tree:   https://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux.git kgdb/for-next
head:   2277b492582d5525244519f60da6f9daea5ef41a
commit: 2277b492582d5525244519f60da6f9daea5ef41a [4/4] kdb: Fix stack crawling on 'running' CPUs that aren't the master
config: sh-allyesconfig (attached as .config)
compiler: sh4-linux-gcc (GCC) 7.4.0
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        git checkout 2277b492582d5525244519f60da6f9daea5ef41a
        # save the attached .config to linux build tree
        GCC_VERSION=7.4.0 make.cross ARCH=sh 

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

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.

All warnings (new ones prefixed by >>):

   kernel/debug/debug_core.c: In function 'kdb_dump_stack_on_cpu':
>> kernel/debug/debug_core.c:452:17: warning: array subscript is outside array bounds [-Warray-bounds]
     if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
           ~~~~~~~~~^~~~~
   kernel/debug/debug_core.c:469:33: warning: array subscript is outside array bounds [-Warray-bounds]
     kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
   kernel/debug/debug_core.c:470:18: warning: array subscript is outside array bounds [-Warray-bounds]
     while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
            ~~~~~~~~~^~~~~

vim +452 kernel/debug/debug_core.c

   443	
   444	#ifdef CONFIG_KGDB_KDB
   445	void kdb_dump_stack_on_cpu(int cpu)
   446	{
   447		if (cpu == raw_smp_processor_id()) {
   448			dump_stack();
   449			return;
   450		}
   451	
 > 452		if (!(kgdb_info[cpu].exception_state & DCPU_IS_SLAVE)) {
   453			kdb_printf("ERROR: Task on cpu %d didn't stop in the debugger\n",
   454				   cpu);
   455			return;
   456		}
   457	
   458		/*
   459		 * In general, architectures don't support dumping the stack of a
   460		 * "running" process that's not the current one.  From the point of
   461		 * view of the Linux, kernel processes that are looping in the kgdb
   462		 * slave loop are still "running".  There's also no API (that actually
   463		 * works across all architectures) that can do a stack crawl based
   464		 * on registers passed as a parameter.
   465		 *
   466		 * Solve this conundrum by asking slave CPUs to do the backtrace
   467		 * themselves.
   468		 */
   469		kgdb_info[cpu].exception_state |= DCPU_WANT_BT;
   470		while (kgdb_info[cpu].exception_state & DCPU_WANT_BT)
   471			cpu_relax();
   472	}
   473	#endif
   474	

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