-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 H. Peter Anvin wrote: > The 6-word limit is a red herring. There is at least two ways to deal > with it (and this doesn't mean wiping the legacy stuff we already have): > > - Let each architecture pick a calling convention and redefine the > architecture-independent bits to take an arbitrary number of arguments. > This is a one-time panarchitectural change. > [...]
Just think beyond wishful thinking for a moment. What does it take to come up with something completely new and grand? Let's start at the basic: you need to signal that the new syscall calling convention is used. Since the syscall entry code is limited (at least the likes of syscall/sysenter, it would be easy enough to use int $0x81 in addition to int $0x80) you would have to extend the use of the syscall number while keeping binary compatibility. This means additional costs for every single syscall. Once you're past that, how do you implement the expandable syscall parameter count? There are two ways: - - pass to the real sys_* implementations the number of provided syscall parameters and have each function figure out what this means - - dynamically construct a call to the sys_* functions where the syscall magic adds an appropriate number of parameters filled with zeros. This is quite complicated and, more importantly, it requires that you have code/data somewhere which specifies how many parameters each of the sys_* function actually requires. The actual sys_* code and the data has to be kept in sync at all times. A maintenance nightmare. The handling of syscalls with many parameters should not at all be a driver of this design at all. Syscalls shouldn't be that complicated, I completely agree with ingo. I'm perfectly willing to give you the benefit of doubt, show us a design for what you're proposing which is not slower than the current code, doesn't impact existing code, and solves the problem in a nice and clean way. I cannot really see it now but I might miss something. The sys_indirect approach ain't pretty but it does it jobs, doesn't impact performance, and is expandable in direction we *know* we will want to go very soon. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org iD8DBQFHS1X12ijCOnn/RHQRAihRAJwLNJ9fT8GTv6MAoO6RZGOub07sGgCdGBLR frXyQVB8Oh5VgWY5YJhpitg= =FuBx -----END PGP SIGNATURE----- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
