On 11/17/21 5:04 PM, Joanne Koong wrote:
This patch adds the kernel-side and API changes for a new helper
function, bpf_for_each:
long bpf_for_each(u32 nr_interations, void *callback_fn,
void *callback_ctx, u64 flags);
bpf_for_each invokes the "callback_fn" nr_iterations number of times
or until the callback_fn returns 1.
A few things to please note:
~ The "u64 flags" parameter is currently unused but is included in
case a future use case for it arises.
~ In the kernel-side implementation of bpf_for_each (kernel/bpf/bpf_iter.c),
bpf_callback_t is used as the callback function cast.
~ A program can have nested bpf_for_each calls but the program must
still adhere to the verifier constraint of its stack depth (the stack depth
cannot exceed MAX_BPF_STACK))
~ The next patch will include the tests and benchmark
Signed-off-by: Joanne Koong <joannekoong@xxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 23 +++++++++++++++++++++++
kernel/bpf/bpf_iter.c | 32 ++++++++++++++++++++++++++++++++
kernel/bpf/helpers.c | 2 ++
kernel/bpf/verifier.c | 28 ++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 23 +++++++++++++++++++++++
6 files changed, 109 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6deebf8bf78f..d9b69a896c91 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2107,6 +2107,7 @@ extern const struct bpf_func_proto bpf_get_socket_ptr_cookie_proto;
extern const struct bpf_func_proto bpf_task_storage_get_proto;
extern const struct bpf_func_proto bpf_task_storage_delete_proto;
extern const struct bpf_func_proto bpf_for_each_map_elem_proto;
+extern const struct bpf_func_proto bpf_for_each_proto;
extern const struct bpf_func_proto bpf_btf_find_by_name_kind_proto;
extern const struct bpf_func_proto bpf_sk_setsockopt_proto;
extern const struct bpf_func_proto bpf_sk_getsockopt_proto;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index bd0c9f0487f6..ea5098920ed2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4750,6 +4750,28 @@ union bpf_attr {
* The number of traversed map elements for success, **-EINVAL** for
* invalid **flags**.
*
+ * long bpf_for_each(u32 nr_iterations, void *callback_fn, void *callback_ctx, u64 flags)
+ * Description
+ * For **nr_iterations**, call **callback_fn** function with
+ * **callback_ctx** as the context parameter.
+ * The **callback_fn** should be a static function and
+ * the **callback_ctx** should be a pointer to the stack.
+ * The **flags** is used to control certain aspects of the helper.
+ * Currently, the **flags** must be 0.
+ *
+ * long (\*callback_fn)(u32 index, void \*ctx);
+ *
+ * where **index** is the current index in the iteration. The index
+ * is zero-indexed.
+ *
+ * If **callback_fn** returns 0, the helper will continue to the next
+ * iteration. If return value is 1, the helper will skip the rest of
+ * the iterations and return. Other return values are not used now.
+ *
+ * Return
+ * The number of iterations performed, **-EINVAL** for invalid **flags**
+ * or a null **callback_fn**.
I think verifier enforced non-null callback_fn, right?
+ *
* long bpf_snprintf(char *str, u32 str_size, const char *fmt, u64 *data, u32 data_len)
* Description
* Outputs a string into the **str** buffer of size **str_size**
@@ -5105,6 +5127,7 @@ union bpf_attr {
FN(sock_from_file), \
FN(check_mtu), \
FN(for_each_map_elem), \
+ FN(for_each), \
Please put for_each helper at the end of list. Otherwise, it will break
uapi.
FN(snprintf), \
FN(sys_bpf), \
FN(btf_find_by_name_kind), \
diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index b2ee45064e06..cb742c50898a 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -714,3 +714,35 @@ const struct bpf_func_proto bpf_for_each_map_elem_proto = {
.arg3_type = ARG_PTR_TO_STACK_OR_NULL,
.arg4_type = ARG_ANYTHING,
};
+
[...]
