[okl4-developer] OKL4 v2.1: Building an XIP image

[Frank Kaiser]

Hello

 

Since our AT91RM9200 platform has a NOR-Flash, it would be convenient to
use the XIP (eXecution In Place) option of the build system (to get the
image started w/o U-Boot's tftpboot). The first thing which surprised me
is that it is not sufficient to declare the NOR flash in the machines
class with the attribute memory['rom']. This is just ignored as long as
one does not specify XIP=1 on the command line. There seems to be no way
to specify the XIP option in the machines class: I found nothing in
tools/build.py or anywhere that evaluates an XIP-related attribute set
by the current machine.

However, with the command line option I did not get what I expected. My
machine has this memory configuration:

    memory['virtual']  = [Region(0x90000000L, 0xE0000000L)]

    memory['physical'] = [Region(0x20000000L, 0x21000000L)]

    memory['rom']      = [Region(0x10020000L, 0x11000000L)]

Readelf lists the following section information of image.boot:

Section Headers:

  [Nr] Name              Type            Addr     Off    Size   ES Flg
Lk Inf Al

  [ 0]                   NULL            00000000 000000 000000 00
0   0  0

  [ 1] kernel.text       PROGBITS        10020000 008000 011484 00  AX
0   0 16

  [ 2] kernel.rodata     PROGBITS        10031484 019484 00693c 00   A
0   0  4

  [ 3] kernel.kdebug     PROGBITS        10037dc0 01fdc0 004690 00  AX
0   0  4

  [ 4] kernel.init       PROGBITS        1003c450 024450 001f40 00  AX
0   0  4

  [ 5] kernel.roinit     PROGBITS        1003e390 026390 000300 00   A
0   0  4

  [ 6] kernel.data       PROGBITS        20000000 028000 001600 00  WA
0   0 1024

  [ 7] kernel.got        PROGBITS        20001600 029600 000004 00  WA
0   0  4

  [ 8] kernel.got.plt    PROGBITS        20001604 029604 00000c 04  WA
0   0  4

  [ 9] kernel.kdebug-dat PROGBITS        20001610 029610 00041c 00  WA
0   0  4

  [10] kernel.bss        NOBITS          20001a2c 029a2c 0036e0 00  WA
0   0  8

  [11] kernel.kspace     PROGBITS        20008000 030000 004000 00  WA
0   0 16384

  [12] kernel.traps      PROGBITS        2000c000 034000 001000 00  WA
0   0 4096

  [13] kernel.utcb_page  PROGBITS        2000d000 035000 001000 00  WA
0   0 4096

  [14] ig_server.text    PROGBITS        20068000 038000 00c73c 00  AX
0   0  4

  [15] ig_server.rodata  PROGBITS        2007473c 04473c 001873 00   A
0   0  4

  [16] ig_server.data    PROGBITS        20007000 047000 000224 00  WA
0   0  4

  [17] ig_server.got     PROGBITS        20007224 047224 000010 04  WA
0   0  4

  [18] ig_server.bss     NOBITS          20007238 047238 00012c 00  WA
0   0  8

  [19] event.text        PROGBITS        20078000 048000 004b7c 00  AX
0   0  4

  [20] event.rodata      PROGBITS        2007cb7c 04cb7c 0006f3 00   A
0   0  4

  [21] event.data        PROGBITS        20077270 04f270 000108 00  WA
0   0  4

  [22] event.got         PROGBITS        20077378 04f378 000010 04  WA
0   0  4

  [23] event.bss         NOBITS          20077388 04f388 000120 00  WA
0   0  4

  [24] vostimer.text     PROGBITS        200a4000 054000 004f00 00  AX
0   0  4

  [25] vostimer.rodata   PROGBITS        200a8f00 058f00 00069f 00   A
0   0  4

  [26] vostimer.data     PROGBITS        200a15a0 0595a0 000138 00  WA
0   0  4

  [27] vostimer.got      PROGBITS        200a16d8 0596d8 000010 04  WA
0   0  4

  [28] vostimer.bss      NOBITS          200a16e8 0596e8 0003d0 00  WA
0   0  4

  [29] bootinfo          PROGBITS        200aa000 05a000 002000 00  WA
0   0  0

  [30] .shstrtab         STRTAB          00000000 05c000 00019e 00
0   0  1

  [31] .strtab           STRTAB          00000000 05c19e 00dcd1 00
0   0  1

  [32] .symtab           SYMTAB          00000000 069e6f 00cb10 10
31   0  0

One can clearly see that only the kernel code and rom data are allocated
in the flash memory. IGUANA's code and rom data reside in RAM, and also
the bootinfo section. I doubt that the above memory configuration is
runnable, since after power-on the IGUANA stuff just won't be there.
I checked the gta01_xip build for comparison, and it showed the same
memory configuration. Did I miss a command line option to get IGUANA
into XIP configuration as well?

Another problem is the allocation of the kernel.data section. Its
position at the start of the RAM results in a clash with the ARM globals
which are hard-wired to the start address of the RAM. I mentioned this a
while ago
(http://n2.nabble.com/Re%3A-OKL4-v2.1%3A-ARM-startup-code-overwrites-its
elf-tp219821p219821.html), and it was said that space will be reserved
for the ARM globals. The above list does not give an indication that
this is the case.

 

Regards

Frank

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