objtool: Fix another stack overflow in validate_branch()

The insn state is getting saved on the stack twice for each recursive
iteration.  No need for that, once is enough.

Fixes the following reported stack overflow:

  drivers/scsi/qla2xxx/qla_dbg.o: error: SIGSEGV: objtool stack overflow!
  Segmentation fault

Fixes: 7058984 ("objtool: Add option to trace function validation")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Closes: https://lore.kernel.org/90956545-2066-46e3-b547-10c884582eb0@app.fastmail.com
Link: https://patch.msgid.link/8b97f62d083457f3b0a29a424275f7957dd3372f.1772821683.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

Author: jpoimboe

tools/objtool/check.c

@@ -3748,7 +3748,7 @@ static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
 static int validate_branch(struct objtool_file *file, struct symbol *func,
 			   struct instruction *insn, struct insn_state state);
 static int do_validate_branch(struct objtool_file *file, struct symbol *func,
-			      struct instruction *insn, struct insn_state state);
+			      struct instruction *insn, struct insn_state *state);
 
 static int validate_insn(struct objtool_file *file, struct symbol *func,
 			 struct instruction *insn, struct insn_state *statep,
@@ -4013,7 +4013,7 @@ static int validate_insn(struct objtool_file *file, struct symbol *func,
  * tools/objtool/Documentation/objtool.txt.
  */
 static int do_validate_branch(struct objtool_file *file, struct symbol *func,
-			      struct instruction *insn, struct insn_state state)
+			      struct instruction *insn, struct insn_state *state)
 {
 	struct instruction *next_insn, *prev_insn = NULL;
 	bool dead_end;
@@ -4044,7 +4044,7 @@ static int do_validate_branch(struct objtool_file *file, struct symbol *func,
 			return 1;
 		}
 
-		ret = validate_insn(file, func, insn, &state, prev_insn, next_insn,
+		ret = validate_insn(file, func, insn, state, prev_insn, next_insn,
 				    &dead_end);
 
 		if (!insn->trace) {
@@ -4055,7 +4055,7 @@ static int do_validate_branch(struct objtool_file *file, struct symbol *func,
 		}
 
 		if (!dead_end && !next_insn) {
-			if (state.cfi.cfa.base == CFI_UNDEFINED)
+			if (state->cfi.cfa.base == CFI_UNDEFINED)
 				return 0;
 			if (file->ignore_unreachables)
 				return 0;
@@ -4080,7 +4080,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 	int ret;
 
 	trace_depth_inc();
-	ret = do_validate_branch(file, func, insn, state);
+	ret = do_validate_branch(file, func, insn, &state);
 	trace_depth_dec();
 
 	return ret;