On Thu, Jun 12, 2025 at 4:56 PM Alexei Starovoitov <alexei.starovoi...@gmail.com> wrote: > > On Thu, Jun 12, 2025 at 4:27 PM Andrii Nakryiko > <andrii.nakry...@gmail.com> wrote: > > > > On Thu, Jun 12, 2025 at 2:40 PM Alexei Starovoitov > > <alexei.starovoi...@gmail.com> wrote: > > > > > > On Thu, Jun 12, 2025 at 2:29 PM Andrii Nakryiko > > > <andrii.nakry...@gmail.com> wrote: > > > > > > > > On Wed, Jun 11, 2025 at 8:49 AM Tao Chen <chen.dyl...@linux.dev> wrote: > > > > > > > > > > The bpf_d_path() function may fail. If it does, > > > > > clear the user buf, like bpf_probe_read etc. > > > > > > > > > > > > > But that doesn't mean we *have to* do memset(0) for bpf_d_path(), > > > > though. Especially given that path buffer can be pretty large (4KB). > > > > > > > > Is there an issue you are trying to address with this, or is it more > > > > of a consistency clean up? Note, that more or less recently we made > > > > this zero filling behavior an option with an extra flag > > > > (BPF_F_PAD_ZEROS) for newer APIs. And if anything, bpf_d_path() is > > > > more akin to variable-sized string probing APIs rather than > > > > fixed-sized bpf_probe_read* family. > > > > > > All old helpers had this BPF_F_PAD_ZEROS behavior > > > (or rather should have had). > > > So it makes sense to zero in this helper too for consistency. > > > I don't share performance concerns. This is an error path. > > > > It's just a bizarre behavior as it stands right now. > > > > On error, you'll have a zeroed out buffer, OK, good so far. > > > > On success, though, you'll have a buffer where first N bytes are > > filled out with good path information, but then the last sizeof(buf) - > > N bytes would be, effectively, garbage. > > > > All in all, you can't use that buffer as a key for hashmap looking > > (because of leftover non-zeroed bytes at the end), yet on error we > > still zero out bytes for no apparently useful reason. > > > > And then for the bpf_path_d_path(). What do we do about that one? It > > doesn't have zeroing out either in the error path, nor in the success > > path. So just more inconsistency all around. > > Consistency with bpf_path_d_path() kfunc is indeed missing. > > Ok, since you insist, dropped this patch, and force pushed.
Great, thank you!
