio-irqfd-clea Stopped[UnNo] 00:00:04
[37227.591276] 153 jbd2/vda-8 Stopped[In] 00:00:05
[37227.591591] 154 ext4-rsv-conver Stopped[UnNo] 00:00:05
[37227.592152] 155 kworker/0:1H Stopped[UnNo] 00:00:05
[37227.592673] 170 syslogd Stopped[In] 00:00:08
[37227.593004] 174 klogd Stopped[In] 00:00:08
[37227.593326] 185 irqbalance Stopped[In] 00:00:09
[37227.593589] 199 dbus-daemon Stopped[In] 00:00:11
[37227.593881] 205 rpcbind Stopped[In] 00:00:11
[37227.594208] 239 dhcpcd Stopped[In] 00:00:15
[37227.594559] 245 dropbear Stopped[In] 00:00:16
[37227.594881] 259 rpc.statd Stopped[In] 00:00:20
[37227.595217] 275 rpc.mountd Stopped[In] 00:00:21
[37227.595503] 280 sh Stopped[In] 00:00:22
[37227.595901] 290 dropbear Stopped[In] 00:14:19
[37227.596589] 291 sh Stopped[In] 00:14:20
[37227.597007] 393 kworker/0:2 Stopped[UnNo] 01:41:33
[37227.597347] 594 kworker/u4:0 Stopped[UnNo] 09:54:22
[37227.597643] 599 kworker/u4:2 Stopped[UnNo] 10:07:30
[37227.598210] 615 insmod running 10:20:26
[37227.598819] Code Section: 0x0000000000400000 -- 0x0000000000418140
[37227.599265] Data Section: 0x0000000000428cb8 -- 0x0000000000429380
[37227.599595] Stack: 0x0000ffffca7d5ee0
[37227.600168] Task size: 0x1000000000000
[37227.600428] VMA Count: 21
[37227.600729] VMA # 1: 0x0000000000400000 -- 0x0000000000419000
[37227.601051] VMA # 2: 0x0000000000428000 -- 0x0000000000429000
[37227.601342] VMA # 3: 0x0000000000429000 -- 0x000000000042a000
[37227.601660] VMA # 4: 0x0000000017717000 -- 0x0000000017738000
[37227.601973] VMA # 5: 0x0000ffff8358e000 -- 0x0000ffff835c7000
[37227.602305] VMA # 6: 0x0000ffff835c7000 -- 0x0000ffff836f9000
[37227.602641] VMA # 7: 0x0000ffff836f9000 -- 0x0000ffff83709000
[37227.602948] VMA # 8: 0x0000ffff83709000 -- 0x0000ffff8370d000
[37227.603251] VMA # 9: 0x0000ffff8370d000 -- 0x0000ffff8370f000
[37227.603589] VMA # 10: 0x0000ffff8370f000 -- 0x0000ffff83713000
[37227.604284] VMA # 11: 0x0000ffff83713000 -- 0x0000ffff83724000
[37227.604666] VMA # 12: 0x0000ffff83724000 -- 0x0000ffff83733000
[37227.604967] VMA # 13: 0x0000ffff83733000 -- 0x0000ffff83734000
[37227.605267] VMA # 14: 0x0000ffff83734000 -- 0x0000ffff83735000
[37227.605555] VMA # 15: 0x0000ffff83735000 -- 0x0000ffff83751000
[37227.605868] VMA # 16: 0x0000ffff8375a000 -- 0x0000ffff8375e000
[37227.606198] VMA # 17: 0x0000ffff8375e000 -- 0x0000ffff8375f000
[37227.606550] VMA # 18: 0x0000ffff8375f000 -- 0x0000ffff83760000
[37227.606859] VMA # 19: 0x0000ffff83760000 -- 0x0000ffff83761000
[37227.607190] VMA # 20: 0x0000ffff83761000 -- 0x0000ffff83763000
[37227.607519] VMA # 21: 0x0000ffffca7b6000 -- 0x0000ffffca7d7000
#
# rmmod proc_info.ko
[37230.392163] proinfo_module: exitAn example of how to use Per-CPU variable.
# insmod per_cpu_vars.ko
[ 488.653524] mod: init
[ 488.654033] smp_processor_id: 0
[ 488.654445] num_online_cpus: 2
[ 488.655747] --- Variable (var_static) before modification
[ 488.656645] cpu # 0 <> 0
[ 488.657235] cpu # 1 <> 0
[ 488.657795] --- Variable (var_dynamic) before modification
[ 488.658462] cpu # 0 <> 0
[ 488.659018] cpu # 1 <> 0
[ 488.660225]
[ 488.660225] ============================================
[ 488.660871] --- Variable (var_static) after modification
[ 488.661543] cpu # 0 <> 786
[ 488.662023] cpu # 1 <> 0
[ 488.662493] --- Variable (var_dynamic) before modification
[ 488.663776] cpu # 0 <> 3
[ 488.664198] cpu # 1 <> 0
#
# rmmod per_cpu_vars.ko
[ 498.671965] mod: exit
#An example of how to use kthread.
# insmod kthread_simple.ko
[ 110.613839] kthread_simple: loading out-of-tree module taints kernel.
[ 110.638790] kt: init
[ 110.639656] Setup kthread...
