On Fri, 9 Dec 2011 10:29:07 -0500 Chris Metcalf <cmetcalf@xxxxxxxxxx> wrote: > When using the "compat" APIs, architectures will generally want to > be able to make direct syscalls to msgsnd(), shmctl(), etc., and > in the kernel we would want them to be handled directly by > compat_sys_xxx() functions, as is true for other compat syscalls. > > However, for historical reasons, several of the existing compat IPC > syscalls do not do this. semctl() expects a pointer to the fourth > argument, instead of the fourth argument itself. msgsnd(), msgrcv() > and shmat() expect arguments in different order. > > This change adds an __ARCH_WANT_OLD_COMPAT_IPC define that can be > set in <asm/compat.h> to preserve this behavior for ports that use it > (x86, sparc, powerpc, s390, and mips). No actual semantics are changed > for those architectures, and there is only a minimal amount of code > refactoring in ipc/compat.c. > > Newer architectures like tile (and perhaps future architectures such > as arm64 and unicore64) should not supply this define, and thus can > avoid having any IPC-specific code at all in their architecture-specific > compat layer. In the same vein, if this define is omitted, IPC_64 mode > is assumed, since that's what the <asm-generic> headers expect. > > The workaround code in "tile" for msgsnd() and msgrcv() is removed > with this change; it also fixes the bug that shmat() and semctl() were > not being properly handled. What would we need to do to get all architectures using the new interfaces, and remove __ARCH_WANT_OLD_COMPAT_IPC? Regarding the implementation: rather than patching the header files, it would be more conventional (and arguably better) to add select ARCH_WANT_OLD_COMPAT_IPC to arch/*/Kconfig, then use CONFIG_ARCH_WANT_OLD_COMPAT_IPC.
