Jiri Olsa wrote:
> hi,
> adding d_path helper to return full path for 'path' object.
>
> I originally added and used 'file_path' helper, which did the same,
> but used 'struct file' object. Then realized that file_path is just
> a wrapper for d_path, so we'd cover more calling sites if we add
> d_path helper and allowed resolving BTF object within another object,
> so we could call d_path also with file pointer, like:
>
> bpf_d_path(&file->f_path, buf, size);
>
> This feature is mainly to be able to add dpath (filepath originally)
> function to bpftrace:
>
> # bpftrace -e 'kfunc:vfs_open { printf("%s\n", dpath(args->path)); }'
>
> v3 changes:
> - changed tests to use seleton and vmlinux.h [Andrii]
> - refactored to define ID lists in C object [Andrii]
> - changed btf_struct_access for nested ID check,
> instead of adding new function for that [Andrii]
> - fail build with CONFIG_DEBUG_INFO_BTF if libelf is not detected [Andrii]
>
> Also available at:
> https://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
> bpf/d_path
>
> thanks,
> jirka
Hi Jira, Apologize for waiting until v3 to look at this series, but a
couple general requests as I review this.
In the cover letter can we get some more details. The above is really
terse/cryptic in my opinion. The bpftrace example gives good motiviation,
but nothing above mentions a new .BTF_ids section and the flow to create
and use this section.
Also if we add a BTF_ids section adding documentation in btf.rst should
happen as well. I would like to see something in the ELF File Format
Interface section and BTF Generation sections.
I'm not going to nitpick if its in this series or a stand-alone patch
but do want to see it. So far the Documentation on BTF is fairly
good and I want to avoid these kind of gaps.
Thanks!
John
