[PATCH v15 00/11] livepatch: Atomic replace feature

From: Petr Mladek
Date: Wed Jan 09 2019 - 07:43:41 EST

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Hi,

The atomic replace allows to create cumulative patches. They
are useful when you maintain many livepatches and want to remove
one that is lower on the stack. In addition it is very useful when
more patches touch the same function and there are dependencies
between them.

I kindly ask reviewers to concentrate on bugs and really confusing
names, comments, or commit messages. Even simple changes are not
always simple when rebasing. Also review is not trivial.

Feel free to report any problems and ideas. But I suggest
to do any non-critical changes on top of this patchset
when possible.

This is also why I did not add missing kzalloc error handling
and did not fix non-static warnings in the selftests. They
are not critical. And the discussion about the fixes
in sample directory was quite long.

PS: I am sorry that I lost nerves with the last review.
It was perfect time to report cosmetic problems. I just
was a bit overloaded and tired. Also it was a bit sad to
realize how bad my English was. I am going to hide under
some stone now.

Changes against v14:

+ Rename klp_active -> klp_added [Josh]

+ Do not clear klp_added variable in klp_free*() [Josh]

+ Rename klp_init_patch_before_free() -> klp_init_patch_early()
[Josh]

+ Do not call klp_free_patch() when
kobject_init_and_add(&patch->kobj) fails in 3rd patch.
The final code stays the same after the refactoring
in 5th patch. [Josh]

+ Better 4th patch subject [Josh]

+ Use safe iterators in klp_free() functions already in 7th
patch instead of in 8th [Josh]

+ Rename free_all -> nops_only and revert the logic in
klp_free*() and klp_unpatch_object*() functions [Josh]

+ Do not refuse loading conflicting patches. Just remove
the ordering (stacking) [Josh]

+ fixed typos, improved wording [all]

Changes against v13:

+ Rename old_addr -> old_func instead of new_func -> new_addr. [Josh]

+ Do not add the helper macros to define structures. [Miroslav, Josh]

+ Add custom kobj_alive flag to reliably handle kobj state. [Miroslav]

+ Avoid renaming .forced flag to .module_put by calling klp_free
functions only with taken module reference. [Josh]

+ Use list_add_tail() instead of list_add() when updating the dynamic
lists of klp_object and klp_func structures. Note that this
required also updating the order of messages from the pre/post
callbacks in the selftest. [Josh, Miroslav]

+ Do not unnecessarily initialize ret variable in klp_add_nops(). [Miroslav]

+ Got rid of klp_discard_replaced_stuff(). [Josh]

+ Updated commit messages, comments and documentation, especially
the section "Livepatch life-cycle" [Josh, Miroslav]

Changes against v12:

+ Finish freeing the patch using workqueues to prevent
deadlock against kobject code.

+ Check for valid pointers when initializing the dynamic
lists objects and functions.

+ Mark klp_free_objects_dynamic() static.

+ Improved documentation and fixed typos

Changes against v11:

+ Functional changes:

+ Livepatches get automatically unregistered when disabled.
Note that the sysfs interface disappears at this point.
It simplifies the API and code. The only drawback is that
the patch can be enabled again only by reloading the module.

+ Refuse to load conflicting patches. The same function can
be patched again only by a new cumulative patch that
replaces all older ones.

+ Non-conflicting patches can be loaded and disabled in any
order.

+ API related changes:

+ Change void *new_func -> unsigned long new_addr in
struct klp_func.

+ Several new macros to hide implementation details and
avoid casting when defining struct klp-func and klp_object.

+ Remove obsolete klp_register_patch() klp_unregister_patch() API

+ Change in selftest against v4:

+ Use new macros to define struct klp_func and klp_object.

+ Remove klp_register_patch()/klp_unregister_patch() calls.

+ Replace load_mod() + wait_for_transition() with three
variants load_mod(), load_lp(), load_lp_nowait(). IMHO,
it is easier to use because we need to detect the end
of transaction another way after disable_lp() now.

+ Replaced unload_mod() with two variants unload_mod(),
unload_lp() to match the above change.

+ Wait for the end of transition in disable_lp()
instead of the unreliable check of the sysfs interface.

Note that I did not touch the logs with expected result.
They stay exactly the same as in v4 posted by Joe.
I hope that it is a good sign ;-)

Changes against v10:

+ Bug fixes and functional changes:
+ Handle Nops in klp_ftrace_handled() to avoid infinite loop [Mirek]
+ Really add dynamically allocated klp_object into the list [Petr]
+ Clear patch->replace when transition finishes [Josh]

+ Refactoring and clean up [Josh]:
+ Replace enum types with bools
+ Avoid using ERR_PTR
+ Remove too paranoid warnings
+ Distinguish registered patches by a flag instead of a list
+ Squash some functions
+ Update comments, documentation, and commit messages
+ Squashed and split patches to do more controversial changes later

Changes against v9:

+ Fixed check of valid NOPs for already loaded objects,
regression introduced in v9 [Joe, Mirek]
+ Allow to replace even disabled patches [Evgenii]

