Multiprocessor support #1
Description
Currently, HyperDbg only puts a single logical CPU into VMX mode. HyperDbg
will still run on a machine with multiple logical processors, but not very
well - pressing F12 to break into HyperDbg will only break 25% of the time
on a 4 CPU box, since the keyboard I/O is only getting intercepted on one
CPU.
(Note: When I say processor or CPU below, I mean a logical processor, not a
physical one. A dual-core processor with HT enabled has 4 logical
processors).
These changes will need to be made to HyperDbg to support multiple
processors:
1. Each CPU needs its own vmxInitState and associated memory regions (VMXON
region, VMCS region, VMEXIT handler stack memory, I/O bitmap, IDT, etc),
2. VMXON needs called on each processor
3. Each CPU needs its own guest context (CPU_CONTEXT) structure, and any
function that references the context needs to be able to get the right
context for the CPU it's running on.
4. Any global structures that can be modified by more than one processor
will need a lock
5. The cleanup/exit code needs to take all of this into account
6. I'm sure there are other issues
It's possible to count the logical processors and get the ID of the current
processor in a OS-independent way with CPUID(1). Getting code to run on a
specific processor is something that is OS-specific though - you have to
ask the OS to run a thread on a certain processor by setting the affinity
mask. In Windows this can be done with ZwSetInformationThread(2).
Since a major goal of HyperDbg is to have a platform independent core, I
don't want to muddy up vmx.c with a bunch of Windows-specific API calls
(although it already makes calls to the Windows kernel's Mm* functions to
allocate memory...).
With that in mind, here's what I propose:
1. Move any code that requires Windows APIs in vmx.c to a file that
identifies it as platform-dependent, maybe "vmx-windows.c". Most of
VmxInitialize() and VmxFinalize() will need to implemented in a platform-
dependent way. #ifdef's can be used to call the right code for the platform
HyperDbg is built on. Anyone who wants to implement support for other OS's
can add a vmx-linux.c or vmx-freebsd.c or whatever.
2. Add a function that can identify the current processor and get the
correct guest context for it. This will be needed by many functions in
vmx.c and vmhandlers.c. This should be done platform-independently.
3. Review the code to see if there are any other issues that need taken
into account for multiple processors.
References:
(1): Intel Processor Identification and the CPUID Instruction -
http://www.intel.com/assets/pdf/appnote/241618.pdf
(2): Processor Affinity in a driver -
http://www.osronline.com/showThread.cfm?link=26006
Original issue reported on code.google.com by [email protected] on 31 May 2010 at 2:17