| 1 |
28 |
unneback |
<!-- Copyright (C) 2003 Red Hat, Inc. -->
|
| 2 |
|
|
<!-- This material may be distributed only subject to the terms -->
|
| 3 |
|
|
<!-- and conditions set forth in the Open Publication License, v1.0 -->
|
| 4 |
|
|
<!-- or later (the latest version is presently available at -->
|
| 5 |
|
|
<!-- http://www.opencontent.org/openpub/). -->
|
| 6 |
|
|
<!-- Distribution of the work or derivative of the work in any -->
|
| 7 |
|
|
<!-- standard (paper) book form is prohibited unless prior -->
|
| 8 |
|
|
<!-- permission is obtained from the copyright holder. -->
|
| 9 |
|
|
<HTML
|
| 10 |
|
|
><HEAD
|
| 11 |
|
|
><TITLE
|
| 12 |
|
|
>Porting</TITLE
|
| 13 |
|
|
><meta name="MSSmartTagsPreventParsing" content="TRUE">
|
| 14 |
|
|
<META
|
| 15 |
|
|
NAME="GENERATOR"
|
| 16 |
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
|
| 17 |
|
|
"><LINK
|
| 18 |
|
|
REL="HOME"
|
| 19 |
|
|
TITLE="eCos Reference Manual"
|
| 20 |
|
|
HREF="ecos-ref.html"><LINK
|
| 21 |
|
|
REL="UP"
|
| 22 |
|
|
TITLE="eCos Synthetic Target"
|
| 23 |
|
|
HREF="hal-synth-arch.html"><LINK
|
| 24 |
|
|
REL="PREVIOUS"
|
| 25 |
|
|
TITLE="Writing New Devices - host"
|
| 26 |
|
|
HREF="synth-new-host.html"><LINK
|
| 27 |
|
|
REL="NEXT"
|
| 28 |
|
|
TITLE="SA11X0 USB Device Driver"
|
| 29 |
|
|
HREF="devs-usb-sa11x0-ref.html"></HEAD
|
| 30 |
|
|
><BODY
|
| 31 |
|
|
CLASS="REFENTRY"
|
| 32 |
|
|
BGCOLOR="#FFFFFF"
|
| 33 |
|
|
TEXT="#000000"
|
| 34 |
|
|
LINK="#0000FF"
|
| 35 |
|
|
VLINK="#840084"
|
| 36 |
|
|
ALINK="#0000FF"
|
| 37 |
|
|
><DIV
|
| 38 |
|
|
CLASS="NAVHEADER"
|
| 39 |
|
|
><TABLE
|
| 40 |
|
|
SUMMARY="Header navigation table"
|
| 41 |
|
|
WIDTH="100%"
|
| 42 |
|
|
BORDER="0"
|
| 43 |
|
|
CELLPADDING="0"
|
| 44 |
|
|
CELLSPACING="0"
|
| 45 |
|
|
><TR
|
| 46 |
|
|
><TH
|
| 47 |
|
|
COLSPAN="3"
|
| 48 |
|
|
ALIGN="center"
|
| 49 |
|
|
>eCos Reference Manual</TH
|
| 50 |
|
|
></TR
|
| 51 |
|
|
><TR
|
| 52 |
|
|
><TD
|
| 53 |
|
|
WIDTH="10%"
|
| 54 |
|
|
ALIGN="left"
|
| 55 |
|
|
VALIGN="bottom"
|
| 56 |
|
|
><A
|
| 57 |
|
|
HREF="synth-new-host.html"
|
| 58 |
|
|
ACCESSKEY="P"
|
| 59 |
|
|
>Prev</A
|
| 60 |
|
|
></TD
|
| 61 |
|
|
><TD
|
| 62 |
|
|
WIDTH="80%"
|
| 63 |
|
|
ALIGN="center"
|
| 64 |
|
|
VALIGN="bottom"
|
| 65 |
|
|
></TD
|
| 66 |
|
|
><TD
|
| 67 |
|
|
WIDTH="10%"
|
| 68 |
|
|
ALIGN="right"
|
| 69 |
|
|
VALIGN="bottom"
|
| 70 |
|
|
><A
|
| 71 |
|
|
HREF="devs-usb-sa11x0-ref.html"
|
| 72 |
|
|
ACCESSKEY="N"
|
| 73 |
|
|
>Next</A
|
| 74 |