Changes against v8:

+ Fixed handling of statically defined struct klp_object
with empty array of functions [Joe, Mirek]
+ Removed redundant func->new_func assignment for NOPs [Mirek]
+ Improved some wording [Mirek]

Changes against v7:

+ Fixed handling of NOPs for not-yet-loaded modules
+ Made klp_replaced_patches list static [Mirek]
+ Made klp_free_object() public later [Mirek]
+ Fixed several reported typos [Mirek, Joe]
+ Updated documentation according to the feedback [Joe]
+ Added some Acks [Mirek]

Changes against v6:

+ used list_move when disabling replaced patches [Jason]
+ renamed KLP_FUNC_ORIGINAL -> KLP_FUNC_STATIC [Mirek]
+ used klp_is_func_type() in klp_unpatch_object() [Mirek]
+ moved static definition of klp_get_or_add_object() [Mirek]
+ updated comment about synchronization in forced mode [Mirek]
+ added user documentation
+ fixed several typos

Jason Baron (2):
livepatch: Use lists to manage patches, objects and functions
livepatch: Add atomic replace

Joe Lawrence (1):
selftests/livepatch: introduce tests

Petr Mladek (8):
livepatch: Change unsigned long old_addr -> void *old_func in struct
klp_func
livepatch: Shuffle klp_enable_patch()/klp_disable_patch() code
livepatch: Consolidate klp_free functions
livepatch: Don't block the removal of patches loaded after a forced
transition
livepatch: Simplify API by removing registration step
livepatch: Remove Nop structures when unused
livepatch: Atomic replace and cumulative patches documentation
livepatch: Remove ordering (stacking) of the livepatches

Documentation/livepatch/callbacks.txt | 489 +------------
Documentation/livepatch/cumulative-patches.txt | 102 +++
Documentation/livepatch/livepatch.txt | 167 +++--
MAINTAINERS | 1 +
include/linux/livepatch.h | 50 +-
kernel/livepatch/core.c | 790 +++++++++++++--------
kernel/livepatch/core.h | 5 +
kernel/livepatch/patch.c | 57 +-
kernel/livepatch/patch.h | 5 +-
kernel/livepatch/transition.c | 34 +-
lib/Kconfig.debug | 22 +-
lib/Makefile | 2 +
lib/livepatch/Makefile | 15 +
lib/livepatch/test_klp_atomic_replace.c | 57 ++
lib/livepatch/test_klp_callbacks_busy.c | 43 ++
lib/livepatch/test_klp_callbacks_demo.c | 121 ++++
lib/livepatch/test_klp_callbacks_demo2.c | 93 +++
lib/livepatch/test_klp_callbacks_mod.c | 24 +
lib/livepatch/test_klp_livepatch.c | 51 ++
lib/livepatch/test_klp_shadow_vars.c | 236 ++++++
samples/livepatch/livepatch-callbacks-demo.c | 13 +-
samples/livepatch/livepatch-sample.c | 13 +-
samples/livepatch/livepatch-shadow-fix1.c | 14 +-
samples/livepatch/livepatch-shadow-fix2.c | 14 +-
tools/testing/selftests/Makefile | 1 +
tools/testing/selftests/livepatch/Makefile | 8 +
tools/testing/selftests/livepatch/README | 43 ++
tools/testing/selftests/livepatch/config | 1 +
tools/testing/selftests/livepatch/functions.sh | 203 ++++++
.../testing/selftests/livepatch/test-callbacks.sh | 587 +++++++++++++++
.../testing/selftests/livepatch/test-livepatch.sh | 168 +++++
.../selftests/livepatch/test-shadow-vars.sh | 60 ++
32 files changed, 2546 insertions(+), 943 deletions(-)
create mode 100644 Documentation/livepatch/cumulative-patches.txt
create mode 100644 lib/livepatch/Makefile
create mode 100644 lib/livepatch/test_klp_atomic_replace.c
create mode 100644 lib/livepatch/test_klp_callbacks_busy.c
create mode 100644 lib/livepatch/test_klp_callbacks_demo.c
create mode 100644 lib/livepatch/test_klp_callbacks_demo2.c
create mode 100644 lib/livepatch/test_klp_callbacks_mod.c
create mode 100644 lib/livepatch/test_klp_livepatch.c
create mode 100644 lib/livepatch/test_klp_shadow_vars.c
create mode 100644 tools/testing/selftests/livepatch/Makefile
create mode 100644 tools/testing/selftests/livepatch/README
create mode 100644 tools/testing/selftests/livepatch/config
create mode 100644 tools/testing/selftests/livepatch/functions.sh
create mode 100755 tools/testing/selftests/livepatch/test-callbacks.sh
create mode 100755 tools/testing/selftests/livepatch/test-livepatch.sh
create mode 100755 tools/testing/selftests/livepatch/test-shadow-vars.sh

--
2.13.7

Next message: Petr Mladek: "[PATCH v15 01/11] livepatch: Change unsigned long old_addr -> void *old_func in struct klp_func"
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