From e3e88e1d86c21be4bd359c620f4bb20474b9a280 Mon Sep 17 00:00:00 2001 From: Sebastian Huber Date: Mon, 26 Jun 2017 09:36:56 +0200 Subject: Add CONTRIBUTING.md --- CONTRIBUTING.md | 305 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 305 insertions(+) create mode 100644 CONTRIBUTING.md (limited to 'CONTRIBUTING.md') diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md new file mode 100644 index 00000000..6afae337 --- /dev/null +++ b/CONTRIBUTING.md @@ -0,0 +1,305 @@ +Guidelines for Developing and Contributing Code +=============================================== + +Introduction +------------ + +This guide aims to help developing and contributing code to the libbsd. One +goal of the libbsd is to stay in synchronization with FreeBSD. This is only +feasible if certain rules are in place. Otherwise, managing more than a +thousand imported source files will become too labour intensive eventually. + +What is in the Git Repository +----------------------------- + +The libbsd a self-contained kit with FreeBSD and RTEMS components pre-merged. +The Waf wscript in libbsd is automatically generated. + +Any changes to source in the `freebsd` directories will need to be merged +upstream into our master FreeBSD checkout, the `freebsd-org` submodule. + +The repository contains two FreeBSD source trees. In the `freebsd` directory +are the so called *managed* FreeBSD sources used to build the BSD library. The +FreeBSD source in `freebsd-org` is the *master* version. The +`freebsd-to-rtems.py` script is used to transfer files between the two trees. +In general terms, if you have modified managed FreeBSD sources, you will need +to run the script in *revert* or *reverse* mode using the `-R` switch. This +will copy the source back to your local copy of the master FreeBSD source so +you can run `git diff` against the upstream FreeBSD source. If you want to +transfer source files from the master FreeBSD source to the manged FreeBSD +sources, then you must run the script in *forward* mode (the default). + +Organization +------------ + +The top level directory contains a few directories and files. The following +are important to understand + +* `freebsd-to-rtems.py` - script to convert to and free FreeBSD and RTEMS trees, +* `create-kernel-namespace.sh` - script to create the kernel namespace header RTEMS, reverse that + -r|--rtems RTEMS Libbsd directory (default: '.') + -f|--freebsd FreeBSD SVN directory (default: 'freebsd-org') + -v|--verbose enable verbose output mode +``` + +In its default mode of operation, freebsd-to-rtems.py is used to copy code +from FreeBSD to the rtems-libbsd tree and perform transformations. In forward +mode, the script may be requested to just generate the Waf script. + +In *reverse mode*, this script undoes those transformations and copies +the source code back to the *master* FreeBSD tree. This allows us to do +'git diff', evaluate changes made by the RTEMS Project, and report changes +back to FreeBSD upstream. + +In either mode, the script may be asked to perform a dry-run or be verbose. +Also, in either mode, the script is also smart enough to avoid copying over +files which have not changed. This means that the timestamps of files are +not changed unless the contents change. The script will also report the +number of files which changed. In verbose mode, the script will print +the name of the files which are changed. + +To add or update files in the RTEMS FreeBSD tree first run the *reverse mode* +and move the current set of patches FreeBSD. The script may warn you if a file +is not present at the destination for the direction. This can happen as files +not avaliable at the FreeBSD snapshot point have been specially added to the +RTEMS FreeBSD tree. Warnings can also appear if you have changed the list of +files in libbsd.py. The reverse mode will result in the FreeBSD having +uncommitted changes. You can ignore these. Once the reverse process has +finished edit libbsd.py and add any new files then run the forwad mode to bring +those files into the RTEMS FreeBSD tree. + +The following is an example forward run with no changes. + +``` +$ ./freebsd-to-rtems.py -v +Verbose: yes (1) +Dry Run: no +Diff Mode Enabled: no +Only Generate Build Scripts: no +RTEMS Libbsd Directory: . +FreeBSD SVN Directory: freebsd-org +Direction: forward +Forward from FreeBSD GIT into . +0 file(s) were changed: +``` + +The script may also be used to generate a diff in either forward or reverse +direction. + +You can add more than one verbose option (-v) to the command line and get more +detail and debug level information from the command. + +FreeBSD Version of Imported Files and Directories +------------------------------------------------- + +* *, trunk, 2017-04-04, 642b174daddbd0efd9bb5f242c43f4ab4db6869f. + +How to import code from FreeBSD +------------------------------- + +* In case you import files from a special FreeBSD version, then update the list above. +* Run `git status` and make sure your working directory is clean. +* Run `./freebsd-to-rtems.py -R` +* Run `./freebsd-to-rtems.py` +* Run `git status` and make sure your working directory is clean. If you see modified files, then the `freebsd-to-rtems.py` script needs to be fixed first. +* Add the files to import to `libbsd.py`. +* Run `./freebsd-to-rtems.py` +* Immediately check in the imported files without the changes to `libbsd_waf.py`. Do not touch the imported files yourself at this point. +* Port the imported files to RTEMS. See 'Rules for Modifying FreeBSD Source'. +* Add a test to the testsuite if possible. +* Run `./create-kernel-namespace.sh` if you imported kernel space headers. Add only your new defines via `git add -p rtemsbsd/include/machine/rtems-bsd-kernel-namespace.h`. +* Create one commit from this. + +The -S or --stats option generates reports the changes we have made to +FreeBSD. If the code has been reserved