[8f5adbc] | 1 | RTEMS BSD USB and TCP/IP Developers Guide |
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| 2 | ========================================= |
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| 3 | Joel Sherrill <joel.sherrill@oarcorp.com> |
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| 4 | :Author Initials: JRS |
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| 5 | :toc: |
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| 6 | :icons: |
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| 7 | :numbered: |
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| 8 | :website: http://www.rtems.org/ |
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| 9 | |
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| 10 | RTEMS uses FreeBSD as the source of its TCP/IP and USB stacks. |
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| 11 | This is a developers guide which captures information on the |
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| 12 | process of merging code from FreeBSD, building this library, |
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| 13 | RTEMS specific support files, and general guidelines on what |
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| 14 | modifications to the FreeBSD source are permitted. |
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| 15 | |
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[e392fdb7] | 16 | Goals of this effort are: |
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| 17 | |
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| 18 | * Update TCP/IP and provide USB in RTEMS |
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| 19 | * Ease updating to future FreeBSD versions |
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| 20 | * Ease tracking changes in FreeBSD code |
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| 21 | * Minimize manual changes in FreeBSD code |
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| 22 | * Define stable kernel/device driver API which is implemented |
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| 23 | by both RTEMS and FreeBSD. This is the foundation of the port. |
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| 24 | |
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| 25 | We will work to push our changes upstream to the FreeBSD Project |
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| 26 | and minimize changes required at each update point. |
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| 27 | |
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[8f5adbc] | 28 | ************************************************************** |
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| 29 | This is a work in progress and is very likely to be incomplete. |
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| 30 | Please help by adding to it. |
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| 31 | ************************************************************** |
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| 32 | |
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| 33 | == Source Code Version Information |
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| 34 | |
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| 35 | * FreeBSD 8.2 SVN r222496 |
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| 36 | * RTEMS 4.11 |
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| 37 | - BSP must have support for all new BSD sys sections |
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| 38 | - It is preferable if the BSP uses linkcmds.base. |
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| 39 | - BSP must be from an architecture with Programmable Interrupt Controller |
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| 40 | interrupt model. |
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| 41 | |
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[e392fdb7] | 42 | The FreeBSD 8.2 SVN checkout will generally be referred to as the |
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[9e3ba38] | 43 | FreeBSD source in this document. An archive of the FreeBSD 8.2 SVN |
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[a3d2498] | 44 | archive used is located at |
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| 45 | http://www.rtems.org/ftp/pub/rtems/people/joel/freebsd/ |
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| 46 | The SVN checkout command is this |
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| 47 | svn co http://svn.freebsd.org/base/releng/8.2/sys/ -r222496 freebsd-8.2 |
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[e392fdb7] | 48 | |
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[560eccf] | 49 | == Issues and To Do |
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| 50 | * Sebastian Huber: mentioned some simple test code which would verify |
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| 51 | that the BSD code/and or USB stack was initialized. This has been |
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| 52 | sent to Joel Sherrill and is pending merger. |
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| 53 | |
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| 54 | * Sebastian Huber and Joel Sherrill discussed the need for a a basic USB |
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| 55 | functionality test that is known to work on qemu pc. |
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| 56 | |
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[8f5adbc] | 57 | * Adapt generic IRQ PIC interface code to Simple Vectored Interrupt Model |
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| 58 | so that those architectures can use new TCP/IP and USB code. |
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[560eccf] | 59 | |
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[8f5adbc] | 60 | * in_cksum implementations for architectures not supported by FreeBSD. |
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| 61 | This will require figuring out where to put implementations that do |
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| 62 | not originate from FreeBSD and are populated via the script. |
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[560eccf] | 63 | |
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| 64 | * FreeBSD generic in_cksum implementation is missing in_cksum_split so |
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| 65 | currently cannot be used. |
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| 66 | |
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| 67 | * How does one initialize the TCP/IP stack? |
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| 68 | |
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| 69 | * linker section issues: I have undefined symbols for |
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| 70 | _bsd__start_set_sysinit_set and _bsd__stop_set_sysinit_set. |
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| 71 | Is this the only type of new section magic? What about the old sysctl_set? |
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| 72 | I added this to my linkcmds. |
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| 73 | |
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| 74 | [listing] |
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| 75 | ---- |
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| 76 | /* sysinit section? */ |
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| 77 | . = ALIGN (16); |
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| 78 | _bsd__start_set_sysinit_set = .; |
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| 79 | *(set_sys_init_*); |
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| 80 | _bsd__stop_set_sysinit_set = .; |
