The 'noux_bash.run' script has become able to present the user with an
interactive bash shell for executing various coreutils programs. It is
still pretty limited, i.e., the environment is not correctly passed to
child processes and pipes are not supported. But bash and coreutils are
operational.
This patch removes the hardcoded parent cap for the new child by
introducing a facility called 'poke' similar to copy-to-user. This
change makes the fork mechanism kernel-agnostic. The 'noux_fork'
test works on L4/Fiasco, OKL4, NOVA, Fiasco.OC, and L4ka::Pistachio.
Linux is not supported yet.
The resource virtualization layer has been extended to support sub RM
sessions because this feature is used by the dynamic linker. Currently,
the address space of the forking process is copied eagerly. However,
different dataspace types are treated differently. For example, only RAM
dataspaces are copied but no ROM dataspaces.
At the libc side, a setjmp/longjmp-based trampoline mechanism is used to
implement the continuation of the main thread inside the new process.
This procedure is also responsible for re-establishing the relationship
to the new process' parent as well as its Noux session.
This version is still in flux and has many rough edges. It is tied to
OKL4 for now.
Because 'Noux::Child' implements several abstract Genode interfaces, the
'Genode::' prefix became almost ubiquitous, making the code harder to
read. By importing the 'Genode' namespace into the 'Noux' namespace,
this patch remedies this inconvenience.
To implement fork semantics, we need to customize the bootstrapping of
the newly created process, in particular the startup of the main thread.
The CPU session interface provides a suitable hook. By virtualizing the
CPU connection of the process to core, we can defer (and parametrize)
the startup of the main thread. Furthermore, this enables us to detect
illegal attempts by the Noux process to create threads in addition to
the main thread.
By letting Noux processes talk to service implementations local to the
Noux server, we can track RAM allocations and RM operations. This is
needed as a prerequisite to implement fork.
When reading the values of environment variables supplied via Genode
config mechanism, the XML attribute values were taken as is. On the libc
side, however, the values are processed using Genode's 'Arg_string'
functions. When unquoted, 'Arg_string' expects values to be either
identifiers or numbers. In the general case, however, env values cannot
be expected to satisfy these requirements. Hence, it is better to always
quote these values when reading the XML config. An alternative (maybe
better) solution would be to not use the 'Arg_string' classes in the
libc side.
