• Mathieu Desnoyers's avatar
    x86: Fix fixmap page order for FIX_TEXT_POKE0,1 · 12b9d7cc
    Mathieu Desnoyers authored
    Masami reported:
    
    > Since the fixmap pages are assigned higher address to lower,
    > text_poke() has to use it with inverted order (FIX_TEXT_POKE1
    > to FIX_TEXT_POKE0).
    
    I prefer to just invert the order of the fixmap declaration.
    It's simpler and more straightforward.
    
    Backward fixmaps seems to be used by both x86 32 and 64.
    
    It's really rare but a nasty bug, because it only hurts when
    instructions to patch are crossing a page boundary. If this
    happens, the fixmap write accesses will spill on the following
    fixmap, which may very well crash the system. And this does not
    crash the system, it could leave illegal instructions in place.
    Thanks Masami for finding this.
    
    It seems to have crept into the 2.6.30-rc series, so this calls
    for a -stable inclusion.
    Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
    Acked-by: default avatarMasami Hiramatsu <mhiramat@redhat.com>
    Cc: <stable@kernel.org>
    LKML-Reference: <20090701213722.GH19926@Krystal>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    12b9d7cc
fixmap.h 6.14 KB