On Sat, Jan 25, 2025 at 5:05 PM Levi Zim <[email protected]> wrote: > > On 2025/1/26 00:58, Alexei Starovoitov wrote: > > On Sat, Jan 25, 2025 at 12:30 AM Levi Zim via B4 Relay > > <[email protected]> wrote: > >> From: Levi Zim <[email protected]> > >> > >> This patch add a helper function bpf_probe_read_kernel_dynptr: > >> > >> long bpf_probe_read_kernel_dynptr(const struct bpf_dynptr *dst, > >> u32 offset, u32 size, const void *unsafe_ptr, u64 flags); > > We stopped adding helpers years ago. > > Only new kfuncs are allowed. > > Sorry, I didn't know that. Just asking, is there any > documentation/discussion > about stopping adding helpers? > > I will switch the implementation to kfuncs in v3. > > > This particular one doesn't look useful as-is. > > The same logic can be expressed with > > - create dynptr > > - dynptr_slice > > - copy_from_kernel > > By copy_from_kernel I assume you mean bpf_probe_read_kernel. The problem > with dynptr_slice_rdwr and probe_read_kernel is that they only support a > compile-time constant size [1]. > > But in order to best utilize the space on a BPF ringbuf, it is possible > to reserve a > variable length of space as dynptr on a ringbuf with > bpf_ringbuf_reserve_dynptr.
That makes sense. The commit log didn't call it out. Please spell out the motivation clearly. Also why bpf_probe_read_kernel_common ? Do we need to memset() it on failure?
