This patch implements 'execve' in Genode's libc.
The mechanism relies on the dynamic linker's ability to replace the
loaded binary while keeping crucial libraries - in particular the libc -
intact. The state outside the libc is wiped. For this reason, all libc
internal state needed beyond the 'execve' call must be allocated on a
heap separate from the application-owned malloc heap. E.g.,
libc-internal file-descriptor objects must not be allocated or refer to
any memory object allocated from the malloc heap.
Issue #3481
The libc already supports the configuration of 'stdin', 'stdout', and
'stderr' using '<libc>' config attributes. This patch equips the libc
with the additional ability to pre-initialize any other file descriptor.
A file descriptor is configured as follows:
<config>
...
<libc ...>
<fd id="3" path="/dev/log" writeable="yes" readable="no" seek="10"/>
...
</libc>
</config>
Furthermore, this patch moves the FD initialization code from the VFS
plugin to the libc kernel initialization because opening the FDs
depends on 'malloc' ('strdup'), which should not be used at early
'Libc::Kernel' initialization time.
Issue #3478
This patch replaces the former use of an Allocator_avl with the Id_space
utility, which is safer to use and allows for the iteration of all
elements. The iteration over open file descriptors is needed for
implementing 'fork'.
Issue #3478
Besides adapting the components to the use of base/log.h, the patch
cleans up a few base headers, i.e., it removes unused includes from
root/component.h, specifically base/heap.h and
ram_session/ram_session.h. Hence, components that relied on the implicit
inclusion of those headers have to manually include those headers now.
While adjusting the log messages, I repeatedly stumbled over the problem
that printing char * arguments is ambiguous. It is unclear whether to
print the argument as pointer or null-terminated string. To overcome
this problem, the patch introduces a new type 'Cstring' that allows the
caller to express that the argument should be handled as null-terminated
string. As a nice side effect, with this type in place, the optional len
argument of the 'String' class could be removed. Instead of supplying a
pair of (char const *, size_t), the constructor accepts a 'Cstring'.
This, in turn, clears the way let the 'String' constructor use the new
output mechanism to assemble a string from multiple arguments (and
thereby getting rid of snprintf within Genode in the near future).
To enforce the explicit resolution of the char * ambiguity, the 'char *'
overload of the 'print' function is marked as deleted.
Issue #1987
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
