On Tue, Jan 20, 2004 at 07:31:57PM +0100, Ralf Baechle wrote:
> On Tue, Jan 20, 2004 at 08:42:15PM +0300, Pavel Kiryukhin wrote:
>
> > Hi all,
> > my question - does endiannes matters in sigset translation in
> > sys32_rt_sigtimedwait (arch/mips/signal32.c)?
>
> Think about where bit 33 ends for a big endian machine with an without
> the conversion.
No, I'm pretty sure Pavel's right.
-#ifdef __MIPSEB__
case 1: these.sig[0] = these32.sig[0] | (((long)these32.sig[1]) << 32);
-#endif
-#ifdef __MIPSEL__
- case 1: these.sig[0] = these32.sig[1] | (((long)these32.sig[0]) << 32);
-#endif
Consider a 64-bit sigset. 32-bit userland, 64-bit kernel. Here's a
userland sigset with signal 33 set, only, on a little endian target.
Word 1, least significant bit, right?
byte address in memory
1 2 3 4 5 6 7 8
val 0 0 0 0 0 0 0 1
Obviously, as a 64-bit integer the sigset looks different. There it's
supposed to be 1 << (33 - 1).
val 0 0 0 1 0 0 0 0
So the correct algorithm to convert a userspace sigset to a kernel
sigset is to shift the second word left 32 bits, and leave the first
word right aligned, and or them together. Which is what using the
__MIPSEB__ case does.
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer
