From: Mykyta Yatsenko <yatsenko@xxxxxxxx>
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 <yatsenko@xxxxxxxx>
---
kernel/bpf/helpers.c | 37 +++++++++++++++++++++++++++++++++++++
kernel/bpf/verifier.c | 3 +++
2 files changed, 40 insertions(+)
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;
}
+__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;
+ __u8 *src_slice, *dst_slice;
+ int err = 0;
+
+ 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);
+ } else if (src_slice) {
+ err = __bpf_dynptr_write(dst, dst_off, src_slice, size, 0);
+ } else if (dst_slice) {
+ err = __bpf_dynptr_read(dst_slice, size, src, src_off, 0);
+ } else {
+ u32 off = 0;
+ char buf[256];
+
+ if (bpf_dynptr_check_off_len(dst, dst_off, size) ||
+ bpf_dynptr_check_off_len(src, src_off, size))
+ return -E2BIG;
+
+ while (err == 0 && off < size) {
+ u32 chunk_sz = min(sizeof(buf), size - off);
+
+ err = err ?: __bpf_dynptr_read(buf, chunk_sz, src, src_off + off, 0);
+ err = err ?: __bpf_dynptr_write(dst, dst_off + off, buf, chunk_sz, 0);
+ off += chunk_sz;
+ }
+ }
+ return err;
+}
+
__bpf_kfunc void *bpf_cast_to_kern_ctx(void *obj)
{
return obj;
@@ -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
--- 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)
--
2.48.1
