tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/entry
head:   095b7a3e7745e6fb7cf0a1c09967c4f43e76f8f4
commit: aa9712e07f82a5458f2f16c100c491d736240d60 [23/80] x86/entry/common: 
Protect against instrumentation
config: x86_64-allyesconfig (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 
e6658079aca6d971b4e9d7137a3a2ecbc9c34aec)
reproduce:
        wget 
https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O 
~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        git checkout aa9712e07f82a5458f2f16c100c491d736240d60
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kbuild test robot <[email protected]>

All warnings (new ones prefixed by >>, old ones prefixed by <<):

>> arch/x86/entry/common.c:234:24: warning: no previous prototype for function 
>> 'prepare_exit_to_usermode' [-Wmissing-prototypes]
__visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs)
^
arch/x86/entry/common.c:234:19: note: declare 'static' if the function is not 
intended to be used outside of this translation unit
__visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs)
^
static
>> arch/x86/entry/common.c:296:24: warning: no previous prototype for function 
>> 'syscall_return_slowpath' [-Wmissing-prototypes]
__visible noinstr void syscall_return_slowpath(struct pt_regs *regs)
^
arch/x86/entry/common.c:296:19: note: declare 'static' if the function is not 
intended to be used outside of this translation unit
__visible noinstr void syscall_return_slowpath(struct pt_regs *regs)
^
static
2 warnings generated.

vim +/prepare_exit_to_usermode +234 arch/x86/entry/common.c

   233  
 > 234  __visible noinstr void prepare_exit_to_usermode(struct pt_regs *regs)
   235  {
   236          instrumentation_begin();
   237          __prepare_exit_to_usermode(regs);
   238          instrumentation_end();
   239          exit_to_user_mode();
   240  }
   241  
   242  #define SYSCALL_EXIT_WORK_FLAGS                         \
   243          (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT |      \
   244           _TIF_SINGLESTEP | _TIF_SYSCALL_TRACEPOINT)
   245  
   246  static void syscall_slow_exit_work(struct pt_regs *regs, u32 
cached_flags)
   247  {
   248          bool step;
   249  
   250          audit_syscall_exit(regs);
   251  
   252          if (cached_flags & _TIF_SYSCALL_TRACEPOINT)
   253                  trace_sys_exit(regs, regs->ax);
   254  
   255          /*
   256           * If TIF_SYSCALL_EMU is set, we only get here because of
   257           * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
   258           * We already reported this syscall instruction in
   259           * syscall_trace_enter().
   260           */
   261          step = unlikely(
   262                  (cached_flags & (_TIF_SINGLESTEP | _TIF_SYSCALL_EMU))
   263                  == _TIF_SINGLESTEP);
   264          if (step || cached_flags & _TIF_SYSCALL_TRACE)
   265                  tracehook_report_syscall_exit(regs, step);
   266  }
   267  
   268  static void __syscall_return_slowpath(struct pt_regs *regs)
   269  {
   270          struct thread_info *ti = current_thread_info();
   271          u32 cached_flags = READ_ONCE(ti->flags);
   272  
   273          CT_WARN_ON(ct_state() != CONTEXT_KERNEL);
   274  
   275          if (IS_ENABLED(CONFIG_PROVE_LOCKING) &&
   276              WARN(irqs_disabled(), "syscall %ld left IRQs disabled", 
regs->orig_ax))
   277                  local_irq_enable();
   278  
   279          rseq_syscall(regs);
   280  
   281          /*
   282           * First do one-time work.  If these work items are enabled, we
   283           * want to run them exactly once per syscall exit with IRQs on.
   284           */
   285          if (unlikely(cached_flags & SYSCALL_EXIT_WORK_FLAGS))
   286                  syscall_slow_exit_work(regs, cached_flags);
   287  
   288          local_irq_disable();
   289          __prepare_exit_to_usermode(regs);
   290  }
   291  
   292  /*
   293   * Called with IRQs on and fully valid regs.  Returns with IRQs off in a
   294   * state such that we can immediately switch to user mode.
   295   */
 > 296  __visible noinstr void syscall_return_slowpath(struct pt_regs *regs)
   297  {
   298          instrumentation_begin();
   299          __syscall_return_slowpath(regs);
   300          instrumentation_end();
   301          exit_to_user_mode();
   302  }
   303  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]

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