linux-kernel - Re: [PATCH v2 1/4] bug: Remove redundant condition check in report

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Date:   Tue, 23 Feb 2021 11:25:12 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Andrew Scull <ascull@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        julien.thierry.kdev@...il.com, will@...nel.org,
        catalin.marinas@....com, kernel-team@...roid.com,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v2 1/4] bug: Remove redundant condition check in
 report_bug

On Tue, 23 Feb 2021 15:57:56 +0000
Andrew Scull <ascull@...gle.com> wrote:

> report_bug() will return early if it cannot find a bug corresponding to
> the provided address. The subsequent test for the bug will always be
> true so remove it.

Fixes: 1b4cfe3c0a30d ("lib/bug.c: exclude non-BUG/WARN exceptions from report_bug()")

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> 
> Signed-off-by: Andrew Scull <ascull@...gle.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> ---
>  lib/bug.c | 33 +++++++++++++++------------------
>  1 file changed, 15 insertions(+), 18 deletions(-)
> 
> diff --git a/lib/bug.c b/lib/bug.c
> index 7103440c0ee1..4ab398a2de93 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -158,30 +158,27 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
>  
>  	file = NULL;
>  	line = 0;
> -	warning = 0;
>  
> -	if (bug) {
>  #ifdef CONFIG_DEBUG_BUGVERBOSE
>  #ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
> -		file = bug->file;
> +	file = bug->file;
>  #else
> -		file = (const char *)bug + bug->file_disp;
> +	file = (const char *)bug + bug->file_disp;
>  #endif
> -		line = bug->line;
> +	line = bug->line;
>  #endif
> -		warning = (bug->flags & BUGFLAG_WARNING) != 0;
> -		once = (bug->flags & BUGFLAG_ONCE) != 0;
> -		done = (bug->flags & BUGFLAG_DONE) != 0;
> -
> -		if (warning && once) {
> -			if (done)
> -				return BUG_TRAP_TYPE_WARN;
> -
> -			/*
> -			 * Since this is the only store, concurrency is not an issue.
> -			 */
> -			bug->flags |= BUGFLAG_DONE;
> -		}
> +	warning = (bug->flags & BUGFLAG_WARNING) != 0;
> +	once = (bug->flags & BUGFLAG_ONCE) != 0;
> +	done = (bug->flags & BUGFLAG_DONE) != 0;
> +
> +	if (warning && once) {
> +		if (done)
> +			return BUG_TRAP_TYPE_WARN;
> +
> +		/*
> +		 * Since this is the only store, concurrency is not an issue.
> +		 */
> +		bug->flags |= BUGFLAG_DONE;
>  	}
>  
>  	/*