objtool: Support retpoline jump detection for vmlinux.o

Objtool converts direct retpoline jumps to type INSN_JUMP_DYNAMIC, since
that's what they are semantically.

That conversion doesn't work in vmlinux.o validation because the
indirect thunk function is present in the object, so the intra-object
jump check succeeds before the retpoline jump check gets a chance.

Rearrange the checks: check for a retpoline jump before checking for an
intra-object jump.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/4302893513770dde68ddc22a9d6a2a04aca491dd.1611263461.git.jpoimboe@redhat.com

tools/objtool/check.c

@@ -781,10 +781,6 @@ static int add_jump_destinations(struct objtool_file *file)
 		} else if (reloc->sym->type == STT_SECTION) {
 			dest_sec = reloc->sym->sec;
 			dest_off = arch_dest_reloc_offset(reloc->addend);
-		} else if (reloc->sym->sec->idx) {
-			dest_sec = reloc->sym->sec;
-			dest_off = reloc->sym->sym.st_value +
-				   arch_dest_reloc_offset(reloc->addend);
 		} else if (!strncmp(reloc->sym->name, "__x86_indirect_thunk_", 21) ||
 			   !strncmp(reloc->sym->name, "__x86_retpoline_", 16)) {
 			/*
@@ -798,6 +794,10 @@ static int add_jump_destinations(struct objtool_file *file)
 
 			insn->retpoline_safe = true;
 			continue;
+		} else if (reloc->sym->sec->idx) {
+			dest_sec = reloc->sym->sec;
+			dest_off = reloc->sym->sym.st_value +
+				   arch_dest_reloc_offset(reloc->addend);
 		} else {
 			/* external sibling call */
 			insn->call_dest = reloc->sym;