• Petr Mladek's avatar
    livepatch: Remove ordering (stacking) of the livepatches · d67a5372
    Petr Mladek authored
    The atomic replace and cumulative patches were introduced as a more secure
    way to handle dependent patches. They simplify the logic:
    
      + Any new cumulative patch is supposed to take over shadow variables
        and changes made by callbacks from previous livepatches.
    
      + All replaced patches are discarded and the modules can be unloaded.
        As a result, there is only one scenario when a cumulative livepatch
        gets disabled.
    
    The different handling of "normal" and cumulative patches might cause
    confusion. It would make sense to keep only one mode. On the other hand,
    it would be rude to enforce using the cumulative livepatches even for
    trivial and independent (hot) fixes.
    
    However, the stack of patches is not really necessary any longer.
    The patch ordering was never clearly visible via the sysfs interface.
    Also the "normal" patches need a lot of caution anyway.
    
    Note that the list of enabled patches is still necessary but the ordering
    is not longer enforced.
    
    Otherwise, the code is ready to disable livepatches in an random order.
    Namely, klp_check_stack_func() always looks for the function from
    the livepatch that is being disabled. klp_func structures are just
    removed from the related func_stack. Finally, the ftrace handlers
    is removed only when the func_stack becomes empty.
    Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
    Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
    Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
    Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
    d67a5372
cumulative-patches.txt 3.85 KB