objtool: Don't use ignore flag for fake jumps

The ignore flag is set on fake jumps in order to keep
add_jump_destinations() from setting their jump_dest, since it already
got set when the fake jump was created.

But using the ignore flag is a bit of a hack.  It's normally used to
skip validation of an instruction, which doesn't really make sense for
fake jumps.

Also, after the next patch, using the ignore flag for fake jumps can
trigger a false "why am I validating an ignored function?" warning.

Instead just add an explicit check in add_jump_destinations() to skip
fake jumps.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/71abc072ff48b2feccc197723a9c52859476c068.1557766718.git.jpoimboe@redhat.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

tools/objtool/check.c

@@ -28,6 +28,8 @@
 #include <linux/hashtable.h>
 #include <linux/kernel.h>
 
+#define FAKE_JUMP_OFFSET -1
+
 struct alternative {
 	struct list_head list;
 	struct instruction *insn;
@@ -568,7 +570,7 @@ static int add_jump_destinations(struct objtool_file *file)
 		    insn->type != INSN_JUMP_UNCONDITIONAL)
 			continue;
 
-		if (insn->ignore)
+		if (insn->ignore || insn->offset == FAKE_JUMP_OFFSET)
 			continue;
 
 		rela = find_rela_by_dest_range(insn->sec, insn->offset,
@@ -745,10 +747,10 @@ static int handle_group_alt(struct objtool_file *file,
 		clear_insn_state(&fake_jump->state);
 
 		fake_jump->sec = special_alt->new_sec;
-		fake_jump->offset = -1;
+		fake_jump->offset = FAKE_JUMP_OFFSET;
 		fake_jump->type = INSN_JUMP_UNCONDITIONAL;
 		fake_jump->jump_dest = list_next_entry(last_orig_insn, list);
-		fake_jump->ignore = true;
+		fake_jump->func = orig_insn->func;
 	}
 
 	if (!special_alt->new_len) {