Merge branch 'bpf_iter-BTF_ID-at-build-time'

Yonghong Song says:

====================
Commit 5a2798ab32ba
("bpf: Add BTF_ID_LIST/BTF_ID/BTF_ID_UNUSED macros")
implemented a mechanism to compute btf_ids at kernel build
time which can simplify kernel implementation and reduce
runtime overhead by removing in-kernel btf_id calculation.

This patch set tried to use this mechanism to compute
btf_ids for bpf_skc_to_*() helpers and for btf_id_or_null ctx
arguments specified during bpf iterator registration.
Please see individual patch for details.

Changelogs:
  v1 -> v2:
    - v1 ([1]) is only for bpf_skc_to_*() helpers. This version
      expanded it to cover ctx btf_id_or_null arguments
    - abandoned the change of "extern u32 name[]" to
      "static u32 name[]" for BPF_ID_LIST local "name" definition.
      gcc 9 incurred a compilation error.

 [1]: https://lore.kernel.org/bpf/20200717184706.3476992-1-yhs@fb.com/T
====================

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

3 files changed, 19 insertions, 6 deletions

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 03d6d43bb1d6..ee36b7f60936 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -3672,7 +3672,6 @@ struct btf *btf_parse_vmlinux(void)
 		goto errout;
 
 	bpf_struct_ops_init(btf, log);
-	init_btf_sock_ids(btf);
 
 	btf_verifier_env_free(env);
 	refcount_set(&btf->refcnt, 1);
@@ -3818,16 +3817,17 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type,
 		return true;
 
 	/* this is a pointer to another type */
-	info->reg_type = PTR_TO_BTF_ID;
 	for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {
 		const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];
 
 		if (ctx_arg_info->offset == off) {
 			info->reg_type = ctx_arg_info->reg_type;
-			break;
+			info->btf_id = ctx_arg_info->btf_id;
+			return true;
 		}
 	}
 
+	info->reg_type = PTR_TO_BTF_ID;
 	if (tgt_prog) {
 		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);
 		if (ret > 0) {
diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index c69071e334bf..8a7af11b411f 100644
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -4,6 +4,7 @@
 #include <linux/fs.h>
 #include <linux/filter.h>
 #include <linux/kernel.h>
+#include <linux/btf_ids.h>
 
 struct bpf_iter_seq_map_info {
 	u32 mid;
@@ -81,7 +82,10 @@ static const struct seq_operations bpf_map_seq_ops = {
 	.show	= bpf_map_seq_show,
 };
 
-static const struct bpf_iter_reg bpf_map_reg_info = {
+BTF_ID_LIST(btf_bpf_map_id)
+BTF_ID(struct, bpf_map)
+
+static struct bpf_iter_reg bpf_map_reg_info = {
 	.target			= "bpf_map",
 	.seq_ops		= &bpf_map_seq_ops,
 	.init_seq_private	= NULL,
@@ -96,6 +100,7 @@ static const struct bpf_iter_reg bpf_map_reg_info = {
 
 static int __init bpf_map_iter_init(void)
 {
+	bpf_map_reg_info.ctx_arg_info[0].btf_id = *btf_bpf_map_id;
 	return bpf_iter_reg_target(&bpf_map_reg_info);
 }
 
diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
index 4dbf2b6035f8..2feecf095609 100644
--- a/kernel/bpf/task_iter.c
+++ b/kernel/bpf/task_iter.c
@@ -7,6 +7,7 @@
 #include <linux/fs.h>
 #include <linux/fdtable.h>
 #include <linux/filter.h>
+#include <linux/btf_ids.h>
 
 struct bpf_iter_seq_task_common {
 	struct pid_namespace *ns;
@@ -312,7 +313,11 @@ static const struct seq_operations task_file_seq_ops = {
 	.show	= task_file_seq_show,
 };
 
-static const struct bpf_iter_reg task_reg_info = {
+BTF_ID_LIST(btf_task_file_ids)
+BTF_ID(struct, task_struct)
+BTF_ID(struct, file)
+
+static struct bpf_iter_reg task_reg_info = {
 	.target			= "task",
 	.seq_ops		= &task_seq_ops,
 	.init_seq_private	= init_seq_pidns,
@@ -325,7 +330,7 @@ static const struct bpf_iter_reg task_reg_info = {
 	},
 };
 
-static const struct bpf_iter_reg task_file_reg_info = {
+static struct bpf_iter_reg task_file_reg_info = {
 	.target			= "task_file",
 	.seq_ops		= &task_file_seq_ops,
 	.init_seq_private	= init_seq_pidns,
@@ -344,10 +349,13 @@ static int __init task_iter_init(void)
 {
 	int ret;
 
+	task_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
 	ret = bpf_iter_reg_target(&task_reg_info);
 	if (ret)
 		return ret;
 
+	task_file_reg_info.ctx_arg_info[0].btf_id = btf_task_file_ids[0];
+	task_file_reg_info.ctx_arg_info[1].btf_id = btf_task_file_ids[1];
 	return bpf_iter_reg_target(&task_file_reg_info);
 }
 late_initcall(task_iter_init);