Hi Christophe,

I love your patch! Perhaps something to improve:

[auto build test WARNING on powerpc/next]
[also build test WARNING on v5.8 next-20200806]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/powerpc-mm-sanity_check_fault-should-work-for-all-not-only-BOOK3S/20200807-012433
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-allyesconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
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
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=powerpc 

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/powerpc/mm/fault.c:567:6: warning: no previous prototype for '__bad_page_fault' [-Wmissing-prototypes]
     567 | void __bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
         |      ^~~~~~~~~~~~~~~~

vim +/__bad_page_fault +567 arch/powerpc/mm/fault.c

   561	
   562	/*
   563	 * bad_page_fault is called when we have a bad access from the kernel.
   564	 * It is called from the DSI and ISI handlers in head.S and from some
   565	 * of the procedures in traps.c.
   566	 */
 > 567	void __bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
   568	{
   569		int is_write = page_fault_is_write(regs->dsisr);
   570	
   571		/* kernel has accessed a bad area */
   572	
   573		switch (TRAP(regs)) {
   574		case 0x300:
   575		case 0x380:
   576		case 0xe00:
   577			pr_alert("BUG: %s on %s at 0x%08lx\n",
   578				 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
   579				 "Unable to handle kernel data access",
   580				 is_write ? "write" : "read", regs->dar);
   581			break;
   582		case 0x400:
   583		case 0x480:
   584			pr_alert("BUG: Unable to handle kernel instruction fetch%s",
   585				 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
   586			break;
   587		case 0x600:
   588			pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
   589				 regs->dar);
   590			break;
   591		default:
   592			pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
   593				 regs->dar);
   594			break;
   595		}
   596		printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
   597			regs->nip);
   598	
   599		if (task_stack_end_corrupted(current))
   600			printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
   601	
   602		die("Kernel access of bad area", regs, sig);
   603	}
   604	

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