[RFC v5 04/57] objtool: check: Ignore empty alternative groups

[Julien Thierry]

Atlernative section can contain entries for alternatives with no
instructions. Objtool will currently crash when handling such an entry.

Just skip that entry, but still give a warning to discourage useless
entries.

Signed-off-by: Julien Thierry <jthierry@xxxxxxxxxx>
---
 tools/objtool/check.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5968e6f08891..27e5380e0e0b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -866,6 +866,13 @@ static int add_special_section_alts(struct objtool_file *file)
 		}
 
 		if (special_alt->group) {
+			if (!special_alt->orig_len) {
+				WARN("empty alternative entry at %s+0x%lx",
+				     orig_insn->sec->name,
+				     orig_insn->offset);
+				continue;
+			}
+
 			ret = handle_group_alt(file, special_alt, orig_insn,
 					       &new_insn);
 			if (ret)
-- 
2.21.0