tree:   https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/no_sce
head:   bfaecaf0dad8f61e80285125f4895c9737e3d6d8
commit: bfaecaf0dad8f61e80285125f4895c9737e3d6d8 [2/2] [EVIL] Run with EFER.SCE = 0
config: i386-allyesconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?id=bfaecaf0dad8f61e80285125f4895c9737e3d6d8
        git remote add luto https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git
        git fetch --no-tags luto x86/no_sce
        git checkout bfaecaf0dad8f61e80285125f4895c9737e3d6d8
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

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

All errors (new ones prefixed by >>):

   arch/x86/kernel/traps.c: In function 'exc_invalid_op':
>> arch/x86/kernel/traps.c:273:3: error: implicit declaration of function 'do_syscall_64'; did you mean 'NR_syscalls'? [-Werror=implicit-function-declaration]
     273 |   do_syscall_64(regs->ax, regs);
         |   ^~~~~~~~~~~~~
         |   NR_syscalls
   cc1: some warnings being treated as errors


vim +273 arch/x86/kernel/traps.c

   250	
   251	DEFINE_IDTENTRY_RAW(exc_invalid_op)
   252	{
   253		irqentry_state_t state;
   254	
   255		/*
   256		 * We use UD2 as a short encoding for 'CALL __WARN', as such
   257		 * handle it before exception entry to avoid recursive WARN
   258		 * in case exception entry is the one triggering WARNs.
   259		 */
   260		if (!user_mode(regs) && handle_bug(regs))
   261			return;
   262	
   263		if (user_mode(regs)) {
   264			/*
   265			 * emulate SYSCALL.  I have no idea why ax is a separate
   266			 * argument.  it's probably my fault.
   267			 *
   268			 * Don't think too hard about the entry mess here.
   269			 * This needs to be cleaned up so that syscalls can
   270			 * be cleanly executed from "irqentry" context.
   271			 */
   272			regs->ip += 2;  /* world's best emulator */
 > 273			do_syscall_64(regs->ax, regs);
   274			return;
   275		}
   276	
   277		state = irqentry_enter(regs);
   278		instrumentation_begin();
   279		handle_invalid_op(regs);
   280		instrumentation_end();
   281		irqentry_exit(regs, state);
   282	}
   283	

---
0-DAY CI Kernel Test Service, Intel Corporation
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