[U-Boot] sparc and .udiv/.rem/.urem/.umul/etc... link errors

[Mike Frysinger]

On Wednesday 19 October 2011 05:05:22 Daniel Hellstrom wrote:
> On 10/13/2011 05:44 PM, Mike Frysinger wrote:
> > On Thursday 13 October 2011 04:45:27 Daniel Hellstrom wrote:
> >> On 10/13/2011 07:33 AM, Mike Frysinger wrote:
> >>> it seems that these symbols are usually implemented in the C library on
> >>> sparc systems, but under u-boot, we don't have that luxury.  Linux
> >>> itself simply imports the relevant asm files from glibc into their lib
> >>> subdir.  without these, building u-boot for sparc targets with sparc
> >>> linux compilers fail.  any desire to make this work ?  or just continue
> >>> to force everyone to install a dedicated sparc-elf compiler ?
> >> 
> >> The .udiv/.rem ... functions are implemented by libgcc
> > 
> > that is target dependent
> > 
> >> Sparc-linux toolchains will generate ELF binaries for Linux, that is not
> >> what we want?
> > 
> > the file format is fine, but the supplementary libgcc for sparc-linux
> > targets does not include these symbols.  it relies on the C library to
> > provide them.
> > 
> > glibc sparc system:
> > $ readelf -s /lib/libc.so.6 | grep '[.]u'
> > 
> >    1231: 000f41e0    20 FUNC    GLOBAL DEFAULT   10 .urem@@GLIBC_2.0
> >    1369: 000f41a0    12 FUNC    GLOBAL DEFAULT   10 .udiv@@GLIBC_2.0
> >    1557: 000f4160    20 FUNC    GLOBAL DEFAULT   10 .umul@@GLIBC_2.0
> > 
> > and if you look at gcc's source tree in gcc/config/sparc/t-*, you'll see
> > that these libgcc routines are included for elf and leon targets, but
> > not linux.
> > 
> > so whenever i build u-boot using a sparc-linux-gnu cross-compiler, it
> > fails to link due to missing these symbols.  if i use sparc-elf, it
> > links fine.
> 
> Ok I see. I'm not a GCC guru, but my sparc-linux- toolchain (built with
> crosstool-ng) has a libgcc.a in lib/gcc/sparc-leon-linux-gnu/4.4.2 which
> includes the .mul/.div functions. I guess that is not the sparc-linux
> target but sparc-leon-linux though. Could we use 'sparc-linux-gcc
> -print-libgcc-file-name' in u-boot?

right, you got those funcs because you're targeting leon.  -print-libgcc-name 
doesn't help when using sparc-linux-gcc as that just gets you the libgcc.a 
that's missing these symbols :).  and that's already what the u-boot build 
system is doing (see $(PLATFORM_LIBGCC) in top level Makefile).

what i'm semi proposing is that we implement USE_PRIVATE_LIBGCC for sparc 
platforms.  or at least import these symbols that sparc-linux gcc targets 
expect to be in the C library.

in either case it should be easy to do -- just copy the files from the kernel.
-mike
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