[mhiramat:kprobes/fprobe 8/12] arch/x86/kernel/rethook.c:14:23: warning: no previous prototype for function 'arch_rethook_trampoline_callback'

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git kprobes/fprobe
head:   0bd36e652ac2be74b19f414d0b20aaef6521ac82
commit: 23f61cf25dd4c1cf50adce7ebe0e2ae65bef5b78 [8/12] fprobe: Add exit_handler support
config: x86_64-allyesconfig (https://download.01.org/0day-ci/archive/20220309/202203090445.eMw6Gp37-lkp@intel.com/config)
compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project 4e115b7d881136947c083e12f62010bc6b1d3f00)
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
        # https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/commit/?id=23f61cf25dd4c1cf50adce7ebe0e2ae65bef5b78
        git remote add mhiramat https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git
        git fetch --no-tags mhiramat kprobes/fprobe
        git checkout 23f61cf25dd4c1cf50adce7ebe0e2ae65bef5b78
        # 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=x86_64 SHELL=/bin/bash arch/x86/kernel/

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

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/rethook.c:14:23: warning: no previous prototype for function 'arch_rethook_trampoline_callback' [-Wmissing-prototypes]
   __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
                         ^
   arch/x86/kernel/rethook.c:14:18: note: declare 'static' if the function is not intended to be used outside of this translation unit
   __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
                    ^
                    static 
   1 warning generated.


vim +/arch_rethook_trampoline_callback +14 arch/x86/kernel/rethook.c

31ffbcef413de8 Masami Hiramatsu 2022-02-09  10  
31ffbcef413de8 Masami Hiramatsu 2022-02-09  11  /*
31ffbcef413de8 Masami Hiramatsu 2022-02-09  12   * Called from arch_rethook_trampoline
31ffbcef413de8 Masami Hiramatsu 2022-02-09  13   */
31ffbcef413de8 Masami Hiramatsu 2022-02-09 @14  __used __visible void arch_rethook_trampoline_callback(struct pt_regs *regs)
31ffbcef413de8 Masami Hiramatsu 2022-02-09  15  {
31ffbcef413de8 Masami Hiramatsu 2022-02-09  16  	unsigned long *frame_pointer;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  17  
31ffbcef413de8 Masami Hiramatsu 2022-02-09  18  	/* fixup registers */
31ffbcef413de8 Masami Hiramatsu 2022-02-09  19  	regs->cs = __KERNEL_CS;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  20  #ifdef CONFIG_X86_32
31ffbcef413de8 Masami Hiramatsu 2022-02-09  21  	regs->gs = 0;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  22  #endif
31ffbcef413de8 Masami Hiramatsu 2022-02-09  23  	regs->ip = (unsigned long)&arch_rethook_trampoline;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  24  	regs->orig_ax = ~0UL;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  25  	regs->sp += sizeof(long);
31ffbcef413de8 Masami Hiramatsu 2022-02-09  26  	frame_pointer = &regs->sp + 1;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  27  
31ffbcef413de8 Masami Hiramatsu 2022-02-09  28  	/*
31ffbcef413de8 Masami Hiramatsu 2022-02-09  29  	 * The return address at 'frame_pointer' is recovered by the
31ffbcef413de8 Masami Hiramatsu 2022-02-09  30  	 * arch_rethook_fixup_return() which called from this
31ffbcef413de8 Masami Hiramatsu 2022-02-09  31  	 * rethook_trampoline_handler().
31ffbcef413de8 Masami Hiramatsu 2022-02-09  32  	 */
31ffbcef413de8 Masami Hiramatsu 2022-02-09  33  	rethook_trampoline_handler(regs, (unsigned long)frame_pointer);
31ffbcef413de8 Masami Hiramatsu 2022-02-09  34  
31ffbcef413de8 Masami Hiramatsu 2022-02-09  35  	/*
31ffbcef413de8 Masami Hiramatsu 2022-02-09  36  	 * Copy FLAGS to 'pt_regs::sp' so that arch_rethook_trapmoline()
31ffbcef413de8 Masami Hiramatsu 2022-02-09  37  	 * can do RET right after POPF.
31ffbcef413de8 Masami Hiramatsu 2022-02-09  38  	 */
31ffbcef413de8 Masami Hiramatsu 2022-02-09  39  	regs->sp = regs->flags;
31ffbcef413de8 Masami Hiramatsu 2022-02-09  40  }
31ffbcef413de8 Masami Hiramatsu 2022-02-09  41  NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
31ffbcef413de8 Masami Hiramatsu 2022-02-09  42  

:::::: The code at line 14 was first introduced by commit
:::::: 31ffbcef413de82a1b0afc177b5d85364495f0cd rethook: x86: Add rethook x86 implementation

:::::: TO: Masami Hiramatsu <mhiramat@kernel.org>
:::::: CC: Masami Hiramatsu <mhiramat@kernel.org>

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