On Linux, we want to attach additional attributes to processes, i.e.,
the chroot location, the designated UID, and GID. Instead of polluting
the generic code with such Linux-specific platform details, I introduced
the new 'Native_pd_args' type, which can be customized for each
platform. The platform-dependent policy of init is factored out in the
new 'pd_args' library.
The new 'base-linux/run/lx_pd_args.run' script can be used to validate
the propagation of those attributes into core.
Note that this patch does not add the interpretation of the new UID and
PID attributes by core. This will be subject of a follow-up patch.
Related to #510.
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.
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.
This patch replaces the first attempt to resolve the ambiguity of using
the size_t type that occurred when 'loader_session.h' was included
alongside libc headers. Instead of explicitly qualifying each occurrence
of the type, the new solution defines 'size_t' within the 'Loader' namespace.
Fixes#253
The compiler complained about ambigous references when compiling a
lx_hybrid program using the loader session. Here are some error
messages:
genode/os/include/loader_session/loader_session.h:72: error: reference to 'size_t' is ambiguous
/usr/lib/gcc/i486-linux-gnu/4.4.5/include/stddef.h:211: error: candidates are: typedef unsigned int size_t
genode/base/include/base/stdint.h:25: error: typedef unsigned int Genode::size_t
genode/os/include/loader_session/loader_session.h:72: error: reference to 'size_t' is ambiguous
/usr/lib/gcc/i486-linux-gnu/4.4.5/include/stddef.h:211: error: candidates are: typedef unsigned int size_t
genode/base/include/base/stdint.h:25: error: typedef unsigned int Genode::size_t
...
This commit qualifies size_t using the Genode namespace which fixes
the compilation.
The original loader service was primarily motivated by the
browser-plugin scenario presented on our live CD. The new version
implements a more general session interface, which widens the
application scope of the service and, at the same time, reduces its
implementation complexity.
The complexity reduction is achieved by removing the original limitation
of supplying the new sub system as a single binary blob only. The server
used to implement heuristics and functionality for dealing with
different kinds of blobs such as ELF images or TAR archives. This has
been replaced by a session-local ROM service, which can be equipped with
an arbitrary number of ROM modules supplied by the loader client prior
starting the new sub system. Even though the TAR support has been
removed, a separate instance of the 'tar_rom' service can be used within
the subsystem to provide the formerly built-in functionality.
