diff options
| -rw-r--r-- | Documentation/livepatch/callbacks.txt | 605 | ||||
| -rw-r--r-- | include/linux/livepatch.h | 26 | ||||
| -rw-r--r-- | kernel/livepatch/core.c | 52 | ||||
| -rw-r--r-- | kernel/livepatch/core.h | 40 | ||||
| -rw-r--r-- | kernel/livepatch/patch.c | 1 | ||||
| -rw-r--r-- | kernel/livepatch/transition.c | 45 | ||||
| -rw-r--r-- | samples/livepatch/Makefile | 3 | ||||
| -rw-r--r-- | samples/livepatch/livepatch-callbacks-busymod.c | 72 | ||||
| -rw-r--r-- | samples/livepatch/livepatch-callbacks-demo.c | 234 | ||||
| -rw-r--r-- | samples/livepatch/livepatch-callbacks-mod.c | 53 |
10 files changed, 1114 insertions, 17 deletions
diff --git a/Documentation/livepatch/callbacks.txt b/Documentation/livepatch/callbacks.txt new file mode 100644 index 000000000000..c9776f48e458 --- /dev/null +++ b/Documentation/livepatch/callbacks.txt @@ -0,0 +1,605 @@ +====================== +(Un)patching Callbacks +====================== + +Livepatch (un)patch-callbacks provide a mechanism for livepatch modules +to execute callback functions when a kernel object is (un)patched. They +can be considered a "power feature" that extends livepatching abilities +to include: + + - Safe updates to global data + + - "Patches" to init and probe functions + + - Patching otherwise unpatchable code (i.e. assembly) + +In most cases, (un)patch callbacks will need to be used in conjunction +with memory barriers and kernel synchronization primitives, like +mutexes/spinlocks, or even stop_machine(), to avoid concurrency issues. + +Callbacks differ from existing kernel facilities: + + - Module init/exit code doesn't run when disabling and re-enabling a + patch. + + - A module notifier can't stop a to-be-patched module from loading. + +Callbacks are part of the klp_object structure and their implementation +is specific to that klp_object. Other livepatch objects may or may not +be patched, irrespective of the target klp_object's current state. + +Callbacks can be registered for the following livepatch actions: + + * Pre-patch - before a klp_object is patched + + * Post-patch - after a klp_object has been patched and is active + across all tasks + + * Pre-unpatch - before a klp_object is unpatched (ie, patched code is + active), used to clean up post-patch callback + resources + + * Post-unpatch - after a klp_object has been patched, all code has + been restored and no tasks are running patched code, + used to cleanup pre-patch callback resources + +Each callback is optional, omitting one does not preclude specifying any +other. However, the livepatching core executes the handlers in +symmetry: pre-patch callbacks have a post-unpatch counterpart and +post-patch callbacks have a pre-unpatch counterpart. An unpatch +callback will only be executed if its corresponding patch callback was +executed. Typical use cases pair a patch handler that acquires and +configures resources with an unpatch handler tears down and releases +those same resources. + +A callback is only executed if its host klp_object is loaded. For +in-kernel vmlinux targets, this means that callbacks will always execute +when a livepatch is enabled/disabled. For patch target kernel modules, +callbacks will only execute if the target module is loaded. When a +module target is (un)loaded, its callbacks will execute only if the +livepatch module is enabled. + +The pre-patch callback, if specified, is expected to return a status +code (0 for success, -ERRNO on error). An error status code indicates +to the livepatching core that patching of the current klp_object is not +safe and to stop the current patching request. (When no pre-patch +callback is provided, the transition is assumed to be safe.) If a +pre-patch callback returns failure, the kernel's module loader will: + + - Refuse to load a livepatch, if the livepatch is loaded after + targeted code. + + or: + + - Refuse to load a module, if the livepatch was already successfully + loaded. + +No post-patch, pre-unpatch, or post-unpatch callbacks will be executed +for a given klp_object if the object failed to patch, due to a failed +pre_patch callback or for any other reason. + +If a patch transition is reversed, no pre-unpatch handlers will be run +(this follows the previously mentioned symmetry -- pre-unpatch callbacks +will only occur if their corresponding post-patch callback executed). + +If the object did successfully patch, but the patch transition never +started for some reason (e.g., if another object failed to patch), +only the post-unpatch callback will be called. + + +Example Use-cases +================= + +Update global data +------------------ + +A pre-patch callback can be useful to update a global variable. For +example, 75ff39ccc1bd ("tcp: make challenge acks less predictable") +changes a global sysctl, as well as patches the tcp_send_challenge_ack() +function. + +In this case, if we're being super paranoid, it might make sense to +patch the data *after* patching is complete with a post-patch callback, +so that tcp_send_challenge_ack() could first be changed to read +sysctl_tcp_challenge_ack_limit with READ_ONCE. + + +Support __init and probe function patches +----------------------------------------- + +Although __init and probe functions are not directly livepatch-able, it +may be possible to implement similar updates via pre/post-patch +callbacks. + +48900cb6af42 ("virtio-net: drop NETIF_F_FRAGLIST") change the way that +virtnet_probe() initialized its driver's net_device features. A +pre/post-patch callback could iterate over all such devices, making a +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 + + % 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 diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index d08eddc00497..fc5c1be3f6f4 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -87,10 +87,35 @@ struct klp_func { bool transition; }; +struct klp_object; + +/** + * struct klp_callbacks - pre/post live-(un)patch callback structure + * @pre_patch: executed before code patching + * @post_patch: executed after code patching + * @pre_unpatch: executed before code unpatching + * @post_unpatch: executed after code unpatching + * @post_unpatch_enabled: flag indicating if post-unpatch callback + * should run + * + * All callbacks are optional. Only the pre-patch callback, if provided, + * will be unconditionally executed. If the parent klp_object fails to + * patch for any reason, including a non-zero error status returned from + * the pre-patch callback, no further callbacks will be executed. + */ +struct klp_callbacks { + int (*pre_patch)(struct klp_object *obj); + void (*post_patch)(struct klp_object *obj); + void (*pre_unpatch)(struct klp_object *obj); + void (*post_unpatch)(struct klp_object *obj); + bool post_unpatch_enabled; +}; + /** * struct klp_object - kernel object structure for live patching * @name: module name (or NULL for vmlinux) * @funcs: function entries for functions to be patched in the object + * @callbacks: functions to be executed pre/post (un)patching * @kobj: kobject for sysfs resources * @mod: kernel module associated with the patched object * (NULL for vmlinux) @@ -100,6 +125,7 @@ struct klp_object { /* external */ const char *name; struct klp_func *funcs; + struct klp_callbacks callbacks; /* internal */ struct kobject kobj; diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index bf8c8fd72589..de9e45dca70f 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -54,11 +54,6 @@ static bool klp_is_module(struct klp_object *obj) return obj->name; } -static bool klp_is_object_loaded(struct klp_object *obj) -{ - return !obj->name || obj->mod; -} - /* sets obj->mod if object is not vmlinux and module is found */ static void klp_find_object_module(struct klp_object *obj) { @@ -285,6 +280,11 @@ static int klp_write_object_relocations(struct module *pmod, static int __klp_disable_patch(struct klp_patch *patch) { + struct klp_object *obj; + + if (WARN_ON(!patch->enabled)) + return -EINVAL; + if (klp_transition_patch) return -EBUSY; @@ -295,6 +295,10 @@ static int __klp_disable_patch(struct klp_patch *patch) klp_init_transition(patch, KLP_UNPATCHED); + klp_for_each_object(patch, obj) + if (obj->patched) + klp_pre_unpatch_callback(obj); + /* * Enforce the order of the func->transition writes in * klp_init_transition() and the TIF_PATCH_PENDING writes in @@ -388,13 +392,18 @@ static int __klp_enable_patch(struct klp_patch *patch) if (!klp_is_object_loaded(obj)) continue; - ret = klp_patch_object(obj); + ret = klp_pre_patch_callback(obj); if (ret) { - pr_warn("failed to enable patch '%s'\n", - patch->mod->name); + pr_warn("pre-patch callback failed for object '%s'\n", + klp_is_module(obj) ? obj->name : "vmlinux"); + goto err; + } - klp_cancel_transition(); - return ret; + ret = klp_patch_object(obj); + if (ret) { + pr_warn("failed to patch object '%s'\n", + klp_is_module(obj) ? obj->name : "vmlinux"); + goto err; } } @@ -403,6 +412,11 @@ static int __klp_enable_patch(struct klp_patch *patch) patch->enabled = true; return 0; +err: + pr_warn("failed to enable patch '%s'\n", patch->mod->name); + + klp_cancel_transition(); + return ret; } /** @@ -854,9 +868,15 @@ static void klp_cleanup_module_patches_limited(struct module *mod, * is in transition. */ if (patch->enabled || patch == klp_transition_patch) { + + if (patch != klp_transition_patch) + klp_pre_unpatch_callback(obj); + pr_notice("reverting