Commit a2818ee4 authored by Joe Lawrence's avatar Joe Lawrence Committed by Jiri Kosina
Browse files

selftests/livepatch: introduce tests 



Add a few livepatch modules and simple target modules that the included
regression suite can run tests against:

  - basic livepatching (multiple patches, atomic replace)
  - pre/post (un)patch callbacks
  - shadow variable API

Signed-off-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: default avatarMiroslav Benes <mbenes@suse.cz>
Tested-by: default avatarAlice Ferrazzi <alice.ferrazzi@gmail.com>
Acked-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent d67a5372

Documentation/livepatch/callbacks.txt

+5 −484
Original line number Diff line number Diff line
@@ -118,488 +118,9 @@ similar change to their hw_features value. (Client functions of the 
value may need to be updated accordingly.)





Test cases

==========



What follows is not an exhaustive test suite of every possible livepatch

pre/post-(un)patch combination, but a selection that demonstrates a few

important concepts.  Each test case uses the kernel modules located in

the samples/livepatch/ and assumes that no livepatches are loaded at the

beginning of the test.





Test 1

------



Test a combination of loading a kernel module and a livepatch that

patches a function in the first module.  (Un)load the target module

before the livepatch module:



- load target module

- load livepatch

- disable livepatch

- unload target module

- unload livepatch



First load a target module:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   34.475708] livepatch_callbacks_mod: livepatch_callbacks_mod_init



On livepatch enable, before the livepatch transition starts, pre-patch

callbacks are executed for vmlinux and livepatch_callbacks_mod (those

klp_objects currently loaded).  After klp_objects are patched according

to the klp_patch, their post-patch callbacks run and the transition

completes:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   36.503719] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   36.504213] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   36.504238] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   36.504721] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   36.505849] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   37.727133] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   37.727232] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   37.727860] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   37.728792] livepatch: 'livepatch_callbacks_demo': patching complete



Similarly, on livepatch disable, pre-patch callbacks run before the

unpatching transition starts.  klp_objects are reverted, post-patch

callbacks execute and the transition completes:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   38.510209] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   38.510234] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   38.510982] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   38.512209] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   39.711132] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   39.711210] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   39.711779] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   39.712735] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko

  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [   42.534183] livepatch_callbacks_mod: livepatch_callbacks_mod_exit





Test 2

------



This test is similar to the previous test, but (un)load the livepatch

module before the target kernel module.  This tests the livepatch core's

module_coming handler:



- load livepatch

- load target module

- disable livepatch

- unload livepatch

- unload target module





On livepatch enable, only pre/post-patch callbacks are executed for

currently loaded klp_objects, in this case, vmlinux:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   44.553328] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   44.553997] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   44.554049] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   44.554845] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   45.727128] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   45.727212] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   45.727961] livepatch: 'livepatch_callbacks_demo': patching complete



When a targeted module is subsequently loaded, only its pre/post-patch

callbacks are executed:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   46.560845] livepatch: applying patch 'livepatch_callbacks_demo' to loading module 'livepatch_callbacks_mod'

  [   46.561988] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [   46.563452] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [   46.565495] livepatch_callbacks_mod: livepatch_callbacks_mod_init



On livepatch disable, all currently loaded klp_objects' (vmlinux and

livepatch_callbacks_mod) pre/post-unpatch callbacks are executed:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   48.568885] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   48.568910] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   48.569441] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   48.570502] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   49.759091] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   49.759171] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   49.759742] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   49.760690] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko

  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [   52.592283] livepatch_callbacks_mod: livepatch_callbacks_mod_exit





Test 3

------



Test loading the livepatch after a targeted kernel module, then unload

the kernel module before disabling the livepatch.  This tests the

livepatch core's module_going handler:



- load target module

- load livepatch

- unload target module

- disable livepatch

- unload livepatch



First load a target module, then the livepatch:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   54.607948] livepatch_callbacks_mod: livepatch_callbacks_mod_init



