livepatch's consistency model requires that no live patched function must be found on any task's stack during a transition process after a live patch is applied. It is achieved by walking through stacks of all blocked tasks.
The user might also want to define more functions to search for without them being patched at all. It may either help with preparing a live patch, which would otherwise require additional touches to achieve the consistency, or it can be used to overcome deficiencies the stack checking inherently has. For example, GCC may optimize a function so that a part of it is moved to a different section and the function would jump to it. This child function would not be found on a stack in this case, but it may be important to search for it so that, again, the consistency is achieved.
The patch set adds a new API which allows the user to specify such functions.
The first patch is only preparatory. The main work is in the second one. The third patch adds a test.
Originally, I wanted to add it all to klp_patch struct, but it makes more sense to do it on klp_object level. It is also easier to reuse as much of the existing code as possible in that case.
I am not good with naming so bike-shedding is welcome. Reviews even more.
Miroslav Benes (3): livepatch: Move the initialization of old_func to a new function livepatch: Allow user to specify functions to search for on a stack selftests/livepatch: Test of the API for specifying functions to search for on a stack
include/linux/livepatch.h | 11 +++ kernel/livepatch/core.c | 50 ++++++++--- kernel/livepatch/transition.c | 21 +++-- lib/Kconfig.debug | 1 + lib/livepatch/Makefile | 4 +- lib/livepatch/test_klp_funcstack_demo.c | 61 +++++++++++++ lib/livepatch/test_klp_funcstack_mod.c | 72 +++++++++++++++ tools/testing/selftests/livepatch/Makefile | 3 +- .../selftests/livepatch/test-func-stack.sh | 88 +++++++++++++++++++ 9 files changed, 293 insertions(+), 18 deletions(-) create mode 100644 lib/livepatch/test_klp_funcstack_demo.c create mode 100644 lib/livepatch/test_klp_funcstack_mod.c create mode 100755 tools/testing/selftests/livepatch/test-func-stack.sh