linux-kernel - Re: [PATCH] x86/hw_breakpoints: Return -EINVAL in default case in hw_breakpoint_arch

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Message-ID: <CAKwvOdkjoavonG0siOmUq4X-Qngvkn3JHcQ3Hee_h2wJ1AZjeg@mail.gmail.com>
Date:   Thu, 7 Mar 2019 16:53:34 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] x86/hw_breakpoints: Return -EINVAL in default case in hw_breakpoint_arch_parse

On Thu, Mar 7, 2019 at 1:28 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> When building with -Wsometimes-uninitialized, Clang warns:
>
> arch/x86/kernel/hw_breakpoint.c:355:2: warning: variable 'align' is used
> uninitialized whenever switch default is taken
> [-Wsometimes-uninitialized]
>
> It's not wrong but we can see that arch_build_bp_info will only ever
> initialize hw->len to one of the specified switch cases. We can easily
> silence Clang by just returning -EINVAL in the default case so that we
> can never use align without initializing it first.

And the call site just bubbles up return codes anyways.  Thanks for sending.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

>
> Link: https://github.com/ClangBuiltLinux/linux/issues/392
> Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---
>  arch/x86/kernel/hw_breakpoint.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c
> index ff9bfd40429e..d73083021002 100644
> --- a/arch/x86/kernel/hw_breakpoint.c
> +++ b/arch/x86/kernel/hw_breakpoint.c
> @@ -354,6 +354,7 @@ int hw_breakpoint_arch_parse(struct perf_event *bp,
>  #endif
>         default:
>                 WARN_ON_ONCE(1);
> +               return -EINVAL;
>         }
>
>         /*
> --
> 2.21.0
>


-- 
Thanks,
~Nick Desaulniers