Re: sparc64: Optimized immediate value implementation build error

[Mathieu Desnoyers]

* David Miller (davem@xxxxxxxxxxxxx) wrote:
> From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
> Date: Mon, 13 Oct 2008 22:17:04 -0400
> 
> > * David Miller (davem@xxxxxxxxxxxxx) wrote:
> > > From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
> > > Date: Mon, 13 Oct 2008 19:37:53 -0400
> > > 
> > > > * David Miller (davem@xxxxxxxxxxxxx) wrote:
> > > > > From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
> > > > > Date: Fri, 3 Oct 2008 16:10:07 -0400
> > > > > 
> > > > > > I ran a cross-compiler on the -lttng tree
> > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/compudj/linux-2.6-lttng.git
> > > > > > 
> > > > > > to build the sparc64 arch, and ran across this build error :
> > > > > > 
> > > > > > /home/compudj/git/morestable/linux-2.6-lttng/include/trace/sched.h: In function `do_fork':
> > > > > > /home/compudj/git/morestable/linux-2.6-lttng/include/trace/sched.h:38: warning: asm operand 1 probably doesn't match constraints
> > > > > > /home/compudj/git/morestable/linux-2.6-lttng/include/trace/sched.h:38: error: impossible constraint in `asm'
> > > > > > /home/compudj/git/morestable/linux-2.6-lttng/include/trace/sched.h:38: warning: 'value' might be used uninitialized in this function
> > > > > > make[2]: *** [kernel/fork.o] Error 1
> > > > > > 
> > > > > > I think it's caused by :
> > > > > > http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=commit;h=c76bfa90a6eb02651368a152b3646aa672d9e625
> > > > > 
> > > > > It can't be "caused by" that commit because that's the initial
> > > > > immediate value sparc64 support I wrote and the tree very much compiled
> > > > > properly when I did test builds way back then.
> > > > > 
> > > > > I don't have time to look further into this right now, sorry.
> > > > 
> > > > Ok, I'll dig into this. I use gcc 3.4.5, that could be my problem; it's
> > > > broken on x86_64. I'll do some testing in this direction. Also, I see
> > > > that you have used .uaword and declared "int" in your sparc64
> > > > implementation to encode pointers. Am I missing something or should it
> > > > be "long" and either .word or .xword (32 or 64 bits) ?
> > > 
> > > long would be for ".uaxword", ".uaword" is 32-bit.  It means
> > > "UnAligned WORD"
> > > 
> > 
> > Ok, it's fixed.
> 
> How? :-)
> 

The int -> long uses commit 
http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=commitdiff;h=3940305f7248f269ae330982bcd6d51d5c55c2f4

Which adds a sparc asm.h to abstract the 32/64 bits "pointer" type at
the assembler level. It's inspired from x86 32/64 :

diff --git a/arch/sparc/include/asm/asm.h b/arch/sparc/include/asm/asm.h
new file mode 100644 (file)
index 0000000..2be3d10
--- /dev/null
+++ b/arch/sparc/include/asm/asm.h
@@ -0,0 +1,19 @@
+#ifndef _ASM_SPARC_ASM_H
+#define _ASM_SPARC_ASM_H
+
+#ifdef __ASSEMBLY__
+# define __ASM_FORM(x) x
+#else
+# define __ASM_FORM(x) " " #x " "
+#endif
+
+#ifdef CONFIG_SPARC32
+# define __ASM_SEL(a,b)        __ASM_FORM(a)
+#else
+# define __ASM_SEL(a,b)        __ASM_FORM(b)
+#endif
+
+#define _ASM_PTR       __ASM_SEL(.word, .xword)
+#define _ASM_UAPTR     __ASM_SEL(.uaword, .uaxword)
+
+#endif /* _ASM_SPARC_ASM_H */

I also check for the compiler version to only enable immediate values if
gcc is >= 4.0.0. I suspect that sparc64 gcc has similar issues x86_64
gcc 3.x has with base+offset addresses and "i" inline asm constraint.

This is done in commit :
http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=commit;h=3c1106cf88f849a381c0bc01ccb185a3911e6a51

But my cross-compiler for sparc64 is only gcc 3.4.5 and I did not
succeed to find the right versions of gcc/glibc and binutils working
together to cross-build with a gcc >= 4.0.0 on x86_64. So some testing
is welcome.

> > If someone has access to a sparc64 gcc >= 4.0.0 compiler (native or
> > cross) and some spare cycles, if would be interesting to build test this
> > with CONFIG_IMMEDIATE=y and with CONFIG_TRACEPOINTS=y and
> > CONFIG_MARKERS=y :
> > 
> > git://git.kernel.org/pub/scm/linux/kernel/git/compudj/linux-2.6-lttng.git
> > branch : 2.6.27-lttng-0.40
> 
> I just checked out 0.39 and was building it to try and reproduce your failure.
> I'll pull in 0.40 next.

I'm looking forward to hear about the results. Thanks !

Mathieu


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Mathieu Desnoyers
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