[PATCH v13 00/12] livepatch: Atomic replace feature

Petr Mladek
2018-10-15T12:37:26Z

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.

Now, the question is if 13 is a lucky number. I hope so
and that this version might get merged. Any feedback?
Not only from Mirek, please ;-)

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 (9):
livepatch: Change void *new_func -> unsigned long new_addr in struct
klp_func
livepatch: Helper macros to define livepatch structures
livepatch: Shuffle klp_enable_patch()/klp_disable_patch() code
livepatch: Consolidate klp_free functions
livepatch: Refuse to unload only livepatches available during 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 and refuse loading conflicting patches

Documentation/livepatch/callbacks.txt | 489 +-----------
Documentation/livepatch/cumulative-patches.txt | 102 +++
Documentation/livepatch/livepatch.txt | 131 ++--
MAINTAINERS | 1 +
include/linux/livepatch.h | 84 ++-
kernel/livepatch/core.c | 826 ++++++++++++++-------
kernel/livepatch/core.h | 4 +
kernel/livepatch/patch.c | 41 +-
kernel/livepatch/patch.h | 1 +
kernel/livepatch/transition.c | 33 +-
lib/Kconfig.debug | 21 +
lib/Makefile | 2 +
lib/livepatch/Makefile | 15 +
lib/livepatch/test_klp_atomic_replace.c | 53 ++
lib/livepatch/test_klp_callbacks_busy.c | 43 ++
lib/livepatch/test_klp_callbacks_demo.c | 109 +++
lib/livepatch/test_klp_callbacks_demo2.c | 89 +++
lib/livepatch/test_klp_callbacks_mod.c | 24 +
lib/livepatch/test_klp_livepatch.c | 47 ++
lib/livepatch/test_klp_shadow_vars.c | 236 ++++++
samples/livepatch/livepatch-callbacks-demo.c | 68 +-
samples/livepatch/livepatch-sample.c | 26 +-
samples/livepatch/livepatch-shadow-fix1.c | 34 +-
samples/livepatch/livepatch-shadow-fix2.c | 34 +-
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, 2597 insertions(+), 987 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

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2.13.7