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[86.26.115.213]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-390cd866afesm6520531f8f.18.2025.02.26.10.32.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2025 10:32:13 -0800 (PST) From: Mykyta Yatsenko To: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com Cc: Mykyta Yatsenko Subject: [PATCH bpf-next v3 2/3] bpf/helpers: introduce bpf_dynptr_copy kfunc Date: Wed, 26 Feb 2025 18:32:00 +0000 Message-ID: <20250226183201.332713-3-mykyta.yatsenko5@gmail.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250226183201.332713-1-mykyta.yatsenko5@gmail.com> References: <20250226183201.332713-1-mykyta.yatsenko5@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Mykyta Yatsenko Introducing bpf_dynptr_copy kfunc allowing copying data from one dynptr to 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 Signed-off-by: Mykyta Yatsenko --- kernel/bpf/helpers.c | 55 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 6600aa4492ec..264afa0effb0 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2770,6 +2770,60 @@ __bpf_kfunc int bpf_dynptr_clone(const struct bpf_dynptr *p, return 0; } +/** + * bpf_dynptr_copy() - Copy data from one dynptr to another. + * @dst_ptr: Destination dynptr - where data should be copied to + * @dst_off: Offset into the destination dynptr + * @src_ptr: Source dynptr - where data should be copied from + * @src_off: Offset into the source dynptr + * @size: Length of the data to copy from source to destination + * + * Copies data from source dynptr to destination dynptr + */ +__bpf_kfunc int bpf_dynptr_copy(struct bpf_dynptr *dst_ptr, u32 dst_off, + struct bpf_dynptr *src_ptr, u32 src_off, u32 size) +{ + struct bpf_dynptr_kern *dst = (struct bpf_dynptr_kern *)dst_ptr; + struct bpf_dynptr_kern *src = (struct bpf_dynptr_kern *)src_ptr; + void *src_slice, *dst_slice; + char buf[256]; + u32 off; + + src_slice = bpf_dynptr_slice(src_ptr, src_off, NULL, size); + dst_slice = bpf_dynptr_slice_rdwr(dst_ptr, dst_off, NULL, size); + + if (src_slice && dst_slice) { + memmove(dst_slice, src_slice, size); + return 0; + } + + if (src_slice) + return __bpf_dynptr_write(dst, dst_off, src_slice, size, 0); + + if (dst_slice) + return __bpf_dynptr_read(dst_slice, size, src, src_off, 0); + + if (bpf_dynptr_check_off_len(dst, dst_off, size) || + bpf_dynptr_check_off_len(src, src_off, size)) + return -E2BIG; + + off = 0; + while (off < size) { + u32 chunk_sz = min_t(u32, sizeof(buf), size - off); + int err = 0; + + err = __bpf_dynptr_read(buf, chunk_sz, src, src_off + off, 0); + if (err) + return err; + err = __bpf_dynptr_write(dst, dst_off + off, buf, chunk_sz, 0); + if (err) + return err; + + off += chunk_sz; + } + return 0; +} + __bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj) { return obj; @@ -3218,6 +3272,7 @@ 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