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| 81 | |
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| 82 | ---- |
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| 83 | |
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| 84 | * Convert all BSP linkcmds to use a linkcmds.base so the sections are |
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| 85 | easier to insert. |
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| 86 | |
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| 87 | * rtems-bsd-init-with-irq.c: |
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| 88 | rtems_bsd_initialize_with_interrupt_server() has reference to |
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| 89 | rtems_interrupt_server_initialize() and this method is unimplemented |
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| 90 | - XXX BSP implements pieces |
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| 91 | - BSPs using this software stack must support it apparently. |
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| 92 | - What about Simple Vectored architectures? |
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| 93 | |
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| 94 | * maxproc variable referenced by rtems-bsd-resource.c. What should it |
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| 95 | be set to? |
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| 96 | |
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| 97 | * ngroups_max variable referenced by rtems-bsd-prot.c. - What should |
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| 98 | it be set to? |
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[8f5adbc] | 99 | |
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[86bc9a7] | 100 | * NIC Device Drivers |
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| 101 | - Only common NIC drivers have been included in the initial set. These do not |
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| 102 | include any system on chip or ISA drivers. |
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| 103 | - The ISA drivers require more BSD infrastructure to be addressed. This was |
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| 104 | outside the scope of the initial porting effort. |
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| 105 | |
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[8f5adbc] | 106 | == FreeBSD Source |
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| 107 | |
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| 108 | You should be able to rely on FreebSD manual pages and documentation |
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| 109 | for details on the code itself. |
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| 110 | |
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| 111 | === Automatically Generated FreeBSD Files |
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| 112 | |
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| 113 | The FreeBSD source tarball includes a file named Makefile.rtems which |
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[455aa3a] | 114 | has stanzas to automatically generate some files using awk. For details |
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| 115 | on this, see http://www.freebsd.org/cgi/man.cgi?query=kobj&apropos=0&sektion=0&manpath=FreeBSD+9.0-RELEASE&arch=default&format=html |
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[8f5adbc] | 116 | |
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[455aa3a] | 117 | XXX This needs more detail. |
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[8f5adbc] | 118 | |
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| 119 | === Rules for Modifying FreeBSD Source |
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| 120 | |
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| 121 | * Only add lines. Subtract code by added "ifndef __rtems__". This makes |
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| 122 | merging easier in the future. |
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| 123 | |
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| 124 | == libbsd Source |
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| 125 | |
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| 126 | === What is in git |
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| 127 | |
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| 128 | The git source is a self-contained kit with FreeBSD and RTEMS components |
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| 129 | pre-merged. The Makefile in this kit is automatically generated. |
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| 130 | |
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| 131 | Any changes to sources in the freebsd or contrib directories will need to |
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| 132 | be merged upstream into our master FreeBSD svn checkout. |
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| 133 | |
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[560eccf] | 134 | The FreeBSD sources managed in RTEMS libbsd git repository (e.g. contrib |
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| 135 | and freebsd directories) contain the "managed" version of the |
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| 136 | FreeBSD source. The FreeBSD SVN source is the "master" version. The |
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| 137 | freebsd-to-rtems.py script is used to transfer files between the two |
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| 138 | trees. In general terms, if you have modified FreeBSD in the RTEMS libbsd |
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| 139 | tree, you want to run the script in "revert" or "reverse" mode to move |
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| 140 | the source back so you can run an "svn diff" against the upstream FreeBSD |
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| 141 | source. If you want to transfer source from the FreeBSD SVN checkout to |
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| 142 | the RTEMS libbsd tree, then you want to run the script in "forward" or |
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| 143 | default mode. |
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| 144 | |
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[455aa3a] | 145 | === Building RTEMS libbsd source |
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[8f5adbc] | 146 | |
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[455aa3a] | 147 | You need to configure RTEMS for the desired BSP and install it. The |
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| 148 | following is the script used to build the powerpc/psim BSP for our |
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| 149 | internal testing purposes: |
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| 150 | |
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| 151 | [listing] |
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| 152 | ---- |
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| 153 | #! /bin/sh |
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| 154 | |
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| 155 | cd ${HOME}/newbsd |
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| 156 | rm -rf b-psim |
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| 157 | mkdir b-psim |
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| 158 | cd b-psim |
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| 159 | ../git/rtems/configure --target=powerpc-rtems4.11 \ |
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| 160 | --enable-rtemsbsp=psim --disable-networking \ |