|
|
></TD
|
| 75 |
|
|
></TR
|
| 76 |
|
|
></TABLE
|
| 77 |
|
|
><HR
|
| 78 |
|
|
ALIGN="LEFT"
|
| 79 |
|
|
WIDTH="100%"></DIV
|
| 80 |
|
|
><H1
|
| 81 |
|
|
><A
|
| 82 |
|
|
NAME="SYNTH-PORTING">Porting</H1
|
| 83 |
|
|
><DIV
|
| 84 |
|
|
CLASS="REFNAMEDIV"
|
| 85 |
|
|
><A
|
| 86 |
|
|
NAME="AEN18705"
|
| 87 |
|
|
></A
|
| 88 |
|
|
><H2
|
| 89 |
|
|
>Name</H2
|
| 90 |
|
|
>Porting -- Adding support for other hosts</DIV
|
| 91 |
|
|
><DIV
|
| 92 |
|
|
CLASS="REFSECT1"
|
| 93 |
|
|
><A
|
| 94 |
|
|
NAME="SYNTH-PORTING-DESCRIPTION"
|
| 95 |
|
|
></A
|
| 96 |
|
|
><H2
|
| 97 |
|
|
>Description</H2
|
| 98 |
|
|
><P
|
| 99 |
|
|
>The initial development effort of the eCos synthetic target happened
|
| 100 |
|
|
on x86 Linux machines. Porting to other platforms involves addressing
|
| 101 |
|
|
a number of different issues. Some ports should be fairly
|
| 102 |
|
|
straightforward, for example a port to Linux on a processor other than
|
| 103 |
|
|
an x86. Porting to Unix or Unix-like operating systems other than
|
| 104 |
|
|
Linux may be possible, but would involve more effort. Porting to a
|
| 105 |
|
|
completely different operating system such as Windows would be very
|
| 106 |
|
|
difficult. The text below complements the eCos Porting Guide.
|
| 107 |
|
|
</P
|
| 108 |
|
|
></DIV
|
| 109 |
|
|
><DIV
|
| 110 |
|
|
CLASS="REFSECT1"
|
| 111 |
|
|
><A
|
| 112 |
|
|
NAME="SYNTH-PORTING-LINUX"
|
| 113 |
|
|
></A
|
| 114 |
|
|
><H2
|
| 115 |
|
|
>Other Linux Platforms</H2
|
| 116 |
|
|
><P
|
| 117 |
|
|
>Porting the synthetic target to a Linux platform that uses a processor
|
| 118 |
|
|
other than x86 should be straightforward. The simplest approach is to
|
| 119 |
|
|
copy the existing <TT
|
| 120 |
|
|
CLASS="FILENAME"
|
| 121 |
|
|
>i386linux</TT
|
| 122 |
|
|
>
|
| 123 |
|
|
directory tree in the <TT
|
| 124 |
|
|
CLASS="FILENAME"
|
| 125 |
|
|
>hal/synth</TT
|
| 126 |
|
|
>
|
| 127 |
|
|
hierarchy, then rename and edit the ten or so files in this package.
|
| 128 |
|
|
Most of the changes should be pretty obvious, for example on a 64-bit
|
| 129 |
|
|
processor some new data types will be needed in the
|
| 130 |
|
|
<TT
|
| 131 |
|
|
CLASS="FILENAME"
|
| 132 |
|
|
>basetype.h</TT
|
| 133 |
|
|
> header file. It will also be necessary
|
| 134 |
|
|
to update the toplevel <TT
|
| 135 |
|
|
CLASS="FILENAME"
|
| 136 |
|
|
>ecos.db</TT
|
| 137 |
|
|
> database with an
|
| 138 |
|
|
entry for the new HAL package, and a new target entry will be needed.
