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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: Tony Luck <tony.luck@intel.com> |
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