patch '%s' on unloading module '%s'\n", patch->mod->name, obj->mod->name); klp_unpatch_object(obj); + + klp_post_unpatch_callback(obj); } klp_free_object_loaded(obj); @@ -906,13 +926,25 @@ int klp_module_coming(struct module *mod) pr_notice("applying patch '%s' to loading module '%s'\n", patch->mod->name, obj->mod->name); + ret = klp_pre_patch_callback(obj); + if (ret) { + pr_warn("pre-patch callback failed for object '%s'\n", + obj->name); + goto err; + } + ret = klp_patch_object(obj); if (ret) { pr_warn("failed to apply patch '%s' to module '%s' (%d)\n", patch->mod->name, obj->mod->name, ret); + + klp_post_unpatch_callback(obj); goto err; } + if (patch != klp_transition_patch) + klp_post_patch_callback(obj); + break; } } diff --git a/kernel/livepatch/core.h b/kernel/livepatch/core.h index c74f24c47837..cc3aa708e0b4 100644 --- a/kernel/livepatch/core.h +++ b/kernel/livepatch/core.h @@ -1,6 +1,46 @@ #ifndef _LIVEPATCH_CORE_H #define _LIVEPATCH_CORE_H +#include <linux/livepatch.h> + extern struct mutex klp_mutex; +static inline bool klp_is_object_loaded(struct klp_object *obj) +{ + return !obj->name || obj->mod; +} + +static inline int klp_pre_patch_callback(struct klp_object *obj) +{ + int ret = 0; + + if (obj->callbacks.pre_patch) + ret = (*obj->callbacks.pre_patch)(obj); + + obj->callbacks.post_unpatch_enabled = !ret; + + return ret; +} + +static inline void klp_post_patch_callback(struct klp_object *obj) +{ + if (obj->callbacks.post_patch) + (*obj->callbacks.post_patch)(obj); +} + +static inline void klp_pre_unpatch_callback(struct klp_object *obj) +{ + if (obj->callbacks.pre_unpatch) + (*obj->callbacks.pre_unpatch)(obj); +} + +static inline void klp_post_unpatch_callback(struct klp_object *obj) +{ + if (obj->callbacks.post_unpatch_enabled && + obj->callbacks.post_unpatch) + (*obj->callbacks.post_unpatch)(obj); + + obj->callbacks.post_unpatch_enabled = false; +} + #endif /* _LIVEPATCH_CORE_H */ diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c index 52c4e907c14b..82d584225dc6 100644 --- a/kernel/livepatch/patch.c +++ b/kernel/livepatch/patch.c @@ -28,6 +28,7 @@ #include <linux/slab.h> #include <linux/bug.h> #include <linux/printk.h> +#include "core.h" #include "patch.h" #include "transition.h" diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c index b004a1fb6032..56add6327736 100644 --- a/kernel/livepatch/transition.c +++ b/kernel/livepatch/transition.c @@ -82,6 +82,10 @@ static void klp_complete_transition(void) unsigned int cpu; bool immediate_func = false; + pr_debug("'%s': completing %s transition\n", + klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + if (klp_target_state == KLP_UNPATCHED) { /* * All tasks have transitioned to KLP_UNPATCHED so we can now @@ -109,9 +113,6 @@ static void klp_complete_transition(void) } } - if (klp_target_state == KLP_UNPATCHED && !immediate_func) - module_put(klp_transition_patch->mod); - /* Prevent klp_ftrace_handler() from seeing KLP_UNDEFINED state */ if (klp_target_state == KLP_PATCHED) klp_synchronize_transition(); @@ -130,6 +131,27 @@ static void klp_complete_transition(void) } done: + klp_for_each_object(klp_transition_patch, obj) { + if (!klp_is_object_loaded(obj)) + continue; + if (klp_target_state == KLP_PATCHED) + klp_post_patch_callback(obj); + else if (klp_target_state == KLP_UNPATCHED) + klp_post_unpatch_callback(obj); + } + + pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + + /* + * See complementary comment in __klp_enable_patch() for why we + * keep the module reference for immediate patches. + */ + if (!klp_transition_patch->immediate && !immediate_func && + klp_target_state == KLP_UNPATCHED) { + module_put(klp_transition_patch->mod); + } + klp_target_state = KLP_UNDEFINED; klp_transition_patch = NULL; } @@ -145,6 +167,9 @@ void klp_cancel_transition(void) if (WARN_ON_ONCE(klp_target_state != KLP_PATCHED)) return; + pr_debug("'%s': canceling patching transition, going to unpatch\n", + klp_transition_patch->mod->name); + klp_target_state = KLP_UNPATCHED; klp_complete_transition(); } @@ -408,9 +433,6 @@ void klp_try_complete_transition(void) } success: - pr_notice("'%s': %s complete\n", klp_transition_patch->mod->name, - klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); - /* we're done, now cleanup the data structures */ klp_complete_transition(); } @@ -426,7 +448,8 @@ void klp_start_transition(void) WARN_ON_ONCE(klp_target_state == KLP_UNDEFINED); - pr_notice("'%s': %s...