Method for executing a 32-bit flat address program during a system management mode interrupt
View Patent ↗A method and system for executing 32-bit flat address programs during a System Management Interrupt. The system provides a 16-bit SMI routine that is given control when an SMI occurs. That routine initially saves the state of the processor and then executes an instruction to switch to protected mode. When in protected mode, the routine transfers control to 32-bit code. The 32-bit code uses a global descriptor table that is different from that used by the interrupted operating system. When the 32-bit code completes, it restores the saved processor state and returns from the interrupt by executing an RSM instruction.
1. A method in a computer system having a global descriptor table register for executing code during a system management mode interrupt (SMI), the method comprising:
upon occurrence of the SMI,
saving state of the computer system;
switching the computer system to protected mode;
replacing first contents of the global descriptor table register that point to a first global descriptor table in use when the system management mode interrupt occurred with second contents that point to a second global descriptor table that is distinct from the first global descriptor table;
executing 32-bit code using the second global descriptor table; and
upon completion of the execution of the 32-bit code,
restoring the saved state of the computer system; and
returning from the occurrence of the SMI.
2. The method of claim 1 wherein the 32-bit code is an operating system kernel for loading and running programs during the occurrence of the system management mode interrupt.
3. The method of claim 2 wherein the programs are Windows Portable Executable programs.
4. The method of claim 1 wherein the computer system is based on an Intel Pentium processor.
5. The method of claim 1 wherein the computer system is based on an Intel-compatible processor.
6. The method of claim 1 wherein the 32-bit code is selected from the group consisting of a remote console program, a remote boot program, a remote diagnostics program, a remote restart program, and a debugging program.
7. The method of claim 1 wherein the computer system has a foreground operating system, and wherein the 32-bit code executes transparently to the foreground operating system.
8. The method of claim 1 wherein the computer system has a foreground operating system, and wherein the 32-bit code executes even if the foreground operating system has crashed or stopped.
9. The method of claim 1 wherein the computer system has a foreground operating system, and wherein the 32-bit code executes when the foreground operating system crashes or stops.
10. The method of claim 1 wherein the 32-bit code is loaded into memory from a ROM.
11. The method of claim 1 wherein the 32-bit code is loaded into memory from a Flash ROM.
12. The method of claim 1 wherein a processor switches to system management mode and executes the SMI in response to a signal received on an input line of the processor.
13. The method of claim 12 wherein the input line is an SMI input line.
14. The method for claim 1 wherein a processor switches to system management mode and executes the SMI in response to a message received via a front side bus of the processor.
15. The method of claim 1 wherein a processor chip set is the source of the SMI.
16. The method of claim 1 wherein a Northbridge controller is the source of the SMI.
17. The method of claim 1 wherein a Southbridge controller is the source of the SMI.
18. The method of claim 1 wherein an electronic circuit is the source of the SMI.
19. The method of claim 1 wherein returning from the occurrence of the interrupt is accomplished by executing an RSM instruction.