Merge tag 'objtool_urgent_for_v5.11_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull objtool fixes from Borislav Petkov:

 - Adjust objtool to handle a recent binutils change to not generate
   unused symbols anymore.

 - Revert the fail-the-build-on-fatal-errors objtool strategy for now
   due to the ever-increasing matrix of supported toolchains/plugins and
   them causing too many such fatal errors currently.

 - Do not add empty symbols to objdump's rbtree to accommodate clang
   removing section symbols.

* tag 'objtool_urgent_for_v5.11_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Don't fail on missing symbol table
  objtool: Don't fail the kernel build on fatal errors
  objtool: Don't add empty symbols to the rbtree

Author: torvalds

tools/objtool/check.c

@@ -2928,14 +2928,10 @@ int check(struct objtool_file *file)
 	warnings += ret;
 
 out:
-	if (ret < 0) {
-		/*
-		 *  Fatal error.  The binary is corrupt or otherwise broken in
-		 *  some way, or objtool itself is broken.  Fail the kernel
-		 *  build.
-		 */
-		return ret;
-	}
-
+	/*
+	 *  For now, don't fail the kernel build on fatal warnings.  These
+	 *  errors are still fairly common due to the growing matrix of
+	 *  supported toolchains and their recent pace of change.
+	 */
 	return 0;
 }

tools/objtool/elf.c

@@ -380,8 +380,11 @@ static int read_symbols(struct elf *elf)
 
 	symtab = find_section_by_name(elf, ".symtab");
 	if (!symtab) {
-		WARN("missing symbol table");
-		return -1;
+		/*
+		 * A missing symbol table is actually possible if it's an empty
+		 * .o file.  This can happen for thunk_64.o.
+		 */
+		return 0;
 	}
 
 	symtab_shndx = find_section_by_name(elf, ".symtab_shndx");
@@ -448,6 +451,13 @@ static int read_symbols(struct elf *elf)
 		list_add(&sym->list, entry);
 		elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx);
 		elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name));
+
+		/*
+		 * Don't store empty STT_NOTYPE symbols in the rbtree.  They
+		 * can exist within a function, confusing the sorting.
+		 */
+		if (!sym->len)
+			rb_erase(&sym->node, &sym->sec->symbol_tree);
 	}
 
 	if (stats)