linux-kernel - kernel/module.c:4478:14: warning: variable 'exit' set but not used

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Date:   Sun, 2 Jan 2022 06:58:00 +0800
From:   kernel test robot <lkp@...el.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     llvm@...ts.linux.dev, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Jessica Yu <jeyu@...nel.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Miroslav Benes <mbenes@...e.cz>
Subject: kernel/module.c:4478:14: warning: variable 'exit' set but not used

Hi Arnd,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   278218f6778bc7d6f8b67199446c56cec7ebb841
commit: 0d67e332e6df72f43eaa21228daa3a79e23093f3 module: fix clang CFI with MODULE_UNLOAD=n
date:   3 months ago
config: arm64-randconfig-r022-20220101 (https://download.01.org/0day-ci/archive/20220102/202201020600.rl5oKvlD-lkp@intel.com/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 7cd109b92c72855937273a6c8ab19016fbe27d33)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0d67e332e6df72f43eaa21228daa3a79e23093f3
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 0d67e332e6df72f43eaa21228daa3a79e23093f3
        # save the config file to linux build tree
        mkdir build_dir
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> kernel/module.c:4478:14: warning: variable 'exit' set but not used [-Wunused-but-set-variable]
           exitcall_t *exit;
                       ^
   1 warning generated.


vim +/exit +4478 kernel/module.c

^1da177e4c3f41 Linus Torvalds 2005-04-16  4473  
cf68fffb66d60d Sami Tolvanen  2021-04-08  4474  static void cfi_init(struct module *mod)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4475  {
cf68fffb66d60d Sami Tolvanen  2021-04-08  4476  #ifdef CONFIG_CFI_CLANG
cf68fffb66d60d Sami Tolvanen  2021-04-08  4477  	initcall_t *init;
cf68fffb66d60d Sami Tolvanen  2021-04-08 @4478  	exitcall_t *exit;
cf68fffb66d60d Sami Tolvanen  2021-04-08  4479  
cf68fffb66d60d Sami Tolvanen  2021-04-08  4480  	rcu_read_lock_sched();
cf68fffb66d60d Sami Tolvanen  2021-04-08  4481  	mod->cfi_check = (cfi_check_fn)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4482  		find_kallsyms_symbol_value(mod, "__cfi_check");
cf68fffb66d60d Sami Tolvanen  2021-04-08  4483  	init = (initcall_t *)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4484  		find_kallsyms_symbol_value(mod, "__cfi_jt_init_module");
cf68fffb66d60d Sami Tolvanen  2021-04-08  4485  	exit = (exitcall_t *)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4486  		find_kallsyms_symbol_value(mod, "__cfi_jt_cleanup_module");
cf68fffb66d60d Sami Tolvanen  2021-04-08  4487  	rcu_read_unlock_sched();
cf68fffb66d60d Sami Tolvanen  2021-04-08  4488  
cf68fffb66d60d Sami Tolvanen  2021-04-08  4489  	/* Fix init/exit functions to point to the CFI jump table */
cf68fffb66d60d Sami Tolvanen  2021-04-08  4490  	if (init)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4491  		mod->init = *init;
0d67e332e6df72 Arnd Bergmann  2021-09-27  4492  #ifdef CONFIG_MODULE_UNLOAD
cf68fffb66d60d Sami Tolvanen  2021-04-08  4493  	if (exit)
cf68fffb66d60d Sami Tolvanen  2021-04-08  4494  		mod->exit = *exit;
0d67e332e6df72 Arnd Bergmann  2021-09-27  4495  #endif
cf68fffb66d60d Sami Tolvanen  2021-04-08  4496  
cf68fffb66d60d Sami Tolvanen  2021-04-08  4497  	cfi_module_add(mod, module_addr_min);
cf68fffb66d60d Sami Tolvanen  2021-04-08  4498  #endif
cf68fffb66d60d Sami Tolvanen  2021-04-08  4499  }
cf68fffb66d60d Sami Tolvanen  2021-04-08  4500  

:::::: The code at line 4478 was first introduced by commit
:::::: cf68fffb66d60d96209446bfc4a15291dc5a5d41 add support for Clang CFI

:::::: TO: Sami Tolvanen <samitolvanen@...gle.com>
:::::: CC: Kees Cook <keescook@...omium.org>

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org