• Linus Torvalds's avatar
    x86-64: page faults from user mode are always user faults · dbe3ed1c
    Linus Torvalds authored
    Randy Dunlap noticed an interesting "crashme" behaviour on his dual
    Prescott Xeon setup, where he gets page faults with the error code
    having a zero "user" bit, but the register state points back to user
    mode.
    
    This may be a CPU microcode buglet triggered by some strange instruction
    pattern that crashme generates, and loading a microcode update seems to
    possibly have fixed it.
    
    Regardless, we really should trust the register state more than the
    error code, since it's really the register state that determines whether
    we can actually send a signal, or whether we're in kernel mode and need
    to oops/kill the process in the case of a page fault.
    
    Cc: Randy Dunlap <rdunlap@xenotime.net>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    dbe3ed1c
fault.c 16.9 KB