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[bpf-next,v14,0/2] bpf: adding get_fd_path helper

Message ID cover.1576629200.git.ethercflow@gmail.com
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Series bpf: adding get_fd_path helper | expand


Wenbo Zhang Dec. 18, 2019, 12:56 a.m. UTC
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 v13:

* Fix this helper's description to be consistent with comments in d_path

* Fix error handling logic fill zeroes not '0's

Changes since v12:

* Rename to get_fd_patch

* Fix test issue on big-endian machines

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_fd_path for mapping a file descriptor to a
  selftests/bpf: test for bpf_get_fd_path() from tracepoint

 include/uapi/linux/bpf.h                      |  29 ++-
 kernel/trace/bpf_trace.c                      |  69 +++++++
 tools/include/uapi/linux/bpf.h                |  29 ++-
 .../selftests/bpf/prog_tests/get_fd_path.c    | 171 ++++++++++++++++++
 .../selftests/bpf/progs/test_get_fd_path.c    |  43 +++++
 5 files changed, 339 insertions(+), 2 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/get_fd_path.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_get_fd_path.c