Detecting modification to computer memory by a DMA device

A method, comprising the steps of:

• monitoring DMA (direct memory access) memory write transactions of a computer by monitoring circuitry designed to record an indication of a memory location written by a DMA memory write transaction, the circuitry being designed to record the indication without being informed of the memory write transaction beforehand;
• reading the indication from a CPU of the computer.

Computer circuitry, comprising:

• (direct memory access) monitoring circuitry designed to monitor DMA memory write transactions to a main memory of a computer by a DMA device of the computer and to record an indication of a location in the main memory written by the DMA memory write transaction, the DMA monitoring circuitry designed to operate without being informed of the DMA memory write transaction by a CPU of the computer before initiation of the DMA memory write transaction, and to provide the indication to the CPU on request.

A method, comprising the steps of:

• by a first process of a computer, generating a second representation in a computer memory of information stored in the memory in a first representation;
• reporting to the first process that the first representation is overwritten by a DMA memory write transaction initiated by a second process, without the second process informing the first process of the DMA memory write transaction, the reporting guaranteed to occur no later than the next access of the second representation following the DMA memory write transaction.

A computer comprising:

• a CPU programmed to execute first and second processes, the first process programmed to generate a second representation in a computer memory of information of the second process stored in the memory in a first representation;
• DMA monitoring circuitry designed to detect when the first representation is overwritten by a DMA (direct memory access) memory write transaction initiated by the second process, without the second process informing the first process of the DMA memory write transaction, the detecting guaranteed to occur no later than the next access of the second representation following the DMA memory write transaction.

A computer comprising:

• a main memory divided into pages for management by a virtual memory manager, the manager programmed to manage the pages using a table stored in the memory;
• a plurality of registers outside the address space of the main memory, and circuitry designed to record indications of modification to pages of the main memory into the registers;
• wherein the virtual memory management tables do not provide backing store for the modification indications stored in the registers.

A method, comprising the steps of:

• monitoring DMA (direct memory access) memory write transactions, and recording an indication of a location in a main memory written by the DMA memory write transaction, the monitored DMA memory write transactions being writes to a main memory of a computer by a DMA device of the computer, circuitry and/or software for the monitoring and recording being designed to perform the monitoring and recording independently of circuitry and/or software for initiation or control of the monitored DMA transactions;
• and
• at the request of a CPU of the computer, providing the indication to the CPU.

An apparatus, comprising:

• circuitry and/or software designed to monitor DMA (direct memory access) memory write transactions, and designed to record an indication of a location in the main memory written by the DMA memory write transaction, and to provide the recorded indication to the CPU on request;
• the monitored DMA memory write transactions being writes to a main memory of a computer by a DMA device of the computer;
• the DMA monitoring circuitry/software being designed to perform the monitoring and recording independently of circuitry and/or software for initiation or control of the monitored DMA transactions.