International Business Machines Corporation

Scott Alan Plaetzer

Richard Karl Kirkman

Jeffrey A Grantz

Robert Milton Smith

Ralph O Conder

William N Tindall

Steven Jay Munroe

Michael Joseph Corrigan

Patrick Joseph McCarthy

Kevin Jack Erickson

James William Stopyro

Brian Eldridge Clark

Paul LuVerne Godtland

Donald Arthur Morrison

Patrick James Christenson

A method, apparatus, system, and signal-bearing medium that in an embodiment map a pointer to a target indirectly via a pointer map. In an embodiment, the pointer map is stored in a reserved area and an entry for the pointer in the pointer map includes a back-pointer containing an address of the pointer and a target-address containing the address of the target. When the pointer is accessed, the pointer is checked to ensure its contents point at the entry in the pointer map in the reserved area and that the back-pointer in the pointer map entry points back at the pointer. In this way, pointers are protected from being modified illegitimately.

Secure pointers

A multi-tasking computer operating system allocates a respective virtual address space to each task. A portion of virtual address space is reserved as a shared address space (SAS) region, the SAS region occupying the same range of virtual addresses in the virtual address space of each task. Certain classes of data intended for sharing among multiple tasks are assigned unique and persistent addresses in the range of the shared address space region. Preferably, certain facilities are added to a conventional base operating system to support the SAS region and associated function. These include a join facility for initiating a task to the SAS region, an attach facility for attaching blocks of memory within the SAS region, and a paging facility for retrieving a page within the SAS region from storage. In this manner, it is possible for a multi-tasking multiple virtual address space computer system to assume the advantages of a single level store computer system when performing certain tasks.

Computer system having shared address space among multiple virtual address spaces

An apparatus and method provide simultaneous local and global addressing capabilities in a computer system. A global address space is defined that may be accessed by all processes. In addition, each process has a local address space that is local (and therefore available) only to that process. An address space processor is implemented in software to perform system functions that distinguish between local addresses and global addresses. In the preferred embodiments, the local address space has a size that is a multiple of the size of a segment of global address space. When the hardware indicates a page fault, the address space processor determines whether the address being translated is a local address or a global address. If the address is a local address, the address space processor uses a local directory to process the page fault. If the address is a global address, the address space processor uses a global directory to process the page fault. When the hardware indicates an addressing error because a computed address crosses a global segment boundary, the address space processor determines whether the address is a local address or a global address. If the address is a global address, the address space processor indicates an addressing error. If the address is a local address, the address space processor determines whether the address is within the process' local address space, and indicates an addressing error if the address is outside the process' local address space. Instructions are allowed to operate on both local and global addresses because the address space processor handles either type of address whenever software assistance is required, such as for servicing a page fault or checking a segment boundary crossing. In addition, the address space processor dynamically checks the addressing compatibility of called code before passing control to the called code.

Apparatus and method for providing simultaneous local and global addressing using software to distinguish between local and global addresses

An improved method and system is described for generalized handling of conditions occurring during program execution in a computer system having a multi-language Condition Manager (CM). A general signaling routine having object code for an external entry point suitable for linking to application programs written in any language supporting external calls is used. The signaling routine may be used by programs to eliminate the step of checking return codes from subroutines by coding the subroutine to automatically signal the proper condition to the CM which in conjunction with user defined condition handlers takes proper actions in response to the condition. A general condition token which may be used as a feedback token is defined as a condition identifier, a format code for the condition identifier, a severity code for the condition, a control code for a facility identifier, a facility identifier and an optional handle for instance specific information. The signaling routine and the feedback token are used by subroutines which can optionally provide for passing an address, where a feedback token can be stored. The subroutine signals conditions if the severity of the condition is greater than a threshold or else stores a feedback token at the address.

Computer program product and program storage device for representing and

Method for representing and signaling run-time program conditions

Growing community of inventors

Rochester, MN, United States of America

Scott Alan Plaetzer