Re: glibc 2.2.4 on the mpc860 cpu

[Andreas Jaeger]

Axel Kittenberger <address@hidden> writes:

> Hi!
>
> I just cross-compiled glibc 2.2.4 for the powerpc mpc860. I think I'll report 
> what problems I ran across and how I worked them around, maybe helping to 
> improve a little coming glibc releases. It are most dirty fixes, maybe not 
> suited for the mainline like this, but they provide some hints.
>
> The file sysdeps/powerpc/fclrexcept.c seems to contain floating point 
> operations, as the 860 doesn't have a FPU and failed to compile when 
> configured with --without-fp I moved it to sysdeps/powerpc/fpu/fclrexcept.c

This has been done already in the development version.

> In sysdeps/powerpc/Makefile I commented out line 7
> ifeq ($(subdir),math)
> # libm-support += fenv_const fe_nomask
> endif
> as they also inherit some FPU stuff.

Also fixed.

> sysdeps/powerpc/memset.S is broken! That was a bitch to find as my new ld.so 
> constantly crashed. I approximated the error with debug outputs in ld.so. One 
> cannot run ld.so in gdb(server), or can I? After searching on the web 
> afterwards it seems to be a well known problem, memset.S assumes a 32 byte 
> cache line, but the little mpc has just 16 bytes. Simple fix was of course 
> just to delete it. Don't know how this problem can be cleanly solved, but I 
> think resetting memory by using advantage of the cash line is rendered 
> unusable because the routine can't know how big it is. Still the "normal" 
> assembler memset might be quite faster than the generic c one. Another 
> possibilty would be to define a macro when compiled with --with-cpu=860 to 
> define the cache line to 16. (In the archives the problem seems to be the 
> same but the other way around as the power3 cpu seems to have a 64 byte 
> cacheline)

There's unfortunatly no real solution for this yet.

> I've configured glibc with the prefix=/usr as this is the destination on the 
> target. However for the cross-compiler I installed it otherwhere by specifing 
> a installroot like /usr/local/cross (of course, since I want to keep my glibc 
> for the x86 on my host machine :o)) 
> However the created file /usr/local/cross/usr/lib/libc.so contains a link to 
> /lib/libc.so.6 beeing the libc of my host not the target. Since the 

Since you gave prefix, it uses that prefix.  installroot is for
installing it somewhere else and then moving it around or packaging
it.

> crosscompiler stumbles over this when trying to link an application, I hand 
> edited the file to point to the target glibc /usr/local/cross/lib/libc.so.6


Andreas
-- 
 Andreas Jaeger
  SuSE Labs address@hidden
   private address@hidden
    http://www.suse.de/~aj