Secure identification of execution contexts
A virtual-machine-based system that identifies an application or process in a virtual machine in order to locate resources associated with the identified application. Access to the located resources is then controlled based on a context of the identified application. Those applications without the necessary context will have a different view of the resource.
1. In a computer system comprising a virtual machine monitor (VMM) running on system hardware and supporting a virtual machine (VM) having a first execution context running therein, a method of facilitating a guest operating system (OS) running in the VM to perform at least one function for the first execution context comprising:
the VMM intercepting a first event from the first execution context to the guest OS;
the VMM confirming an identity of the first execution context;
if the identity is confirmed:
the VMM saving a state of the first execution context in a memory space provided for the identified first execution context and passing a second event to the guest OS, the second event being a function of the first event and comprising control return location information;
the guest OS processing the second event and returning control as a function of the control return location information;
the VMM receiving a request to resume the first execution context;
the VMM determining if the request to resume the first execution context is valid; and
if the request to resume is valid, the VMM restoring the saved state of the first execution context; and
the first execution context resuming operation.
2. The method of claim 1 , wherein the first event comprises at least one of:
a virtual hardware interrupt;
a virtual software interrupt;
a virtual hardware fault; and
a control transfer instruction.
3. The method of claim 1 , wherein at least one of: the VMM confirming the identity of the first execution context and determining if the request to resume the first execution context is valid comprises:
the VMM receiving first identifying data corresponding to the first execution context;
the VMM retrieving second data as a function of the received first identifying data;
the VMM retrieving third data as a function of the received first identifying data; and
the VMM confirming the identity of the first execution context as a function of the retrieved second and third data.
4. The method of claim 3 , further comprising:
retrieving the second data from an address space corresponding to the first execution context; and
retrieving the third data from an address space corresponding to the VMM.
5. The method of claim 3 , wherein the first identifying data comprises a first identifier value and a first memory address associated with the first execution context, the method further comprising:
the VMM retrieving the second data as a function of the first memory address.
6. The method of claim 5 , further comprising:
the VMM retrieving the third data as a function of the first identifier value.
7. The method of claim 6 , further comprising:
the VMM retrieving the third data from an address space corresponding to the VMM; and
the VMM retrieving the second data from an address space corresponding to the first execution context.
8. The method of claim 1 , wherein the VMM saving a state of the identified first execution context comprises:
saving contents of registers associated with the identified first execution context at predetermined locations associated with the identified first execution context; and
clearing one or more registers associated with the identified first execution context.
9. The method of claim 8 , further comprising:
modifying a return instruction pointer (IP) register and a stack pointer (SP) register and providing the modified IP and SP information to the guest OS as the control return location information.
10. The method of claim 9 , further comprising:
modifying the IP and SP information with values in locations that are not associated with the identified first execution context.
11. The method of claim 8 , further comprising:
modifying one or more registers to identify control return instructions to the guest OS.
12. The method of claim 1 , further comprising:
the VMM providing the guest OS with access to first data associated with the identified first execution context in a format different from a format in which the identified first execution context accesses the first data.
13. A computer program product for use with a virtual machine monitor (VMM) running on system hardware and supporting a virtual machine (VM) having a first execution context running therein, the computer program product comprising a non-transitory computer readable medium having computer readable program code embodied thereon for performing a method of facilitating a guest operating system (OS) running in the VM to perform at least one function for the first execution context, the method comprising:
the VMM intercepting a first event from the first execution context to the guest OS;
the VMM confirming an identity of the first execution context;
if the identity is confirmed:
the VMM saving a state of the first execution context in a memory space provided for the identified first execution context and passing a second event to the guest OS, the second event being a function of the first event and comprising control return location information;
the guest OS processing the second event and returning control as a function of the control return location information;
the VMM receiving a request to resume the first execution context;
the VMM determining if the request to resume the first execution context is valid; and
if the request to resume is valid, the VMM restoring the saved state of the first execution context; and
the first execution context resuming operation.
14. The computer program product of claim 13 , wherein the first event comprises at least one of:
a virtual hardware interrupt;
a virtual software interrupt;
a virtual hardware fault; and
a control transfer instruction.
15. The computer program product of claim 13 , wherein at least one of: the VMM confirming the identity of the first execution context and determining if the request to resume the first execution context is valid comprises:
the VMM receiving first identifying data corresponding to the first execution context;
the VMM retrieving second data as a function of the received first identifying data;
the VMM retrieving third data as a function of the received first identifying data; and
the VMM confirming the identity of the first execution context as a function of the retrieved second and third data.
16. The computer program product of claim 15 , the method further comprising:
retrieving the second data from an address space corresponding to the first execution context; and
retrieving the third data from an address space corresponding to the VMM.
17. The computer program product of claim 15 , wherein the first identifying data comprises a first identifier value and a first memory address associated with the first execution context, the method further comprising:
the VMM retrieving the second data as a function of the first memory address.
18. The computer program product of claim 17 , the method further comprising:
the VMM retrieving the third data as a function of the first identifier value.
19. The computer program product of claim 18 , the method further comprising:
the VMM retrieving the third data from an address space corresponding to the VMM; and
the VMM retrieving the second data from an address space corresponding to the first execution context.
20. The computer program product of claim 13 , wherein the VMM saving a state of the identified first execution context comprises:
saving contents of registers associated with the identified first execution context at predetermined locations associated with the identified first execution context; and
clearing one or more registers associated with the identified first execution context.
21. The computer program product of claim 20 , the method further comprising:
modifying a return instruction pointer (IP) register and a stack pointer (SP) register and providing the modified IP and SP information to the guest OS as the control return location information.
22. The computer program product of claim 21 , the method further comprising:
modifying the IP and SP information with values in locations that are not associated with the identified first execution context.
23. The computer program product of claim 20 , the method further comprising:
modifying one or more registers to identify control return instructions to the guest OS.
24. The computer program product of claim 13 , the method further comprising:
the VMM providing the guest OS with access to first data associated with the identified first execution context in a format different from a format in which the identified first execution context accesses the first data.