linux-kernel - Re: [PATCH v5 03/18] ACPI / table: Count matched and successfully parsed entries without specifying max entries

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <54734844.1070505@linaro.org>
Date:	Mon, 24 Nov 2014 16:01:24 +0100
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Hanjun Guo <hanjun.guo@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>,
	Olof Johansson <olof@...om.net>,
	Grant Likely <grant.likely@...aro.org>,
	Will Deacon <will.deacon@....com>,
	Graeme Gregory <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Jon Masters <jcm@...hat.com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <marc.zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles.Garcia-Tobin@....com, Kangkang.Shen@...wei.com,
	linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org
Subject: Re: [PATCH v5 03/18] ACPI / table: Count matched and successfully
 parsed entries without specifying max entries

On 24.11.2014 16:16, Rafael J. Wysocki wrote:
> On Monday, November 24, 2014 09:34:24 AM Tomasz Nowicki wrote:
>> On 24.11.2014 02:45, Rafael J. Wysocki wrote:
>>> On Friday, October 17, 2014 09:36:59 PM Hanjun Guo wrote:
>>>> From: Tomasz Nowicki <tomasz.nowicki@...aro.org>
>>>>
>>>> It is very useful to traverse all available table entries without max
>>>> number of expected entries type. Current acpi_parse_entries()
>>>> implementation gives that feature but it does not count those entries,
>>>> it returns 0 instead, so fix it to count matched and successfully
>>>> entries and return it.
>>>
>>> Hmm.  I guess that the goal is for count to only be incremented when the
>>> condition is satisfied entirely, while without the patch it may be incremented
>>> even if that isn't the case.
>>
>> That would be our goal if patch would look like:
>> -		    && (!max_entries || count++ < max_entries))
>> +		    && (!max_entries && count++ < max_entries)) {
>> but then we can not walk through all available entries (with max_entries==0)
>
> No, that's not what I was trying to say. :-)
>
>>>
>>> I'm not sure how that is related to the above paragraph, however.
>>>
>>
>> Previous changelog is not clear, let me rewrite it:
>>
>> acpi_parse_entries() allows to traverse all available table entries (aka
>> subtables) by passing max_entries parameter equal to 0. But for that use
>> case acpi_parse_entries() does not inform caller how many entries were
>> matched and for how many entries handler was run against. That patch is
>> going to fix it.
>
> Do I understand correctly that count is only ever incremented by current code
> if max_entries is different from 0?

Right. Currently "count" is incremented only if max_entries > 0.

Tomasz

>
>
>>>> NOTE: This change has no impact to x86 and ia64 archs since existing code
>>>> checks for error occurrence only (acpi_parse_entries(...,0) < 0).
>>>>
>>>> Acked-by: Grant Likely <grant.likely@...aro.org>
>>>> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@...aro.org>
>>>> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
>>>> ---
>>>>    drivers/acpi/tables.c |    5 ++++-
>>>>    1 file changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
>>>> index 21ae521..b18e45e 100644
>>>> --- a/drivers/acpi/tables.c
>>>> +++ b/drivers/acpi/tables.c
>>>> @@ -225,10 +225,13 @@ acpi_parse_entries(unsigned long table_size,
>>>>    	while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
>>>>    	       table_end) {
>>>>    		if (entry->type == entry_id
>>>> -		    && (!max_entries || count++ < max_entries))
>>>> +		    && (!max_entries || count < max_entries)) {
>>>>    			if (handler(entry, table_end))
>>>>    				return -EINVAL;
>>>>
>>>> +			count++;
>>>> +		}
>>>> +
>>>>    		/*
>>>>    		 * If entry->length is 0, break from this loop to avoid
>>>>    		 * infinite loop.
>>>>
>>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
>> the body of a message to majordomo@...r.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/