vmlinux.o: warning: objtool: smpboot_entry+0xa4: start_secondary() missing __noreturn in .c/.h or NORETURN() in noreturns.h

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   a95f71ad3e2e224277508e006580c333d0a5fe36
commit: 1b2f4706c6a20ab6ac41533dd8032d54322076e3 LoongArch: Use UNWIND_HINT_END_OF_STACK for entry points
date:   7 weeks ago
config: loongarch-randconfig-r072-20260220 (https://download.01.org/0day-ci/archive/20260221/202602210907.BdeqLsP5-lkp@xxxxxxxxx/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
smatch version: v0.5.0-8994-gd50c5a4c
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260221/202602210907.BdeqLsP5-lkp@xxxxxxxxx/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602210907.BdeqLsP5-lkp@xxxxxxxxx/

All warnings (new ones prefixed by >>):

   vmlinux.o: warning: objtool: kernel_entry+0xf0: start_kernel() missing __noreturn in .c/.h or NORETURN() in noreturns.h
>> vmlinux.o: warning: objtool: smpboot_entry+0xa4: start_secondary() missing __noreturn in .c/.h or NORETURN() in noreturns.h
   vmlinux.o: warning: objtool: _samsung_clk_register_pll+0x11c: unreachable instruction
   vmlinux.o: warning: objtool: kernel_kexec+0xdc: machine_kexec() missing __noreturn in .c/.h or NORETURN() in noreturns.h
   vmlinux.o: warning: objtool: gdb_serial_stub+0x7b8: machine_restart() missing __noreturn in .c/.h or NORETURN() in noreturns.h

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https://github.com/intel/lkp-tests/wiki