|
| 139 |
|
|
</P
|
| 140 |
|
|
><P
|
| 141 |
|
|
>Obviously a different processor will have different register sets and
|
| 142 |
|
|
calling conventions, so the code for saving and restoring thread
|
| 143 |
|
|
contexts and for implementing <TT
|
| 144 |
|
|
CLASS="FUNCTION"
|
| 145 |
|
|
>setjmp</TT
|
| 146 |
|
|
> and
|
| 147 |
|
|
<TT
|
| 148 |
|
|
CLASS="FUNCTION"
|
| 149 |
|
|
>longjmp</TT
|
| 150 |
|
|
> will need to be updated. The exact way of
|
| 151 |
|
|
performing Linux system calls will vary: on x86 linux this usually
|
| 152 |
|
|
involves pushing some registers on the stack and then executing an
|
| 153 |
|
|
<TT
|
| 154 |
|
|
CLASS="LITERAL"
|
| 155 |
|
|
>int 0x080</TT
|
| 156 |
|
|
> trap instruction, but on a different
|
| 157 |
|
|
processor the arguments might be passed in registers instead and
|
| 158 |
|
|
certainly a different trap instruction will be used. The startup code
|
| 159 |
|
|
is written in assembler, but needs to do little more than extract the
|
| 160 |
|
|
process' argument and environment variables and then jump to the main
|
| 161 |
|
|
<TT
|
| 162 |
|
|
CLASS="FUNCTION"
|
| 163 |
|
|
>linux_entry</TT
|
| 164 |
|
|
> function provided by the
|
| 165 |
|
|
architectural synthetic target HAL package.
|
| 166 |
|
|
</P
|
| 167 |
|
|
><P
|
| 168 |
|
|
>The header file <TT
|
| 169 |
|
|
CLASS="FILENAME"
|
| 170 |
|
|
>hal_io.h</TT
|
| 171 |
|
|
> provided by the
|
| 172 |
|
|
architectural HAL package provides various structure definitions,
|
| 173 |
|
|
function prototypes, and macros related to system calls. These are
|
| 174 |
|
|
correct for x86 linux, but there may be problems on other processors.
|
| 175 |
|
|
For example a structure field that is currently defined as a 32-bit
|
| 176 |
|
|
number may in fact may be a 64-bit number instead.
|
| 177 |
|
|
</P
|
| 178 |
|
|
><P
|
| 179 |
|
|
>The synthetic target's memory map is defined in two files in the
|
| 180 |
|
|
<TT
|
| 181 |
|
|
CLASS="FILENAME"
|
| 182 |
|
|
>include/pkgconf</TT
|
| 183 |
|
|
> subdirectory.
|
| 184 |
|
|
For x86 the default memory map involves eight megabytes of read-only
|
| 185 |
|
|
memory for the code at location 0x1000000 and another eight megabytes
|
| 186 |
|
|
for data at 0x2000000. These address ranges may be reserved for other
|
| 187 |
|
|
purposes on the new architecture, so may need changing. There may be
|
| 188 |
|
|
some additional areas of memory allocated by the system for other
|
| 189 |
|
|
purposes, for example the startup stack and any environment variables,
|
| 190 |
|
|
but usually eCos applications can and should ignore those.
|
| 191 |
|
|
</P
|
| 192 |
|
|
><P
|
| 193 |
|
|
>Other HAL functionality such as interrupt handling, diagnostics, and
|
| 194 |
|
|
the system clock are provided by the architectural HAL package and
|
| 195 |
|
|
should work on different processors with few if any changes. There may
|
| 196 |
|
|
be some problems in the code that interacts with the I/O auxiliary
|
| 197 |
|
|
because of lurking assumptions about endianness or the sizes of
|
| 198 |
|
|
various data types.
