From: Alexei Starovoitov <ast@kernel.org>
Date: Wed, 1 Dec 2021 10:10:33 -0800
Subject: libbpf: Support init of inner maps in light skeleton.
Patch-mainline: v5.17-rc1
Git-commit: be05c94476f3cf4fdc29feab4ed1053187323296
References: jsc#PED-1368

Add ability to initialize inner maps in light skeleton.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211201181040.23337-11-alexei.starovoitov@gmail.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 tools/lib/bpf/bpf_gen_internal.h |    1 +
 tools/lib/bpf/gen_loader.c       |   27 +++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.c           |    6 +++---
 3 files changed, 31 insertions(+), 3 deletions(-)

--- a/tools/lib/bpf/bpf_gen_internal.h
+++ b/tools/lib/bpf/bpf_gen_internal.h
@@ -67,5 +67,6 @@ void bpf_gen__record_attach_target(struc
 void bpf_gen__record_extern(struct bpf_gen *gen, const char *name, bool is_weak,
 			    bool is_typeless, int kind, int insn_idx);
 void bpf_gen__record_relo_core(struct bpf_gen *gen, const struct bpf_core_relo *core_relo);
+void bpf_gen__populate_outer_map(struct bpf_gen *gen, int outer_map_idx, int key, int inner_map_idx);
 
 #endif
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -1066,6 +1066,33 @@ void bpf_gen__map_update_elem(struct bpf
 	emit_check_err(gen);
 }
 
+void bpf_gen__populate_outer_map(struct bpf_gen *gen, int outer_map_idx, int slot,
+				 int inner_map_idx)
+{
+	int attr_size = offsetofend(union bpf_attr, flags);
+	int map_update_attr, key;
+	union bpf_attr attr;
+
+	memset(&attr, 0, attr_size);
+	pr_debug("gen: populate_outer_map: outer %d key %d inner %d\n",
+		 outer_map_idx, slot, inner_map_idx);
+
+	key = add_data(gen, &slot, sizeof(slot));
+
+	map_update_attr = add_data(gen, &attr, attr_size);
+	move_blob2blob(gen, attr_field(map_update_attr, map_fd), 4,
+		       blob_fd_array_off(gen, outer_map_idx));
+	emit_rel_store(gen, attr_field(map_update_attr, key), key);
+	emit_rel_store(gen, attr_field(map_update_attr, value),
+		       blob_fd_array_off(gen, inner_map_idx));
+
+	/* emit MAP_UPDATE_ELEM command */
+	emit_sys_bpf(gen, BPF_MAP_UPDATE_ELEM, map_update_attr, attr_size);
+	debug_ret(gen, "populate_outer_map outer %d key %d inner %d",
+		  outer_map_idx, slot, inner_map_idx);
+	emit_check_err(gen);
+}
+
 void bpf_gen__map_freeze(struct bpf_gen *gen, int map_idx)
 {
 	int attr_size = offsetofend(union bpf_attr, map_fd);
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4971,9 +4971,9 @@ static int init_map_in_map_slots(struct
 		fd = bpf_map__fd(targ_map);
 
 		if (obj->gen_loader) {
-			pr_warn("// TODO map_update_elem: idx %td key %d value==map_idx %td\n",
-				map - obj->maps, i, targ_map - obj->maps);
-			return -ENOTSUP;
+			bpf_gen__populate_outer_map(obj->gen_loader,
+						    map - obj->maps, i,
+						    targ_map - obj->maps);
 		} else {
 			err = bpf_map_update_elem(map->fd, &i, &fd, 0);
 		}