Re: fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.

[Alexandre Ghiti]

Hi Dan,

On 18/02/2025 15:21, Dan Carpenter wrote:
> On Tue, Feb 18, 2025 at 08:39:21AM +0800, Philip Li wrote:
> > + Dan
> >
> > Hi Dan,
> >
> > On Mon, Feb 17, 2025 at 01:12:03PM +0000, David Laight wrote:
> > > On Mon, 17 Feb 2025 13:06:49 +0100
> > > Alexandre Ghiti <alex@xxxxxxxx> wrote:
> > >
> > > > Hi Christoph,
> > > >
> > > > On 17/02/2025 10:24, Christoph Hellwig wrote:
> > > > > On Mon, Feb 17, 2025 at 01:53:08PM +0800, kernel test robot wrote:
> > > > > > New smatch warnings:
> > > > > > fs/xfs/xfs_buf.c:1534 xfs_buf_submit_bio() warn: unsigned '_x' is never less than zero.
> > > > > Looks like this is an issue in the riscv virt_to_page implementation
> > > > > which also shows up in various other places.  Any chance this could get
> > > > > fixed in the riscv code?
> > > >
> > > > To me, the only test that could give rise to this warning is the last
> > > > part of:
> > > >
> > > > #define is_linear_mapping(x) \
> > > >           ((x) >= PAGE_OFFSET && (!IS_ENABLED(CONFIG_64BIT) || (x) <
> > > > PAGE_OFFSET + KERN_VIRT_SIZE))
> > > >
> > > > But given that the config is a 32-bit config, it should not be evaluated
> > > > at all.
> > > >
> > > > Could that be a false-positive and then an issue in smatch?
> > > Why is smatch even looking.
> > > The equivalent check in gcc has been moved to -W2 because of all false positives.
> The Smatch check is a bit more sophisticated than the GCC check...
> I think if you removed the (!IS_ENABLED(CONFIG_64BIT) condition then
> Smatch wouldn't trigger a warning here.  How would I duplicate this
> warning?  The "ARCH=riscv make.cross" command does a 64bit build.


riscv uses the same toolchain for both 32 and 64-bit, if you look at the 
faulty config, you can see that CONFIG_32BIT is enabled so it actually 
is a 32-bit build.

Thanks for jumping in,

Alex


> Screw it, I can just silence this warning based on that it's a kernel
> build and the variable is called "_x".
>
> regards,
> dan carpenter
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@xxxxxxxxxxxxxxxxxxx
> http://lists.infradead.org/mailman/listinfo/linux-riscv