[ 110.645811] Start kthread...
[ 110.646479] - Task: # 1
[ 110.646914] kt_callback -- START
[ 110.647541] kt_callback -- Doing working (4294919881)
[ 114.675702] kt_callback -- Doing working (4294920888)
[ 116.691169] kt_callback -- Doing working (4294921392)
[ 118.706855] kt_callback -- Doing working (4294921896)
[ 120.722338] kt_callback -- Doing working (4294922400)
[ 122.739178] kt_callback -- Doing working (4294922904)
[ 124.755093] kt_callback -- Doing working (4294923408)
[ 126.770213] kt_callback -- Doing working (4294923912)
[ 128.787190] kt_callback -- Doing working (4294924416)
[ 130.802212] kt_callback -- Doing working (4294924920)
[ 132.819519] kt_callback -- Doing working (4294925424)
[ 134.834881] kt_callback -- Doing working (4294925928)
[ 136.850894] kt_callback -- Doing working (4294926432)
[ 138.866667] kt_callback -- Doing working (4294926936)
# rmmod kthread_simple.ko
[ 144.515812] kt: exit
[ 144.914943] kt_callback -- ENDAn example of kthread which can put in different states using device interface.
# insmod kthread_advanced.ko
[ 6135.380992] cd: init
[ 6135.390749] Setup kthread...
[ 6135.394460] Start kthread...
[ 6135.395504] - Task: # 1
[ 6135.396174] cd: device(/dev/chdev) is create
[ 6135.396968] - Major number # 235
[ 6135.397738] - minor number # 0
[ 6135.403838] kt_callback -- START
# [ 6138.411780] task_state -- running
[ 6141.579159] task_state -- running
[ 6144.610556] task_state -- running
[ 6147.719321] task_state -- running
[ 6150.742247] task_state -- running
[ 6153.808043] task_state -- running
[ 6156.849512] task_state -- running
[ 6159.874557] task_state -- running
[ 6162.898715] task_state -- running
[ 6164.638231] task_state -- suspend
[ 6188.854869] task_state -- resume
[ 6188.856184] task_state -- suspend
[ 6202.501738] task_state -- resume
[ 6205.512596] task_state -- running
[ 6208.534654] task_state -- running
[ 6211.562560] task_state -- running
[ 6214.760988] task_state -- running
[ 6217.886862] task_state -- running
[ 6220.920993] task_state -- running
[ 6223.951613] task_state -- running
[ 6226.992809] task_state -- running
[ 6230.017034] task_state -- running
[ 6233.042452] task_state -- running
[ 6235.684908] task_state -- stop
[ 6235.690136] kt_callback -- END
# rmmod kthread_advanced.ko
[ 6244.914722] cd: exit
## echo "1" > /dev/chdev
# echo "4" > /dev/chdev
# echo "4" > /dev/chdev
# echo "2" > /dev/chdevAn example of how to create/use notification chain.
# ls
notify_chain_consumer.ko notify_chain_publisher.ko
# insmod notify_chain_publisher.ko
[ 7210.060161] Notify chain publisher: init
# insmod notify_chain_consumer.ko
[ 7215.046885] Notify chain consumer: init
# [ 7215.460016] Notify chain consumer: notification # 0x83
[ 7215.972452] Notify chain consumer: notification # 0x82
[ 7216.484327] Notify chain consumer: notification # 0x83
[ 7216.996201] Notify chain consumer: notification # 0x82
[ 7217.508260] Notify chain consumer: notification # 0x83
[ 7218.020057] Notify chain consumer: notification # 0x82
[ 7218.531963] Notify chain consumer: notification # 0x83
[ 7219.044564] Notify chain consumer: notification # 0x82
[ 7219.556412] Notify chain consumer: notification # 0x83
[ 7220.068214] Notify chain consumer: notification # 0x82
[ 7220.580056] Notify chain consumer: notification # 0x83
[ 7221.092416] Notify chain consumer: notification # 0x82
[ 7221.604269] Notify chain consumer: notification # 0x83
#
# rmmod notify_chain_*.ko
[ 7231.289578] Notify chain consumer: exit
#An example of how to use mutex.
# insmod lock_mutex.ko
[ 7179.267261] lockmod: init
[ 7179.268022] Setup mutex...
[ 7179.268274] Setup kthread...
[ 7179.288063] Start kthreads...
[ 7179.288489] - Read task # 1
[ 7179.288761] - Write task # 1
[ 7179.289633] lockmod_read_callback -- START
[ 7179.293438] lockmod_read_callback -- Doing working (0)
[ 7179.298124] lockmod_write_callback -- START
# [ 7181.555485] lockmod_read_callback -- Doing working (0)
rmmod [ 7185.613442] lockmod_read_callback -- Doing working (2)
[ 7187.629618] lockmod_read_callback -- Doing working (2)
# rmmod lock_mutex.ko
[ 7189.584263] lockmod: exit
[ 7190.671527] lockmod_write_callback -- END
[ 7190.676295] lockmod_read_callback -- Doing working (3)
[ 7192.715941] lockmod_read_callback -- END
#
An example of how to use spin lock.
# insmod lock_spin_lock.ko
[ 7463.213732] lockmod: init
[ 7463.214213] Setup spin lock...
[ 7463.214393] Setup kthread...
