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: https://github.com/iovisor/bcc/issues/237 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 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 code * Fix signed-off name Wenbo Zhang (2): bpf: add new helper get_fd_path for mapping a file descriptor to a pathname 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 -- 2.17.1
