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

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