[ 7463.218114] Start kthreads...
[ 7463.219204] - Read task # 1
[ 7463.219570] - Write task # 1
[ 7463.226368] lockmod_read_callback -- START
[ 7463.226826] lockmod_read_callback -- Doing working (0)
[ 7463.233915] lockmod_write_callback -- START
# [ 7465.263678] lockmod_read_callback -- Doing working (2)
[ 7467.276488] lockmod_read_callback -- Doing working (4)
[ 7469.304131] lockmod_read_callback -- Doing working (6)
[ 7471.344288] lockmod_read_callback -- Doing working (8)
[ 7473.360127] lockmod_read_callback -- Doing working (10)
[ 7475.375307] lockmod_read_callback -- Doing working (12)
[ 7477.388274] lockmod_read_callback -- Doing working (14)
rmmod [ 7479.408382] lockmod_read_callback -- Doing working (16)
# rmmod lock_s[ 7481.418612] lockmod_read_callback -- Doing working (18)
# rmmod lock_spin_lock.ko
[ 7482.256574] lockmod: exit
[ 7482.699630] lockmod_write_callback -- END
[ 7483.438937] lockmod_read_callback -- END
#An example of how to use spin lock (read-write).
# insmod work_queue_delayed.ko
[ 383.526096] wq: init
[ 383.526796] Create work queue...
[ 383.531937] Create work to be done...
[ 383.532559] Queue a work...
[ 383.533017] Current time: 4294988102 jiffies
[ 383.534545] wq: init -- end
# [ 393.747500] wq_work_handler -- START [4294990656 jiffies]
[ 393.748829] wq_work_handler -- Doing working
[ 403.986202] wq_work_handler -- END
[ 1122.622695] mod: init
[ 1122.623535] Setup rw spin lock...
[ 1122.624134] Setup kthread (reader # 1)...
[ 1122.628617] Setup kthread (reader # 2)...
[ 1122.632624] Setup kthread (writer)...
[ 1122.638801] Start kthreads...
[ 1122.639733] - Read task # 1: # 1
[ 1122.640412] mod_read_callback (303 -- read_thread_1) -- START
[ 1122.640837] - Read task # 2: # 1
[ 1122.642603] - Write task: # 1
[ 1122.646566] mod_write_callback (305 -- write_thread) -- START
[ 1122.647524] mod_write_callback (305 -- write_thread) -- work (0)
[ 1122.648230] mod_read_callback (303 -- read_thread_1) -- work (1)
[ 1122.655702] mod_read_callback (304 -- read_thread_2) -- START
[ 1122.656453] mod_read_callback (304 -- read_thread_2) -- work (1)
# [ 1124.659235] mod_read_callback (303 -- read_thread_1) -- work (1)
[ 1124.691121] mod_read_callback (304 -- read_thread_2) -- work (1)
[ 1125.907277] mod_write_callback (305 -- write_thread) -- work (1)
[ 1126.675390] mod_read_callback (303 -- read_thread_1) -- work (2)
[ 1126.706486] mod_read_callback (304 -- read_thread_2) -- work (2)
[ 1128.691254] mod_read_callback (303 -- read_thread_1) -- work (2)
[ 1128.723350] mod_read_callback (304 -- read_thread_2) -- work (2)
[ 1128.979217] mod_write_callback (305 -- write_thread) -- work (2)
[ 1130.706340] mod_read_callback (303 -- read_thread_1) -- work (3)
[ 1130.739037] mod_read_callback (304 -- read_thread_2) -- work (3)
[ 1132.051443] mod_write_callback (305 -- write_thread) -- work (3)
[ 1132.723584] mod_read_callback (303 -- read_thread_1) -- work (4)
[ 1132.755438] mod_read_callback (304 -- read_thread_2) -- work (4)
[ 1134.739379] mod_read_callback (303 -- read_thread_1) -- work (4)
[ 1134.771130] mod_read_callback (304 -- read_thread_2) -- work (4)
[ 1135.123221] mod_write_callback (305 -- write_thread) -- work (4)
[ 1136.755387] mod_read_callback (303 -- read_thread_1) -- work (5)
[ 1136.787345] mod_read_callback (304 -- read_thread_2) -- work (5)
[ 1138.195593] mod_write_callback (305 -- write_thread) -- work (5)
[ 1138.771092] mod_read_callback (303 -- read_thread_1) -- work (6)
[ 1138.803358] mod_read_callback (304 -- read_thread_2) -- work (6)
[ 1140.787087] mod_read_callback (303 -- read_thread_1) -- work (6)
[ 1140.818852] mod_read_callback (304 -- read_thread_2) -- work (6)
[ 1141.267785] mod_write_callback (305 -- write_thread) -- work (6)
[ 1142.803494] mod_read_callback (303 -- read_thread_1) -- work (7)
[ 1142.835191] mod_read_callback (304 -- read_thread_2) -- work (7)
[ 1144.339339] mod_write_callback (305 -- write_thread) -- work (7)
[ 1144.819012] mod_read_callback (303 -- read_thread_1) -- work (8)
[ 1144.851463] mod_read_callback (304 -- read_thread_2) -- work (8)
[ 1146.835101] mod_read_callback (303 -- read_thread_1) -- work (8)
[ 1146.867705] mod_read_callback (304 -- read_thread_2) -- work (8)
[ 1147.411098] mod_write_callback (305 -- write_thread) -- work (8)
