This patch adds two helper functions, bpf_dynptr_read and
bpf_dynptr_write:
long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset);
long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len);
The dynptr passed into these functions must be valid dynptrs that have
been initialized.
Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/uapi/linux/bpf.h | 19 +++++++++
kernel/bpf/helpers.c | 78 ++++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 19 +++++++++
3 files changed, 116 insertions(+)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 081a55540aa5..efe2505650e6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5221,6 +5221,23 @@ union bpf_attr {
* 'bpf_ringbuf_discard'.
* Return
* Nothing. Always succeeds.
+ *
+ * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset)
+ * Description
+ * Read *len* bytes from *src* into *dst*, starting from *offset*
+ * into *src*.
+ * Return
+ * 0 on success, -E2BIG if *offset* + *len* exceeds the length
+ * of *src*'s data, -EINVAL if *src* is an invalid dynptr.
+ *
+ * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len)
+ * Description
+ * Write *len* bytes from *src* into *dst*, starting from *offset*
+ * into *dst*.
+ * Return
+ * 0 on success, -E2BIG if *offset* + *len* exceeds the length
+ * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*
+ * is a read-only dynptr.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5424,6 +5441,8 @@ union bpf_attr {
FN(ringbuf_reserve_dynptr), \
FN(ringbuf_submit_dynptr), \
FN(ringbuf_discard_dynptr), \
+ FN(dynptr_read), \
+ FN(dynptr_write), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index abb08999ff56..8cef3fb0d143 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1417,12 +1417,24 @@ const struct bpf_func_proto bpf_kptr_xchg_proto = {
*/
#define DYNPTR_MAX_SIZE ((1UL << 24) - 1)
#define DYNPTR_TYPE_SHIFT 28
+#define DYNPTR_SIZE_MASK 0xFFFFFF
+#define DYNPTR_RDONLY_BIT BIT(31)
+
+static bool bpf_dynptr_is_rdonly(struct bpf_dynptr_kern *ptr)
+{
+ return ptr->size & DYNPTR_RDONLY_BIT;
+}
static void bpf_dynptr_set_type(struct bpf_dynptr_kern *ptr, enum bpf_dynptr_type type)
{
ptr->size |= type << DYNPTR_TYPE_SHIFT;
}
+static u32 bpf_dynptr_get_size(struct bpf_dynptr_kern *ptr)
+{
+ return ptr->size & DYNPTR_SIZE_MASK;
+}
+
int bpf_dynptr_check_size(u32 size)
{
return size > DYNPTR_MAX_SIZE ? -E2BIG : 0;
@@ -1442,6 +1454,16 @@ void bpf_dynptr_set_null(struct bpf_dynptr_kern *ptr)
memset(ptr, 0, sizeof(*ptr));
}
+static int bpf_dynptr_check_off_len(struct bpf_dynptr_kern *ptr, u32 offset, u32 len)
+{
+ u32 size = bpf_dynptr_get_size(ptr);
+
+ if (len > size || offset > size - len)
+ return -E2BIG;
+
+ return 0;
+}
+
BPF_CALL_4(bpf_dynptr_from_mem, void *, data, u32, size, u64, flags, struct bpf_dynptr_kern *, ptr)
{
int err;
@@ -1475,6 +1497,58 @@ const struct bpf_func_proto bpf_dynptr_from_mem_proto = {
.arg4_type = ARG_PTR_TO_DYNPTR | DYNPTR_TYPE_LOCAL | MEM_UNINIT,
};
+BPF_CALL_4(bpf_dynptr_read, void *, dst, u32, len, struct bpf_dynptr_kern *, src, u32, offset)
+{
+ int err;
+
+ if (!src->data)
+ return -EINVAL;
+
+ err = bpf_dynptr_check_off_len(src, offset, len);
+ if (err)
+ return err;
+
+ memcpy(dst, src->data + src->offset + offset, len);
+
+ return 0;
+}
+
+const struct bpf_func_proto bpf_dynptr_read_proto = {
+ .func = bpf_dynptr_read,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg2_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg3_type = ARG_PTR_TO_DYNPTR,
+ .arg4_type = ARG_ANYTHING,
+};
+
+BPF_CALL_4(bpf_dynptr_write, struct bpf_dynptr_kern *, dst, u32, offset, void *, src, u32, len)
+{
+ int err;
+
+ if (!dst->data || bpf_dynptr_is_rdonly(dst))
+ return -EINVAL;
+
+ err = bpf_dynptr_check_off_len(dst, offset, len);
+ if (err)
+ return err;
+
+ memcpy(dst->data + dst->offset + offset, src, len);
+
+ return 0;
+}
+
+const struct bpf_func_proto bpf_dynptr_write_proto = {
+ .func = bpf_dynptr_write,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_DYNPTR,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_PTR_TO_MEM | MEM_RDONLY,
+ .arg4_type = ARG_CONST_SIZE_OR_ZERO,
+};
+
const struct bpf_func_proto bpf_get_current_task_proto __weak;
const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_proto __weak;
@@ -1537,6 +1611,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_strncmp_proto;
case BPF_FUNC_dynptr_from_mem:
return &bpf_dynptr_from_mem_proto;
+ case BPF_FUNC_dynptr_read:
+ return &bpf_dynptr_read_proto;
+ case BPF_FUNC_dynptr_write:
+ return &bpf_dynptr_write_proto;
default:
break;
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 081a55540aa5..efe2505650e6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5221,6 +5221,23 @@ union bpf_attr {
* 'bpf_ringbuf_discard'.
* Return
* Nothing. Always succeeds.
+ *
+ * long bpf_dynptr_read(void *dst, u32 len, struct bpf_dynptr *src, u32 offset)
+ * Description
+ * Read *len* bytes from *src* into *dst*, starting from *offset*
+ * into *src*.
+ * Return
+ * 0 on success, -E2BIG if *offset* + *len* exceeds the length
+ * of *src*'s data, -EINVAL if *src* is an invalid dynptr.
+ *
+ * long bpf_dynptr_write(struct bpf_dynptr *dst, u32 offset, void *src, u32 len)
+ * Description
+ * Write *len* bytes from *src* into *dst*, starting from *offset*
+ * into *dst*.
+ * Return
+ * 0 on success, -E2BIG if *offset* + *len* exceeds the length
+ * of *dst*'s data, -EINVAL if *dst* is an invalid dynptr or if *dst*
+ * is a read-only dynptr.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -5424,6 +5441,8 @@ union bpf_attr {
FN(ringbuf_reserve_dynptr), \
FN(ringbuf_submit_dynptr), \
FN(ringbuf_discard_dynptr), \
+ FN(dynptr_read), \
+ FN(dynptr_write), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.30.2
