Re: [PATCH 2/3] busybox: Add setsid and cttyhack for tiny DISTRO_FEATURE

[Darren Hart <dvhart@linux.intel.com>]

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On 06/14/2012 12:05 AM, Khem Raj wrote:
> On 6/13/2012 10:19 PM, Darren Hart wrote:
>> When building very small systems, it can be useful to spawn a
>> shell from a simple init script, rather than a full System V Init
>>  process. This requires the shell be the session leader and be
>> able to open the controlling terminal if it is to have job
>> control.
> 
>> Enable CONFIG_CTTYHACK and CONFIG_SETSID to enable this for 
>> distros defining the "tiny" DISTRO_FEATURE.
> 
>> Signed-off-by: Darren Hart <dvhart@linux.intel.com> CC: OE Core 
>> <openembedded-core@lists.openembedded.org> --- 
>> meta/recipes-core/busybox/busybox.inc |    2 ++ 1 files changed,
>> 2 insertions(+), 0 deletions(-)
> 
>> diff --git a/meta/recipes-core/busybox/busybox.inc 
>> b/meta/recipes-core/busybox/busybox.inc index 5b83d32..d07ba7e 
>> 100644 --- a/meta/recipes-core/busybox/busybox.inc +++ 
>> b/meta/recipes-core/busybox/busybox.inc @@ -57,6 +57,8 @@ def 
>> features_to_busybox_settings(d): busybox_cfg('nls', 
>> distro_features, 'CONFIG_LOCALE_SUPPORT', cnf, rem) 
>> busybox_cfg('ipv4', distro_features, 
>> 'CONFIG_FEATURE_IFUPDOWN_IPV4', cnf, rem) busybox_cfg('ipv6', 
>> distro_features, 'CONFIG_FEATURE_IFUPDOWN_IPV6', cnf, rem) + 
>> busybox_cfg('tiny', distro_features, 'CONFIG_SETSID', cnf, rem)
>> + busybox_cfg('tiny', distro_features, 'CONFIG_CTTYHACK', cnf,
>> rem) return "\n".join(cnf), "\n".join(rem)
> 
>> # X, Y = ${@features_to_uclibc_settings(d)}
> 
> Enabling cttyhack and setsid could be a good thing in general 
> (thinking of initramfs kind of images) so I would propose to enable
> it by default and not introduce another distro knob here. How much
> does busybox code size grow which these two features turned on.?

So this struck me as strange, but I did it twice to make sure I didn't
mess something up:

BEFORE
- -rwxr-xr-x 1 dvhart dvhart 2799417 2012-06-15 15:06 busybox
- -rwxr-xr-x 1 dvhart dvhart 547872 2012-06-15 15:06 busybox_stripped

AFTER (w/ SETSID and CTTYHACK)
- -rwxr-xr-x 1 dvhart dvhart 2805195 2012-06-15 14:45 busybox
- -rwxr-xr-x 1 dvhart dvhart 547872 2012-06-15 15:05 busybox_stripped

DELTA
         busybox: 5778
busybox_stripped: 0

The difference is <6k for the unstripped binary, and 0 bytes for the
stripped binary. It must have something to do with the way busybox
builds and enables features. The above was using my host strip
command. I also tried building the rootfs with and without these
features and comparing the cross-stripped binaries in the rootfs,
delta is also 0 bytes.

So the cost is "negligible" and there is a clear advantage to having
these two options enabled. I'll resend with a two line change to the
defconfig to enable them.

- --
Darren

> 
> otherwise second best thing is to keep it in poky-tiny distro
> layer which wants to set the policy
> 
> _______________________________________________ Openembedded-core
> mailing list Openembedded-core@lists.openembedded.org 
> http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/openembedded-core
>
> 
- -- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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