On 7/18/24 4:51 AM, Lin Yikai wrote:
v1:
- patch 2:
- [1/2] add bpf_file_d_path helper
- [2/2] add selftest to it
Hi, we are looking to add the "bpf_file_d_path" helper,
used to retrieve the path from a struct file object.
bpf_file_d_path(void *file, char *dst, u32 size);
It's worth noting that the "file" parameter is defined as "void*" type.
* Our problems *
Previously, we encountered issues
on some user-space operating systems(OS):
1.Difficulty using vmlinux.h
(1) The OS lacks support for bpftool.
We can not use:
"bpftool btf dump file /sys/kernel/btf/vmlinux format c > vmlinux.h".
Bpftool need a separate complex cross-compilation environment to build.
(2) Many duplicate definitions between OS and vmlinux.h.
(3) The vmlinux.h size is large (2.8MB on arm64/Android),
causing increased ebpf prog size and user space consumption.
The compiled bpf prog size is increased by 2.8MB because it included vmlinux.h?
2.The "struct file" has many internal variables and definitions,
and maybe change along with Linux version iterations,
making it hard to copy it to OS.
If vmlinux.h is not convenience in your use case, you can try to define "struct
file" with __attribute__((preserve_access_index)) and the libbpf will adjust the
bpf prog against the running kernel.
There was a discussion a year ago about bpf helpers freeze. No new helper can be
added since then. The same goes for this one.
pw-bot: cr
