kpatch: Add subcommand '--enabling' to adjust new sysfs attribute 'st…

[wardenjohn]

…ack_order' of livepatch

Add an sub command of kpatch list with '--enabling' option to adjust kernel new attribute 'stack_order' of livepatch of kernel v6.13 or later.

Now, using 'kpatch list --enabling' can output the enabling function in the system and the relationship from the livepatch module -> livepatch object -> livepatch function.

PS: This is a pre-commit. This patch should be merged after the 'stack_order' patch is merged into kernel v6.13 or later.

[joe-lawrence]

fyi for reviewers, here is a sample output when loading the kernel's kselftest modules used during the test of this sysfs feature:

$ kpatch list --enabling
Loaded patch modules:
test_klp_callbacks_demo [enabled]
test_klp_livepatch [enabled]
test_klp_syscall [enabled]

Installed patch modules:

The function enabling in the system:
Module                   Object                   Function
test_klp_syscall         vmlinux                  __x64_sys_getpid
test_klp_callbacks_demo  test_klp_callbacks_busy  busymod_work_func
test_klp_livepatch       vmlinux                  cmdline_proc_show

A few thoughts:

1. I don't think this patch handles the in-transition case. If I understand the associated kernel change, if the livepatch is currently transitioning, then it's stack order shouldn't be considered (otherwise this display would incorrectly imply that it's active).
2. Would similar information be useful even without the livepatch stack_order sysfs feature. By this I mean, it might be useful if patchset commit 1 introduced the display of the livepatched functions (regardless of which one is actually active). Then patchset commit 2 would take into considering the stack_order (if present) to note the currently active or inactive ones.
3. The answer to (2) would better phrase "The function enabling in the system" heading to something like "Currently livepatched functions". Likewise for the subcommand, "--enabling" would be "--functions".

Note that these aren't necessarily changes that I'm requesting, but I think a greater conversation around the display and feature would make sense first.