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| 161 | --enable-tests=samples \ |
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| 162 | --prefix=${HOME}/newbsd/bsp-install >c.log 2>&1 && \ |
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| 163 | make >b.log 2>&1 && \ |
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| 164 | make install >i.log 2>&1 |
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| 165 | echo $? |
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| 166 | ---- |
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| 167 | |
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| 168 | Then edit the file config.inc to set RTEMS_MAKEFILE_PATH appropriately |
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| 169 | to indicate the ${prefix}/${target}/${BSP}. Continuing on the above, |
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| 170 | the config.inc used to match the above is: |
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| 171 | |
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| 172 | [listing] |
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| 173 | ---- |
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| 174 | RTEMS_MAKEFILE_PATH = ${HOME}/newbsd/bsp-install/powerpc-rtems4.11/psim/ |
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| 175 | INSTALL_BASE = ${HOME}/newbsd/install |
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| 176 | ---- |
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| 177 | |
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| 178 | The above installs the RTEMS libbsd kit into a separate place from |
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| 179 | RTEMS and the BSP. The RTEMS libbsd tests are built against an installed |
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| 180 | image of the RTEMS libbsd. By keeping it in a separate installation point |
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| 181 | from RTEMS itself, this makes it easier to remove a libbsd installation |
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| 182 | and have a clean test point. |
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[8f5adbc] | 183 | |
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| 184 | [listing] |
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| 185 | ---- |
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| 186 | make |
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| 187 | make install |
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| 188 | make -C testsuite |
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| 189 | ---- |
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| 190 | |
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| 191 | At this point, we expect multiple linker errors. That is what we are |
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| 192 | currently working on. |
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| 193 | |
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| 194 | === Organization |
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| 195 | |
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| 196 | The top level directory contains a few directories and files. The following |
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| 197 | are important to understand: |
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| 198 | |
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| 199 | * freebsd-to-rtems.py - script to convert to and free FreeBSD and RTEMS trees |
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| 200 | * Makefile - automatically generated |
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| 201 | * contrib/ - from FreeBSD by script. |
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| 202 | * freebsd/ - from FreeBSD by script. |
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| 203 | * rtemsbsd/ - RTEMS specific implementations of FreeBSD kernel support routines. |
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| 204 | * testsuite/ - RTEMS specific tests |
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| 205 | * libbsd.txt - Documentation in Asciidoc |
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| 206 | |
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[e392fdb7] | 207 | == Moving Code Between FreeBSD SVN and RTEMS libbsd |
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| 208 | |
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| 209 | The script freebsd-to-rtems.py is used to copy code from FreeBSD to the |
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| 210 | RTEMS libbsd tree and to reverse this process. This script attempts to |
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| 211 | automate this process as much as possible and performs some transformations |
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| 212 | on the FreeBSD code. Its command line arguments are shown below: |
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| 213 | |
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| 214 | [listing] |
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| 215 | ---- |
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| 216 | freebsd-to-rtems.py [args] |
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| 217 | -?|-h|--help print this and exit |
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| 218 | -d|--dry-run run program but no modifications |
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[7326d96] | 219 | -D|--diff provide diff of files between trees |
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[e392fdb7] | 220 | -e|--early-exit evaluate arguments, print results, and exit |
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| 221 | -m|--makefile just generate Makefile |
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| 222 | -R|--reverse default FreeBSD -> RTEMS, reverse that |
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| 223 | -r|--rtems RTEMS directory |
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| 224 | -f|--freebsd FreeBSD directory |
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| 225 | -v|--verbose enable verbose output mode |
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| 226 | ---- |
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| 227 | |
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| 228 | In its default mode of operation, freebsd-to-rtems.py is used to copy code |
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| 229 | from FreeBSD to the RTEMS libbsd tree and perform transformations. In forward |
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| 230 | mode, the script may be requested to just generate the Makefile. |
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| 231 | |
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| 232 | In "reverse mode", this script undoes those transformations and copies |
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| 233 | the source code back to the FreeBSD SVN tree. This allows us to do |
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| 234 | 'svn diff', evaluate changes made by the RTEMS Project, and report changes |
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| 235 | back to FreeBSD upstream. |
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| 236 | |
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| 237 | In either mode, the script may be asked to perform a dry-run or be verbose. |
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| 238 | Also, in either mode, the script is also smart enough to avoid copying over |
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| 239 | files which have not changed. This means that the timestamps of files are |
