1 files changed, 33 insertions, 1 deletions

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4da6bfb8a98d..fa9bf364545c 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1983,6 +1983,11 @@ static int handle_insn_ops(struct instruction *insn, struct insn_state *state)
 	list_for_each_entry(op, &insn->stack_ops, list) {
 		int res;
 
+		if (insn->alt_group) {
+			WARN_FUNC("alternative modifies stack", insn->sec, insn->offset);
+			return -1;
+		}
+
 		res = update_cfi_state(insn, &state->cfi, op);
 		if (res)
 			return res;
@@ -2150,6 +2155,30 @@ static int validate_return(struct symbol *func, struct instruction *insn, struct
 }
 
 /*
+ * Alternatives should not contain any ORC entries, this in turn means they
+ * should not contain any CFI ops, which implies all instructions should have
+ * the same same CFI state.
+ *
+ * It is possible to constuct alternatives that have unreachable holes that go
+ * unreported (because they're NOPs), such holes would result in CFI_UNDEFINED
+ * states which then results in ORC entries, which we just said we didn't want.
+ *
+ * Avoid them by copying the CFI entry of the first instruction into the whole
+ * alternative.
+ */
+static void fill_alternative_cfi(struct objtool_file *file, struct instruction *insn)
+{
+	struct instruction *first_insn = insn;
+	int alt_group = insn->alt_group;
+
+	sec_for_each_insn_continue(file, insn) {
+		if (insn->alt_group != alt_group)
+			break;
+		insn->cfi = first_insn->cfi;
+	}
+}
+
+/*
  * Follow the branch starting at the given instruction, and recursively follow
  * any other branches (jumps).  Meanwhile, track the frame pointer state at
  * each instruction and validate all the rules described in
@@ -2200,7 +2229,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 
 		insn->visited |= visited;
 
-		if (!insn->ignore_alts) {
+		if (!insn->ignore_alts && !list_empty(&insn->alts)) {
 			bool skip_orig = false;
 
 			list_for_each_entry(alt, &insn->alts, list) {
@@ -2215,6 +2244,9 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 				}
 			}
 
+			if (insn->alt_group)
+				fill_alternative_cfi(file, insn);
+
 			if (skip_orig)
 				return 0;
 		}