[bpf-next,v4,0/9] Implement task_local_storage

Message

KP Singh Nov. 5, 2020, 2:47 p.m. UTC

From: KP Singh <[e-mail]>

# v3 -> v4

- Move the patch that exposes spin lock helpers to LSM programs as the
  first patch as some of the changes in the implementation are actually
  for spin locks.
- Clarify the comment in the bpf_task_storage_{get, delete} helper as
  discussed with Martin.
- Added Martin's ack and rebased.

# v2 -> v3

- Added bpf_spin_locks to the selftests for local storage, found that
  these are not available for LSM programs.
- Made spin lock helpers available for LSM programs (except sleepable
  programs which need more work).
- Minor fixes for includes and added short commit messages for patches
  that were split up for libbpf and bpftool.
- Added Song's acks.

# v1 -> v2

- Updated the refcounting for task_struct and simplified conversion
  of fd -> struct pid.
- Some fixes suggested by Martin and Andrii, notably:
   * long return type for the bpf_task_storage_delete helper (update
     for bpf_inode_storage_delete will be sent separately).
   * Remove extra nullness check to task_storage_ptr in map syscall
     ops.
   * Changed the argument signature of the BPF helpers to use
     task_struct pointer in uapi headers.
   * Remove unnecessary verifier logic for the bpf_get_current_task_btf
     helper.
   * Split the changes for bpftool and libbpf.
- Exercised syscall operations for local storage (kept a simpler verison
  in test_local_storage.c, the eventual goal will be to update
  sk_storage_map.c for all local storage types).
- Formatting fixes + Rebase.

We already have socket and inode local storage since [1]

This patch series:

* Implements bpf_local_storage for task_struct.
* Implements the bpf_get_current_task_btf helper which returns a BTF
  pointer to the current task. Not only is this generally cleaner
  (reading from the task_struct currently requires BPF_CORE_READ), it
  also allows the BTF pointer to be used in task_local_storage helpers.
* In order to implement this helper, a RET_PTR_TO_BTF_ID is introduced
  which works similar to RET_PTR_TO_BTF_ID_OR_NULL but does not require
  a nullness check.
* Implements a detection in selftests which uses the
  task local storage to deny a running executable from unlinking itself.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=f836a56e84ffc9f1a1cd73f77e10404ca46a4616

KP Singh (9):
  bpf: Allow LSM programs to use bpf spin locks
  bpf: Implement task local storage
  libbpf: Add support for task local storage
  bpftool: Add support for task local storage
  bpf: Implement get_current_task_btf and RET_PTR_TO_BTF_ID
  bpf: Fix tests for local_storage
  bpf: Update selftests for local_storage to use vmlinux.h
  bpf: Add tests for task_local_storage
  bpf: Exercise syscall operations for inode and sk storage

 include/linux/bpf.h                           |   1 +
 include/linux/bpf_lsm.h                       |  23 ++
 include/linux/bpf_types.h                     |   1 +
 include/uapi/linux/bpf.h                      |  48 +++
 kernel/bpf/Makefile                           |   1 +
 kernel/bpf/bpf_lsm.c                          |   8 +
 kernel/bpf/bpf_task_storage.c                 | 315 ++++++++++++++++++
 kernel/bpf/syscall.c                          |   3 +-
 kernel/bpf/verifier.c                         |  37 +-
 kernel/trace/bpf_trace.c                      |  16 +
 security/bpf/hooks.c                          |   2 +
 .../bpf/bpftool/Documentation/bpftool-map.rst |   3 +-
 tools/bpf/bpftool/bash-completion/bpftool     |   2 +-
 tools/bpf/bpftool/map.c                       |   4 +-
 tools/include/uapi/linux/bpf.h                |  48 +++
 tools/lib/bpf/libbpf_probes.c                 |   1 +
 .../bpf/prog_tests/test_local_storage.c       | 182 +++++++++-
 .../selftests/bpf/progs/local_storage.c       | 103 ++++--
 18 files changed, 741 insertions(+), 57 deletions(-)
 create mode 100644 kernel/bpf/bpf_task_storage.c