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| 240 | not changed unless the contents change. The script will also report the |
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| 241 | number of files which changed. In verbose mode, the script will print |
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| 242 | the name of the files which are changed. |
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| 243 | |
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| 244 | The following is an example forward run with no changes. |
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| 245 | |
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| 246 | [listing] |
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| 247 | ---- |
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| 248 | $ ~/newbsd/git/libbsd-8.2/freebsd-to-rtems.py \ |
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| 249 | -r /home/joel/newbsd/git/libbsd-8.2 \ |
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| 250 | -f /home/joel/newbsd/libbsd/freebsd-8.2 -v |
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| 251 | Verbose: yes |
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| 252 | Dry Run: no |
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| 253 | Only Generate Makefile: no |
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| 254 | RTEMS Directory: /home/joel/newbsd/git/libbsd-8.2 |
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| 255 | FreeBSD Directory: /home/joel/newbsd/libbsd/freebsd-8.2 |
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| 256 | Direction: forward |
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| 257 | Generating into /home/joel/newbsd/git/libbsd-8.2 |
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| 258 | 0 files were changed. |
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| 259 | ---- |
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| 260 | |
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[7326d96] | 261 | The script may also be used to generate a diff in either forward or reverse |
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| 262 | direction. |
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| 263 | |
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[455aa3a] | 264 | == Initialization of RTEMS Libbsd |
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| 265 | |
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| 266 | The initialization of the RTEMS Libbsd is based on the FreeBSD SYSINIT |
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| 267 | infrastructure. This is simply because we are initializing a subset of |
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| 268 | FreeBSD. For details refer to http://www.freebsd.org/cgi/man.cgi?query=SYSINIT&sektion=9&apropos=0&manpath=FreeBSD+9-current |
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| 269 | |
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| 270 | The key to initializing a system is to ensure that the desired device |
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| 271 | drivers are explicitly pulled into the linked application. This plus |
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| 272 | linking against the Libsd library will pull in the necessary FreeBSD |
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| 273 | infrastructure. The SYSINIT structures are automatically built at link |
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| 274 | time and the various initialization routines will thus be executed in' |
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| 275 | the correct order. |
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| 276 | |
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| 277 | XXX This needs more details. |
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[00ee241] | 278 | |
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| 279 | === SYSCTL_NODE Example |
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| 280 | |
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| 281 | During development, we had an undefined reference to |
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| 282 | _bsd_sysctl__net_children that we had trouble tracking down. Thanks to |
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| 283 | Chris Johns, we located it. He explained how to read SYSCTL_NODE |
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| 284 | definitions. This line from freebsd/netinet/in_proto.c is attempting |
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| 285 | to add the "inet" node to the parent node "_net". |
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| 286 | |
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| 287 | [listing] |
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| 288 | ---- |
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| 289 | SYSCTL_NODE(_net, PF_INET, inet, CTLFLAG_RW, 0, |
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| 290 | "Internet Family"); |
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| 291 | ---- |
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| 292 | |
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| 293 | Our problem was that we could not find where _bsd_sysctl__net_children |
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| 294 | was defined. Chris suggested that when in doubt compile with -save-temps |
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| 295 | and look at the preprocessed .i files. But he did not need that. He |
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| 296 | explained that this the symbol name _bsd_sysctl__net_children was |
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| 297 | automatically generated by a SYSCTL_NODE as follows: |
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| 298 | |
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| 299 | * _bsd_ - added by RTEMS modifications to SYSCTL_NODE macro |
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| 300 | * sysctl_ - boilerplace added by SYSCTL_NODE macro |
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| 301 | * "" - empty string for parent node |
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| 302 | * net - name of SYSCTL_NODE |
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| 303 | * children - added by SYSCTL macros |
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| 304 | |
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| 305 | This was all generated by a support macro declaring the node as this: |
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| 306 | |
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| 307 | [listing] |
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| 308 | ---- |
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| 309 | struct sysctl_oid_list SYSCTL_NODE_CHILDREN(parent, name); |
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| 310 | ---- |
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| 311 | |
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| 312 | Given this information, we located this SYSCTL_NODE declaration in |
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| 313 | kern/kern_mib.c |
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| 314 | |
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| 315 | [listing] |
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| 316 | ---- |
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| 317 | SYSCTL_NODE(, CTL_KERN, kern, CTLFLAG_RW, 0, |
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| 318 | "High kernel, proc, limits &c"); |
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| 319 | ---- |
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| 320 | |
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