Using the host compiler in this case seems to be an artifact from an
older change. On x86_64, this approach ended in unsable hybrid binaries
due to incompatible handling of non-trivial return values, i.e.
structures. See '-freg-struct-return' in GCC manual page:
"[...] If there is no standard convention, GCC defaults to
-fpcc-struct-return, except on targets where GCC is the principal
compiler. In those cases, we can choose the standard, and we chose
the more efficient register return alternative."
In other words: All x86_64 Linux systems break the ABI standard :-(
The thread ID reported to core was not always initialized prior the RPC
call. The 'startup_lock' ensures that the thread is completely
initialized before this information gets propagated.
Since the recent move of the process creation into core, the original chroot trampoline
mechanism implemented in 'os/src/app/chroot' does not work anymore. A
process could simply escape the chroot environment by spawning a new
process via core's PD service. Therefore, this patch moves the chroot
support into core. So the chroot policy becomes mandatory part of the
process creation. For each process created by core, core checks for
'root' argument of the PD session. If a path is present, core takes the
precautions needed to execute the new process in the specified chroot
environment.
This conceptual change implies minor changes with respect to the Genode
API and the configuration of the init process. The API changes are the
enhancement of the 'Genode::Child' and 'Genode::Process' constructors to
take the root path as argument. Init supports the specification of a
chroot per process by specifying the new 'root' attribute to the
'<start>' node of the process. In line with these changes, the
'Loader::Session::start' function has been enhanced with the additional
(optional) root argument.
When building in hybrid Linux/Genode mode, there exist two definitions
of 'size_t', one in the 'Genode' namespace and one imported from the
glibc headers.
On Linux, we use the session label for naming the corresponding Linux
process. When looking up the processes via 'ps', the Genode process
hierarchy becomes immediately visible.
Genode used to create new processes by directly forking from the
respective Genode parent using the process library. The forking process
created a PD session at core merely for propagating the PID of the new
process into core (for later destruction). This traditional mechanisms
has the following disadvantages:
First, the PID reported by the creating process to core cannot easily be
validated by core. Therefore core has to trust the PD client to not
specify a PID of an existing process, which would happen to be killed
once the PD session gets destructed. This problem is documented by
issue #318. Second, there is no way for a Genode process to detect the
failure of its any grandchildren. The immediate parent of a faulting
process could use the SIGCHLD-and-waitpid mechanism to observe its
children but this mechanism does not work transitively.
By performing the process creation exclusively within core, all Genode
processes become immediate child processes of core. Hence, core can
respond to failures of any of those processes and reflect such
conditions via core's session interfaces. Furthermore, the PID
associated to a PD session is locally known within core and cannot be
forged anymore. In fact, there is actually no need at all to make
processes aware of any PIDs of other processes.
Please note that this patch breaks the 'chroot' mechanism that comes in
the form of the 'os/src/app/chroot' program. Because all processes are
forked from core, a chroot'ed process could sneak outside its chroot
environment by just creating a new Genode process. To address this
issue, the chroot mechanism must be added to core.
This patch simplifies the system call bindings. The common syscall
bindings in 'src/platform/' have been reduced to the syscalls needed by
non-core programs. The additional syscalls that are needed solely by
core have been moved to 'src/core/include/core_linux_syscalls.h'.
Furthermore, the resource path is not used outside of core anymore.
Hence, we could get rid of the rpath library. The resource-path code has
been moved to 'src/core/include/resource_path.h'. The IPC-related parts
of 'src/platform' have been moved to the IPC library. So there is now a
clean separation between low-level syscall bindings (in 'src/platform')
and higher-level code.
The code for the socket-descriptor registry is now located in the
'src/base/ipc/socket_descriptor_registry.h' header. The interface is
separated from 'ipc.cc' because core needs to access the registry from
outside the ipc library.
Thanks to the exclusive use of SCM rights for delegating access rights
to memory objects and RPC entrypoints, Genode processes outside of core
won't need to access any files.
