JP2008209990A - Invalid process detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an invalid process detection apparatus facilitating identification of an invalid process. <P>SOLUTION: The invalid process detection apparatus temporarily stores, in a storage device 31, register information transmitted from a memory 20 to a CPU 10 (step S2). This information on a signal is determined by steps S3, S4, S5. Thereby, an invalid process is detected and invalid information thereon is also written into an invalid process information area (step S8). Not only the invalid process is identified, but also invalid information can be detected, which is thus advantageous to system debugging processing significantly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an unauthorized process detection device that detects an unauthorized process in a real-time OS in which a plurality of interrupt processes are executed.

  Conventionally, a real-time OS capable of executing a plurality of processes (tasks) in real time has been widely used in one-chip microcomputers such as control systems and computers, and in recent years, there has been a growing demand for such OSs. Furthermore, this real-time OS is also required to be compatible with a multimedia system that handles various data.

  As for the specific operation of the real-time OS, when a new program is interrupted while the CPU is executing the program, the address of the program being executed and the value of the processing result are saved in a save area (register) of the memory. These registers include general-purpose registers that can be used for calculation and dedicated registers, program counters, flag registers, stack pointers, and the like whose purpose of use has been determined. For example, the program counter stores which address (the address next to the address during execution of the old program) is read next, and the general-purpose register stores the processing result during execution of the old program. . After the new program is executed, the memory address and processing result written in the save area are read out, and the processing of the old program is executed from this address and processing result.

On the other hand, in the development of a system, an external bus is monitored by connecting an ICE (In Circuit Emulator) to the CPU, and debugging processing is performed to detect bugs such as unauthorized access. However, CPUs used in recent embedded systems have become unable to connect ICE due to the high speed operation and the relationship of taking peripheral devices into the same package. As an alternative, there is a JTAG system (an emulator using a debugging function built in the CPU) as a method for performing a debugging process. However, in this JTAG system, when the CPU itself hangs, the internal information of the CPU cannot be read.
As described above, in the real-time OS system, it is difficult to detect bugs, that is, to identify an unauthorized process (task).

Therefore, there is a bug detection device as described in Patent Documents 1 and 2.
Document 1 discloses a failure diagnosis device that sets an address range in the bus monitoring device and diagnoses that access to this address is illegal. Document 2 sets the upper and lower limits of the stack area address. However, a stack overflow detection circuit that detects a stack overflow when the saved information exceeds the address is disclosed.
JP-A-8-16426 Japanese Patent Laid-Open No. 9-198258

  In the devices described in the above documents, it is possible to monitor the behavior of the bus in hardware, but when the cause is in the software, it is difficult to identify the process that has been illegally accessed or the process that has caused the stack overflow. Met.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide an unauthorized process detection device that can easily identify an unauthorized process.

In order to solve the above-described problem, the invention described in claim 1 is a system in which a real-time OS for executing processing of a plurality of processes by real-time interrupt processing is mounted, and the plurality of processes are In an unauthorized process detection device for a system, comprising: a CPU that executes sequentially; a memory that sequentially stores and stores the process information; and a task switch that switches process information.
The save area range setting means for setting the save area range of the memory, the storage means for temporarily storing information by the process written / read in the save area, and the information is switched by the task switch. A determination unit that determines that the process stored in the storage unit is an unauthorized process when it is determined that the process is not performed and / or the data amount of the process is determined to be greater than or equal to the data amount corresponding to the range of the save area And providing an unauthorized process detection device characterized by comprising:

  The unauthorized process detection apparatus according to claim 1, wherein the determination unit determines that the information by the process has not been switched by the task switch, and / or the data amount of the process corresponds to the range of the save area If it is determined that the data amount is exceeded, the process temporarily stored in the storage means is regarded as an unauthorized process. This makes it possible to easily identify an unauthorized process.

