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

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

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On 06/15/2012 03:22 PM, Darren Hart wrote:
> 
> 
> 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.

Sorry, I hit the menuconfig/sstate bug. There is a 2560 byte
difference for including these two features. Seems reasonable to me. A
new patch has been sent to the list.

- --
Darren

> 
> -- Darren
> 
> 
>> otherwise second best thing is to keep it in poky-tiny distro 
>> layer which wants to set the policy
> 
>> _______________________________________________
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>
>> 
> 
> 
> _______________________________________________ Openembedded-core
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> 
- -- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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