call int80 callback from x86_64 syscall instruction

[lunixbochs]

If there's an interrupt callback registered, this forces the x86_64 syscall instruction to simulate an int $80 callback and advance PC.

[aquynh]

this looks good. can you please add a sample with SYSCALL instruction to sample_x86.c or sample_x86.py?

thanks.

[lunixbochs]

Added SYSCALL test in sample_x86.py

[aquynh]

merged, thanks.

do you think that we should do something so the callback knows that this comes from SYSCALL rather than INT 0x80?

[lunixbochs]

It's better to be explicit, but this method does work for me right now. The ABI doesn't change in the handler either way afaik. I'm not sure what the alternative would look like. Maybe a non-interrupt handler that's just for SYSCALL-like instructions?

[aquynh]

i just committed a change to handle SYSCALL/SYSENTER instructions separately, so we do not share the callback with interrupts: e1baf2f.

@lunixbochs: with this you will need to modify your usercorn code accordingly.

thanks.