• Michael Neuling's avatar
    powerpc/tm: Fix userspace stack corruption on signal delivery for active transactions · 2b3f8e87
    Michael Neuling authored
    When in an active transaction that takes a signal, we need to be careful with
    the stack.  It's possible that the stack has moved back up after the tbegin.
    The obvious case here is when the tbegin is called inside a function that
    returns before a tend.  In this case, the stack is part of the checkpointed
    transactional memory state.  If we write over this non transactionally or in
    suspend, we are in trouble because if we get a tm abort, the program counter
    and stack pointer will be back at the tbegin but our in memory stack won't be
    valid anymore.
    
    To avoid this, when taking a signal in an active transaction, we need to use
    the stack pointer from the checkpointed state, rather than the speculated
    state.  This ensures that the signal context (written tm suspended) will be
    written below the stack required for the rollback.  The transaction is aborted
    becuase of the treclaim, so any memory written between the tbegin and the
    signal will be rolled back anyway.
    
    For signals taken in non-TM or suspended mode, we use the
    normal/non-checkpointed stack pointer.
    
    Tested with 64 and 32 bit signals
    Signed-off-by: default avatarMichael Neuling <mikey@neuling.org>
    Cc: <stable@vger.kernel.org> # v3.9
    Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    2b3f8e87
transactional_memory.txt 7.89 KB