linux-kernel - Re: [PATCH] scripts/decodecode: fix trapping instruction formatting

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Date:   Mon, 20 Apr 2020 10:59:55 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ivan Delalande <colona@...sta.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] scripts/decodecode: fix trapping instruction formatting

On Sun, Apr 19, 2020 at 03:36:53PM -0700, Ivan Delalande wrote:
> If the trapping instruction contains a ':', for a memory access through
> segment registers for example, the sed substitution will insert the '*'
> marker in the middle of the instruction instead of the line address:
> 
> 	2b:   65 48 0f c7 0f          cmpxchg16b %gs:*(%rdi)          <-- trapping instruction
> 
> I started to think I had forgotten some quirk of the assembly syntax
> before noticing that it was actually coming from the script. Fix it to
> add the address marker at the right place for these instructions:
> 
> 	28:   49 8b 06                mov    (%r14),%rax
> 	2b:*  65 48 0f c7 0f          cmpxchg16b %gs:(%rdi)           <-- trapping instruction
> 	30:   0f 94 c0                sete   %al
> 
> Fixes: 18ff44b189e2 ("scripts/decodecode: make faulting insn ptr more robust")
> Signed-off-by: Ivan Delalande <colona@...sta.com>
> ---
>  scripts/decodecode | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/scripts/decodecode b/scripts/decodecode
> index ba8b8d5834e6..fbdb325cdf4f 100755
> --- a/scripts/decodecode
> +++ b/scripts/decodecode
> @@ -126,7 +126,7 @@ faultlinenum=$(( $(wc -l $T.oo  | cut -d" " -f1) - \
>  faultline=`cat $T.dis | head -1 | cut -d":" -f2-`
>  faultline=`echo "$faultline" | sed -e 's/\[/\\\[/g; s/\]/\\\]/g'`
>  
> -cat $T.oo | sed -e "${faultlinenum}s/^\(.*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
> +cat $T.oo | sed -e "${faultlinenum}s/^\([^:]*:\)\(.*\)/\1\*\2\t\t<-- trapping instruction/"
>  echo
>  cat $T.aa
>  cleanup
> -- 

Nice catch, thanks.

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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