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Tue, 18 Feb 2025 17:01:37 -0800 (PST) Message-ID: <26e5634a565e9b1e31813e12df9db670b590e93b.camel@gmail.com> Subject: Re: [PATCH bpf-next 2/3] bpf/helpers: introduce bpf_dynptr_copy kfunc From: Eduard Zingerman To: Mykyta Yatsenko , bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com Cc: Mykyta Yatsenko Date: Tue, 18 Feb 2025 17:01:32 -0800 In-Reply-To: <20250218190027.135888-3-mykyta.yatsenko5@gmail.com> References: <20250218190027.135888-1-mykyta.yatsenko5@gmail.com> <20250218190027.135888-3-mykyta.yatsenko5@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.3 (3.54.3-1.fc41) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-02-18 at 19:00 +0000, Mykyta Yatsenko wrote: > From: Mykyta Yatsenko >=20 > Introducing bpf_dynptr_copy kfunc allowing copying data from one dynptr t= o > another. This functionality is useful in scenarios such as capturing XDP > data to a ring buffer. > The implementation consists of 4 branches: > * A fast branch for contiguous buffer capacity in both source and > destination dynptrs > * 3 branches utilizing __bpf_dynptr_read and __bpf_dynptr_write to copy > data to/from non-contiguous buffer >=20 > Signed-off-by: Mykyta Yatsenko > --- Acked-by: Eduard Zingerman > kernel/bpf/helpers.c | 37 +++++++++++++++++++++++++++++++++++++ > kernel/bpf/verifier.c | 3 +++ > 2 files changed, 40 insertions(+) >=20 > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 2833558c3009..ac5fbdfc504d 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2770,6 +2770,42 @@ __bpf_kfunc int bpf_dynptr_clone(const struct bpf_= dynptr *p, > return 0; > } Nit: it would be nice to have a docstring here, as for other dynptr functio= ns. > +__bpf_kfunc int bpf_dynptr_copy(struct bpf_dynptr *dst_ptr, u32 dst_off, > + struct bpf_dynptr *src_ptr, u32 src_off, u32 size) [...] > @@ -3174,6 +3210,7 @@ BTF_ID_FLAGS(func, bpf_dynptr_is_null) > BTF_ID_FLAGS(func, bpf_dynptr_is_rdonly) > BTF_ID_FLAGS(func, bpf_dynptr_size) > BTF_ID_FLAGS(func, bpf_dynptr_clone) > +BTF_ID_FLAGS(func, bpf_dynptr_copy) > #ifdef CONFIG_NET > BTF_ID_FLAGS(func, bpf_modify_return_test_tp) > #endif > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index e7bc74171c99..3c567bfcc582 100644 Nit: There is no need to add bpf_dynptr_copy to special kfuncs list. This list is maintained to get BTF ids of several kfuncs w/o lookup, like so: 'special_kfunc_list[KF_bpf_dynptr_slice]'. Which is useful when writing custom semantic rules for such functions. There are no special rules for bpf_dynptr_copy, hence entry in the special_kfunc_list is not needed. > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -11781,6 +11781,7 @@ enum special_kfunc_type { > KF_bpf_dynptr_slice, > KF_bpf_dynptr_slice_rdwr, > KF_bpf_dynptr_clone, > + KF_bpf_dynptr_copy, > KF_bpf_percpu_obj_new_impl, > KF_bpf_percpu_obj_drop_impl, > KF_bpf_throw, > @@ -11819,6 +11820,7 @@ BTF_ID(func, bpf_dynptr_from_xdp) > BTF_ID(func, bpf_dynptr_slice) > BTF_ID(func, bpf_dynptr_slice_rdwr) > BTF_ID(func, bpf_dynptr_clone) > +BTF_ID(func, bpf_dynptr_copy) > BTF_ID(func, bpf_percpu_obj_new_impl) > BTF_ID(func, bpf_percpu_obj_drop_impl) > BTF_ID(func, bpf_throw) > @@ -11857,6 +11859,7 @@ BTF_ID_UNUSED > BTF_ID(func, bpf_dynptr_slice) > BTF_ID(func, bpf_dynptr_slice_rdwr) > BTF_ID(func, bpf_dynptr_clone) > +BTF_ID(func, bpf_dynptr_copy) > BTF_ID(func, bpf_percpu_obj_new_impl) > BTF_ID(func, bpf_percpu_obj_drop_impl) > BTF_ID(func, bpf_throw)