linux-kernel - Re: [tip:x86/cpu 2/3] arch/x86/kernel/alternative.c:96:10: warning: Undefined behaviour, pointer arithmetic 'x86nops+10' is out of bounds.

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Date:   Tue, 16 Mar 2021 09:27:03 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     kernel test robot <lkp@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [tip:x86/cpu 2/3] arch/x86/kernel/alternative.c:96:10: warning:
 Undefined behaviour, pointer arithmetic 'x86nops+10' is out of bounds.

Yet another useless report!

On Tue, Mar 16, 2021 at 07:50:10AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/cpu
> head:   301cddc21a157a3072d789a3097857202e550a24
> commit: a89dfde3dc3c2dbf56910af75e2d8b11ec5308f6 [2/3] x86: Remove dynamic NOP selection
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> 
> cppcheck possible warnings: (new ones prefixed by >>, may not real problems)

What's cppcheck?

That?

Description-en: tool for static C/C++ code analysis (CLI)
 Cppcheck is a command-line tool that tries to detect bugs that your


> >> arch/x86/kernel/alternative.c:96:10: warning: Undefined behaviour, pointer arithmetic 'x86nops+10' is out of bounds. [pointerOutOfBounds]
>     x86nops + 1 + 2 + 3 + 4,
>             ^
>    arch/x86/kernel/alternative.c:97:10: warning: Undefined behaviour, pointer arithmetic 'x86nops+15' is out of bounds. [pointerOutOfBounds]
>     x86nops + 1 + 2 + 3 + 4 + 5,
>             ^
>    arch/x86/kernel/alternative.c:98:10: warning: Undefined behaviour, pointer arithmetic 'x86nops+21' is out of bounds. [pointerOutOfBounds]
>     x86nops + 1 + 2 + 3 + 4 + 5 + 6,
>             ^
>    arch/x86/kernel/alternative.c:99:10: warning: Undefined behaviour, pointer arithmetic 'x86nops+28' is out of bounds. [pointerOutOfBounds]
>     x86nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
>             ^
> >> arch/x86/kernel/ftrace.c:304:7: warning: union member 'ftrace_op_code_union::code' is never used. [unusedStructMember]
>     char code[OP_REF_SIZE];
>          ^

How do you trigger this?

/me ignores it until there's some info on how those things can be
reproduced.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette