Re: [PATCH v5 3/3] asm-generic/io.h: warn in inb() and friends with undefined PCI_IOBASE

Hi Niklas,

I love your patch! Perhaps something to improve:

[auto build test WARNING on soc/for-next]
[also build test WARNING on asm-generic/master v5.13-rc1 next-20210510]
[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/Niklas-Schnelle/asm-generic-io-h-Silence-Wnull-pointer-arithmetic-warning-on-PCI_IOBASE/20210510-165435
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
config: h8300-randconfig-r035-20210510 (attached as .config)
compiler: h8300-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
        # https://github.com/0day-ci/linux/commit/fa75946a8988026bee808b5840438a3908f0a65b
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Niklas-Schnelle/asm-generic-io-h-Silence-Wnull-pointer-arithmetic-warning-on-PCI_IOBASE/20210510-165435
        git checkout fa75946a8988026bee808b5840438a3908f0a65b
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=h8300 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All warnings (new ones prefixed by >>):

   In file included from include/linux/kernel.h:10,
                    from drivers/media/rc/nuvoton-cir.c:25:
   include/linux/scatterlist.h: In function 'sg_set_buf':
   include/asm-generic/page.h:89:50: warning: ordered comparison of pointer with null pointer [-Wextra]
      89 | #define virt_addr_valid(kaddr) (((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
         |                                                  ^~
   include/linux/compiler.h:78:42: note: in definition of macro 'unlikely'
      78 | # define unlikely(x) __builtin_expect(!!(x), 0)
         |                                          ^
   include/linux/scatterlist.h:137:2: note: in expansion of macro 'BUG_ON'
     137 |  BUG_ON(!virt_addr_valid(buf));
         |  ^~~~~~
   include/linux/scatterlist.h:137:10: note: in expansion of macro 'virt_addr_valid'
     137 |  BUG_ON(!virt_addr_valid(buf));
         |          ^~~~~~~~~~~~~~~
   drivers/media/rc/nuvoton-cir.c: In function 'nvt_get_rx_ir_data':

quoted

drivers/media/rc/nuvoton-cir.c:761:15: warning: iteration 32 invokes undefined behavior [-Waggressive-loop-optimizations]

     761 |   nvt->buf[i] = nvt_cir_reg_read(nvt, CIR_SRXFIFO);
         |   ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   drivers/media/rc/nuvoton-cir.c:760:2: note: within this loop
     760 |  for (i = 0; i < fifocount; i++)
         |  ^~~


vim +761 drivers/media/rc/nuvoton-cir.c

fbdc781c6ba974 drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-08  747  
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  748  /* copy data from hardware rx fifo into driver buffer */
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  749  static void nvt_get_rx_ir_data(struct nvt_dev *nvt)
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  750  {
6db0168821fa4e drivers/media/rc/nuvoton-cir.c Heiner Kallweit 2016-08-02  751  	u8 fifocount;
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  752  	int i;
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  753  
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  754  	/* Get count of how many bytes to read from RX FIFO */
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  755  	fifocount = nvt_cir_reg_read(nvt, CIR_RXFCONT);
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  756  
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  757  	nvt_dbg("attempting to fetch %u bytes from hw rx fifo", fifocount);
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  758  
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  759  	/* Read fifocount bytes from CIR Sample RX FIFO register */
6db0168821fa4e drivers/media/rc/nuvoton-cir.c Heiner Kallweit 2016-08-02  760  	for (i = 0; i < fifocount; i++)
6db0168821fa4e drivers/media/rc/nuvoton-cir.c Heiner Kallweit 2016-08-02 @761  		nvt->buf[i] = nvt_cir_reg_read(nvt, CIR_SRXFIFO);
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  762  
bacf8351f23cfd drivers/media/rc/nuvoton-cir.c Heiner Kallweit 2016-08-02  763  	nvt->pkts = fifocount;
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  764  	nvt_dbg("%s: pkts now %d", __func__, nvt->pkts);
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  765  
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  766  	nvt_process_rx_ir_data(nvt);
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  767  }
6d2f5c27880c2c drivers/media/IR/nuvoton-cir.c Jarod Wilson    2010-10-07  768  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

On Mon, May 10, 2021 at 3:08 PM kernel test robot [off-list ref] wrote:

   In file included from include/linux/kernel.h:10,
                    from drivers/media/rc/nuvoton-cir.c:25:
   include/linux/scatterlist.h: In function 'sg_set_buf':
   include/asm-generic/page.h:89:50: warning: ordered comparison of pointer with null pointer [-Wextra]
      89 | #define virt_addr_valid(kaddr) (((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
         |                                                  ^~
   include/linux/compiler.h:78:42: note: in definition of macro 'unlikely'
      78 | # define unlikely(x) __builtin_expect(!!(x), 0)
         |                                          ^
   include/linux/scatterlist.h:137:2: note: in expansion of macro 'BUG_ON'
     137 |  BUG_ON(!virt_addr_valid(buf));
         |  ^~~~~~
   include/linux/scatterlist.h:137:10: note: in expansion of macro 'virt_addr_valid'
     137 |  BUG_ON(!virt_addr_valid(buf));
         |          ^~~~~~~~~~~~~~~
   drivers/media/rc/nuvoton-cir.c: In function 'nvt_get_rx_ir_data':

quoted

quoted

drivers/media/rc/nuvoton-cir.c:761:15: warning: iteration 32 invokes undefined behavior [-Waggressive-loop-optimizations]

     761 |   nvt->buf[i] = nvt_cir_reg_read(nvt, CIR_SRXFIFO);

I think you can ignore this one, it's a preexisting issue with this
driver that gets uncovered by your patch: if "fifocount" is read from
a broken device as 0xff, the loop causes a buffer overflow.

The code is already unreachable because the interrupt handler
will have aborted already, so the compiler's dead code elimination
should have shut up that warning, but adding a range check
before the loop would address this as well.

As far as I can tell, this warning only shows up when building with
"make W=1".

       Arnd