libbpf: Preliminary support for fd_idx

mainline inclusion
from mainline-5.14-rc1
commit e2fa0156
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5EUVD
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e2fa0156a434c140998aa16ecad329e4bc19f263

-------------------------------------------------

Prep libbpf to use FD_IDX kernel feature when generating loader program.
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-14-alexei.starovoitov@gmail.com
(cherry picked from commit e2fa0156)
Signed-off-by: NWang Yufen <wangyufen@huawei.com>

tools/lib/bpf/libbpf.c

@@ -412,6 +412,8 @@ struct module_btf {
 	int fd;
 };
 
+struct bpf_gen;
+
 struct bpf_object {
 	char name[BPF_OBJ_NAME_LEN];
 	char license[64];
@@ -432,6 +434,8 @@ struct bpf_object {
 	bool loaded;
 	bool has_subcalls;
 
+	struct bpf_gen *gen_loader;
+
 	/*
 	 * Information when doing elf related work. Only valid if fd
 	 * is valid.
@@ -6445,19 +6449,34 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog)
 
 		switch (relo->type) {
 		case RELO_LD64:
-			insn[0].src_reg = BPF_PSEUDO_MAP_FD;
-			insn[0].imm = obj->maps[relo->map_idx].fd;
+			if (obj->gen_loader) {
+				insn[0].src_reg = BPF_PSEUDO_MAP_IDX;
+				insn[0].imm = relo->map_idx;
+			} else {
+				insn[0].src_reg = BPF_PSEUDO_MAP_FD;
+				insn[0].imm = obj->maps[relo->map_idx].fd;
+			}
 			break;
 		case RELO_DATA:
-			insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
 			insn[1].imm = insn[0].imm + relo->sym_off;
-			insn[0].imm = obj->maps[relo->map_idx].fd;
+			if (obj->gen_loader) {
+				insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
+				insn[0].imm = relo->map_idx;
+			} else {
+				insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
+				insn[0].imm = obj->maps[relo->map_idx].fd;
+			}
 			break;
 		case RELO_EXTERN_VAR:
 			ext = &obj->externs[relo->sym_off];
 			if (ext->type == EXT_KCFG) {
-				insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
-				insn[0].imm = obj->maps[obj->kconfig_map_idx].fd;
+				if (obj->gen_loader) {
+					insn[0].src_reg = BPF_PSEUDO_MAP_IDX_VALUE;
+					insn[0].imm = obj->kconfig_map_idx;
+				} else {
+					insn[0].src_reg = BPF_PSEUDO_MAP_VALUE;
+					insn[0].imm = obj->maps[obj->kconfig_map_idx].fd;
+				}
 				insn[1].imm = ext->kcfg.data_off;
 			} else /* EXT_KSYM */ {
 				if (ext->ksym.type_id) { /* typed ksyms */