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   56.613919] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   56.614411] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   56.614436] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   56.614818] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   56.615656] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   57.759070] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   57.759147] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   57.759621] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_LIVE] Normal state

  [   57.760307] livepatch: 'livepatch_callbacks_demo': patching complete



When a target module is unloaded, the livepatch is only reverted from

that klp_object (livepatch_callbacks_mod).  As such, only its pre and

post-unpatch callbacks are executed when this occurs:



  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [   58.623409] livepatch_callbacks_mod: livepatch_callbacks_mod_exit

  [   58.623903] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away

  [   58.624658] livepatch: reverting patch 'livepatch_callbacks_demo' on unloading module 'livepatch_callbacks_mod'

  [   58.625305] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away



When the livepatch is disabled, pre and post-unpatch callbacks are run

for the remaining klp_object, vmlinux:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   60.638420] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   60.638444] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   60.638996] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   61.727088] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   61.727165] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   61.727985] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko





Test 4

------



This test is similar to the previous test, however the livepatch is

loaded first.  This tests the livepatch core's module_coming and

module_going handlers:



- load livepatch

- load target module

- unload target module

- disable livepatch

- unload livepatch



First load the livepatch:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   64.661552] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   64.662147] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   64.662175] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   64.662850] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   65.695056] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   65.695147] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   65.695561] livepatch: 'livepatch_callbacks_demo': patching complete



When a targeted kernel module is subsequently loaded, only its

pre/post-patch callbacks are executed:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   66.669196] livepatch: applying patch 'livepatch_callbacks_demo' to loading module 'livepatch_callbacks_mod'

  [   66.669882] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [   66.670744] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [   66.672873] livepatch_callbacks_mod: livepatch_callbacks_mod_init



When the target module is unloaded, the livepatch is only reverted from

the livepatch_callbacks_mod klp_object.  As such, only pre and

post-unpatch callbacks are executed when this occurs:



  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [   68.680065] livepatch_callbacks_mod: livepatch_callbacks_mod_exit

  [   68.680688] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away

  [   68.681452] livepatch: reverting patch 'livepatch_callbacks_demo' on unloading module 'livepatch_callbacks_mod'

  [   68.682094] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   70.689225] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   70.689256] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   70.689882] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   71.711080] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   71.711481] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   71.711988] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko





Test 5

------



A simple test of loading a livepatch without one of its patch target

klp_objects ever loaded (livepatch_callbacks_mod):



- load livepatch

- disable livepatch

- unload livepatch



Load the livepatch:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   74.711081] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   74.711595] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   74.711639] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   74.712272] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   75.743137] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   75.743219] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   75.743867] livepatch: 'livepatch_callbacks_demo': patching complete



As expected, only pre/post-(un)patch handlers are executed for vmlinux:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   76.716254] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   76.716278] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   76.716666] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   77.727089] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   77.727194] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   77.727907] livepatch: 'livepatch_callbacks_demo': unpatching complete

Other Examples

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



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko





Test 6

------



Test a scenario where a vmlinux pre-patch callback returns a non-zero

status (ie, failure):



- load target module

- load livepatch -ENODEV

- unload target module



First load a target module:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   80.740520] livepatch_callbacks_mod: livepatch_callbacks_mod_init



Load the livepatch module, setting its 'pre_patch_ret' value to -19

(-ENODEV).  When its vmlinux pre-patch callback executed, this status

code will propagate back to the module-loading subsystem.  The result is

that the insmod command refuses to load the livepatch module:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko pre_patch_ret=-19

  [   82.747326] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   82.747743] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   82.747767] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   82.748237] livepatch: pre-patch callback failed for object 'vmlinux'

  [   82.748637] livepatch: failed to enable patch 'livepatch_callbacks_demo'

  [   82.749059] livepatch: 'livepatch_callbacks_demo': canceling transition, going to unpatch

  [   82.749060] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   82.749868] livepatch: 'livepatch_callbacks_demo': unpatching complete

