On 2025/1/28 06:04, Alexei Starovoitov wrote:
On Sat, Jan 25, 2025 at 5:05 PM Levi Zim <rsworkt...@outlook.com> wrote:
On 2025/1/26 00:58, Alexei Starovoitov wrote:
> On Sat, Jan 25, 2025 at 12:30 AM Levi Zim via B4 Relay
> <devnull+rsworktech.outlook....@kernel.org> wrote:
>> From: Levi Zim <rsworkt...@outlook.com>
>>
>> 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.
Thanks for the advice! I will include it in v3.
Also why bpf_probe_read_kernel_common ?
Do we need to memset() it on failure?
Since the current patch is basically a thin wrapper around
bpf_probe_read_kernel,
I think we'd better not deviate from the wrapped function.
