• Chris Metcalf's avatar
    [PATCH v3] ipc: provide generic compat versions of IPC syscalls · 48b25c43
    Chris Metcalf authored
    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 config option that can be
    set 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 select this option, and thus can
    avoid having any IPC-specific code at all in their architecture-specific
    compat layer.  In the same vein, if this option is not selected, 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.
    Reviewed-by: default avatarArnd Bergmann <arnd@arndb.de>
    Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
    48b25c43
compat.h 20.2 KB