• David Mosberger-Tang's avatar
    [IA64] fix syscall-optimization goof · a37d98f6
    David Mosberger-Tang authored
    Sadly, I goofed in this syscall-tuning patch:
    
    ChangeSet 1.1966.1.40 2005/01/22 13:31:05 davidm@hpl.hp.com
      [IA64] Improve ia64_leave_syscall() for McKinley-type cores.
    
      Optimize ia64_leave_syscall() a bit better for McKinley-type cores.
      The patch looks big, but that's mostly due to renaming r16/r17 to r2/r3.
      Good for a 13 cycle improvement.
    
    The problem is that the size of the physical stacked registers was
    loaded into the wrong register (r3 instead of r17).  Since r17 by
    coincidence always had the value 1, this had the effect of turning
    rse_clear_invalid into a no-op.  That poses the risk of leaking kernel
    state back to user-land and is hence not acceptable.
    
    The fix below is simple, but unfortunately it costs us about 28 cycles
    in syscall overhead. ;-(
    
    Unfortunately, there isn't much we can do about that since those
    registers have to be cleared one way or another.
    
    	--david
    Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
    a37d98f6
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