• Tony Luck's avatar
    [IA64] Workaround for RSE issue · 4dcc29e1
    Tony Luck authored
    Problem: An application violating the architectural rules regarding
    operation dependencies and having specific Register Stack Engine (RSE)
    state at the time of the violation, may result in an illegal operation
    fault and invalid RSE state.  Such faults may initiate a cascade of
    repeated illegal operation faults within OS interruption handlers.
    The specific behavior is OS dependent.
    
    Implication: An application causing an illegal operation fault with
    specific RSE state may result in a series of illegal operation faults
    and an eventual OS stack overflow condition.
    
    Workaround: OS interruption handlers that switch to kernel backing
    store implement a check for invalid RSE state to avoid the series
    of illegal operation faults.
    
    The core of the workaround is the RSE_WORKAROUND code sequence
    inserted into each invocation of the SAVE_MIN_WITH_COVER and
    SAVE_MIN_WITH_COVER_R19 macros.  This sequence includes hard-coded
    constants that depend on the number of stacked physical registers
    being 96.  The rest of this patch consists of code to disable this
    workaround should this not be the case (with the presumption that
    if a future Itanium processor increases the number of registers, it
    would also remove the need for this patch).
    
    Move the start of the RBS up to a mod32 boundary to avoid some
    corner cases.
    
    The dispatch_illegal_op_fault code outgrew the spot it was
    squatting in when built with this patch and CONFIG_VIRT_CPU_ACCOUNTING=y
    Move it out to the end of the ivt.
    Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
    4dcc29e1
sections.h 1.04 KB