\n", klp_transition_patch->mod->name, + pr_notice("'%s': starting %s transition\n", + klp_transition_patch->mod->name, klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); /* @@ -482,6 +505,9 @@ void klp_init_transition(struct klp_patch *patch, int state) */ klp_target_state = state; + pr_debug("'%s': initializing %s transition\n", patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching" : "unpatching"); + /* * If the patch can be applied or reverted immediately, skip the * per-task transitions. @@ -547,6 +573,11 @@ void klp_reverse_transition(void) unsigned int cpu; struct task_struct *g, *task; + pr_debug("'%s': reversing transition from %s\n", + klp_transition_patch->mod->name, + klp_target_state == KLP_PATCHED ? "patching to unpatching" : + "unpatching to patching"); + klp_transition_patch->enabled = !klp_transition_patch->enabled; klp_target_state = !klp_target_state; diff --git a/samples/livepatch/Makefile b/samples/livepatch/Makefile index 539e81d433cd..2472ce39a18d 100644 --- a/samples/livepatch/Makefile +++ b/samples/livepatch/Makefile @@ -2,3 +2,6 @@ obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-sample.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-mod.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix1.o obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-shadow-fix2.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-demo.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-mod.o +obj-$(CONFIG_SAMPLE_LIVEPATCH) += livepatch-callbacks-busymod.o diff --git a/samples/livepatch/livepatch-callbacks-busymod.c b/samples/livepatch/livepatch-callbacks-busymod.c new file mode 100644 index 000000000000..80d06e103f1b --- /dev/null +++ b/samples/livepatch/livepatch-callbacks-busymod.c @@ -0,0 +1,72 @@ +/* + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +/* + * livepatch-callbacks-busymod.c - (un)patching callbacks demo support module + * + * + * Purpose + * ------- + * + * Simple module to demonstrate livepatch (un)patching callbacks. + * + * + * Usage + * ----- + * + * This module is not intended to be standalone. See the "Usage" + * section of livepatch-callbacks-mod.c. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/workqueue.h> +#include <linux/delay.h> + +static int sleep_secs; +module_param(sleep_secs, int, 0644); +MODULE_PARM_DESC(sleep_secs, "sleep_secs (default=0)"); + +static void busymod_work_func(struct work_struct *work); +static DECLARE_DELAYED_WORK(work, busymod_work_func); + +static void busymod_work_func(struct work_struct *work) +{ + pr_info("%s, sleeping %d seconds ...\n", __func__, sleep_secs); + msleep(sleep_secs * 1000); + pr_info("%s exit\n", __func__); +} + +static int livepatch_callbacks_mod_init(void) +{ + pr_info("%s\n", __func__); + schedule_delayed_work(&work, + msecs_to_jiffies(1000 * 0)); + return 0; +} + +static void livepatch_callbacks_mod_exit(void) +{ + cancel_delayed_work_sync(&work); + pr_info("%s\n", __func__); +} + +module_init(livepatch_callbacks_mod_init); +module_exit(livepatch_callbacks_mod_exit); +MODULE_LICENSE("GPL"); diff --git a/samples/livepatch/livepatch-callbacks-demo.c b/samples/livepatch/livepatch-callbacks-demo.c new file mode 100644 index 000000000000..3d115bd68442 --- /dev/null +++ b/samples/livepatch/livepatch-callbacks-demo.c @@ -0,0 +1,234 @@ +/* + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +/* + * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo + * + * + * Purpose + * ------- + * + * Demonstration of registering livepatch (un)patching callbacks. + * + * + * Usage + * ----- + * + * Step 1 - load the simple module + * + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * + * + * Step 2 - load the demonstration livepatch (with callbacks) + * + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * + * Step 3 - cleanup + * + * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled + * rmmod livepatch_callbacks_demo + * rmmod livepatch_callbacks_mod + * + * Watch dmesg output to see livepatch enablement, callback execution + * and patching operations for both vmlinux and module targets. + * + * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and + * livepatch-callbacks-demo.ko to observe what happens when a + * target module is loaded after a livepatch with callbacks. + * + * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch + * callback return status. Try setting up a non-zero status + * such as -19 (-ENODEV): + * + * # Load demo livepatch, vmlinux is patched + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * # Setup next pre-patch callback to return -ENODEV + * echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret + * + * # Module loader refuses to load the target module + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device + * + * NOTE: There is a second target module, + * livepatch-callbacks-busymod.ko, available for experimenting + * with livepatch (un)patch callbacks. This module contains + * a 