|
| 199 |
|
|
</P
|
| 200 |
|
|
><P
|
| 201 |
|
|
>When porting to other processors, a number of sources of information
|
| 202 |
|
|
are likely to prove useful. Obviously the Linux kernel sources and
|
| 203 |
|
|
header files constitute the ultimate authority on how things work at
|
| 204 |
|
|
the system call level. The GNU C library sources may also prove very
|
| 205 |
|
|
useful: for a normal Linux application it is the C library that
|
| 206 |
|
|
provides the startup code and the system call interface.
|
| 207 |
|
|
</P
|
| 208 |
|
|
></DIV
|
| 209 |
|
|
><DIV
|
| 210 |
|
|
CLASS="REFSECT1"
|
| 211 |
|
|
><A
|
| 212 |
|
|
NAME="SYNTH-PORTING-UNIX"
|
| 213 |
|
|
></A
|
| 214 |
|
|
><H2
|
| 215 |
|
|
>Other Unix Platforms</H2
|
| 216 |
|
|
><P
|
| 217 |
|
|
>Porting to a Unix or Unix-like operating system other than Linux would
|
| 218 |
|
|
be somewhat more involved. The first requirement is toolchains: the
|
| 219 |
|
|
GNU compilers, gcc and g++, must definitely be used; use of other GNU
|
| 220 |
|
|
tools such as the linker may be needed as well, because eCos depends
|
| 221 |
|
|
on functionality such as prioritizing C++ static constructors, and
|
| 222 |
|
|
other linkers may not implement this or may implement it in a
|
| 223 |
|
|
different and incompatible way. A closely related requirement is the
|
| 224 |
|
|
use of ELF format for binary executables: if the operating system
|
| 225 |
|
|
still uses an older format such as COFF then there are likely to be
|
| 226 |
|
|
problems because they do not provide the flexibility required by eCos.
|
| 227 |
|
|
</P
|
| 228 |
|
|
><P
|
| 229 |
|
|
>In the architectural HAL there should be very little code that is
|
| 230 |
|
|
specific to Linux. Instead the code should work on any operating
|
| 231 |
|
|
system that provides a reasonable implementation of the POSIX
|
| 232 |
|
|
standard. There may be some problems with program startup, but those
|
| 233 |
|
|
could be handled at the architectural level. Some changes may also be
|
| 234 |
|
|
required to the exception handling code. However one file which will
|
| 235 |
|
|
present a problem is <TT
|
| 236 |
|
|
CLASS="FILENAME"
|
| 237 |
|
|
>hal_io.h</TT
|
| 238 |
|
|
>, which contains
|
| 239 |
|
|
various structure definitions and macros used with the system call
|
| 240 |
|
|
interface. It is likely that many of these definitions will need
|
| 241 |
|
|
changing, and it may well be appropriate to implement variant HAL
|
| 242 |
|
|
packages for the different operating systems where this information
|
| 243 |
|
|
can be separated out. Another possible problem is that the generic
|
| 244 |
|
|
code assumes that system calls such as
|
| 245 |
|
|
<TT
|
| 246 |
|
|
CLASS="FUNCTION"
|
| 247 |
|
|
>cyg_hal_sys_write</TT
|
| 248 |
|
|
> are available. On an operating
|
| 249 |
|
|
system other than Linux it is possible that some of these are not
|
| 250 |
|
|
simple system calls, and instead wrapper functions will need to be
|
| 251 |
|
|
implemented at the variant HAL level.
|
| 252 |
|
|
</P
|
| 253 |
|
|
><P
|
| 254 |
|
|
>The generic I/O auxiliary code should be fairly portable to other Unix
|
| 255 |
|
|
platforms. However some of the device drivers may contain code that is
|
| 256 |
|
|
specific to Linux, for example the <TT
|
| 257 |
|
|
CLASS="LITERAL"
|
| 258 |
|
|
>PF_PACKET</TT
|
| 259 |
|
|
> socket
|
| 260 |
|
|
address family and the ethertap virtual tunnelling interface. These
|
| 261 |
|
|
may prove quite difficult to port.