into the original FreeBSD tree it will +show nothing has changed. To see what we have change: + +``` +$ cd freebsd-org +$ git checkout -- . +$ cd .. +$ ./freebsd-to-rtems.py -R -S -d + ``` + +The report lists the files change based on the opacity level. The opacity is a +measure on how much of a file differs from the original FreeBSD source. The +lower the value the more transparent the source file it. + +Porting of User-Space Utilities +------------------------------ + +The theory behind the described method is to put all BSS and initialized data +objects into a named section. This section then will be saved before the code is +executed and restored after it has finished. This method limits to a single +threaded execution of the application but minimizes the necessary changes to the +original FreeBSD code. + +* Import and commit the unchanged source files like described above. +* Add the files to the libbsd.py and build them. +* Check the sources for everything that can be made const. This type of patches + should go back to the upstream FreeBSD sources. +* Move static variables out of functions if necessary (search for + "static"). These patches most likely will not be accepted into FreeBSD. +* Add a rtems_bsd_command_PROGNAME() wrapper function to the source file + containing the main function (e.g. PROGNAME = pfctl). For an example look at + `rtems_bsd_command_pfctl()` in `freebsd/sbin/pfctl/pfctl.c`. +* You probably have to use getopt_r() instead of getopt(). Have a look at + `freebsd/sbin/pfctl/pfctl.c`. +* Build the libbsd without optimization. +* Use the `userspace-header-gen.py` to generate some necessary header + files. It will generate one `rtems-bsd-PROGNAME-MODULE-data.h` per object file, one + `rtems-bsd-PROGNAME-namespace.h` and one `rtems-bsd-PROGNAME-data.h`. To call + the script, you have to compile the objects and afterwards run the helper + script with a call similar to this one: + `python ./userspace-header-gen.py build/arm-rtems4.12-xilinx_zynq_a9_qemu/freebsd/sbin/pfctl/*.o -p pfctl` + Replace the name (given via -p option) by the name of the userspace tool. It + has to match the name that is used in the RTEMS linker set further below. +* If you regenerated files that have already been generated, you may have to + remove RTEMS-specific names from the namespace. The defaults (linker set names + and rtems_bsd_program_xxx) should already be filtered. +* Put the generated header files into the same folder like the source files. +* Include `PROGNAME-rtems-bsd-namespace.h` at the top of each source file and + the `PROGNAME-rtems-bsd-MODULE-data.h` after the include section of the + corresponding source files. +* Include `machine/rtems-bsd-program.h` at the top of the include block in each + source file. +* Create one compilable commit. + +Rules for Modifying FreeBSD Source +---------------------------------- + +Changes in FreeBSD files must be done using `__rtems__` C pre-processor guards. +This makes synchronization with the FreeBSD upstream easier and is very +important. Patches which do not follow these rules will be rejected. Only add +lines. If your patch contains lines starting with a `-`, then this is wrong. +Subtract code by added `#ifndef __rtems__`. For example: + +```c +/* Global variables for the kernel. */ + +#ifndef __rtems__ +/* 1.1 */ +extern char kernelname[MAXPATHLEN]; +#endif /* __rtems__ */ + +extern int tick; /* usec per tick (1000000 / hz) */ +``` + +```c +#if defined(_KERNEL) || defined(_WANT_FILE) +#ifdef __rtems__ +#include +#include +#endif /* __rtems__ */ +/* + * Kernel descriptor table. + * One entry for each open kernel vnode and socket. + * + * Below is the list of locks that protects members in struct file. + * + * (f) protected with mtx_lock(mtx_pool_find(fp)) + * (d) cdevpriv_mtx + * none not locked + */ +``` + +```c +extern int profprocs; /* number of process's profiling */ +#ifndef __rtems__ +extern volatile int ticks; +#else /* __rtems__ */ +#include +#define ticks _Watchdog_Ticks_since_boot +#endif /* __rtems__ */ + +#endif /* _KERNEL */ +``` + +Add nothing (even blank lines) before or after the `__rtems__` guards. Always +include a `__rtems__` in the guards to make searches easy, so use + +* `#ifndef __rtems__`, +* `#ifdef __rtems__`, +* `#else /* __rtems__ */`, and +* `#endif /* __rtems__ */`. + +The guards must start at the begin of the line. Examples for wrong guards: + +```c +static void +guards_must_start_at_the_begin_of_the_line(int j) +{ + + /* WRONG */ + #ifdef __rtems__ + return (j + 1); + #else /* __rtems__ */ + return (j + 2); + #endif /* __rtems__ */ +} + +static void +missing_rtems_comments_in_the_guards(int j) +{ + +#ifdef __rtems__ + return (j + 3); +/* WRONG */ +#else + return (j + 4); +#endif +} +``` + +The FreeBSD build and configuration system uses option header files, e.g. +`#include "opt_xyz.h"` in an unmodified FreeBSD file. This include is +transformed by the import script into `#include `. Do +not disable option header includes via guards. Instead, add an empty option +header, e.g. `touch rtemsbsd/include/rtems/bsd/local/opt_xyz.h`. +```c +/* WRONG */ +#ifndef __rtems__ +#include +#endif /* __rtems__ */ +``` + +In general, provide empty header files and do not guard includes. + +For new code use +[STYLE(9)](http://www.freebsd.org/cgi/man.cgi?query=style&apropos=0&sektion=9). + +Do not format original FreeBSD code. Do not perform white space changes even +if you get git commit warnings. + +Automatically Generated FreeBSD Files +------------------------------------- + +Some source and header files are automatically generated during the FreeBSD +build process. The `Makefile.todo` file performs this manually. The should be +included in `freebsd-to-rtems.py` script some time in the future. For details, +see also +[KOBJ(9)](http://www.freebsd.org/cgi/man.cgi?query=kobj&sektion=9&apropos=0). -- cgit v1.2.3