On Mon, Mar 15, 2010 at 04:18:33PM +1100, Benjamin Herrenschmidt wrote: > On Sun, 2010-03-14 at 22:06 -0700, David Miller wrote: > > From: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> > > Date: Mon, 15 Mar 2010 15:48:13 +1100 > > > > > As it is, any 32-bit app using syscall() on any of the syscalls that > > > takes 64-bit arguments will be broken, unless the app itself breaks up > > > the argument, but the the order of the hi and lo part is different > > > between BE and LE architectures ;-) > > > > I think it is even different on the same endian architectures, > > f.e. mips I think. MIPS passes arguments in the endian order that is low/high for little endian rsp high/low for big endian. > > There is no way to do this without some arch specific code > > to handle things properly, really. > > Right, but to what extent ? IE. do we always need the callers using > syscall() directly to know it all, or can we to some extent handle some > of it inside glibc ? > > For example, if powerpc glibc is fixed so that syscall() takes a 64-bit > first argument (or calls via some macro to add a dummy 32-bit argument), > the register alignment will be preserved, and things will work just > fine. > > IE. It may not fix all problems with all archs, but in this case, it > will fix the common cases for powerpc at least :-) And any other arch > that has the exact same alignment problem. > > Or is there any good reason -not- to do that in glibc ? Syscall is most often used for new syscalls that have no syscall stub in glibc yet, so the user of syscall() encodes this ABI knowledge. If at a later stage syscall() is changed to have this sort of knowledge we break the API. This is something only the kernel can get right. Ralf -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html