linux-kernel - Re: [PATCH v3] powerpc: fix EDEADLOCK redefinition error in uapi/asm/errno.h

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Message-ID: <87r1jaeclf.fsf@mpe.ellerman.id.au>
Date:   Fri, 16 Apr 2021 20:41:00 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Tony Ambardar <tony.ambardar@...il.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arch <linux-arch@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Stable <stable@...r.kernel.org>, Rosen Penev <rosenp@...il.com>
Subject: Re: [PATCH v3] powerpc: fix EDEADLOCK redefinition error in
 uapi/asm/errno.h

Tony Ambardar <tony.ambardar@...il.com> writes:
> Hello Michael,
>
> The latest version of this patch addressed all feedback I'm aware of
> when submitted last September, and I've seen no further comments from
> reviewers since then.
>
> Could you please let me know where this stands and if anything further
> is needed?

Sorry, it's still sitting in my inbox :/

I was going to reply to suggest we split the tools change out. The
headers under tools are usually updated by another maintainer, I think
it might even be scripted.

Anyway I've applied your patch and done that (dropped the change to
tools/.../errno.h), which should also mean the stable backport is more
likely to work automatically.

It will hit mainline in v5.13-rc1 and then be backported to the stable
trees.

I don't think you actually need the tools version of the header updated
to fix your bug? In which case we can probably just wait for it to be
updated automatically when the tools headers are sync'ed with the kernel
versions.

cheers


> On Thu, 17 Sept 2020 at 06:54, Tony Ambardar <tony.ambardar@...il.com> wrote:
>>
>> A few archs like powerpc have different errno.h values for macros
>> EDEADLOCK and EDEADLK. In code including both libc and linux versions of
>> errno.h, this can result in multiple definitions of EDEADLOCK in the
>> include chain. Definitions to the same value (e.g. seen with mips) do
>> not raise warnings, but on powerpc there are redefinitions changing the
>> value, which raise warnings and errors (if using "-Werror").
>>
>> Guard against these redefinitions to avoid build errors like the following,
>> first seen cross-compiling libbpf v5.8.9 for powerpc using GCC 8.4.0 with
>> musl 1.1.24:
>>
>>   In file included from ../../arch/powerpc/include/uapi/asm/errno.h:5,
>>                    from ../../include/linux/err.h:8,
>>                    from libbpf.c:29:
>>   ../../include/uapi/asm-generic/errno.h:40: error: "EDEADLOCK" redefined [-Werror]
>>    #define EDEADLOCK EDEADLK
>>
>>   In file included from toolchain-powerpc_8540_gcc-8.4.0_musl/include/errno.h:10,
>>                    from libbpf.c:26:
>>   toolchain-powerpc_8540_gcc-8.4.0_musl/include/bits/errno.h:58: note: this is the location of the previous definition
>>    #define EDEADLOCK       58
>>
>>   cc1: all warnings being treated as errors
>>
>> CC: Stable <stable@...r.kernel.org>
>> Reported-by: Rosen Penev <rosenp@...il.com>
>> Signed-off-by: Tony Ambardar <Tony.Ambardar@...il.com>
>> ---
>> v1 -> v2:
>>  * clean up commit description formatting
>>
>> v2 -> v3: (per Michael Ellerman)
>>  * drop indeterminate 'Fixes' tags, request stable backports instead
>> ---
>>  arch/powerpc/include/uapi/asm/errno.h       | 1 +
>>  tools/arch/powerpc/include/uapi/asm/errno.h | 1 +
>>  2 files changed, 2 insertions(+)
>>
>> diff --git a/arch/powerpc/include/uapi/asm/errno.h b/arch/powerpc/include/uapi/asm/errno.h
>> index cc79856896a1..4ba87de32be0 100644
>> --- a/arch/powerpc/include/uapi/asm/errno.h
>> +++ b/arch/powerpc/include/uapi/asm/errno.h
>> @@ -2,6 +2,7 @@
>>  #ifndef _ASM_POWERPC_ERRNO_H
>>  #define _ASM_POWERPC_ERRNO_H
>>
>> +#undef EDEADLOCK
>>  #include <asm-generic/errno.h>
>>
>>  #undef EDEADLOCK
>> diff --git a/tools/arch/powerpc/include/uapi/asm/errno.h b/tools/arch/powerpc/include/uapi/asm/errno.h
>> index cc79856896a1..4ba87de32be0 100644
>> --- a/tools/arch/powerpc/include/uapi/asm/errno.h
>> +++ b/tools/arch/powerpc/include/uapi/asm/errno.h
>> @@ -2,6 +2,7 @@
>>  #ifndef _ASM_POWERPC_ERRNO_H
>>  #define _ASM_POWERPC_ERRNO_H
>>
>> +#undef EDEADLOCK
>>  #include <asm-generic/errno.h>
>>
>>  #undef EDEADLOCK
>> --
>> 2.25.1
>>