Philippe De Swert wrote: > Hello people, > > I have a custom build module with some float operations in it. I build a > 2.4.17 kernel for a mips32 core (BCM6348 chip). It boots up fine, busybox > works nicely, also some other apps like dropbear and thttpd do what they are > expected to do. > > I build everything with soft-floats using a uclibc toolchain (kernel + > filesystem). This is the configuration of my toolchain. > > ~#mips-linux-gcc -v > Reading specs from > /vobs/linux/tools/3pp-build/gcc/../../mips/gcc/lib/gcc-lib/mips-linux-uclibc/3.3.4/specs > Configured with: > /vobs/linux/tools/3pp-build/gcc/toolchain_build_mips_nofpu/gcc-3.3.4/configure > --prefix=/vobs/linux/tools/3pp-build/gcc/../../mips/gcc > --build=i386-pc-linux-gnu --host=i386-pc-linux-gnu --target=mips-linux-uclibc > --enable-languages=c,c++ --enable-shared --disable-__cxa_atexit > --enable-target-optspace --with-gnu-ld --disable-nls --enable-multilib > --without-float --enable-sjlj-exceptions > Thread model: posix > gcc driver version 3.3.4 executing gcc version 3.3.3 > > The module builds fine also, but when insmodding I get the following error. > > insmod: unresolved symbol __fixdfsi > insmod: unresolved symbol __floatsidf > insmod: unresolved symbol __muldf3 > insmod: unresolved symbol __adddf3 > > As these are all float operations I am wondering about the following things: > > 1.why they are in there? I have a soft-float toolchain.... > 2.Is there float support in the kernel? While googling for it I found a few > things talking about FP point in the kernel. Does it have something to do with > the Algorithmics/MIPS FPU emulator. (Although it does not work emulator or > not. Which I expected because it should only be used by apps which emit FPU > calls, and this should not happen because I use a softfloat toolchain). So I > expect it does not really have something to do with this. > 3.I took care of using the same compiler options as the kernel compilation > uses. I guess this is the correct way, and the problems are thus not related > to this. > > Any pointers to a solution would be helpful. I am trying woth a hard-float > toolchain now (it only takes a while to compile everything). I could also not > dig up anything similar in the archives. > These symbols are defined in libgcc.a, however libgcc.a is normally compiled with options that make it incompatible with kernel modules. There is a trick I have played to work around this. If you do a normal gcc build and then remove gcc/libgcc.a and the gcc/libgcc directory. You can build a kernel compatible version by doing: export LIBGCC2_DEBUG_CFLAGS='-g -G0 -mno-abicalls -fno-pic' make The resulting libgcc.a will be compatible with the kernel. Rename it to something like libgcckernel.a. Now you can link the kernel module adding -lgcckernel and you should be ready to go. David Daney.
