Electrical computers and digital processing systems: memory – Address formation – Address mapping
Reexamination Certificate
2000-01-10
2003-12-02
Sparks, Donald (Department: 2187)
Electrical computers and digital processing systems: memory
Address formation
Address mapping
C711S201000, C711S203000, C711S205000, C711S207000, C708S203000, C710S068000
Reexamination Certificate
active
06658548
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates in general to data processing systems and in particular to data processing systems with protected regions of memory. Still more particularly, the present invention relates to systems and methods for extracting data from a protected region of the memory of a data processing system.
2. Description of the Related Art
Years ago, programs typically accessed the memory of a data processing system by utilizing memory addresses that directly specified physical memory locations. For example, the Intel 8086 processor supports a “real mode” of operation, which allows programs to utilize such a direct memory access method. Subsequent processors, such as the Intel 80286 and higher processors, also support “protected mode” operation, which provides a virtual memory that is translated (or mapped) onto the physical memory of the data processing system by a memory manager. When operating in protected mode, the memory manager interprets any programmatic references to memory as references to virtual memory addresses, rather than physical memory addresses. Consequently, programs executing in protected mode cannot directly access physical memory, and even indirect access to physical memory (i.e., access to physical memory via virtual memory) is limited for any particular program to the physical memory onto which that program's virtual memory is mapped. As far as that program is concerned, the rest of the physical memory of the data processing system is inaccessible (or protected).
Preventing programs from accessing certain regions of physical memory often serves useful purposes, particularly in contexts such as multitasking and memory compression. The present invention recognizes, however, that the ability to analyze data that is stored in protected regions of physical memory can sometimes be useful, particularly for the people who design hardware and software for managing memory.
SUMMARY OF THE INVENTION
In order to permit selective access to protected memory, the present invention introduces a method, system, and program product that loads at least a first part of extraction code into physical memory and, thereafter, activates a memory mapping facility that maps a virtual memory onto the physical memory and prevents programs from accessing a protected memory region of the physical memory. At least a second part of the extraction code is then loaded into the real memory utilizing the memory mapping facility. The extraction code is then executed to deactivate the memory mapping facility and copy data from the protected memory region to a second physical memory region, such that subsequent reactivation of the memory mapping facility will cause a virtual memory region to be mapped onto the second physical memory region.
All objects, features, and advantages of the present invention will become apparent in the following detailed written description, when considered with the following claims.
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Kochar Sumeet
McHugh Mary Joan
Palte James Gerard
Poff Dan Edward
Saccone, Jr. Robert
Bracewell & Patterson LLP
Dinh Ngoc V
International Business Machines - Corporation
Sparks Donald
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