This patch changes the way of how dataspace content is accessed by
processes outside of core. Dataspaces are opened by core only and the
corresponding file descriptors are handed out the other processes via
the 'Linux_dataspace::fd()' RPC function. At the client side, the
returned file descriptor is then used to mmap the file.
Consequently, this patch eliminates all files from 'lx_rpath'. The
path is still needed by core to temporarily create dataspaces and
unix domain sockets. However, those files are unlinked immediately
after their creation.
This patch alleviates the need for any non-core process to create Unix
domain sockets locally. All sockets used for RPC communication are
created by core and subsequently passed to the other processes via RPC
or the parent interface. The immediate benefit is that no process other
than core needs to access the 'rpath' directory in order to communicate.
However, access to 'rpath' is still needed for accessing dataspaces.
Core creates one socket pair per thread on demand on the first call of
the 'Linux_cpu_session::server_sd()' or 'Linux_cpu_session::client_sd()'
functions. 'Linux_cpu_session' is a Linux-specific extension to the CPU
session interface. In addition to the socket accessors, the extension
provides a mechanism to register the PID/TID of a thread. Those
information were formerly propagated into core along with the thread
name as argument to 'create_thread()'.
Because core creates socket pairs for entrypoints, it needs to know all
threads that are potential entrypoints. For lx_hybrid programs, we
hadn't had propagated any thread information into core, yet. Hence, this
patch also contains the code for registering threads of hybrid
applications at core.
This patch eliminates the thread ID portion of the 'Native_capability'
type. The access to entrypoints is now exclusively handled by passing
socket descripts over Unix domain sockets and by inheriting the socket
descriptor of the parent entrypoint at process-creation time.
Each entrypoint creates a socket pair. The server-side socket is bound
to a unique name defined by the server. The client-side socket is then
connected to the same name. Whereas the server-side socket is meant to
be exclusively used by the server to wait for incoming requests, the
client-side socket can be delegated to other processes as payload of RPC
messages (via SCM rights). Anyone who receives a capability over RPC
receives the client-side socket of the entrypoint to which the
capability refers. Given this socket descriptor, the unique name (as
defined by the server) can be requested using 'getpeername'. Using this
name, it is possible to compare socket descriptors, which is important
to avoid duplicates from polluting the limited socket-descriptor name
space.
Wheras this patch introduces capability-based delegation of access
rights to entrypoints, it does not cover the protection of the integrity
of RPC objects. RPC objects are still referenced by a global ID passed
as normal message payload.
This patch adds prinicipal support for transmitting socket descriptors
as RPC payload. Socket descriptors are handled by the linux-specific
implementation of the capability marshalling and unmarshalling functions
in 'ipc.h'. The 'Message' type in 'src/platform/linux_socket.h' has been
extended to carry multiple descriptors in a single message.
Unfortuately, we hit a problem (and potential show stopper) here:
lx_sendmsg failed with -109 in lx_call()
The error code corresponds to ETOOMANYREFS. There is only one place in
the Linux kernel where this error code is used (net/unix/af_unix.c).
The code for 'unix_attach_fds()' suggests that there is a limit with
regard to the maximum number of references for a given Unix domain
socket. When the error occurs, core and init are running. The socket
of core's server entrypoint is present in the '/proc/pid/fd' of those
processes 8 times. The error occurs when core tries to perform an
RPC to the entrypoint to perform 'Ram_session::transfer_quota()'
(base/include/base/child.h at line 248).
By storing the reply socket descriptor inside the 'Ipc_ostream::_dst'
capability instead as part of the connection state object, we can
use the 'explicit_reply' mechanism as usual. Right now, we store
both the tid and socket handle in 'Native_capability::Dst'. In the
final version, the 'tid' member will be gone.
In the final version, the 'socket' will be the only member to remain in
the 'Dst' time. In the transition phase, we store both the old 'tid' and
the 'socket'.