  [   82.765809] insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-demo.ko: No such device



  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [   84.774238] livepatch_callbacks_mod: livepatch_callbacks_mod_exit





Test 7

------



Similar to the previous test, setup a livepatch such that its vmlinux

pre-patch callback returns success.  However, when a targeted kernel

module is later loaded, have the livepatch return a failing status code:



- load livepatch

- setup -ENODEV

- load target module

- disable livepatch

- unload livepatch



Load the livepatch, notice vmlinux pre-patch callback succeeds:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   86.787845] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   86.788325] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   86.788427] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   86.788821] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   87.711069] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   87.711143] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   87.711886] livepatch: 'livepatch_callbacks_demo': patching complete



Set a trap so subsequent pre-patch callbacks to this livepatch will

return -ENODEV:



  % echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret



The livepatch pre-patch callback for subsequently loaded target modules

will return failure, so the module loader refuses to load the kernel

module.  Notice that no post-patch or pre/post-unpatch callbacks are

executed for this klp_object:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [   90.796976] livepatch: applying patch 'livepatch_callbacks_demo' to loading module 'livepatch_callbacks_mod'

  [   90.797834] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [   90.798900] livepatch: pre-patch callback failed for object 'livepatch_callbacks_mod'

  [   90.799652] livepatch: patch 'livepatch_callbacks_demo' failed for module 'livepatch_callbacks_mod', refusing to load module 'livepatch_callbacks_mod'

  [   90.819737] insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device



However, pre/post-unpatch callbacks run for the vmlinux klp_object:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [   92.823547] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [   92.823573] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [   92.824331] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [   93.727128] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [   93.727327] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [   93.727861] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko





Test 8

------



Test loading multiple targeted kernel modules.  This test-case is

mainly for comparing with the next test-case.



- load busy target module (0s sleep),

- load livepatch

- load target module

- unload target module

- disable livepatch

- unload livepatch

- unload busy target module





Load a target "busy" kernel module which kicks off a worker function

that immediately exits:



  % insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=0

  [   96.910107] livepatch_callbacks_busymod: livepatch_callbacks_mod_init

  [   96.910600] livepatch_callbacks_busymod: busymod_work_func, sleeping 0 seconds ...

  [   96.913024] livepatch_callbacks_busymod: busymod_work_func exit



Proceed with loading the livepatch and another ordinary target module,

notice that the post-patch callbacks are executed and the transition

completes quickly:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [   98.917892] livepatch: enabling patch 'livepatch_callbacks_demo'

  [   98.918426] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [   98.918453] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [   98.918955] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [   98.923835] livepatch: 'livepatch_callbacks_demo': starting patching transition

  [   99.743104] livepatch: 'livepatch_callbacks_demo': completing patching transition

  [   99.743156] livepatch_callbacks_demo: post_patch_callback: vmlinux

  [   99.743679] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [   99.744616] livepatch: 'livepatch_callbacks_demo': patching complete



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [  100.930955] livepatch: applying patch 'livepatch_callbacks_demo' to loading module 'livepatch_callbacks_mod'

  [  100.931668] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [  100.932645] livepatch_callbacks_demo: post_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [  100.934125] livepatch_callbacks_mod: livepatch_callbacks_mod_init



  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [  102.942805] livepatch_callbacks_mod: livepatch_callbacks_mod_exit

  [  102.943640] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away

  [  102.944585] livepatch: reverting patch 'livepatch_callbacks_demo' on unloading module 'livepatch_callbacks_mod'

  [  102.945455] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [  104.953815] livepatch: 'livepatch_callbacks_demo': initializing unpatching transition

  [  104.953838] livepatch_callbacks_demo: pre_unpatch_callback: vmlinux

  [  104.954431] livepatch_callbacks_demo: pre_unpatch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [  104.955426] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [  106.719073] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [  106.722633] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [  106.723282] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [  106.724279] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko

  % rmmod samples/livepatch/livepatch-callbacks-busymod.ko

  [  108.975660] livepatch_callbacks_busymod: livepatch_callbacks_mod_exit





Test 9

------



A similar test as the previous one, but force the "busy" kernel module

to do longer work.



