On 02/21/2013 06:12 PM, Doug Goldstein wrote:
On Thu, Feb 21, 2013 at 12:42 PM, Anthony G. Basile
<[email protected]> wrote:
Hi everyone,
This issue has come up in a few bugs so I want to bounce it off the
community. When building packages that need a configured kernel source
tree, many ebuilds inherit linux-info to find configuration info about the
kernel. However, there is the running kernel with its configuration
(/proc/config.gz if it exists), there is the kernel source tree
(/usr/src/linux if it exists and is configured) and both of these can be of
a different version than linux-headers. Since building modules consumes
headers from /usr/include/linux, but uses code from /usr/src/linux and then
these modules are expected to insmod against the running kernel, all of
which can be mismatched, we have a lot of room for breakage. Eg. bug
#458014.
Any ideas about how to deal cleanly with situations like that?
--
Anthony G. Basile, Ph. D.
Chair of Information Technology
D'Youville College
Buffalo, NY 14201
(716) 829-8197
Kernel modules never use /usr/include/linux. That's the uapi headers,
which are now broken out in 3.7 and newer. Kernel modules always use
/usr/src/linux.
There have been a number of issues with the differences between the
user space bits and the kernel space bits wrt to netfilter post 3.0,
so its not surprising that a userspace component is trying to use
/usr/include/linux to frame up a structure to pass into kernel space
via netlink and running into an issue.
This is one of the reasons behind kapi/uapi to make it clear you
shouldn't play with or touch this field/structure/value from user
space.
I'm not sure the separation is so clean. I know userland should only
use /usr/include/linux, but modules could source both indirectly via an
include from /usr/include/linux [1].
But there's still the issue between the running kernel and
/usr/src/linux? In the eclass, linux_config_path() first tries to find
/usr/src/linux/.config and then falls back on /proc/config.gz. This is
too hackly since packages building kernel modules could use the wrong
config file.
Ref.
[1] Take a look at Pablo's rewrite of a patch I submitted to get
<linux/netfilter_ipv4/nf_nat.h> into the kernel:
http://www.spinics.net/lists/netfilter-devel/msg19833.html
There he includes in <linux/netfilter_ipv4/nf_nat.h>
/usr/src/linux/include/net/netfilter/nf_conntrack_tuple.h
So even though the later is kapi, the division from uapi is not so clean.
--
Anthony G. Basile, Ph. D.
Chair of Information Technology
D'Youville College
Buffalo, NY 14201
(716) 829-8197
