mirror of
https://github.com/genodelabs/genode.git
synced 2024-12-21 22:47:50 +00:00
ca971bbfd8
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
73 lines
3.3 KiB
Plaintext
73 lines
3.3 KiB
Plaintext
The C library of the Genode OS Framework is based on the code of FreeBSD. The
|
|
original code is available at the official FreeBSD website.
|
|
|
|
:FreeBSD website: [http://www.freebsd.org]
|
|
|
|
Currently, the libc supports the x86_32, x86_64 and ARM architectures. Support
|
|
for other architectures is planned as future addition.
|
|
|
|
Usage
|
|
-----
|
|
|
|
Before the libc is ready to use, the original FreeBSD source codes must be
|
|
downloaded and integrated with the Genode build system. The Makefile found
|
|
at the top level of the 'libports' repository automates this task. Please make
|
|
sure to have Subversion installed. Then issue the following command from
|
|
within the 'libports/' directory:
|
|
|
|
! make prepare PKG=libc
|
|
|
|
To use the libc in your application, add 'libc' to the 'LIBS' declaration in
|
|
your build-description file. This declaration will make the libc headers
|
|
available for the include path of your target and link the C library. When
|
|
building, make sure that the 'libports' repository is included in your build
|
|
configuration ('<build-dir>/etc/build.conf').
|
|
|
|
Limitations
|
|
-----------
|
|
|
|
The current version of the C library is not thread-safe. For most string and
|
|
math functions, this is not a problem (as these functions do not modify global
|
|
state) but be careful with using more complex functions such as 'malloc' from
|
|
multiple threads. Also, 'errno' may become meaningless when calling libc
|
|
functions from multiple threads.
|
|
|
|
We have left out the following files from the Genode port of the FreeBSD libc:
|
|
:gdtoa libary: 'strtodnrp.c'
|
|
:gen library: 'getosreldate.c'
|
|
:string libary: 'strcoll.c', 'strxfrm.c', 'wcscoll.c', 'wcsxfrm.c'
|
|
:math library: 's_exp2l.c'
|
|
|
|
In the ARM version, the following additional files are excluded:
|
|
:libm: 'e_acosl.c', 'e_asinl.c', 'e_atan2l.c', 'e_hypotl.c', 's_atanl.c',
|
|
's_cosl.c', 's_frexpl.c', 's_nextafterl.c', 's_nexttoward.c',
|
|
's_rintl.c', s_scalbnl.c', 's_sinl.c', 's_tanl.c', 's_fmal.c'
|
|
|
|
Atomic operation on ARM are not supported. Although these operations are
|
|
defined in 'machine/atomic.h', their original FreeBSD implementations are not
|
|
functional because we do not emulate the required FreeBSD environment (see:
|
|
'sysarch.h'). However, these functions are not a regular part of the libc
|
|
anyway and are not referenced from any other libc code.
|
|
|
|
The current back end is quite simplistic and it may help you to revisit the
|
|
current state of the implementation in the 'src/lib/libc' directory. If
|
|
one of the functions in 'dummies.c' is called, you will see an message in your
|
|
debug output:
|
|
! <function-name> called, not yet implemented!
|
|
However, some of the back-end function implemented in the other files have
|
|
dummy semantics but have to remain quiet because they are called from low-level
|
|
libc code.
|
|
|
|
Genode-specific additions
|
|
-------------------------
|
|
|
|
The back end of the libc is tailored to Genode via a flexible plugin concept.
|
|
This concept enables the combination of a variety of Genode-specific interfaces
|
|
with libc-based programs. For example, one program may want to use Genode's LOG
|
|
service as standard output whereas interactive programs might prefer the use of
|
|
Terminal sessions. Further available (entirely optional) back ends include a
|
|
BSD socket implementation based on the lwIP stack and a VFAT file-system back
|
|
end based on libffat. The interfaces used between plugins and the libc are
|
|
located at 'include/libc-plugin/'.
|
|
|