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David Johnson authored
This means that the personality can emulate breakpoints and singlesteps in userspace threads, on behalf of the generic OS Process overlay driver. Thus, the OS Process driver can now be stacked atop the KVM/QEMU driver with real breakpoints. Previously, it could be stacked atop KVM/QEMU, but without userspace breakpoints... so it wasn't especially useful for active debugging. The OS Process driver was previously only able to stack atop the Xen driver, because the Xen driver supported hacked hypervisors that would divert userspace debug exceptions to the driver (as well as kernel debug exceptions). Hacking QEMU's GDB stub to do this was undesireable, and infeasible. (The QEMU/KVM support was built through the GDB driver, because QEMU provides a GDB server stub --- but supporting userspace breakpoints in an overlay driver atop our GDB driver was infeasible due to the "shared page" breakpoint issue. The shared page issue occurs when we place a ...
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