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[Xen-devel] [PATCH v3 00/12] livepatch: new features and fixes

This series introduces new features to the livepatch functionality as
briefly discussed during Xen Developer Summit 2019: [a] and [b].
It also provides a few fixes and some small improvements.

Main changes in v3:
- Fix expectation test to work on Arm
- Add test for metadata (Konrad)
- Minor fixes to documentation

Main changes in v2:
- added new features to livepatch documentation
- added livepatch tests
- enabled Arm support for [5]
- make .modinfo optional for [11]
- fixed typos


1. independent modules (patches: [1], [2])

  * livepatch-build-tools repo dependency [A]

  Livepatch enforces the following buildid-based dependency chain
  between hotpatch modules:
    1) first module depends on given hypervisor buildid
    2) every consecutive module depends on previous module's buildid
  This way proper hotpatch stack order is maintained and enforced.
  While it is important for production hotpatches it limits agility and
  blocks usage of testing or debug hotpatches. These kinds of hotpatch
  modules are typically expected to be loaded at any time irrespective
  of current state of the modules stack.

  [A] livepatch-build: Embed hypervisor build id into every hotpatch

2. pre- and post- apply|revert actions hooks (patches: [3], [4])

  * livepatch-build-tools repo dependency [B]

  This is an implementation of 4 new livepatch module vetoing hooks,
  that can be optionally supplied along with modules.
  Hooks that currently exists in the livepatch mechanism aren't agile
  enough and have various limitations:
  * run only from within a quiescing zone
  * cannot conditionally prevent applying or reverting
  * do not have access to the module context
  To address these limitations the following has been implemented:
  1) pre-apply hook
  2) post-apply hook
  3) pre-revert hook
  4) post-revert hook

  [B] create-diff-object: Handle extra pre-|post- hooks

3. apply|revert actions replacement hooks (patches: [5], [6], [7])

  * livepatch-build-tools repo dependency: [C], [D], [E]

  To increase hotpatching system's agility and provide more flexiable
  long-term hotpatch solution, allow to overwrite the default apply
  and revert action functions with hook-like supplied alternatives.
  The alternative functions are optional and the default functions are
  used by default.

  [C] create-diff-object: Do not create empty .livepatch.funcs section
  [D] create-diff-object: Handle optional apply|revert hooks
  [E] create-diff-object: Add support for applied/reverted marker

4. inline asm hotpatching expectations (patches: [8])

  * livepatch-build-tools repo dependency: [F]

  Expectations are designed as optional feature, since the main use of
  them is planned for inline asm hotpatching.
  The payload structure is modified as each expectation structure is
  part of the livepatch_func structure and hence extends the payload.
  The payload version is bumped to 3 with this change to highlight the
  ABI modification and enforce proper support.
  The expectation is manually enabled during inline asm module
  construction. If enabled, expectation ensures that the expected
  content of memory is to be found at a given patching (old_addr)

  [F] create-diff-object: Add support for expectations

5. runtime hotpatch metadata support (patches: [9], [10], [11])

  Having detailed hotpatch metadata helps to properly identify module's
  origin and version. It also allows to keep track of the history of
  hotpatch loads in the system (at least within dmesg buffer size
  Extend the livepatch list operation to fetch also payloads' metadata.
  This is achieved by extending the sysctl list interface with 2 extra
  guest handles:
  * metadata     - an array of arbitrary size strings
  * metadata_len - an array of metadata strings' lengths (uin32_t each)
  To unify and simplify the interface, handle the modules' name strings
  of arbitrary size by copying them in adhering chunks to the userland.

6. python bindings for livepatch operations (patches: [12])

  Extend the XC python bindings library to support all common livepatch
  operations and actions:
  - status (pyxc_livepatch_status):
  - action (pyxc_livepatch_action):
  - upload (pyxc_livepatch_upload):
  - list (pyxc_livepatch_list):

[b] https://lists.xenproject.org/archives/html/xen-devel/2019-07/msg00846.html

Merged in v1:
  python: Add XC binding for Xen build ID
  livepatch: always print XENLOG_ERR information

Pawel Wieczorkiewicz (12):
  [1] livepatch: Always check hypervisor build ID upon hotpatch upload
  [2] livepatch: Allow to override inter-modules buildid dependency
  [3] livepatch: Export payload structure via livepatch_payload.h
  [4] livepatch: Implement pre-|post- apply|revert hooks
  [5] livepatch: Add support for apply|revert action replacement hooks
  [6] livepatch: Do not enforce ELF_LIVEPATCH_FUNC section presence
  [7] livepatch: Add per-function applied/reverted state tracking marker
  [8] livepatch: Add support for inline asm hotpatching expectations
  [9] livepatch: Add support for modules .modinfo section metadata
  [10] livepatch: Handle arbitrary size names with the list operation
  [11] livepatch: Add metadata runtime retrieval mechanism
  [12] livepatch: Add python bindings for livepatch operations

 .gitignore                                     |   6 +-
 docs/misc/livepatch.pandoc                     | 240 ++++++++-
 tools/libxc/include/xenctrl.h                  |  68 ++-
 tools/libxc/xc_misc.c                          | 162 ++++--
 tools/misc/xen-livepatch.c                     | 258 +++++++---
 tools/python/xen/lowlevel/xc/xc.c              | 273 +++++++++++
 xen/arch/arm/arm32/livepatch.c                 |  12 +-
 xen/arch/arm/arm64/livepatch.c                 |  12 +-
 xen/arch/arm/livepatch.c                       |  10 +-
 xen/arch/x86/livepatch.c                       |  22 +-
 xen/common/livepatch.c                         | 650 +++++++++++++++++++++----
 xen/include/public/sysctl.h                    |  62 ++-
 xen/include/xen/livepatch.h                    |  42 +-
 xen/include/xen/livepatch_payload.h            |  83 ++++
 xen/test/livepatch/Makefile                    | 121 ++++-
 xen/test/livepatch/xen_action_hooks.c          | 102 ++++
 xen/test/livepatch/xen_action_hooks_marker.c   | 112 +++++
 xen/test/livepatch/xen_action_hooks_noapply.c  | 136 ++++++
 xen/test/livepatch/xen_action_hooks_nofunc.c   |  86 ++++
 xen/test/livepatch/xen_action_hooks_norevert.c | 143 ++++++
 xen/test/livepatch/xen_expectations.c          |  41 ++
 xen/test/livepatch/xen_expectations_fail.c     |  42 ++
 xen/test/livepatch/xen_prepost_hooks.c         | 122 +++++
 xen/test/livepatch/xen_prepost_hooks_fail.c    |  75 +++
 24 files changed, 2597 insertions(+), 283 deletions(-)
 create mode 100644 xen/test/livepatch/xen_action_hooks.c
 create mode 100644 xen/test/livepatch/xen_action_hooks_marker.c
 create mode 100644 xen/test/livepatch/xen_action_hooks_noapply.c
 create mode 100644 xen/test/livepatch/xen_action_hooks_nofunc.c
 create mode 100644 xen/test/livepatch/xen_action_hooks_norevert.c
 create mode 100644 xen/test/livepatch/xen_expectations.c
 create mode 100644 xen/test/livepatch/xen_expectations_fail.c
 create mode 100644 xen/test/livepatch/xen_prepost_hooks.c
 create mode 100644 xen/test/livepatch/xen_prepost_hooks_fail.c


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