On Linux, Genode used to represent each RPC object by a socket
descriptor of the receiving thread (entrypoint) and a globally-unique
value that identifies the object. Because the latter was transferred as
plain message payload, clients had to be trusted to not forge the
values. For this reason, Linux could not be considered as a productive
Genode base platform but remained merely a development vehicle.
This patch changes the RPC mechanism such that each RPC object is
represented by a dedicated socket pair. Entrypoints wait on a set of
the local ends of the socket pairs of all RPC objects managed by the
respective entrypoint. The epoll kernel interface is used as the
underlying mechanism to wait for a set of socket descriptors at the
server side.
When delegating a capability, the remote end of the socket pair is
transferred to the recipient along with a plaintext copy of the
socket-descriptor value of the local end. The latter value serves as a
hint for re-identifiying a capability whenever it is delegated back to
its origin. Note that the client is not trusted to preserve this
information. The integrity of the hint value is protected by comparing
the inode values of incoming and already present capablities at the
originating site (whenever the capability is invoked or presented to the
owner of the RPC object).
The new mechanism effectively equips base-linux with Genode's capablity
model as described in the Chapter 3 of the Genode Foundations book.
That said, the sandboxing of components cannot be assumed at this point
because each component has still direct access to the Linux system-call
interface.
This patch is based on the extensive exploration work conducted by
Stefan Thoeni who strongly motivated the inclusion of this feature into
Genode.
Issue #3581
This patch replaces the former prominent use of pointers by references
wherever feasible. This has the following benefits:
* The contract between caller and callee becomes more obvious. When
passing a reference, the contract says that the argument cannot be
a null pointer. The caller is responsible to ensure that. Therefore,
the use of reference eliminates the need to add defensive null-pointer
checks at the callee site, which sometimes merely exist to be on the
safe side. The bottom line is that the code becomes easier to follow.
* Reference members must be initialized via an object initializer,
which promotes a programming style that avoids intermediate object-
construction states. Within core, there are still a few pointers
as member variables left though. E.g., caused by the late association
of 'Platform_thread' objects with their 'Platform_pd' objects.
* If no pointers are present as member variables, we don't need to
manually provide declarations of a private copy constructor and
an assignment operator to avoid -Weffc++ errors "class ... has
pointer data members [-Werror=effc++]".
This patch also changes a few system bindings on NOVA and Fiasco.OC,
e.g., the return value of the global 'cap_map' accessor has become a
reference. Hence, the patch touches a few places outside of core.
Fixes#3135
This patch establishes the sole use of generic headers across all
kernels. The common 'native_capability.h' is based on the version of
base-sel4. All traditional L4 kernels and Linux use the same
implementation of the capability-lifetime management. On base-hw, NOVA,
Fiasco.OC, and seL4, custom implementations (based on their original
mechanisms) are used, with the potential to unify them further in the
future.
This change achieves binary compatibility of dynamically linked programs
across all kernels.
Furthermore, the patch introduces a Native_capability::print method,
which allows the easy output of the kernel-specific capability
representation using the base/log.h API.
Issue #1993
This patch moves the thread operations from the 'Cpu_session'
to the 'Cpu_thread' interface.
A noteworthy semantic change is the meaning of the former
'exception_handler' function, which used to define both, the default
exception handler or a thread-specific signal handler. Now, the
'Cpu_session::exception_sigh' function defines the CPU-session-wide
default handler whereas the 'Cpu_thread::exception_sigh' function
defines the thread-specific one.
To retain the ability to create 'Child' objects without invoking a
capability, the child's initial thread must be created outside the
'Child::Process'. It is now represented by the 'Child::Initial_thread',
which is passed as argument to the 'Child' constructor.
Fixes#1939
This patch unifies the CPU session interface across all platforms. The
former differences are moved to respective "native-CPU" interfaces.
NOVA is not covered by the patch and still relies on a custom version of
the core-internal 'cpu_session_component.h'. However, this will soon be
removed once the ongoing rework of pause/single-step on NOVA is
completed.
Fixes#1922
