qemu discuss - Mar 2007 - Re: [xwin-discuss] snv_48: X libraries breaking System V SPARC ABI?

J?rgen Keil wrote:
>Aren''t system libraries required not to touch application global
registers %g2 - %g4?
>  
>
Yeah, the good old ABI.
x86 readers may need a quick refresh first, especially considering the 
v8 versus v8plus  <--->  versus v9 ABI differences:
http://developers.sun.com/solaris/articles/sparcv9abi.html
http://docs.sun.com/app/docs/doc/816-5138/6mba6ua5p?a=view
>When I look at the disassembly of _XInternAtom in /usr/lib/libX11.so.4
>(from Solaris Nevada snv_48 SPARC), I see that the code is using / thrashing
>global register %g2.
>
>I see code like this:
>
>    _XInternAtom+0x264:     94 10 00 11  mov       %l1, %o2
>    _XInternAtom+0x268:     ac 0d e0 03  and       %l7, 0x3, %l6
>    _XInternAtom+0x26c:     84 0a 60 03  and       %o1, 0x3, %g2
>    _XInternAtom+0x270:     80 95 80 02  orcc      %l6, %g2, %g0
>
>
>Or this:
>
>    _XInternAtom+0x2bc:     c4 0d bf ff  ldub      [%l6 - 0x1], %g2
>    _XInternAtom+0x2c0:     16 bf ff f9  bge       -0x1c        
<_XInternAtom+0x2a4>
>    _XInternAtom+0x2c4:     c4 2d ff ff  stb       %g2, [%l7 - 0x1]
>
>
>This breaks applications like qemu, which is trying to use global registers
%g2 - %g4;
>but some of these global register variables get thrashed by calls into the
X11
>libraries.
>
>Shouldn''t the Solaris X11 shared libraries be compiled with 
-xregs=no%appl ?
>  
>
Aren''t they already, at least in terms of Xorg 7.2 ??

--->>  

# grep -n "xregs=no%appl" 
/mnt/6/Xorg720_alanc/X-src-20070227/XW_NV/open-src/common/Makefile.inc__ORIG
76:DEFAULT_sun4_ARCH_LIB_FLAGS  = -xregs=no%appl
#
>See also Bug ID 4166599
>http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=4166599
> 
>  
>
However, in order to get Xorg running and rocking on sparc (letting qemu 
alone for now), I have a completely different set of _real_ problems!
I permanently get kernel panics (with Xorg built for v8plus), have quite 
a number of funny address alignment issues in the bus scanning code for 
the misc. bridges (i.e. Schizo, Schizo+, Psycho, Simba etc.), especially 
on v9 or v9a (-xmemalign=4i shows best results, but not all PCI_bus''s 
cards are identified with it ... ), then, worse: The pci bus subsystems 
are standardized (though there are still a few differences among 
vendors, i.e. how pci errors are treated, traps etc.).
However, the pci2.2 spec does not cover the underlying bridges, 
unfortunately!
Due to a lack of SUNW-internal specs and documentation my last chance 
was, to browse linux and bsd* kernel sources and relevant parts of Xorg 
code.

My Xorg7.2 patch due on March31st will enable/cover _both_ 
build32(v8plus) and build64(v9) builds, because the pci and sbus/upa bus 
scanning code needs substantial further porting for it to work half as 
good for v9, when compared to how well it already does on / for v8 or 
v8plus.

Martin Bochnig wrote:
>> Shouldn''t the Solaris X11 shared libraries be compiled with  
>> -xregs=no%appl ?
> 
> Aren''t they already, at least in terms of Xorg 7.2 ??
> 
> --->> 
> # grep -n "xregs=no%appl" 
>
/mnt/6/Xorg720_alanc/X-src-20070227/XW_NV/open-src/common/Makefile.inc__ORIG
> 
> 76:DEFAULT_sun4_ARCH_LIB_FLAGS  = -xregs=no%appl
> #
Yes, though libX11 is still compiled in the old X11R6 tree, but it similarly
has in the Imake configs (which aren''t open, but this bit is clearly
not
encumbered):

# ifndef ArchLibraryCCOptions
#  if HasSunC && defined(SparcArchitecture) &&
CCompilerMajorVersion > 3
#   define ArchLibraryCCOptions -xregs=no%appl
#  else
#   define ArchLibraryCCOptions
#  endif
# endif /* ArchLibraryCCOptions */

# ifndef LibraryCCOptions
#  if DoSharedLib && defined(SharedLibraryCCOptions)
#   define LibraryCCOptions SharedLibraryCCOptions ArchLibraryCCOptions
#  else
#   define LibraryCCOptions DefaultCCOptions ArchLibraryCCOptions
#  endif
# endif


-- 
	-Alan Coopersmith-           alan.coopersmith at sun.com
	 Sun Microsystems, Inc. - X Window System Engineering