The livepatching core will refuse to patch a task that is currently

executing a to-be-patched function -- the consistency model stalls the

current patch transition until this safety-check is met.  Test a

scenario where one of a livepatch's target klp_objects sits on such a

function for a long time.  Meanwhile, load and unload other target

kernel modules while the livepatch transition is in progress.



- load busy target module (30s sleep)

- load livepatch

- load target module

- unload target module

- disable livepatch

- unload livepatch

- unload busy target module





Load the "busy" kernel module, this time make it do 30 seconds worth of

work:



  % insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30

  [  110.993362] livepatch_callbacks_busymod: livepatch_callbacks_mod_init

  [  110.994059] livepatch_callbacks_busymod: busymod_work_func, sleeping 30 seconds ...



Meanwhile, the livepatch is loaded.  Notice that the patch transition

does not complete as the targeted "busy" module is sitting on a

to-be-patched function:



  % insmod samples/livepatch/livepatch-callbacks-demo.ko

  [  113.000309] livepatch: enabling patch 'livepatch_callbacks_demo'

  [  113.000764] livepatch: 'livepatch_callbacks_demo': initializing patching transition

  [  113.000791] livepatch_callbacks_demo: pre_patch_callback: vmlinux

  [  113.001289] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [  113.005208] livepatch: 'livepatch_callbacks_demo': starting patching transition



Load a second target module (this one is an ordinary idle kernel

module).  Note that *no* post-patch callbacks will be executed while the

livepatch is still in transition:



  % insmod samples/livepatch/livepatch-callbacks-mod.ko

  [  115.012740] livepatch: applying patch 'livepatch_callbacks_demo' to loading module 'livepatch_callbacks_mod'

  [  115.013406] livepatch_callbacks_demo: pre_patch_callback: livepatch_callbacks_mod -> [MODULE_STATE_COMING] Full formed, running module_init

  [  115.015315] livepatch_callbacks_mod: livepatch_callbacks_mod_init



Request an unload of the simple kernel module.  The patch is still

transitioning, so its pre-unpatch callbacks are skipped:



  % rmmod samples/livepatch/livepatch-callbacks-mod.ko

  [  117.022626] livepatch_callbacks_mod: livepatch_callbacks_mod_exit

  [  117.023376] livepatch: reverting patch 'livepatch_callbacks_demo' on unloading module 'livepatch_callbacks_mod'

  [  117.024533] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_mod -> [MODULE_STATE_GOING] Going away



Finally the livepatch is disabled.  Since none of the patch's

klp_object's post-patch callbacks executed, the remaining klp_object's

pre-unpatch callbacks are skipped:



  % echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled

  [  119.035408] livepatch: 'livepatch_callbacks_demo': reversing transition from patching to unpatching

  [  119.035485] livepatch: 'livepatch_callbacks_demo': starting unpatching transition

  [  119.711166] livepatch: 'livepatch_callbacks_demo': completing unpatching transition

  [  119.714179] livepatch_callbacks_demo: post_unpatch_callback: vmlinux

  [  119.714653] livepatch_callbacks_demo: post_unpatch_callback: livepatch_callbacks_busymod -> [MODULE_STATE_LIVE] Normal state

  [  119.715437] livepatch: 'livepatch_callbacks_demo': unpatching complete



  % rmmod samples/livepatch/livepatch-callbacks-demo.ko

  % rmmod samples/livepatch/livepatch-callbacks-busymod.ko

  [  141.279111] livepatch_callbacks_busymod: busymod_work_func exit

  [  141.279760] livepatch_callbacks_busymod: livepatch_callbacks_mod_exit
 
Sample livepatch modules demonstrating the callback API can be found in

samples/livepatch/ directory.  These samples were modified for use in

kselftests and can be found in the lib/livepatch directory.

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