It would still cause a slowdown, perhaps somewhere critical (interrupt
handler, syscall entry point etc). If a breakpoint is placed in
encryption code or the /dev/random driver, the timing effects would leak
information.
What happens if a breakpoint is placed in the debug trap handler, the
syscall entry point, ret_from_syscall etc.?
> The patch looks fine regardless, but I want to have a robust system, and
> that does mean that even if somebody can trigger a debug trap in the
> kernel (easy to do by just having a read() system call write over
> something you want to get the trap on in user mode) then the kernel should
> not really have to care anyway.
It does make sense for the debug trap to be robust as well.
-- Jamie
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