[ 1148.851240] mod_read_callback (303 -- read_thread_1) -- work (9)
[ 1148.883354] mod_read_callback (304 -- read_thread_2) -- work (9)
[ 1150.482390] mod_write_callback (305 -- write_thread) -- work (9)
[ 1150.867061] mod_read_callback (303 -- read_thread_1) -- work (10)
[ 1150.900246] mod_read_callback (304 -- read_thread_2) -- work (10)
[ 1152.883940] mod_read_callback (303 -- read_thread_1) -- work (10)
[ 1152.914355] mod_read_callback (304 -- read_thread_2) -- work (10)
[ 1153.555129] mod_write_callback (305 -- write_thread) -- work (10)
[ 1154.898720] mod_read_callback (303 -- read_thread_1) -- work (11)
[ 1154.930397] mod_read_callback (304 -- read_thread_2) -- work (11)
[ 1156.626261] mod_write_callback (305 -- write_thread) -- work (11)
[ 1156.914287] mod_read_callback (303 -- read_thread_1) -- work (12)
[ 1156.946528] mod_read_callback (304 -- read_thread_2) -- work (12)
[ 1158.930489] mod_read_callback (303 -- read_thread_1) -- work (12)
[ 1158.962590] mod_read_callback (304 -- read_thread_2) -- work (12)
[ 1159.698262] mod_write_callback (305 -- write_thread) -- work (12)
[ 1160.946304] mod_read_callback (303 -- read_thread_1) -- work (13)
[ 1160.978864] mod_read_callback (304 -- read_thread_2) -- work (13)
[ 1162.771398] mod_write_callback (305 -- write_thread) -- work (13)
[ 1162.963236] mod_read_callback (303 -- read_thread_1) -- work (14)
[ 1162.995347] mod_read_callback (304 -- read_thread_2) -- work (14)
[ 1164.979136] mod_read_callback (303 -- read_thread_1) -- work (14)
[ 1165.010747] mod_read_callback (304 -- read_thread_2) -- work (14)
[ 1165.843107] mod_write_callback (305 -- write_thread) -- work (14)
[ 1166.995087] mod_read_callback (303 -- read_thread_1) -- work (15)
[ 1167.027714] mod_read_callback (304 -- read_thread_2) -- work (15)
[ 1168.915048] mod_write_callback (305 -- write_thread) -- work (15)
[ 1169.011015] mod_read_callback (303 -- read_thread_1) -- work (16)
[ 1169.042119] mod_read_callback (304 -- read_thread_2) -- work (16)
[ 1171.027261] mod_read_callback (303 -- read_thread_1) -- work (16)
[ 1171.058477] mod_read_callback (304 -- read_thread_2) -- work (16)
[ 1171.986270] mod_write_callback (305 -- write_thread) -- work (16)
[ 1173.042936] mod_read_callback (303 -- read_thread_1) -- work (17)
[ 1173.074994] mod_read_callback (304 -- read_thread_2) -- work (17)
[ 1175.059197] mod_write_callback (305 -- write_thread) -- work (17)
[ 1175.060853] mod_read_callback (303 -- read_thread_1) -- work (18)
[ 1175.090941] mod_read_callback (304 -- read_thread_2) -- work (18)
[ 1177.075010] mod_read_callback (303 -- read_thread_1) -- work (18)
[ 1177.106830] mod_read_callback (304 -- read_thread_2) -- work (18)
[ 1178.131275] mod_write_callback (305 -- write_thread) -- work (18)
[ 1179.090251] mod_read_callback (303 -- read_thread_1) -- work (19)
[ 1179.122431] mod_read_callback (304 -- read_thread_2) -- work (19)
[ 1181.106962] mod_read_callback (303 -- read_thread_1) -- work (19)
[ 1181.139426] mod_read_callback (304 -- read_thread_2) -- work (19)
[ 1181.202363] mod_write_callback (305 -- write_thread) -- work (19)
[ 1183.123117] mod_read_callback (303 -- read_thread_1) -- work (20)
[ 1183.155462] mod_read_callback (304 -- read_thread_2) -- work (20)
[ 1184.274816] mod_write_callback (305 -- write_thread) -- work (20)
[ 1185.139375] mod_read_callback (303 -- read_thread_1) -- work (21)
[ 1185.171043] mod_read_callback (304 -- read_thread_2) -- work (21)
[ 1187.155243] mod_read_callback (303 -- read_thread_1) -- work (21)
[ 1187.186446] mod_read_callback (304 -- read_thread_2) -- work (21)
[ 1187.346256] mod_write_callback (305 -- write_thread) -- work (21)
[ 1189.170666] mod_read_callback (303 -- read_thread_1) -- work (22)
[ 1189.202692] mod_read_callback (304 -- read_thread_2) -- work (22)
[ 1190.418493] mod_write_callback (305 -- write_thread) -- work (22)
[ 1191.187600] mod_read_callback (303 -- read_thread_1) -- work (23)
[ 1191.218366] mod_read_callback (304 -- read_thread_2) -- work (23)
[ 1193.203578] mod_read_callback (303 -- read_thread_1) -- work (23)
[ 1193.235053] mod_read_callback (304 -- read_thread_2) -- work (23)
[ 1193.491090] mod_write_callback (305 -- write_thread) -- work (23)
[ 1195.218313] mod_read_callback (303 -- read_thread_1) -- work (24)
[ 1195.250251] mod_read_callback (304 -- read_thread_2) -- work (24)