|
| 262 |
|
|
</P
|
| 263 |
|
|
><P
|
| 264 |
|
|
>The remaining porting task is to implement one or more platform HAL
|
| 265 |
|
|
packages, one per processor type that is supported. This should
|
| 266 |
|
|
involve much the same work as a port to <A
|
| 267 |
|
|
HREF="synth-porting.html#SYNTH-PORTING-LINUX"
|
| 268 |
|
|
>another processor running Linux</A
|
| 269 |
|
|
>.
|
| 270 |
|
|
</P
|
| 271 |
|
|
><P
|
| 272 |
|
|
>When using other Unix operating systems the kernel source code may not
|
| 273 |
|
|
be available, which would make any porting effort more challenging.
|
| 274 |
|
|
However there is still a good chance that the GNU C library will have
|
| 275 |
|
|
been ported already, so its source code may contain much useful
|
| 276 |
|
|
information.
|
| 277 |
|
|
</P
|
| 278 |
|
|
></DIV
|
| 279 |
|
|
><DIV
|
| 280 |
|
|
CLASS="REFSECT1"
|
| 281 |
|
|
><A
|
| 282 |
|
|
NAME="SYNTH-PORTING-OTHER"
|
| 283 |
|
|
></A
|
| 284 |
|
|
><H2
|
| 285 |
|
|
>Windows Platforms</H2
|
| 286 |
|
|
><P
|
| 287 |
|
|
>Porting the current synthetic target code to some version of Windows
|
| 288 |
|
|
or to another non-Unix platform is likely to prove very difficult. The
|
| 289 |
|
|
first hurdle that needs to be crossed is the file format for binary
|
| 290 |
|
|
executables: current Windows implementations do not use ELF, instead
|
| 291 |
|
|
they use their own format PE which is a variant of the rather old and
|
| 292 |
|
|
limited COFF format. It may well prove easier to first write an ELF
|
| 293 |
|
|
loader for Windows executables, rather than try to get eCos to work
|
| 294 |
|
|
within the constraints of PE. Of course that introduces new problems,
|
| 295 |
|
|
for example existing source-level debuggers will still expect
|
| 296 |
|
|
executables to be in PE format.
|
| 297 |
|
|
</P
|
| 298 |
|
|
><P
|
| 299 |
|
|
>Under Linux a synthetic target application is not linked with the
|
| 300 |
|
|
system's C library or any other standard system library. That would
|
| 301 |
|
|
cause confusion, for example both eCos and the system's C library
|
| 302 |
|
|
might try to define the <TT
|
| 303 |
|
|
CLASS="FUNCTION"
|
| 304 |
|
|
>printf</TT
|
| 305 |
|
|
> function, and
|
| 306 |
|
|
introduce complications such as working with shared libraries. For
|
| 307 |
|
|
much the same reasons, a synthetic target application under Windows
|
| 308 |
|
|
should not be linked with any Windows DLL's. If an ELF loader has been
|
| 309 |
|
|
specially written then this may not be much of a problem.
|
| 310 |
|
|
</P
|
| 311 |
|
|
><P
|
| 312 |
|
|
>The next big problem is the system call interface. Under Windows
|
| 313 |
|
|
system calls are generally made via DLL's, and it is not clear that
|
| 314 |
|
|
the underlying trap mechanism is well-documented or consistent between
|
| 315 |
|
|
different releases of Windows.
|
| 316 |
|
|
</P
|
| 317 |
|
|
><P
|
| 318 |
|
|
>The current code depends on the operating system providing an
|
| 319 |
|
|
implementation of POSIX signal handling. This is used for I/O
|
| 320 |
|
|
purposes, for example <TT
|
| 321 |
|
|
CLASS="LITERAL"
|
| 322 |
|
|
>SIGALRM</TT
|
| 323 |
|
|
> is used for the
|
| 324 |
|
|
system clock, and for exceptions. It is not known what equivalent
|
| 325 |
|
|
functionality is available under Windows.
