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to answer my own question, for completeness sake and to save others from the 
same struggles i've been going thru: this is the oh so simple answer, i got 
from Bill Gatliff [off-list ref]

Compiling modules with this:

$ mips-linux-gcc -c -O2 -D__KERNEL__ -Wall -fomit-frame-pointer \
  -fno-strict-aliasing -fno-common -finline-limit=5000 -G 0 -fno-pic \
  -mno-abicalls -mcpu=r4600 -mips2 -mlong-calls -Wa,--trap -DMODULE  \
  chardev.c

fixed the problem.

yes, it does. aparently the important thing is the "-fno-common" flag.

i'd be intererrested in further explanations, if anyone cares... ;)

bruno

On Thursday 17 April 2003 13:29, you wrote:

hello!

i have problems with a kernel module: when i insmod it, i get a
segmentation fault and "Unable to handle kernel paging request at virtual
address 00000004" oops, so as far as i understand it, it seems like
relocation does not occur properly.

i can reproduce the problem with the attached simple test code. when i
insmod only hello_module.o it works fine, but when i insmod the result of
"ld" (mod.o) i get the error. so it seems the problem is with the linker.
or am i using wrong compiler / linker flags or doing something stupid?

i compile with "gcc -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer
-fno-strict-aliasing -mno-abicalls -G 0 -fno-pic -mcpu=r4600 -mips2
-Wa,--trap -pipe -mlong-calls -I/usr/src/linux/include -O3 -D__KERNEL__
-DLINUX -DMESSAGES"

and link with "ld -r -o mod.o hello_module.o b.o"

versions:
* au1500 CPU
* kernel version 2.4.21-pre4 from cvs
* gcc version 3.0.4 (also: gcc version 2.95.4)
* GNU ld version 2.12.90.0.1 20020307 Debian/GNU Linux
* insmod version 2.4.15

objdump -x mod.o says:

---

mod.o:     file format elf32-tradlittlemips
mod.o
architecture: mips:6000, flags 0x00000011:
HAS_RELOC, HAS_SYMS
start address 0x00000000
private flags = 10001001: [abi=O32] [mips2] [not 32bitmode]

Sections:
Idx Name          Size      VMA               LMA               File off
Algn 0 .reginfo      00000018  00000000  00000000  00000034  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA,
LINK_ONCE_SAME_SIZE 1 .text         00000070  00000000  00000000  00000050
2**4
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
  2 .rodata       00000030  00000000  00000000  000000c0  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .modinfo      0000001c  00000000  00000000  000000f0  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  4 .data         00000000  00000000  00000000  00000110  2**4
                  CONTENTS, ALLOC, LOAD, DATA
  5 .sbss         00000000  00000000  00000000  00000110  2**0
                  ALLOC
  6 .bss          00000000  00000000  00000000  00000110  2**4
                  ALLOC
  7 .comment      00000024  00000000  00000000  00000110  2**0
                  CONTENTS, READONLY
  8 .pdr          00000040  00000000  00000000  00000134  2**2
                  CONTENTS, RELOC, READONLY
SYMBOL TABLE:
00000000 l    d  .reginfo       00000000
00000000 l    d  .text  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  .rodata        00000000
00000000 l    d  .modinfo       00000000
00000000 l    d  .data  00000000
00000000 l    d  .sbss  00000000
00000000 l    d  .bss   00000000
00000000 l    d  .comment       00000000
00000000 l    d  .pdr   00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    d  *ABS*  00000000
00000000 l    df *ABS*  00000000 hello_module.c
00000000 l     O .modinfo       0000001b __module_kernel_version
00000000 l    df *ABS*  00000000 b.c
00000004 g     O .scommon       00000004 b
00000038 g     F .text  00000000 cleanup_module
00000000 g     F .text  00000000 init_module
00000000         *UND*  00000000 printk
00000004 g     O .scommon       00000004 glob_int


RELOCATION RECORDS FOR [.text]:
OFFSET   TYPE              VALUE
00000008 R_MIPS_HI16       .rodata
0000000c R_MIPS_LO16       .rodata
00000010 R_MIPS_HI16       printk
00000014 R_MIPS_LO16       printk
00000028 R_MIPS_HI16       glob_int
0000002c R_MIPS_LO16       glob_int
00000040 R_MIPS_HI16       .rodata
00000044 R_MIPS_LO16       .rodata
00000048 R_MIPS_HI16       printk
0000004c R_MIPS_LO16       printk


RELOCATION RECORDS FOR [.pdr]:
OFFSET   TYPE              VALUE
00000000 R_MIPS_32         init_module
00000020 R_MIPS_32         cleanup_module

---

thanks for any hints.

btw: this issue is not related to the one i posted about before ("au1500mm
problems") - which is resolved already and was caused by a wrong
initialization of the dual PHY ethernet hardware.

bruno

- --
4G Mobile Systeme GmbH
Sierichstrasse 149
22299 Hamburg
fon: +49 (0)40 / 48 40 33 28
fax: +49 (0)40 / 48 40 33 30
mail: bruno.randolf@4g-systems.de
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