[ 1196.562204] mod_write_callback (305 -- write_thread) -- work (24)
[ 1197.235065] mod_read_callback (303 -- read_thread_1) -- work (25)
[ 1197.266784] mod_read_callback (304 -- read_thread_2) -- work (25)
[ 1199.251309] mod_read_callback (303 -- read_thread_1) -- work (25)
[ 1199.283093] mod_read_callback (304 -- read_thread_2) -- work (25)
[ 1199.634915] mod_write_callback (305 -- write_thread) -- work (25)
[ 1201.267111] mod_read_callback (303 -- read_thread_1) -- work (26)
[ 1201.299612] mod_read_callback (304 -- read_thread_2) -- work (26)
[ 1202.707106] mod_write_callback (305 -- write_thread) -- work (26)
[ 1203.283423] mod_read_callback (303 -- read_thread_1) -- work (27)
[ 1203.315179] mod_read_callback (304 -- read_thread_2) -- work (27)
[ 1205.298347] mod_read_callback (303 -- read_thread_1) -- work (27)
[ 1205.330450] mod_read_callback (304 -- read_thread_2) -- work (27)
[ 1205.778296] mod_write_callback (305 -- write_thread) -- work (27)
# rmmod lock_rw_spin_lock.ko
[ 1212.399056] mod: exit
[ 1213.363848] mod_read_callback (303 -- read_thread_1) -- work (30)
[ 1213.395388] mod_read_callback (304 -- read_thread_2) -- work (30)
[ 1214.995148] mod_write_callback (305 -- write_thread) -- END
[ 1215.379341] mod_read_callback (303 -- read_thread_1) -- END
[ 1215.403062] mod_read_callback (304 -- read_thread_2) -- END
#An example of how to use seqlock
# insmod lock_seqlock.ko
[ 87.134555] lock_seqlock: loading out-of-tree module taints kernel.
[ 87.160044] mod: init
[ 87.160790] Setup seqlock...
[ 87.161277] Setup kthread (reader # 1)...
[ 87.165792] Setup kthread (reader # 2)...
[ 87.171028] Setup kthread (writer)...
[ 87.176910] Start kthreads...
[ 87.177554] - Read task # 1: # 1
[ 87.178116] - Read task # 2: # 1
[ 87.178886] - Write task: # 1
[ 87.180041] mod_read_callback (245 -- read_thread_1) -- START
[ 87.181998] mod_read_callback (245 -- read_thread_1) -- work (0)
[ 87.192545] mod_write_callback (247 -- write_thread) -- START
[ 87.193637] mod_write_callback (247 -- write_thread) -- work (0)
[ 87.193818] mod_read_callback (246 -- read_thread_2) -- START
[ 87.195780] mod_read_callback (246 -- read_thread_2) -- work (1)
[ 89.226355] mod_read_callback (246 -- read_thread_2) -- work (1)
[ 90.281699] mod_write_callback (247 -- write_thread) -- work (1)
[ 91.208917] mod_read_callback (245 -- read_thread_1) -- work (2)
[ 91.241296] mod_read_callback (246 -- read_thread_2) -- work (2)
[ 91.577222] cfg80211: failed to load regulatory.db
[ 93.224758] mod_read_callback (245 -- read_thread_1) -- work (2)
[ 93.257374] mod_read_callback (246 -- read_thread_2) -- work (2)
[ 93.352562] mod_write_callback (247 -- write_thread) -- work (2)
[ 95.240752] mod_read_callback (245 -- read_thread_1) -- work (3)
[ 95.273404] mod_read_callback (246 -- read_thread_2) -- work (3)
# rmmod lock_seqlock.ko
[ 99.197795] mod: exit
[ 99.272362] mod_read_callback (245 -- read_thread_1) -- work (4)
[ 99.304272] mod_read_callback (246 -- read_thread_2) -- work (4)
[ 99.434230] mod_write_callback (247 -- write_thread) -- END
[ 101.289220] mod_read_callback (245 -- read_thread_1) -- END
[ 101.313045] mod_read_callback (246 -- read_thread_2) -- END
#An example of how to use semaphore.
# insmod lock_semaphore.ko
[ 8589.386225] lockmod: init
[ 8589.386982] Setup mutex...
[ 8589.387193] Setup kthread...
[ 8589.394059] Start kthreads...
[ 8589.394808] - Read task # 1
[ 8589.395052] - Write task # 1
[ 8589.395939] lockmod_read_callback -- START
[ 8589.396214] lockmod_read_callback -- Doing working (0)
[ 8589.407185] lockmod_write_callback -- START
# [ 8592.431087] lockmod_read_callback -- Doing working (1)
[ 8595.522174] lockmod_read_callback -- Doing working (2)
[ 8598.571031] lockmod_read_callback -- Doing working (3)
[ 8601.611084] lockmod_read_callback -- Doing working (4)
[ 8604.650775] lockmod_read_callback -- Doing working (5)
[ 8607.692312] lockmod_read_callback -- Doing working (6)
rmmod [ 8610.733015] lockmod_read_callback -- Doing working (7)
# rmmod lock_semaphore.ko [ 8613.773242] lockmod_read_callback -- Doing working (8)
[ 8613.975061] lockmod: exit
[ 8616.812814] lockmod_write_callback -- END
[ 8616.818651] lockmod_read_callback -- Doing working (9)
[ 8618.903293] lockmod_read_callback -- END
#An example of how to use rw-semaphore.
