linux-kernel - Re: [PATCH] powerpc/64s: Enhance the information in cpu_show_spectre

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Date:   Tue, 29 May 2018 15:24:42 +0000
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Michal Suchánek <msuchanek@...e.de>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Michael Neuling <mikey@...ling.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/64s: Enhance the information in
 cpu_show_spectre_v1()



On 05/29/2018 02:46 PM, Michal Suchánek wrote:
> On Tue, 29 May 2018 16:13:49 +0200
> Christophe LEROY <christophe.leroy@....fr> wrote:
> 
>> Le 28/05/2018 à 15:19, Michal Suchanek a écrit :
>>> We now have barrier_nospec as mitigation so print it in
>>> cpu_show_spectre_v1 when enabled.
>>>
>>> Signed-off-by: Michal Suchanek <msuchanek@...e.de>
>>> ---
>>>    arch/powerpc/kernel/security.c | 5 ++++-
>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/kernel/security.c
>>> b/arch/powerpc/kernel/security.c index 0239383c7e4d..a0c32d53980b
>>> 100644 --- a/arch/powerpc/kernel/security.c
>>> +++ b/arch/powerpc/kernel/security.c
>>> @@ -120,7 +120,10 @@ ssize_t cpu_show_spectre_v1(struct device
>>> *dev, struct device_attribute *attr, c if
>>> (!security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR)) return
>>> sprintf(buf, "Not affected\n");
>>> -	return sprintf(buf, "Vulnerable\n");
>>> +	if (barrier_nospec_enabled)
>>
>>> +		return sprintf(buf, "Mitigation: __user pointer
>>> sanitization\n");
>>> +	else
>>> +		return sprintf(buf, "Vulnerable\n");
>>
>> Checkpatch would tell you that an else is unneeded after a return. So
>> just leave it as it was before.
> 
> Where did you get your copy of checkpatch? The one in Linux tree does
> not do that.

Strange, it should, as checkpatch.pl includes the following code:

# check indentation of any line with a bare else
# (but not if it is a multiple line "if (foo) return bar; else return baz;")
# if the previous line is a break or return and is indented 1 tab more...
		if ($sline =~ /^\+([\t]+)(?:}[ \t]*)?else(?:[ \t]*{)?\s*$/) {
			my $tabs = length($1) + 1;
			if ($prevline =~ /^\+\t{$tabs,$tabs}break\b/ ||
			    ($prevline =~ /^\+\t{$tabs,$tabs}return\b/ &&
			     defined $lines[$linenr] &&
			     $lines[$linenr] !~ /^[ \+]\t{$tabs,$tabs}return/)) {
				WARN("UNNECESSARY_ELSE",
				     "else is not generally useful after a break or return\n" . 
$hereprev);
			}
		}


Anyway, you should remove that 'else' in your patch.
And the other sprintf line is over 80 characters.

Christophe

> 
> Thanks
> 
> Michal
>