linux-kernel - Re: [PATCH] bitmap: parse input from kernel and user buffers

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Date:	Thu, 5 Oct 2006 15:32:43 -0700 (PDT)
From:	"Inaky Perez-Gonzalez" <inaky@...ux.intel.com>
To:	"Reinette Chatre" <reinette.chatre@...ux.intel.com>
Cc:	"Andrew Morton" <akpm@...l.org>,
	"Inaky Perez-Gonzalez" <inaky@...ux.intel.com>,
	"Joe Korty" <joe.korty@...r.com>, "Paul Jackson" <pj@....com>,
	linux-kernel@...r.kernel.org, reinette.chatre@...ux.intel.com
Subject: Re: [PATCH] bitmap: parse input from kernel and user buffers


Reinette Chatre wrote:
> lib/bitmap.c:bitmap_parse() is a library function that received as
> input a user buffer. This seemed to have originated from the way
> the write_proc function of the /proc filesystem operates.
>
> This has been reworked to not use kmalloc and eliminates a lot
> of get_user() overhead by performing one access_ok before using
> __get_user().
> We need to test if we are in kernel or user space (is_user) and access
> the buffer differently. We cannot use __get_user() to access kernel
> addresses in all cases, for example in architectures with separate
> address space for kernel and user.
>
> This function will be useful for other uses as well; for example,
> taking input  for /sysfs instead of /proc, so it was changed to accept
> kernel buffers. We have this use for the Linux UWB project, as part
> as the upcoming bandwidth allocator code.
>
> Only a few routines used this function and they were changed too.
>
> Signed-off-by: Reinette Chatre <reinette.chatre@...ux.intel.com>
Signed-off-by: Inaky Perez-Gonzalez <inaky@...ux.intel.com>
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