[Buildroot] bug when doing clean kernel build?

[Buildroot] bug when doing clean kernel build?

[Kyle Hayes]

I'm not sure if this is a code bug or a user bug :-)

I'm trying to repeat my problems with openssh segfaulting and to do
that I'm trying to build with make xconfig; make clean; make.
However, when I do this, I see that the Linux kernel, 2.6.37, is made
with Pentium Pro selected and I explicitly selected i486 in the
Buildroot config.  I can go in after the make finishes and reconfigure
the kernel again to get the right processor type.  Is this expected
behavior?

Best,
Kyle

[Buildroot] bug when doing clean kernel build?

[Will Moore]

Hi Kyle,

> -----Original Message-----
> From: buildroot-bounces at busybox.net [mailto:buildroot-bounces at busybox.net]
> On Behalf Of Kyle Hayes
> Sent: 17 January 2011 21:01
> 
> I'm not sure if this is a code bug or a user bug :-)
> 
> I'm trying to repeat my problems with openssh segfaulting and to do
> that I'm trying to build with make xconfig; make clean; make.
> However, when I do this, I see that the Linux kernel, 2.6.37, is made
> with Pentium Pro selected and I explicitly selected i486 in the
> Buildroot config.  I can go in after the make finishes and reconfigure
> the kernel again to get the right processor type.  Is this expected
> behavior?

FWIW I believe configuring buildroot with i486 processor builds you a
toolchain for an i486.  A i486 toolchain seems to work well for me on a
vortex86dx.

I tend to configure buildroot to pick up a kernel config:

 make menuconfig

Select "Kernel" then "Linux Kernel".
Select "Kernel configuration (Using a defconfig)" and select "Using a custom
config file".
Select "() Configuration file path" and enter the path to your desired
kernel config.

Others with a better understanding can tell you if what you are experiencing
might be considered a bug...

X-Linux provided kernel configs changed (quite considerably) between v5.6
and v5.7 as to quite what processor / processor features they declare the
vortex86dx to have, the same may be true for the vortex86mx.  Perhaps you
can gain some understanding from a diff of these?

Regards,

Will

> 
> Best,
> Kyle
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

[Buildroot] bug when doing clean kernel build?

[Thomas Petazzoni]

Hello Kyle,

On Mon, 17 Jan 2011 13:01:09 -0800
Kyle Hayes <kyle@greenmonitor.com> wrote:

> I'm trying to repeat my problems with openssh segfaulting and to do
> that I'm trying to build with make xconfig; make clean; make.
> However, when I do this, I see that the Linux kernel, 2.6.37, is made
> with Pentium Pro selected and I explicitly selected i486 in the
> Buildroot config.  I can go in after the make finishes and reconfigure
> the kernel again to get the right processor type.  Is this expected
> behavior?

We do not adjust the CPU selection at the kernel configuration level
according to the CPU selection at the Buildroot level. There is not
necessarly a 1:1 mapping between the two option sets, and it would
require a large amount of boring and unmaintainable code. So we leave
it to the user to provide a kernel configuration that matches the CPU
type being used.

When given a kernel defconfig file, or a kernel configuration file, the
only two configuration modifications that Buildroot does are :

 * Adjust the ARM EABI options according to the ABI selected at
   Buildroot level. This is specific to the ARM architecture.

 * Adjust the initramfs options in case the initramfs filesystem type
   has been choosen.

Other than those two, the defconfig or the configuration file are used
as is.

Generally speaking, it's hardly doable to make sure automatically that
the Buildroot configuration matches the kernel configuration, and do
that properly. You're talking about the CPU selection, but we could
also say that if the user selected the "iptables" userspace package,
then we should also enable Netfilter in the kernel, if the user
selected the "i2c-tools" userspace package, then we should also enable
I2C support (but which drivers ?). As this is not possible, we leave it
to the user to provide a correct configuration.

Buildroot does not do everything automagically. It only automates the
build procedure, but leaves the work of configuring the system to the
system developer.

Regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com