Merge branch 'introduce dummy BPF STRUCT_OPS'

Hou Tao says:

====================

Hi,

Currently the test of BPF STRUCT_OPS depends on the specific bpf
implementation (e.g, tcp_congestion_ops), but it can not cover all
basic functionalities (e.g, return value handling), so introduce
a dummy BPF STRUCT_OPS for test purpose.

Instead of loading a userspace-implemeted bpf_dummy_ops map into
kernel and calling the specific function by writing to sysfs provided
by bpf_testmode.ko, only loading bpf_dummy_ops related prog into
kernel and calling these prog by bpf_prog_test_run(). The latter
is more flexible and has no dependency on extra kernel module.

Now the return value handling is supported by test_1(...) ops,
and passing multiple arguments is supported by test_2(...) ops.
If more is needed, test_x(...) ops can be added afterwards.

Comments are always welcome.
Regards,
Hou

Change Log:
v4:
 * add Acked-by tags in patch 1~4
 * patch 2: remove unncessary comments and update commit message
            accordingly
 * patch 4: remove unnecessary nr checking in dummy_ops_init_args()

v3: https://www.spinics.net/lists/bpf/msg48303.html
 * rebase on bpf-next
 * address comments for Martin, mainly include: merge patch 3 &
   patch 4 in v2, fix names of btf ctx access check helpers,
   handle CONFIG_NET, fix leak in dummy_ops_init_args(), and
   simplify bpf_dummy_init()
 * patch 4: use a loop to check args in test_dummy_multiple_args()

v2: https://www.spinics.net/lists/bpf/msg47948.html
 * rebase on bpf-next
 * add test_2(...) ops to test the passing of multiple arguments
 * a new patch (patch #2) is added to factor out ctx access helpers
 * address comments from Martin & Andrii

v1: https://www.spinics.net/lists/bpf/msg46787.html

RFC: https://www.spinics.net/lists/bpf/msg46117.html
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6deebf8bf78f..c098089c1b54 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1000,6 +1000,10 @@ bool bpf_struct_ops_get(const void *kdata);
 void bpf_struct_ops_put(const void *kdata);
 int bpf_struct_ops_map_sys_lookup_elem(struct bpf_map *map, void *key,
 				       void *value);
+int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_progs *tprogs,
+				      struct bpf_prog *prog,
+				      const struct btf_func_model *model,
+				      void *image, void *image_end);
 static inline bool bpf_try_module_get(const void *data, struct module *owner)
 {
 	if (owner == BPF_MODULE_OWNER)
@@ -1014,6 +1018,22 @@ static inline void bpf_module_put(const void *data, struct module *owner)
 	else
 		module_put(owner);
 }
+
+#ifdef CONFIG_NET
+/* Define it here to avoid the use of forward declaration */
+struct bpf_dummy_ops_state {
+	int val;
+};
+
+struct bpf_dummy_ops {
+	int (*test_1)(struct bpf_dummy_ops_state *cb);
+	int (*test_2)(struct bpf_dummy_ops_state *cb, int a1, unsigned short a2,
+		      char a3, unsigned long a4);
+};
+
+int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
+			    union bpf_attr __user *uattr);
+#endif
 #else
 static inline const struct bpf_struct_ops *bpf_struct_ops_find(u32 type_id)
 {
@@ -1646,6 +1666,29 @@ bool bpf_prog_test_check_kfunc_call(u32 kfunc_id, struct module *owner);
 bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 		    const struct bpf_prog *prog,
 		    struct bpf_insn_access_aux *info);
+
+static inline bool bpf_tracing_ctx_access(int off, int size,
+					  enum bpf_access_type type)
+{
+	if (off < 0 || off >= sizeof(__u64) * MAX_BPF_FUNC_ARGS)
+		return false;
+	if (type != BPF_READ)
+		return false;
+	if (off % size != 0)
+		return false;
+	return true;
+}
+
+static inline bool bpf_tracing_btf_ctx_access(int off, int size,
+					      enum bpf_access_type type,
+					      const struct bpf_prog *prog,
+					      struct bpf_insn_access_aux *info)
+{
+	if (!bpf_tracing_ctx_access(off, size, type))
+		return false;
+	return btf_ctx_access(off, size, type, prog, info);
+}
+
 int btf_struct_access(struct bpf_verifier_log *log, const struct btf *btf,
 		      const struct btf_type *t, int off, int size,
 		      enum bpf_access_type atype,