# insmod lock_rw_semaphore.ko
[ 9332.805410] lockmod: init
[ 9332.806475] Setup rw-semaphore...
[ 9332.806796] Setup kthread...
[ 9332.811062] Start kthreads...
[ 9332.811766] - Read task # 0: 1
[ 9332.812147] - Read task # 1: 1
[ 9332.812593] - Write task: # 1
[ 9332.816513] lockmod_read_callback0 -- START
[ 9332.816929] lockmod_read_callback0 -- Doing working (0)
[ 9332.817811] lockmod_read_callback1 -- START
[ 9332.818152] lockmod_read_callback1 -- Doing working (0)
[ 9332.832991] lockmod_write_callback -- START
# [ 9335.856640] lockmod_read_callback0 -- Doing working (1)
[ 9335.857343] lockmod_read_callback1 -- Doing working (1)
[ 9339.122699] lockmod_read_callback0 -- Doing working (2)
[ 9339.125193] lockmod_read_callback1 -- Doing working (2)
[ 9342.193709] lockmod_read_callback0 -- Doing working (3)
[ 9342.194847] lockmod_read_callback1 -- Doing working (3)
[ 9345.231656] lockmod_read_callback1 -- Doing working (4)
[ 9345.234824] lockmod_read_callback0 -- Doing working (4)
rmmod [ 9348.270767] lockmod_read_callback0 -- Doing working (5)
[ 9348.275197] lockmod_read_callback1 -- Doing working (5)
# rmmod lock_rw_semaphore.ko
[ 9351.188662] lockmod: exit
[ 9351.328923] lockmod_write_callback -- END
[ 9351.332399] lockmod_read_callback0 -- Doing working (6)
[ 9351.335479] lockmod_read_callback1 -- Doing working (6)
[ 9353.356717] lockmod_read_callback0 -- END
[ 9353.361283] lockmod_read_callback1 -- END
#
An example of how to create device interface using kernel module.
# insmod char_device.ko
[10284.207744] cd: init
[10284.217666] cd: device(/dev/chdev) is create
[10284.218597] - Major number # 235
[10284.218850] - minor number # 0
# ls -l /dev/chdev
crw------- 1 root root 235, 0 Jan 29 19:04 /dev/chdev
# rmmod char_device.ko
[10298.025055] cd: exit
# ls -l /dev/c
console cpu_dma_latency
# ls -l /dev/cA character device with FILE I/O support.
# insmod char_device_fops.ko
[10396.352119] cd: init
[10396.363753] cd: device(/dev/chdev) is create
[10396.364155] - Major number # 235
[10396.364401] - minor number # 0
# ls -l /dev/chdev
crw------- 1 root root 235, 0 Jan 29 19:05 /dev/chdev
# echo "test" > /dev/chdev
[10412.121341] cd: open
[10412.133604] cd: write (0)
[10412.135953] cd: release
[10412.136453] === Data found from user ===
[10412.137117] test
[10412.137433]
[10412.137433] ============================
#
# rmmod char_device_fops.ko
[10441.172617] cd: exit
#A kernel module with sysfs interface for static data.
# insmod sysfs_simple.ko
[ 2667.802727] ms: init
[ 2667.804341] Sysfs interface # /sys/test/root
# ls -l /sys/test/root/
total 0
-r--r--r-- 1 root root 4096 Jul 12 00:12 readonly
-rw-r--r-- 1 root root 4096 Jul 12 00:12 readwrite
# cat /sys/test/root/readonly
100
# cat /sys/test/root/readwrite
0
# echo 202 > /sys/test/root/readonly
-sh: can't create /sys/test/root/readonly: Permission denied
# echo 202 > /sys/test/root/readwrite
[ 2990.228589] readwrite = 202
# cat /sys/test/root/readwrite
202
# rmmod sysfs_simple
#A kernel module with sysfs interface for static data. Also supports notification for select and poll APIs.
It is two parts:
-
Kernel side Module to expose data via sysfs.
-
User side App to be used in user space to poll sysfs interface.
To compile app:
aarch64-none-linux-gnu-gcc -o app_poll sysfs_pollable_user_poll.cTo upload to qemu
scp -P 2222 app_poll root@localhost:/root
# ls
app_poll sysfs_pollable.ko
#
# insmod sysfs_pollable.ko
[ 2667.802727] cd: init
[ 2667.804341] Sysfs interface # /sys/test/root
# ls -l /sys/test/root/
total 0
-r--r--r-- 1 root root 4096 Jul 12 00:12 readonly
-rw-r--r-- 1 root root 4096 Jul 12 00:12 readwrite
# cat /sys/test/root/readonly
100
# cat /sys/test/root/readwrite
0
# echo 202 > /sys/test/root/readonly
-sh: can't create /sys/test/root/readonly: Permission denied
#
# echo 202 > /sys/test/root/readwrite
[ 2990.228589] readwrite = 202
# cat /sys/test/root/readwrite
202- Run user space application
# ./app_poll &
# Going to poll....
# echo 204 > /sys/test/root/readwrite
[ 1591.077334] store -> readwrite = 204
Polling is triggered
# buf: 0xD3505360, 204- To remove module
# rmmod sysfs_pollable
#A kernel module with sysfs interface for dynamic data.
