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SubjectRe: New vsyscall emulation breaks JITs
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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