• Petr Mladek's avatar
    livepatch: Allow to call a custom callback when freeing shadow variables · 3b2c77d0
    Petr Mladek authored
    We might need to do some actions before the shadow variable is freed.
    For example, we might need to remove it from a list or free some data
    that it points to.
    
    This is already possible now. The user can get the shadow variable
    by klp_shadow_get(), do the necessary actions, and then call
    klp_shadow_free().
    
    This patch allows to do it a more elegant way. The user could implement
    the needed actions in a callback that is passed to klp_shadow_free()
    as a parameter. The callback usually does reverse operations to
    the constructor callback that can be called by klp_shadow_*alloc().
    
    It is especially useful for klp_shadow_free_all(). There we need to do
    these extra actions for each found shadow variable with the given ID.
    
    Note that the memory used by the shadow variable itself is still released
    later by rcu callback. It is needed to protect internal structures that
    keep all shadow variables. But the destructor is called immediately.
    The shadow variable must not be access anyway after klp_shadow_free()
    is called. The user is responsible to protect this any suitable way.
    
    Be aware that the destructor is called under klp_shadow_lock. It is
    the same as for the contructor in klp_shadow_alloc().
    Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
    Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
    Acked-by: default avatarMiroslav Benes <mbenes@suse.cz>
    Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
    3b2c77d0
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