# insmod sysfs_dynamic.ko
[ 3710.192276] ms: init
[ 3710.194922] Sysfs interface # /sys/test/root
# ls -l /sys/test/root/
total 0
-rw-r--r-- 1 root root 4096 Jul 12 00:30 idx0
-rw-r--r-- 1 root root 4096 Jul 12 00:30 idx1
-rw-r--r-- 1 root root 4096 Jul 12 00:30 idx2
-rw-r--r-- 1 root root 4096 Jul 12 00:30 idx3
# cat /sys/test/root/idx1
1
# echo 900 > /sys/test/root/idx1
[ 3735.822774] store = 900
# cat /sys/test/root/idx1
900
# echo 900 > /sys/test/root/idx3
[ 3740.998096] store = 900
# echo 400 > /sys/test/root/idx3
[ 3756.362723] store = 400
# cat /sys/test/root/idx0
0
# cat /sys/test/root/idx1
900
# cat /sys/test/root/idx2
2
# cat /sys/test/root/idx3
400
# rmmod sysfs_dynamic.ko
[ 3777.702655] ms: exit
#An example how to use timer.
# insmod timer.ko
[ 6014.610336] trmod: init
[ 6014.611195] trmod: Setup timer...
[ 6014.611674] trmod: Setup timeout...
# [ 6014.894695] trmod: timer_callback -- called (one-shot)
#
#
# rmmod timer.ko
[ 6025.484102] trmod: exit
[ 6025.484559] trmod: Delete timer...
#An example how to use timer with repetitive timeout.
# insmod timer_repetitive.ko
[ 7442.674073] trmod: init
[ 7442.674718] trmod: Setup timer...
[ 7442.675151] trmod: Setup timeout...
[ 7443.214988] trmod: timer_callback -- called (repetitive)
[ 7443.470832] trmod: timer_callback -- called (repetitive)
[ 7443.726624] trmod: timer_callback -- called (repetitive)
[ 7443.982685] trmod: timer_callback -- called (repetitive)
[ 7444.238788] trmod: timer_callback -- called (repetitive)
[ 7444.495042] trmod: timer_callback -- called (repetitive)
[ 7444.750681] trmod: timer_callback -- called (repetitive)
[ 7445.006556] trmod: timer_callback -- called (repetitive)
[ 7445.262778] trmod: timer_callback -- called (repetitive)
[ 7445.518715] trmod: timer_callback -- called (repetitive)
[ 7445.774355] trmod: timer_callback -- called (repetitive)
[ 7446.030846] trmod: timer_callback -- called (repetitive)
[ 7446.286816] trmod: timer_callback -- called (repetitive)
# rmmod timer_repetitive.ko
[ 7455.101628] trmod: exit
[ 7455.102999] trmod: Delete timer...
#An example how to use higher resolution timer.
# insmod timer_hr.ko
[11207.958620] hr: init
[11207.959071] Setup timer...
[11207.959256] Start timer...
[11207.965159] hr_timer_callback -- START
[11207.965442] hr_timer_callback -- Doing working
[11207.965639] hr_timer_callback -- END
# rmmod timer_hr.ko
[11248.155893] hr: exit
[11248.156897] Delete timer...
#An example how to use higher resolution timer in repetitive mode.
# insmod timer_hr_repetitive.ko
[ 7170.911353] hr: init
[ 7170.911731] Setup timer...
[ 7170.912005] Start timer...[4296684756 jiffies]
# [ 7172.917504] hr_timer_callback [4296685258 jiffies]
[ 7174.921212] hr_timer_callback [4296685759 jiffies]
[ 7176.961923] hr_timer_callback [4296686269 jiffies]
[ 7178.921332] hr_timer_callback [4296686759 jiffies]
[ 7180.914419] hr_timer_callback [4296687257 jiffies]
[ 7182.916584] hr_timer_callback [4296687758 jiffies]
[ 7184.918601] hr_timer_callback [4296688258 jiffies]
[ 7186.915450] hr_timer_callback [4296688757 jiffies]
[ 7188.921728] hr_timer_callback [4296689259 jiffies]
[ 7190.914254] hr_timer_callback [4296689757 jiffies]
[ 7192.913470] hr_timer_callback [4296690257 jiffies]
[ 7194.981200] hr_timer_callback [4296690774 jiffies]
[ 7196.914013] hr_timer_callback [4296691257 jiffies]
[ 7198.915422] hr_timer_callback [4296691757 jiffies]
[ 7200.917294] hr_timer_callback [4296692258 jiffies]
[ 7202.916724] hr_timer_callback [4296692758 jiffies]
[ 7204.917354] hr_timer_callback [4296693258 jiffies]
[ 7206.916150] hr_timer_callback [4296693757 jiffies]
[ 7208.914838] hr_timer_callback [4296694257 jiffies]
[ 7210.913370] hr_timer_callback [4296694757 jiffies]
[ 7212.917794] hr_timer_callback [4296695258 jiffies]
[ 7214.914670] hr_timer_callback [4296695757 jiffies]
[ 7216.915138] hr_timer_callback [4296696257 jiffies]
[ 7218.914531] hr_timer_callback [4296696757 jiffies]
[ 7220.915391] hr_timer_callback [4296697257 jiffies]
[ 7222.917358] hr_timer_callback [4296697758 jiffies]
[ 7224.920391] hr_timer_callback [4296698258 jiffies]
[ 7226.915757] hr_timer_callback [4296698757 jiffies]
[ 7228.915967] hr_timer_callback [4296699257 jiffies]
[ 7230.838390] hr: exit
[ 7230.838771] Delete timer...An example of how to use tasklet.
