Messages in this thread | | | Date | Fri, 05 Aug 2011 17:32:10 -0700 | From | "H. Peter Anvin" <> | Subject | Re: New vsyscall emulation breaks JITs |
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On 08/05/2011 05:20 PM, Andrew Lutomirski wrote: > > I was thinking of 0x20 - 0x39. 0x40, 0x41, and 0x42 should do the > trick. I'll cook up a patch. > > If you want to keep those vectors available for devices as well, we > could hook do_general_protection instead, but that's a little messy. > Are there x86 machines out there that are starved for interrupt > vectors? >
Yes, but 3 aren't going to matter much.
However, on systems which have interrupt migration enabled we're not using 0x21-0x2f for anything (because we need a single interrupt with absolutely lowest priority). Out of that range, there are a couple of values which should be safe to use because they would be harmless instructions of various forms:
0x24 - AND AL, imm8 0x25 - AND EAX, imm32 0x26 - ES: 0x2C - SUB AL, imm8 0x2D - SUB EAX, imm32 0x2E - CS:
[Cc: Suresh who is the expert on the interrupt assignments]
-hpa
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