linux-kernel - Re: Question of resource

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Wed, 30 Dec 2009 12:04:07 +1100
From:	Ben Nizette <bn@...sdigital.com>
To:	me@...ipebalbi.com
Cc:	Joe Perches <joe@...ches.com>, linux-kernel@...r.kernel.org
Subject: Re: Question of resource_size() implementation


On 30/12/2009, at 11:16 AM, Felipe Balbi wrote:

> On Tue, 2009-12-29 at 16:12 -0800, Joe Perches wrote:
>> On Wed, 2009-12-30 at 01:43 +0200, Felipe Balbi wrote:
>>> I'm wondering whether the +1 in resource_size() is actually necessary.
>>> resource_size() is defined as:
>> []
>>> static inline resource_size_t resource_size(const struct resource *res)
>>> {
>>> 	return res->end - res->start + 1;
>>> }
>>> Are we off-by-one
>>> here ? Or is this all expected ?
>> 
>> Imagine you have 1 byte sized resources.
>> 
>> AREA1 = 0x40000000
>> AREA2 = 0x40000001
>> 
>> area1.start = 0x40000000
>> area1.end   = 0x40000000
>> 
>> area2.start = 0x40000001
>> area2.end   = 0x40000001
> 
> (adding lkml back to the loop)
> 
> in that you wouldn't use any of the SZ_* macros and simply hardcode
> start and end, right ? then you would define:
> 
> area1.start = 0x40000000
> area1.end = 0x40000001

No-o, you'd hardcode

area1.start=0x40000000
area1.end=0x40000000

As Joe wrote.  Then the resource_size would return 1 and ioremap would map the 1 byte starting at 0x400000000, i.e. just 0x400000000.  This is correct.

In your original example you had

		.start	= MEM_AREA1_BASE,
		.end	= MEM_AREA1_BASE + SZ_4K - 1

So resource_size would return SZ_4K and ioremap would map the SZ_4K bytes starting at MEM_AREA1_BASE, i.e. MEM_AREA1_BASE to MEM_AREA1_BASE - 1 /inclusive/.  This is also correct.

	--Ben.

--
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/