From: Niklas Schnelle <schnelle@linux.ibm.com>
To: David Laight <David.Laight@ACULAB.COM>,
Arnd Bergmann <arnd@arndb.de>, Vineet Gupta <vgupta@synopsys.com>,
"David S. Miller" <davem@davemloft.net>
Cc: Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
"clang-built-linux@googlegroups.com"
<clang-built-linux@googlegroups.com>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
"linux-snps-arc@lists.infradead.org"
<linux-snps-arc@lists.infradead.org>,
"sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>
Subject: Re: [PATCH v3 3/3] asm-generic/io.h: Silence -Wnull-pointer-arithmetic warning on PCI_IOBASE
Date: Wed, 21 Apr 2021 13:50:25 +0200 [thread overview]
Message-ID: <aac9ac52de09ff7162fc7caa6e817258d9dd313d.camel@linux.ibm.com> (raw)
In-Reply-To: <bb21141706d7477794453f7f52f6bc98@AcuMS.aculab.com>
On Wed, 2021-04-21 at 11:24 +0000, David Laight wrote:
> From: Niklas Schnelle
> > Sent: 21 April 2021 12:18
> >
> > When PCI_IOBASE is not defined, it is set to 0 such that it is ignored
> > in calls to the readX/writeX primitives. This triggers clang's
> > -Wnull-pointer-arithmetic warning and will result in illegal accesses on
> > platforms that do not support I/O ports if drivers do still attempt to
> > access them.
> >
> > Make things explicit and silence the warning by letting inb() and
> > friends fail with WARN_ONCE() and a 0xff... return in case PCI_IOBASE is
> > not defined.
> ...
> > diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h
> > index c6af40ce03be..aabb0a8186ee 100644
> > --- a/include/asm-generic/io.h
> > +++ b/include/asm-generic/io.h
> ...
> > @@ -458,12 +454,17 @@ static inline void writesq(volatile void __iomem *addr, const void *buffer,
> > #define _inb _inb
> > static inline u8 _inb(unsigned long addr)
> > {
> > +#ifdef PCI_IOBASE
> > u8 val;
> >
> > __io_pbr();
> > val = __raw_readb(PCI_IOBASE + addr);
> > __io_par(val);
> > return val;
> > +#else
> > + WARN_ONCE(1, "No I/O port support\n");
> > + return ~0;
> > +#endif
> > }
> > #endif
>
> I suspect that this might be better not inlined
> when PCI_IOBASE is undefined.
>
> Otherwise you get quite a lot of bloat from all the
> WARN_ONCE() calls.
>
> David
Hmm, I was wondering if we should rather have a large ifdef block of
all these functions stubbed to WARN_ONCE rather than in each function.
As I understand it this would be necessary if we want the inline gone.
They would still be static though so we still get a copy per
compilation unit that uses it or am I misunderstanding?
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>
next prev parent reply other threads:[~2021-04-21 11:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-21 11:17 [PATCH v3 0/3] asm-generic/io.h: Silence -Wnull-pointer-arithmetic warning on PCI_IOBASE Niklas Schnelle
2021-04-21 11:17 ` [PATCH v3 1/3] sparc: explicitly set PCI_IOBASE to 0 Niklas Schnelle
2021-04-21 11:17 ` [PATCH v3 2/3] ARC: io.h: Include asm/bug.h Niklas Schnelle
2021-04-21 11:17 ` [PATCH v3 3/3] asm-generic/io.h: Silence -Wnull-pointer-arithmetic warning on PCI_IOBASE Niklas Schnelle
2021-04-21 11:24 ` David Laight
2021-04-21 11:50 ` Niklas Schnelle [this message]
2021-04-21 11:57 ` Arnd Bergmann
2021-04-21 15:19 ` kernel test robot
2021-04-21 15:38 ` Niklas Schnelle
2021-04-21 16:59 ` kernel test robot
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