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From: Michael Ellerman <mpe@ellerman.id.au>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>, Naresh Kamboju
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Subject: Re: [PATCH] powerpc: drop port I/O helpers for CONFIG_HAS_IOPORT=n
In-Reply-To: <878r1bb2zj.fsf@mail.lhotse>
References: <20240416153331.1617772-1-arnd@kernel.org>
 <878r1bb2zj.fsf@mail.lhotse>
Date: Thu, 18 Apr 2024 16:33:04 +1000
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Michael Ellerman <mpe@ellerman.id.au> writes:
> Arnd Bergmann <arnd@kernel.org> writes:
>> From: Arnd Bergmann <arnd@arndb.de>
>>
>> Calling inb()/outb() on powerpc when CONFIG_PCI is disabled causes
>> a NULL pointer dereference, which is bad for a number of reasons.
>>
>> After my patch to turn on -Werror in linux-next, this caused a
>> compiler-time warning with clang:
>>
>> In file included from arch/powerpc/include/asm/io.h:672:
>> arch/powerpc/include/asm/io-defs.h:43:1: error: performing pointer
>> arithmetic on a null pointer has undefined behavior
>> [-Werror,-Wnull-pointer-arithmetic]
>>    43 | DEF_PCI_AC_NORET(insb, (unsigned long p, void *b, unsigned long c),
>>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>    44 |                  (p, b, c), pio, p)
>>       |                  ~~~~~~~~~~~~~~~~~~
>>
>> In this configuration, CONFIG_HAS_IOPORT is already disabled, and all
>> drivers that use inb()/outb() should now depend on that (some patches are
>> still in the process of getting marged).
>>
>> Hide all references to inb()/outb() in the powerpc code and the definitions
>> when HAS_IOPORT is disabled to remove the possible NULL pointer access.
>> The same should happin in asm-generic in the near future, but for now
>> the empty inb() macros are still defined to ensure the generic version
>> does not get pulled in.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
>> --
>
> This needs a small fixup:

Well, only because my tree doesn't have f0a816fb12da ("/dev/port: don't compile file operations without CONFIG_DEVPORT").

cheers