On Sat, Jun 11, 2011 at 05:50, Jonathan Elchison <JElchison@xxxxxxxxx> wrote:
In arch/m68k/math-emu/multi_arith.h, lsl64() doesn't calculate a
correct HI_WORD(*dest) when count < 32, due to an incorrect shift
operation. ÂThis line:
 ÂHI_WORD(*dest) = (HI_WORD(*dest) << count) | (LO_WORD(*dest) >> count);
...should be...
 ÂHI_WORD(*dest) = (HI_WORD(*dest) << count) | (LO_WORD(*dest) >>
(32 - count));
This function is ifdef'd out, marked as "old code". ÂHowever, I fell
into the same trap into which I suspect others have fallen (or will
fall): ÂOn rare occasion when I need to implement my own library
functions, I depend on the Linux kernel to provide solid code. ÂThis
bug, albeit in old code, led me astray.
I'm asking that this old code (lsl64) be corrected or removed.
I think it's better to just remove all #ifdefed out parts in the code.
diff -up linux-2.6/arch/m68k/math-emu/multi_arith.h
linux-2.6_orig/arch/m68k/math-emu/multi_arith.h
--- linux-2.6/arch/m68k/math-emu/multi_arith.h Â2011-06-10
22:50:32.538711320 -0400
+++ linux-2.6_orig/arch/m68k/math-emu/multi_arith.h   2011-06-10
22:47:43.407285452 -0400
@@ -236,7 +236,7 @@ static inline void lsl64(int count, unsi
Â{
   Âif (count < 32) {
       ÂHI_WORD(*dest) = (HI_WORD(*dest) << count)
- Â Â Â Â Â Â Â Â Â | (LO_WORD(*dest) >> (32 - count));
+ Â Â Â Â Â Â Â Â Â | (LO_WORD(*dest) >> count);
       ÂLO_WORD(*dest) <<= count;
       Âreturn;
   Â}
The patch is reversed?
Gr{oetje,eeting}s,
            Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
             Â Â -- Linus Torvalds
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