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Subject[PATCHv3 bpf-next 0/9] mm/bpf/perf: Store build id in file object
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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@kernel.org/
[2] https://lore.kernel.org/bpf/CA+khW7juLEcrTOd7iKG3C_WY8L265XKNo0iLzV1fE=o-cyeHcQ@mail.gmail.com/
[3] https://lore.kernel.org/bpf/ZABf26mV0D0LS7r%2F@krava/
[4] https://lore.kernel.org/bpf/20230228220714.GJ2825702@dread.disaster.area/
---
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

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