objtool: Rework instruction -> symbol mapping

Currently insn->func contains a instruction -> symbol link for
STT_FUNC symbols. A NULL value is assumed to mean STT_NOTYPE.
However, there are also instructions not covered by any symbol at all.
This can happen due to __weak symbols for example.

Since the current scheme cannot differentiate between no symbol and
STT_NOTYPE symbol, change things around. Make insn->sym point to any
symbol type such that !insn->sym means no symbol and add a helper
insn_func() that check the sym->type to retain the old functionality.

This then prepares the way to add code that depends on the distinction
between STT_NOTYPE and no symbol at all.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

tools/objtool/include/objtool/check.h

@@ -67,11 +67,21 @@ struct instruction {
 	struct reloc *jump_table;
 	struct reloc *reloc;
 	struct list_head alts;
-	struct symbol *func;
+	struct symbol *sym;
 	struct list_head stack_ops;
 	struct cfi_state *cfi;
 };
 
+static inline struct symbol *insn_func(struct instruction *insn)
+{
+	struct symbol *sym = insn->sym;
+
+	if (sym && sym->type != STT_FUNC)
+		sym = NULL;
+
+	return sym;
+}
+
 #define VISITED_BRANCH		0x01
 #define VISITED_BRANCH_UACCESS	0x02
 #define VISITED_BRANCH_MASK	0x03