[PATCH RFC bpf-next 4/7] libbpf: Support BPF_PROG_TYPE_STRUCT_OPS in bpf_gen__prog_load()

[Siddharth Nayyar <sidnayyar@google.com>]

For BPF_PROG_TYPE_STRUCT_OPS programs in light skeletons, load_attr's
expected_attach_type and attach_btf_id hold data blob offsets populated
at runtime by bpf_gen__init_kern_struct_ops().

Emit instructions in bpf_gen__prog_load() to copy the resolved member
index into prog_load_attr.expected_attach_type and unpack the 64-bit
(btf_obj_fd << 32) | kern_type_id value from load_attr->attach_btf_id
into prog_load_attr.attach_btf_id and prog_load_attr.attach_btf_obj_fd.

Signed-off-by: Siddharth Nayyar <sidnayyar@google.com>
---
 tools/lib/bpf/gen_loader.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c
index 6027a2762c35..aaa491463521 100644
--- a/tools/lib/bpf/gen_loader.c
+++ b/tools/lib/bpf/gen_loader.c
@@ -1151,6 +1151,20 @@ void bpf_gen__prog_load(struct bpf_gen *gen,
 		emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_0, BPF_REG_7,
 				      offsetof(union bpf_attr, attach_btf_obj_fd)));
 	}
+	if (prog_type == BPF_PROG_TYPE_STRUCT_OPS) {
+		move_blob2blob(gen, attr_field(prog_load_attr, expected_attach_type), 4,
+			       load_attr->expected_attach_type);
+		emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_1, BPF_PSEUDO_MAP_IDX_VALUE,
+						 0, 0, 0, load_attr->attach_btf_id));
+		emit(gen, BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_1, 0));
+		emit2(gen, BPF_LD_IMM64_RAW_FULL(BPF_REG_0, BPF_PSEUDO_MAP_IDX_VALUE,
+						 0, 0, 0, prog_load_attr));
+		emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_0, BPF_REG_7,
+				      offsetof(union bpf_attr, attach_btf_id)));
+		emit(gen, BPF_ALU64_IMM(BPF_RSH, BPF_REG_7, 32));
+		emit(gen, BPF_STX_MEM(BPF_W, BPF_REG_0, BPF_REG_7,
+				      offsetof(union bpf_attr, attach_btf_obj_fd)));
+	}
 	emit_relos(gen, insns_off);
 	/* emit PROG_LOAD command */
 	emit_sys_bpf(gen, BPF_PROG_LOAD, prog_load_attr, attr_size);

-- 
2.56.0.455.g6c5a503b38-goog