Subject: Re: insmod segfault

From: Bruno Randolf <[email-masked]>
Date: Mon, 5 May 2003 20:06:11 +0200

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 <[email-masked]>

> 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

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