[PATCH v3 00/15] livepatch: hybrid consistency model

Josh Poimboeuf
2016-12-08T18:08:25Z

Dusting the cobwebs off the consistency model again. This is based on
linux-next/master.

v1 was posted on 2015-02-09:

https://lkml.kernel.org/r/cover.1423499826.git.jpoimboe@redhat.com

v2 was posted on 2016-04-28:

https://lkml.kernel.org/r/cover.1461875890.git.jpoimboe@redhat.com

The biggest issue from v2 was finding a decent way to detect preemption
and page faults on the stack of a sleeping task. That problem was
solved by rewriting the x86 stack unwinder. The new unwinder helps
detect such cases by finding all pt_regs on the stack. When
preemption/page faults are detected, the stack is considered unreliable
and the patching of the task is deferred.

For more details about the consistency model, see patch 13/15.

---

v3:
- rebase on new x86 unwinder
- force !HAVE_RELIABLE_STACKTRACE arches to use patch->immediate for
now, because we don't have a way to transition kthreads otherwise
- rebase s390 TIF_PATCH_PENDING patch onto latest entry code
- update barrier comments and move barrier from the end of
klp_init_transition() to its callers
- "klp_work" -> "klp_transition_work"
- "klp_patch_task()" -> "klp_update_patch_state()"
- explicit _TIF_ALLWORK_MASK
- change klp_reverse_transition() to not try to complete transition.
instead modify the work queue delay to zero.
- get rid of klp_schedule_work() in favor of calling
schedule_delayed_work() directly with a KLP_TRANSITION_DELAY
- initialize klp_target_state to KLP_UNDEFINED
- move klp_target_state assignment to before patch->immediate check in
klp_init_transition()
- rcu_read_lock() in klp_update_patch_state(), test the thread flag in
patch task, synchronize_rcu() in klp_complete_transition()
- use kstrtobool() in enabled_store()
- change task_rq_lock() argument type to struct rq_flags
- add several WARN_ON_ONCE assertions for klp_target_state and
task->patch_state

v2:
- "universe" -> "patch state"
- rename klp_update_task_universe() -> klp_patch_task()
- add preempt IRQ tracking (TF_PREEMPT_IRQ)
- fix print_context_stack_reliable() bug
- improve print_context_stack_reliable() comments
- klp_ftrace_handler comment fixes
- add "patch_state" proc file to tid_base_stuff
- schedule work even for !RELIABLE_STACKTRACE
- forked child inherits patch state from parent
- add detailed comment to livepatch.h klp_func definition about the
klp_func patched/transition state transitions
- update exit_to_usermode_loop() comment
- clear all TIF_KLP_NEED_UPDATE flags in klp_complete_transition()
- remove unnecessary function externs
- add livepatch documentation, sysfs documentation, /proc documentation
- /proc/pid/patch_state: -1 means no patch is currently being applied/reverted
- "TIF_KLP_NEED_UPDATE" -> "TIF_PATCH_PENDING"
- support for s390 and powerpc-le
- don't assume stacks with dynamic ftrace trampolines are reliable
- add _TIF_ALLWORK_MASK info to commit log

v1.9:
- revive from the dead and rebased
- reliable stacks!
- add support for immediate consistency model
- add a ton of comments
- fix up memory barriers
- remove "allow patch modules to be removed" patch for now, it still
needs more discussion and thought - it can be done with something
- "proc/pid/universe" -> "proc/pid/patch_status"
- remove WARN_ON_ONCE from !func condition in ftrace handler -- can
happen because of RCU
- keep klp_mutex private by putting the work_fn in core.c
- convert states from int to boolean
- remove obsolete '@state' comments
- several header file and include improvements suggested by Jiri S
- change kallsyms_lookup_size_offset() errors from EINVAL -> ENOENT
- change proc file permissions S_IRUGO -> USR
- use klp_for_each_object/func helpers

---

Jiri Slaby (1):
livepatch/s390: reorganize TIF thread flag bits

Josh Poimboeuf (12):
stacktrace/x86: add function for detecting reliable stack traces
x86/entry: define _TIF_ALLWORK_MASK flags explicitly
livepatch: temporary stubs for klp_patch_pending() and
klp_update_patch_state()
livepatch/x86: add TIF_PATCH_PENDING thread flag
livepatch/powerpc: add TIF_PATCH_PENDING thread flag
livepatch: separate enabled and patched states
livepatch: remove unnecessary object loaded check
livepatch: move patching functions into patch.c
livepatch: use kstrtobool() in enabled_store()
livepatch: store function sizes
livepatch: change to a per-task consistency model
livepatch: add /proc/<pid>/patch_state

Miroslav Benes (2):
livepatch/s390: add TIF_PATCH_PENDING thread flag
livepatch: allow removal of a disabled patch

Documentation/ABI/testing/sysfs-kernel-livepatch | 8 +
Documentation/filesystems/proc.txt | 18 +
Documentation/livepatch/livepatch.txt | 156 ++++++--
arch/Kconfig | 6 +
arch/powerpc/include/asm/thread_info.h | 4 +-
arch/powerpc/kernel/signal.c | 4 +
arch/s390/include/asm/thread_info.h | 24 +-
arch/s390/kernel/entry.S | 31 +-
arch/x86/Kconfig | 1 +
arch/x86/entry/common.c | 9 +-
arch/x86/include/asm/thread_info.h | 11 +-
arch/x86/include/asm/unwind.h | 6 +
arch/x86/kernel/stacktrace.c | 59 ++-
arch/x86/kernel/unwind_frame.c | 1 +
fs/proc/base.c | 15 +
include/linux/init_task.h | 9 +
include/linux/livepatch.h | 66 ++-
include/linux/sched.h | 3 +
include/linux/stacktrace.h | 8 +-
kernel/fork.c | 3 +
kernel/livepatch/Makefile | 2 +-
kernel/livepatch/core.c | 446 +++++++++------------
kernel/livepatch/patch.c | 261 ++++++++++++
kernel/livepatch/patch.h | 33 ++
kernel/livepatch/transition.c | 487 +++++++++++++++++++++++
kernel/livepatch/transition.h | 14 +
kernel/sched/idle.c | 4 +
kernel/stacktrace.c | 12 +-
samples/livepatch/livepatch-sample.c | 8 +-
29 files changed, 1367 insertions(+), 342 deletions(-)
create mode 100644 kernel/livepatch/patch.c
create mode 100644 kernel/livepatch/patch.h
create mode 100644 kernel/livepatch/transition.c
create mode 100644 kernel/livepatch/transition.h

--
2.7.4