A method and device for reliably assessing the integrity of a computer system's software prevents execution of corrupted programs at time of system initialization, enhancing system security. Programs and data comprising the system's trusted software, including all startup processes, are verified before being utilized. Methods to verify the trusted software use a hierarchy of both modification detection codes and public-key digital signature codes. The top-level codes are placed in a protectable non-volatile storage area, and are used by the startup program to verify the integrity of subsequent programs. A trusted initialization program sets a hardware latch to protect the codes in the non-volatile memory from being overwritten by subsequent untrusted programs. The latch is only reset at system restart, when control returns to the bootstrap program. Software reconfiguration is possible with trusted programs that write new top-level codes while the latch is open. The mechanism itself is immune to malicious software attack when the write-protect latch is closed before running untrusted software. Preferred embodiments in an IBM-compatible personal computer uses the reset switch to initiate a trusted path between the user and a program. Damage from certain classes of computer virus and trojan horse attacks is prevented. A system recovery process is described. A related improved method for user authentication uses a read-and -write memory protection latch to prevent access to sensitive authentication data.

Method and apparatus for assessing integrity of computer system software

In a computer that has hardware processor, and a memory, the invention provides a virtual machine monitor (VMM) and a virtual machine (VM) that has at least one virtual processor and is operatively connected to the VMM for running a sequence of VM instructions, which are either directly executable or non-directly executable. The VMM includes both a binary translation sub-system and a direct execution sub-system, as well as a sub-system that determines if VM instructions must be executed using binary translation, or if they can be executed using direct execution. Shadow descriptor tables in the VMM, corresponding to VM descriptor tables, segment tracking and memory tracing are used as factors in the decision of which execution mode to activate. The invention is particularly well-adapted for virtualizing computers in which the hardware processor has an Intel x86 architecture.

Virtualization system including a virtual machine monitor for a computer with a segmented architecture

A virtual machine monitor (VMM) is included in a computer system that has a protected host operating system (HOS). A virtual machine running at least one application via a virtual operating system is connected to the VMM. Both the HOS and the VMM have separate operating contexts and disjoint address spaces, but are both co-resident at system level. A driver that is downloadable into the HOS at system level forms a total context switch between the VMM and HOS contexts. A user-level emulator accepts commands from the VMM via the system-level driver and processes these commands as remote procedure calls. The emulator is able to issue host operating system calls and thereby access the physical system devices via the host operating system. The host operating system itself thus handles execution of certain VMM instructions, such as accessing physical devices.

System and method for virtualizing computer systems

A system and method for displaying digital media files (566) with compulsory advertisement files is disclosed. In one embodiment, the system includes a user interface (500), a media file decryptor (582), an ad manager (514), an intersplicer (518), and a media player (520). The user interface receives input from a user indicating the selection of media files to be presented. The media file decryptor receives and decrypts the selected media files. The ad manager receives and manages ad files from an ad file source. The intersplicer combines the media files with the ad files by providing control signals to the media player, causing the media player to present the ad files with the selected media files. Various embodiments of the invention facilitate the wide distribution of media content in a way that allows the free use of media properties, on demand, with direct consumer exchange capabilities, while at the same time enabling compensation to copyright holders.

Method and apparatus for the free licensing of digital media content

An alternate display content controller provides a technique for controlling a video display separately from and in addition to the content displayed on the operating system display surface. Where the display is a computer monitor, the alternate display content controller interacts with the computer utility operating system and hardware drivers to control allocation of display space and create and control one or more parallel graphical user interfaces adjacent the operating system desktop. An alternate display content controller may be incorporated in either hardware or software. As software, an alternate display content controller may be an application running on the computer operating system, or may include an operating system kernel of varying complexity ranging from dependent on the utility operating system for hardware system services to a parallel system independent of the utility operating system and capable of supporting dedicated applications. The alternate display content controller may also include content and operating software delivered over the internet or any other LAN. The alternate display content controller may also be included in a television decoder/settop box to permit two or more parallel graphical user interfaces to be displayed simultaneously.

Method and system for controlling a complementary user interface on a display surface

The UNIX® and MS-DOS® operating systems are supported in a multi-tasking computer. At the heart of the computer is a microprocessor having protected and non-protected modes. The computer includes special-purpose hardware which prevents the MS-DOS system and its applications, which execute in the non-protected mode, from interfering with the UNIX system and its applications, which execute in the protected mode. In particular, this hardware monitors addresses generated by the computer and, by selectively inhibiting the associated control pulses, prevents the MS-DOS system from, for example, writing in UNIX-system-allocated memory, or accessing I/O devices that the UNIX system is currently using. In addition, a context switching feature is provided whereby the user can select, via a keyboard operation, to have displayed on the computer video monitor at any given time the image generated from the current UNIX system screen data or the image generated from the current MS-DOS system screen data.

Dual operating system computer

A kernel device file system publication system for dynamically enumerating and configuring an instance of a device in the kernel device tree upon request by a user level application. The kernel device file system logically arranges system level devices in a hierarchical tree-like topology defining devices as nodes of a device tree to allow for a top-down access. The top-down access allows devices connecting to the computer system to be configured based on the physical path of the device. This process starts at a bus nexus and drives device configuration down the device tree. The bus configuration interfaces permit each nexus in the device tree hierarchy to participate in the device lookup and readdirs operations performed by the device file system. The device file system path operations are performed as an iterative sequence of bus configure operations, whereby each nexus controls the enumeration and configuration of that nexus' children.

Bus specific device enumeration system and method

One embodiment of the present invention provides a system that uses a directory service to facilitate centralized device naming. The system operates by receiving a registration of a device at a computer system. Next, the system determines if the device has been registered with the directory service. If so, the system retrieves a name of the device from the directory service. If not, the system generates a device name for the device, and registers the device name with the directory service.

Method and apparatus for using a directory service to facilitate centralized device naming

The invention provides efficient apparatus and methods for using direct memory access (DMA) to store and retrieve data and associated check information in fixed-size blocks on a data storage device. A DMA controller of the invention obtains check information from computer main memory rather than computing the check information internally. In accordance with some embodiments of the invention, the DMA controller implements additional registers to specify, for example, the location of check information in computer main memory. The DMA controller itself carries out interleaving of data with its associated check information as it transfers information between main memory and the storage device. In accordance with some aspects of the invention, scatter/gather capability is supported.

Direct memory access transfer of data and check information to and from a data storage device

The UNIX® and $MS-DOS sup R $ operating systems are supported in a multi-tasking computer. At the heart of the computer is a microprocessor having protected and non-protected modes. The computer includes special-purpose hardware which prevents the MS-DOS system and its applications, which execute in the non-protected mode, from interfering with the UNIX system and its applications, which execute in the protected mode. In particular, this hardware monitors addresses generated by the computer and, by selectively inhibiting the associated control pulses, prevents the MS-DOS system from, for example, writing in UNIX-system-allocated memory, or accessing I/O devices that the UNIX system is currently using. In addition, a context switching feature is provided whereby the user can select, via a keyboard operation, to have displayed on the computer video monitor at any given time the image generated from the current UNIX system screen data or the image generated from the current MS-DOS system screen data.

Display context switching arrangement

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