This patch, which was originally created by Christian Helmuth,
represents the first step towards using SCM rights as capability
mechanism on Linux. It employs the SCM rights mechanism for transmitting
a reply capability to the server as argument of each IPC call. The
server will then send its respond to this reply file descriptor. This
way, the reply channel does not need to be globally visible anymore.
The bash-builtin 'pwd' command uses the 'st_dev' and 'st_ino' members of
the 'stat' struct to compare the path from the 'PWD' environment variable
with the path returned by 'getcwd()'. These members don't get set
correctly in Noux and therefore the 'pwd' command sometimes returns wrong
results when building Genode in Noux. With this patch the 'CURDIR' make
variable gets used instead of calling 'pwd'.
Fixes#454.
With this patch an error message gets printed in
'Allocator_avl_base::free()' if the given address is not the start address
of the allocated block.
Fixes#459.
Create the signal context object before the signal receiver object to get the
signal receiver destroyed before the signal context. This avoids a 'specified
signal-context capability has wrong type' warning when the signal receiver
tries to free its managed context on destruction.
Part of #448.
When building the Fiasco.OC kernel, and L4Linux within the Genode build system,
forward the CC, and CXX variables. It might contain useful tools like ccache,
or distcc to speed up compilation. Moreover, don't delete the MAKEFLAGS when
building Fiasco.OC. It hinders parallel builds.
Certain symbols from the libgcc_eh library in cxx that is linked with the
L4Linux kernel were resolved by using kernel internal implementations.
This lead to errors because the complete Linux kernel is built regparm=3.
This patch prefixes the appropriate symbols in the Linux Kernel and its
modules. Moreover, it fixes some warnings introduced by the latest update
to gcc 4.7.
g++ 4.4.5 outputs the following warnings in our code using the loader
session:
.../base/include/base/capability.h: In member function 'typename Genode::Trait::Call_return<typename IF::Ret_type>::Type Genode::Capability<RPC_INTERFACE>::call() const [with IF = Loader::Session::Rpc_view_geometry, RPC_INTERFACE = Loader::Session]':
.../base/include/base/capability.h:207: warning: 'ret.Genode::Capability<Loader::Session>::Return<Loader::Session::Rpc_view_geometry>::_value.Loader::Session::View_geometry::width' may be used uninitialized in this function
.../base/include/base/capability.h:207: warning: 'ret.Genode::Capability<Loader::Session>::Return<Loader::Session::Rpc_view_geometry>::_value.Loader::Session::View_geometry::height' may be used uninitialized in this function
.../base/include/base/capability.h:207: warning: 'ret.Genode::Capability<Loader::Session>::Return<Loader::Session::Rpc_view_geometry>::_value.Loader::Session::View_geometry::buf_x' may be used uninitialized in this function
.../base/include/base/capability.h:207: warning: 'ret.Genode::Capability<Loader::Session>::Return<Loader::Session::Rpc_view_geometry>::_value.Loader::Session::View_geometry::buf_y' may be used uninitialized in this function
This is easily fixed with providing a default constructor.
Because of the C++ rules regarding initialer lists code that used
them for View_geometry had to be modified to use a normal construction
call. In my tests only Nitpicker had to be changed.
Preparation of base-pistachio fails on Ubuntu with dash as /bin/sh as it
does not support non-POSIX features like brace expansion. In this case
expanding in the Makefile via $(addprefix ...) fixes this shortcoming.
With the update to L4ka::Pistachio, we no longer need to patch the
contrib sources. Our patch went upstream in the meanwhile.
Apparently, gcc-4.7 is picky about specifying the '-melf_i386' argument
at the command line of the GCC frontend. We need to make sure to use the
'-Wl,' prefix.
The eglgears application depends on 'sqrt'. With the old tool chain,
this symbol was resolved through the dependencies of the 'gallium'
library. This does not work anymore for the new tool chain.
A similar issue arised for avplay, where we need to explicitly
state the av components in the LIBS declaration of the target.
