setpriv: dump inheritable capability set

setpriv: dump inheritable capability set

The setpriv executable from util-linux also dumps out information on the
different capability sets known by the kernel. By default, these are the
inheritable capabilities, bounding capabilities and (not yet released)
the ambient capabilities, which have been introduced with Linux 4.3.
This patch introduces the ability to dump the set of inheritable
capabilities.

By default, setpriv(1) identifies capabilities by their human-readable
name, for example 'net_admin'. For unknown capabilities, though, it does
instead use the capability's value, for example 'cap_12', which is
equivalent to 'net_admin'. As there is no kernel interface to retrieve
capability names by their index, we have to declare these ourselves,
which adds to setpriv's size.

To counteract, using the human-readble name has been made configurable.
The following sizes are with the 'FEATURE_SETPRIV_CAPABILITY_NAMES'
enabled:

function                                             old     new   delta
.rodata                                           145969  146405    +436
setpriv_main                                         467     842    +375
capabilities                                           -     304    +304

And with 'FEATURE_SETPRIV_CAPABILITY_NAMES' disabled:

function                                             old     new   delta
setpriv_main                                         467     838    +371
.rodata                                           145969  146101    +132

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>