# insmod tasklet.ko
[11354.444642] tl: init
[11354.445198] tl_tasklet_func: Tasklet data
# rmmod tasklet.ko
[11363.968424] tl: exit
#An example of how to use wait queue.
# insmod wait_queue.ko
[ 5362.443697] wq: init
[ 5362.444390] wq: Init wait_queue...
[ 5362.444798] wq: Setup timer...
[ 5362.445315] wq: Setup timeout...
[ 5362.446713] wq: Going to suspend until is not done...
[ 5363.471108] wq: timer_callback -- called (timer_count: 0)
[ 5365.486979] wq: timer_callback -- called (timer_count: 1)
[ 5367.503002] wq: timer_callback -- called (timer_count: 2)
[ 5369.518849] wq: timer_callback -- called (timer_count: 3)
[ 5371.534861] wq: timer_callback -- called (timer_count: 4)
[ 5373.550821] wq: timer_callback -- called (timer_count: 5)
[ 5375.566743] wq: timer_callback -- called (timer_count: 6)
[ 5377.582716] wq: timer_callback -- called (timer_count: 7)
[ 5379.598723] wq: timer_callback -- called (timer_count: 8)
[ 5381.615089] wq: timer_callback -- called (timer_count: 9)
[ 5383.630669] wq: timer_callback -- called (timer_count: 10)
[ 5383.635371] wq: wait_queue is signalled...
[ 5383.637153] wq: delete timer...
[ 5383.639541] wq: init -- done
# rmmod wait_queue
[ 5393.416361] wq: exit
#An example of how to use work queue.
# insmod work_queue_simple.ko
[ 260.216729] wq: init
[ 260.218188] Create work queue...
[ 260.223238] Create work to be done...
[ 260.223870] Queue a work...
[ 260.225050] wq_work_handler -- START
[ 260.226280] wq_work_handler -- Doing working
[ 260.227277] wq: init -- end
# [ 270.354834] wq_work_handler -- END
#- ps before having workqueue
# ps -ef | grep kworker
5 root [kworker/0:0-mm_]
6 root [kworker/0:0H-ev]
7 root [kworker/u4:0-ev]
17 root [kworker/1:0-mm_]
18 root [kworker/1:0H-kb]
21 root [kworker/1:1-mm_]
22 root [kworker/0:1-mm_]
61 root [kworker/u4:1-fl]
62 root [kworker/0:1H-kb]
64 root [kworker/u5:0]
98 root [kworker/1:1H-kb]
172 root [kworker/u4:2-ev]
178 root [kworker/1:2-mm_]
243 root grep kworker- After having module which installed workqueue
# ps -ef | grep kworker
5 root [kworker/0:0-mm_]
6 root [kworker/0:0H-ev]
7 root [kworker/u4:0-ev]
17 root [kworker/1:0-mm_]
18 root [kworker/1:0H-kb]
21 root [kworker/1:1-mm_]
22 root [kworker/0:1-eve]
61 root [kworker/u4:1-ev]
62 root [kworker/0:1H-kb]
64 root [kworker/u5:0]
98 root [kworker/1:1H-kb]
172 root [kworker/u4:2-ev]
178 root [kworker/1:2-mm_]
244 root [kworker/0:2+wq_] <---
254 root grep kworkerAn example of how to use work queue with delayed functionality.
# insmod work_queue_delayed.ko
[ 383.526096] wq: init
[ 383.526796] Create work queue...
[ 383.531937] Create work to be done...
[ 383.532559] Queue a work...
[ 383.533017] Current time: 4294988102 jiffies
[ 383.534545] wq: init -- end
# [ 393.747500] wq_work_handler -- START [4294990656 jiffies]
[ 393.748829] wq_work_handler -- Doing working
[ 403.986202] wq_work_handler -- END
#
# rmmod work_queue_delayed.ko
[ 437.676556] wq: exit
#An example of how to use shared worked.
# insmod work_queue_shared.ko
[ 130.313221] wq: init
[ 130.313868] Create work queue...
[ 130.315272] Create work to be done...
[ 130.315996] Queue a work...
[ 130.317034] wq_work_handler -- START
[ 130.317669] wq_work_handler -- Doing working
[ 130.319163] wq: init -- end
# [ 140.537463] wq_work_handler -- END
# rmmod work_queue_shared.ko
[ 734.248972] wq: exit
#