|
| 326 |
|
|
</P
|
| 327 |
|
|
><P
|
| 328 |
|
|
>Given the above problems a port of the synthetic target to Windows may
|
| 329 |
|
|
or may not be technically feasible, but it would certainly require a
|
| 330 |
|
|
very large amount of effort.
|
| 331 |
|
|
</P
|
| 332 |
|
|
></DIV
|
| 333 |
|
|
><DIV
|
| 334 |
|
|
CLASS="NAVFOOTER"
|
| 335 |
|
|
><HR
|
| 336 |
|
|
ALIGN="LEFT"
|
| 337 |
|
|
WIDTH="100%"><TABLE
|
| 338 |
|
|
SUMMARY="Footer navigation table"
|
| 339 |
|
|
WIDTH="100%"
|
| 340 |
|
|
BORDER="0"
|
| 341 |
|
|
CELLPADDING="0"
|
| 342 |
|
|
CELLSPACING="0"
|
| 343 |
|
|
><TR
|
| 344 |
|
|
><TD
|
| 345 |
|
|
WIDTH="33%"
|
| 346 |
|
|
ALIGN="left"
|
| 347 |
|
|
VALIGN="top"
|
| 348 |
|
|
><A
|
| 349 |
|
|
HREF="synth-new-host.html"
|
| 350 |
|
|
ACCESSKEY="P"
|
| 351 |
|
|
>Prev</A
|
| 352 |
|
|
></TD
|
| 353 |
|
|
><TD
|
| 354 |
|
|
WIDTH="34%"
|
| 355 |
|
|
ALIGN="center"
|
| 356 |
|
|
VALIGN="top"
|
| 357 |
|
|
><A
|
| 358 |
|
|
HREF="ecos-ref.html"
|
| 359 |
|
|
ACCESSKEY="H"
|
| 360 |
|
|
>Home</A
|
| 361 |
|
|
></TD
|
| 362 |
|
|
><TD
|
| 363 |
|
|
WIDTH="33%"
|
| 364 |
|
|
ALIGN="right"
|
| 365 |
|
|
VALIGN="top"
|
| 366 |
|
|
><A
|
| 367 |
|
|
HREF="devs-usb-sa11x0-ref.html"
|
| 368 |
|
|
ACCESSKEY="N"
|
| 369 |
|
|
>Next</A
|
| 370 |
|
|
></TD
|
| 371 |
|
|
></TR
|
| 372 |
|
|
><TR
|
| 373 |
|
|
><TD
|
| 374 |
|
|
WIDTH="33%"
|
| 375 |
|
|
ALIGN="left"
|
| 376 |
|
|
VALIGN="top"
|
| 377 |
|
|
>Writing New Devices - host</TD
|
| 378 |
|
|
><TD
|
| 379 |
|
|
WIDTH="34%"
|
| 380 |
|
|
ALIGN="center"
|
| 381 |
|
|
VALIGN="top"
|
| 382 |
|
|
><A
|
| 383 |
|
|
HREF="hal-synth-arch.html"
|
| 384 |
|
|
ACCESSKEY="U"
|
| 385 |
|
|
>Up</A
|
| 386 |
|
|
></TD
|
| 387 |
|
|
><TD
|
| 388 |
|
|
WIDTH="33%"
|
| 389 |
|
|
ALIGN="right"
|
| 390 |
|
|
VALIGN="top"
|
| 391 |
|
|
>SA11X0 USB Device Driver</TD
|
| 392 |
|
|
></TR
|
| 393 |
|
|
></TABLE
|
| 394 |
|
|
></DIV
|
| 395 |
|
|
></BODY
|
| 396 |
|
|
></HTML
|
| 397 |
|
|
>
|
