This patch replaces exceptions of the PD session RPC interface with
result types.
The change of the quota-transfer RPC functions required the adaptation
of base/quota_transfer.h and base/child.h.
The 'alloc_signal_source' method has been renamed to 'signal_source'
to avoid an exceedingly long name of the corresponding result type.
The Pd_session::map function takes a 'Virt_range' instead of basic-type
arguments.
The 'Signal_source_capability' alias for 'Capability<Signal_source>' has
been removed.
Issue #5245
The new 'Env::try_session' method mirrors the existing 'Env::session'
without implicitly handling exceptions of the types 'Out_of_ram',
'Out_of_caps', 'Insufficient_ram_quota', and 'Insufficient_cap_quota'.
It enables runtime environments like init to reflect those exceptions to
their children instead of paying the costs of implicit session-quota
upgrades out of the own pocket.
By changing the 'Parent_service' to use 'try_session', this patch fixes
a resource-exhaustion problem of init in Sculpt OS that occurred when
the GPU multiplexer created a large batch of IO_MEM sessions, with each
session requiring a second attempt with the session quota upgraded by
4 KiB.
Issue #3767
This patch extracts the child-management functionality from the init
component into a new library called "sandbox". The library API is
located at 'os/include/os/sandbox.h'.
The sandbox API allows for the interaction of the component with the
sandboxed children by providing locally implemented services. This
mechanism is illustrated by the new test at os/src/test/sandbox.
Issue #3601
