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Date:   Sat, 14 Dec 2019 23:01:08 -0500
From:   Wenbo Zhang <>
Subject: [PATCH bpf-next v12 0/2] bpf: adding get_file_path helper

This patch series introduce a bpf helper that can be used to map a file
descriptor to a pathname.

This requirement is mainly discussed here:

This implementation supports both local and mountable pseudo file systems,
and ensure we're in user context which is safe for this helper to run.

Changes since v11:

* only allow tracepoints to make sure it won't dead lock

Changes since v10:

* fix missing fput

Changes since v9:

* Associate help patch with its selftests patch to this series

* Refactor selftests code for further simplification  

Changes since v8:

* format helper description 

Changes since v7:

* Use fget_raw instead of fdget_raw, as fdget_raw is only used inside fs/

* Ensure we're in user context which is safe fot the help to run

* Filter unmountable pseudo filesystem, because they don't have real path

* Supplement the description of this helper function

Changes since v6:

* Fix missing signed-off-by line

Changes since v5:

* Refactor helper avoid unnecessary goto end by having two explicit returns

Changes since v4:

* Rename bpf_fd2path to bpf_get_file_path to be consistent with other
helper's names

* When fdget_raw fails, set ret to -EBADF instead of -EINVAL

* Remove fdput from fdget_raw's error path

* Use IS_ERR instead of IS_ERR_OR_NULL as d_path ether returns a pointer
into the buffer or an error code if the path was too long

* Modify the normal path's return value to return copied string length
including NUL

* Update helper description's Return bits.

* Refactor selftests code for further simplification  

Changes since v3:

* Remove unnecessary LOCKDOWN_BPF_READ

* Refactor error handling section for enhanced readability

* Provide a test case in tools/testing/selftests/bpf

* Refactor sefltests code to use real global variables instead of maps

Changes since v2:

* Fix backward compatibility

* Add helper description

* Refactor selftests use global data instead of perf_buffer to simplified

* Fix signed-off name

Wenbo Zhang (2):
  bpf: add new helper get_file_path for mapping a file descriptor to a
  selftests/bpf: test for bpf_get_file_path() from tracepoint

 include/uapi/linux/bpf.h                      |  29 ++-
 kernel/trace/bpf_trace.c                      |  70 +++++++
 tools/include/uapi/linux/bpf.h                |  29 ++-
 .../selftests/bpf/prog_tests/get_file_path.c  | 171 ++++++++++++++++++
 .../selftests/bpf/progs/test_get_file_path.c  |  43 +++++
 5 files changed, 340 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/get_file_path.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_get_file_path.c


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