From: Marc Gonzalez <marc_gonzalez@sigmadesigns.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Sebastian Frias <sebastian_frias@sigmadesigns.com>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: m(un)map kmalloc buffers to userspace
Date: Wed, 9 Dec 2015 15:07:50 +0100 [thread overview]
Message-ID: <566835B6.9010605@sigmadesigns.com> (raw)
In-Reply-To: <20151209135544.GE30907@dhcp22.suse.cz>
On 09/12/2015 14:55, Michal Hocko wrote:
> On Tue 08-12-15 18:25:31, Sebastian Frias wrote:
>> Hi,
>>
>> We are porting a driver from Linux 3.4.39+ to 4.1.13+, CPU is Cortex-A9.
>>
>> The driver maps kmalloc'ed memory to user space.
>
> This sounds like a terrible idea to me. Why don't you simply use the
> page allocator directly? Try to imagine what would happen if you mmaped
> a kmalloc with a size which is not page aligned? mmaped memory uses
> whole page granularity.
According to the source code, this kernel module calls
kmalloc(1 << 17, GFP_KERNEL | __GFP_REPEAT);
I suppose kmalloc() would return page-aligned memory?
(Note: the kernel module was originally written for 2.4 and was updated
inconsistently over the years.)
Regards.
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next prev parent reply other threads:[~2015-12-09 14:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-08 17:25 Sebastian Frias
2015-12-09 13:55 ` Michal Hocko
2015-12-09 14:07 ` Marc Gonzalez [this message]
2015-12-09 14:32 ` Michal Hocko
2015-12-09 14:53 ` Sebastian Frias
2015-12-09 15:12 ` Michal Hocko
2015-12-09 15:35 ` Sebastian Frias
2015-12-10 11:40 ` Michal Hocko
2015-12-10 12:04 ` Richard Weinberger
2015-12-10 13:37 ` Sebastian Frias
2015-12-10 14:06 ` Michal Hocko
2015-12-10 16:48 ` Sebastian Frias
2015-12-11 9:42 ` Michal Hocko
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