'sleep_secs' parameter that parks the module on one of the + * functions that the livepatch demo module wants to patch. + * Modifying this value and tweaking the order of module loads can + * effectively demonstrate stalled patch transitions: + * + * # Load a target module, let it park on 'busymod_work_func' for + * # thirty seconds + * insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30 + * + * # Meanwhile load the livepatch + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * # ... then load and unload another target module while the + * # transition is in progress + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * rmmod samples/livepatch/livepatch-callbacks-mod.ko + * + * # Finally cleanup + * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled + * rmmod samples/livepatch/livepatch-callbacks-demo.ko + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/livepatch.h> + +static int pre_patch_ret; +module_param(pre_patch_ret, int, 0644); +MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)"); + +static const char *const module_state[] = { + [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state", + [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init", + [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away", + [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up", +}; + +static void callback_info(const char *callback, struct klp_object *obj) +{ + if (obj->mod) + pr_info("%s: %s -> %s\n", callback, obj->mod->name, + module_state[obj->mod->state]); + else + pr_info("%s: vmlinux\n", callback); +} + +/* Executed on object patching (ie, patch enablement) */ +static int pre_patch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); + return pre_patch_ret; +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void post_patch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void pre_unpatch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void post_unpatch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +static void patched_work_func(struct work_struct *work) +{ + pr_info("%s\n", __func__); +} + +static struct klp_func no_funcs[] = { + { } +}; + +static struct klp_func busymod_funcs[] = { + { + .old_name = "busymod_work_func", + .new_func = patched_work_func, + }, { } +}; + +static struct klp_object objs[] = { + { + .name = NULL, /* vmlinux */ + .funcs = no_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { + .name = "livepatch_callbacks_mod", + .funcs = no_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { + .name = "livepatch_callbacks_busymod", + .funcs = busymod_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_callbacks_demo_init(void) +{ + int ret; + + if (!klp_have_reliable_stack() && !patch.immediate) { + /* + * WARNING: Be very careful when using 'patch.immediate' in + * your patches. It's ok to use it for simple patches like + * this, but for more complex patches which change function + * semantics, locking semantics, or data structures, it may not + * be safe. Use of this option will also prevent removal of + * the patch. + * + * See Documentation/livepatch/livepatch.txt for more details. + */ + patch.immediate = true; + pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n"); + } + + ret = klp_register_patch(&patch); + if (ret) + return ret; + ret = klp_enable_patch(&patch); + if (ret) { + WARN_ON(klp_unregister_patch(&patch)); + return ret; + } + return 0; +} + +static void livepatch_callbacks_demo_exit(void) +{ + WARN_ON(klp_unregister_patch(&patch)); +} + +module_init(livepatch_callbacks_demo_init); +module_exit(livepatch_callbacks_demo_exit); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y"); diff --git a/samples/livepatch/livepatch-callbacks-mod.c b/samples/livepatch/livepatch-callbacks-mod.c new file mode 100644 index 000000000000..e610ce29ba44 --- /dev/null +++ b/samples/livepatch/livepatch-callbacks-mod.c @@ -0,0 +1,53 @@ +/* + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version 2 + * of the License, or (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +/* + * livepatch-callbacks-mod.c - (un)patching callbacks demo support module + * + * + * Purpose + * ------- + * + * Simple module to demonstrate livepatch (un)patching callbacks. + * + * + * Usage + * ----- + * + * This module is not intended to be standalone. See the "Usage" + * section of livepatch-callbacks-demo.c. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> + +static int livepatch_callbacks_mod_init(void) +{ + pr_info("%s\n", __func__); + return 0; +} + +static void livepatch_callbacks_mod_exit(void) +{ + pr_info("%s\n", __func__); +} + +module_init(livepatch_callbacks_mod_init); +module_exit(livepatch_callbacks_mod_exit); +MODULE_LICENSE("GPL"); |