samples/bpf: order of prog_fd[] must correspond with ELF order

It is highly problematic that the order of array prog_fd[] depend on
whether or not a bpf program section if referencing any maps or not.

I was implementing an XDP prog using tail calls, and it cause strange
issues that I could not count on the prog_fd[] order of the program,
when I was adjusting the programs...
This caused several days of wasted debugging! :-(

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Author: netoptimizer

kernel/samples/bpf/bpf_load.c

@@ -366,14 +366,16 @@ int load_bpf_relocate_maps_and_attach(int fd)
 		}
 	}
 
-	/* load programs that need map fixup (relocations) */
+	/* process all relo sections, and rewrite bpf insns for maps */
 	for (i = 1; i < ehdr.e_shnum; i++) {
 
 		if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 			continue;
+
 		if (shdr.sh_type == SHT_REL) {
 			struct bpf_insn *insns;
 
+			/* locate prog sec that need map fixup (relocations) */
 			if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
 				    &shdr_prog, &data_prog))
 				continue;
@@ -383,25 +385,14 @@ int load_bpf_relocate_maps_and_attach(int fd)
 				continue;
 
 			insns = (struct bpf_insn *) data_prog->d_buf;
-
-			processed_sec[shdr.sh_info] = true;
-			processed_sec[i] = true;
+			processed_sec[i] = true; /* relo section */
 
 			if (parse_relo_and_apply(data, symbols, &shdr, insns))
 				continue;
-
-			if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
-			    memcmp(shname_prog, "kretprobe/", 10) == 0 ||
-			    memcmp(shname_prog, "tracepoint/", 11) == 0 ||
-			    memcmp(shname_prog, "xdp", 3) == 0 ||
-			    memcmp(shname_prog, "perf_event", 10) == 0 ||
-			    memcmp(shname_prog, "socket", 6) == 0 ||
-			    memcmp(shname_prog, "cgroup/", 7) == 0)
-				load_and_attach(shname_prog, insns, data_prog->d_size);
 		}
 	}
 
-	/* load programs that don't use maps */
+	/* load programs */
 	for (i = 1; i < ehdr.e_shnum; i++) {
 
 		if (processed_sec[i])