[PATCHv3 bpf-next 0/9] mm/bpf/perf: Store build id in file object

[Jiri Olsa]

hi,
this patchset adds build id object pointer to struct file object.

We have several use cases for build id to be used in BPF programs
[2][3].

Having build id pointer stored directly in file object allows to get
build id reliably regardless of the execution context as described
in [3].

Previous iteration [1] stored build id pointer into inode, but it
became clear that struct file object is better place, because we read 
the build id when the file is mmap-ed and as Dave Chinner said [4]:

> Yes, the problem being that we can cache hundreds of millions of
> inodes in memory, and only a very small subset of them are going to
> have open files associated with them. And an even smaller subset are
> going to be mmapped.

thanks,
jirka


v3 changes:
  - moved build id back to file object (discussed in [4])
  - drop patch 4, it's not needed [Andrii]
  - added ack to patch 7 [Andrii]
  - replaced BUILD_ID_SIZE_MAX macro with enum [Andrii]
  - few re-formatting fixes [Andrii]

v2 changes:
  - store build id under inode [Matthew Wilcox]
  - use urandom_read and liburandom_read.so for test [Andrii]
  - add libelf-based helper to fetch build ID from elf [Andrii]
  - store build id or error we got when reading it [Andrii]
  - use full name i_build_id [Andrii]
  - several tests fixes [Andrii]


[1] https://lore.kernel.org/bpf/20230228093206.821563-1-jolsa@xxxxxxxxxx/
[2] https://lore.kernel.org/bpf/CA+khW7juLEcrTOd7iKG3C_WY8L265XKNo0iLzV1fE=o-cyeHcQ@xxxxxxxxxxxxxx/
[3] https://lore.kernel.org/bpf/ZABf26mV0D0LS7r%2F@krava/
[4] https://lore.kernel.org/bpf/20230228220714.GJ2825702@xxxxxxxxxxxxxxxxxxx/
---
Jiri Olsa (9):
      mm: Store build id in file object
      perf: Use file object build id in perf_event_mmap_event
      bpf: Use file object build id in stackmap
      bpf: Switch BUILD_ID_SIZE_MAX to enum
      selftests/bpf: Add read_buildid function
      selftests/bpf: Add err.h header
      selftests/bpf: Replace extract_build_id with read_build_id
      selftests/bpf: Add iter_task_vma_buildid test
      selftests/bpf: Add file_build_id test

 fs/file_table.c                                                  |  3 +++
 include/linux/buildid.h                                          | 21 ++++++++++++++++++-
 include/linux/fs.h                                               |  7 +++++++
 kernel/bpf/stackmap.c                                            | 24 +++++++++++++++++++++-
 kernel/events/core.c                                             | 43 ++++++++++++++++++++++++++++++++++----
 lib/buildid.c                                                    | 42 +++++++++++++++++++++++++++++++++++++
 mm/Kconfig                                                       |  9 ++++++++
 mm/mmap.c                                                        | 18 ++++++++++++++++
 tools/testing/selftests/bpf/Makefile                             |  7 ++++++-
 tools/testing/selftests/bpf/no_build_id.c                        |  6 ++++++
 tools/testing/selftests/bpf/prog_tests/bpf_iter.c                | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/prog_tests/file_build_id.c           | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/prog_tests/stacktrace_build_id.c     | 19 +++++++----------
 tools/testing/selftests/bpf/prog_tests/stacktrace_build_id_nmi.c | 17 ++++++---------
 tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c    | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/err.h                          | 18 ++++++++++++++++
 tools/testing/selftests/bpf/progs/file_build_id.c                | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/progs/profiler.inc.h                 |  3 +--
 tools/testing/selftests/bpf/test_progs.c                         | 25 ----------------------
 tools/testing/selftests/bpf/test_progs.h                         | 11 +++++++++-
 tools/testing/selftests/bpf/trace_helpers.c                      | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/testing/selftests/bpf/trace_helpers.h                      |  5 +++++
 22 files changed, 608 insertions(+), 58 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/no_build_id.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/file_build_id.c
 create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_vma_buildid.c
 create mode 100644 tools/testing/selftests/bpf/progs/err.h
 create mode 100644 tools/testing/selftests/bpf/progs/file_build_id.c