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From:   Niklas Schnelle <schnelle@linux.ibm.com>
To:     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, linux-arch@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        linux-snps-arc@lists.infradead.org, sparclinux@vger.kernel.org
Subject: [PATCH v6 0/3] asm-generic/io.h: Silence -Wnull-pointer-arithmetic warning on PCI_IOBASE
Date:   Mon, 10 May 2021 16:52:31 +0200
Message-Id: <20210510145234.594814-1-schnelle@linux.ibm.com>
MIME-Version: 1.0
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Hi,

This is version 6 of my attempt to get rid of a clang
-Wnull-pointer-arithmetic warning for the use of PCI_IOBASE in
asm-generic/io.h and fix the NULL pointer access it points out.

This was originally found on s390 but should apply to all platforms
leaving PCI_IOBASE undefined while making use of the inb() and friends
helpers from asm-generic/io.h.

This applies cleanly and was compile tested on top of v5.12 for the
previously broken ARC, nds32, h8300 and risc-v architecture. It also
applies cleanly on v5.13-rc1 for which I boot tested it on s390.

I did boot test this only on x86_64 and s390x the former implements
inb() et al itself while the latter would emit a WARN_ONCE() but no
drivers use inb().

Thanks,
Niklas

Changes sinve v5:
- memset() the buffer in insb()/insw()/insl() in the WARN_ONCE() case
  to prevent use of uninitialized data (Arnd)

Changes since v4:
- Added Link to patch 4 (Arnd)
- Improved comment on RISC-V patch mentioning current brokeness (Arnd)

Changes since v3:
- Changed the subject of the last patch to better reflect the actual
  change i.e. the addition of WARN_ONCE() to the helpers not the
  silencing of the clang warning
- Added asm/bug.h to asm-generic/io.h so it doesn't have to be included
  previously by all arches to be available for the WARN_ONCE()
- Added patch for risc-v which defines PCI_IOBASE except when compiled
  for nommu

Changes since v2:
- Improved comment for SPARC PCI_IOBASE definition as suggested
  by David Laight
- Added a patch for ARC which is missing the asm/bug.h include for
  WARN_ONCE() (kernel test robot)
- Added ifdefs to ioport_map() and __pci_ioport_map() since apparently
  at least test configs enable CONFIG_HAS_IOPORT_MAP even on
  architectures which leave PCI_IOBASE unset (kernel test robot for
  nds32 and ARC).

Changes since v1:
- Added patch to explicitly set PCI_IOBASE to 0 on sparc as suggested by
  Arnd Bergmann
- Instead of working around the warning with a uintptr_t PCI_IOBASE make
  inb() and friends explicitly WARN_ONCE() and return 0xff... (Arnd
  Bergmann)

Niklas Schnelle (3):
  sparc: explicitly set PCI_IOBASE to 0
  risc-v: Use generic io.h helpers for nommu
  asm-generic/io.h: warn in inb() and friends with undefined PCI_IOBASE

 arch/riscv/include/asm/io.h |  5 +--
 arch/sparc/include/asm/io.h |  8 +++++
 include/asm-generic/io.h    | 68 ++++++++++++++++++++++++++++++++++---
 3 files changed, 75 insertions(+), 6 deletions(-)

-- 
2.25.1