• Martin Schwidefsky's avatar
    s390: add a system call for guarded storage · 916cda1a
    Martin Schwidefsky authored
    This adds a new system call to enable the use of guarded storage for
    user space processes. The system call takes two arguments, a command
    and pointer to a guarded storage control block:
    
        s390_guarded_storage(int command, struct gs_cb *gs_cb);
    
    The second argument is relevant only for the GS_SET_BC_CB command.
    
    The commands in detail:
    
    0 - GS_ENABLE
        Enable the guarded storage facility for the current task. The
        initial content of the guarded storage control block will be
        all zeros. After the enablement the user space code can use
        load-guarded-storage-controls instruction (LGSC) to load an
        arbitrary control block. While a task is enabled the kernel
        will save and restore the current content of the guarded
        storage registers on context switch.
    1 - GS_DISABLE
        Disables the use of the guarded storage facility for the current
        task. The kernel will cease to save and restore the content of
        the guarded storage registers, the task specific content of
        these registers is lost.
    2 - GS_SET_BC_CB
        Set a broadcast guarded storage control block. This is called
        per thread and stores a specific guarded storage control block
        in the task struct of the current task. This control block will
        be used for the broadcast event GS_BROADCAST.
    3 - GS_CLEAR_BC_CB
        Clears the broadcast guarded storage control block. The guarded-
        storage control block is removed from the task struct that was
        established by GS_SET_BC_CB.
    4 - GS_BROADCAST
        Sends a broadcast to all thread siblings of the current task.
        Every sibling that has established a broadcast guarded storage
        control block will load this control block and will be enabled
        for guarded storage. The broadcast guarded storage control block
        is used up, a second broadcast without a refresh of the stored
        control block with GS_SET_BC_CB will not have any effect.
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    916cda1a
machine_kexec.c 7.03 KB