[BusyBox] Bug: BusyBox insmod segv: More info

[Nathan Field]

After some more testing I found that this only happens when attempting to
load kernel modules that were compiled with the "-g" flag. Since I am
attempting to do kernel module debugging this really screws me. Anyone
have any ideas about what's going wrong here? Again, I'm using GCC v3.2 on
a MIPS target.

	nathan

On Mon, 4 Nov 2002, Nathan Field wrote:

> I believe that I have found a segv bug in busybox insmod versions 0.60.4
> and 0.60.5 (only versions tested) when loading MIPS kernel modules
> compiled with GCC 3.2. Basically when I load some (but not all) kernel
> modules arch_apply_relocation case R_MIPS_32 causes a segv because loc is
> 0x6:
>
> 	[snip]
>   case R_MIPS_32:
>     fprintf(stderr, "[arch_apply_relocation] loc is: 0x%x\n", loc);
>     *loc += v;
>     break;
> 	[snip]
>
> The output is:
> [arch_apply_relocation] R_MIPS_32 case.
> [arch_apply_relocation] loc is: 0x6
> Hit sighandler with 11.
>
> Note that I have installed my own sighandler to see this. The callstack is
> roughly:
> 	insmod_main
> 	obj_relocate
> 	arch_apply_relocation
>
> The eventual result of this segv is that the kernel module shows up as
> "(uninitialized)". The create_module is called, but init_module is not. I
> tried searching around to see if anyone else had encountered this problem,
> but all I could find was:
>
> [BusyBox] insmod problems *sigh*
> [BusyBox] insmod problems HINT
> [BusyBox] insmod problems HINT -- possible patch.
> 	-1 passed to obj_add_symbol in symidx: Not causing my bug, it's
> fixed in my busybox code as referenced in:
> http://www.busybox.net/lists/busybox/2001-June/009221.html
>
> Now for my setup:
> 82) mipsel-uclibc-gcc -v
> Reading specs from
> /opt/toolchains/uclibc/bin/../lib/gcc-lib/mipsel-linux/3.2/specs
> Configured with: ../gcc-3.2/configure
> --prefix=/opt/toolchains/uclibc-crosstools-1.0.0 --target=mipsel-linux
> --enable-target-optspace --disable-nls --with-gnu-ld --enable-shared
> --enable-languages=c,c++ --enable-threads
> --infodir=/opt/toolchains/uclibc-crosstools-1.0.0/info
> --mandir=/opt/toolchains/uclibc-crosstools-1.0.0/man
> --includedir=/opt/toolchains/uclibc-crosstools-1.0.0/mipsel-linux/include
> --with-gxx-include-dir=/opt/toolchains/uclibc-crosstools-1.0.0/mipsel-linux/include/g++-v3
> --disable-checking --program-transform-name=s,^,mipsel-uclibc-,
> Thread model: posix
> gcc version 3.2
>
> BusyBox versions 0.60.4 and 0.60.5.
>
> Kernel 2.4.18, modified to run on a Broadcom 7320 board (MIPS 5kf based).
>
> Unfortunatly I don't believe that I can give the kernel module out to
> anyone because it actually belongs to another company. However, I think
> it's probably safe to show anyone who's interested the output when running
> nm and other utilities over these modules if that would help. Ask and I
> shall deliver.
>
> Has anyone seen this problem before? If not, can anyone see what the
> problem is? I'm guessing that GCC 3.2 is doing something differently that
> insmod isn't expecting, but I haven't figured out what yet.
>
> 	nathan
>
> --
> Nathan Field (ndf at ghs.com)			        Where's the humor?
>
> "If everything seems under control, you're just not going fast enough."
>         -- Mario Andretti
>
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>

------------
Nathan Field  Root is not something to be shared with strangers.

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