The invention according to claim 2 is a system in which a real-time OS for executing processing of a plurality of processes by interrupt processing in real time is mounted, and a CPU that sequentially executes the plurality of processes, and the CPU In an unauthorized process detection device of a system comprising a program counter for storing an address of a process to be executed next and a memory for sequentially saving and storing the information of the process,
A save area range setting means for setting a range of the save area of the memory; a storage means for temporarily storing information by the process written / read in the save area;
It is determined that information that does not match the process to be executed next corresponding to the address stored in the program counter is written / read to / from the save area, and / or the data amount of the process is saved. To provide an unauthorized process detection device comprising: a determination unit that determines that the process stored in the storage unit is an unauthorized process when it is determined that the amount of data is greater than or equal to the range of the area. It is in.

  In the unauthorized process detection apparatus according to claim 2, information that does not match a process to be executed next corresponding to the address stored in the program counter is written to and read from the save area by the determination unit. And / or if it is determined that the data amount of the process is greater than or equal to the data amount corresponding to the range of the save area, the process temporarily stored in the storage means is regarded as an unauthorized process. This makes it possible to easily identify an unauthorized process.

The invention according to claim 3 is a system in which a real-time OS for executing processing of a plurality of processes by interrupt processing in real time is mounted, wherein a CPU that sequentially executes the plurality of processes, In an unauthorized process detection apparatus for a system, comprising: a memory that sequentially saves and stores information; and a program counter that stores an address of a process to be executed next by the CPU.
An unauthorized access range setting means for setting an unauthorized access range of the memory, a storage means for temporarily storing information by the process written to and read from the save area, and an address stored in the program counter are invalid An object of the present invention is to provide an unauthorized process detection apparatus comprising: a determination unit that determines that the process stored in the storage unit is an unauthorized process when the access range is determined.

  According to another aspect of the present invention, when the determination unit determines that the address stored in the program counter is within the range of unauthorized access, the unauthorized process detection device sets the process temporarily stored in the storage unit as an unauthorized process. This makes it possible to easily identify an unauthorized process.

  The unauthorized process detection device according to claim 4, wherein in the unauthorized process detection device described above, when the determination unit determines that the process is an unauthorized process, the process information stored in the storage unit is written to the memory. It is characterized by having a fitting means.

The invention according to claim 5 is a system in which a real-time OS for executing processing of a plurality of processes by interrupt processing in real time is mounted, and a CPU that sequentially executes the plurality of processes; In an unauthorized process detection device of a system comprising: a memory that sequentially saves and stores information; a task switch that switches process information; and a program counter that stores an address of a process to be executed next by the CPU.
Save area range setting means for setting the save area range and unauthorized access range of the memory; storage means for temporarily storing information by the process written to and read from the save area; and When it is determined that information has not been switched by a task switch and / or the data amount of the process is determined to be greater than or equal to the data amount corresponding to the range of the save area, the process stored in the storage unit is It is determined that information that does not match a first determination unit that is an unauthorized process and a process that is executed next corresponding to an address stored in the program counter is written to or read from the save area; And / or determining that the data amount of the process is greater than or equal to the data amount corresponding to the range of the save area If it is determined that the process stored in the storage unit is an unauthorized process, and the address stored in the program counter is determined to be an unauthorized access range, the process is stored in the storage unit. A third determination unit that sets the process as an unauthorized process; and a writing unit that writes information on the process stored in the storage unit to the memory when any of the determination units determines that the process is an unauthorized process; It is another object of the present invention to provide an unauthorized process detection device characterized by comprising:

  The unauthorized process detection apparatus according to claim 5, wherein the first determination unit determines that the information by the process has not been switched by a task switch, and / or the data amount of the process is within a range of the save area If it is determined that the amount of data is equal to or larger than the data amount, the process temporarily stored in the storage means is regarded as an unauthorized process. The second determination means determines that information stored in the program counter that does not match the next process to be executed is written to / read from the save area, and / or the data amount of the process is If it is determined that the amount of data is equal to or greater than the amount corresponding to the range of the save area, the process temporarily stored in the storage unit is determined as an unauthorized process. When the third determination means determines that the address stored in the program counter is within the range of unauthorized access, the process temporarily stored in the storage means is regarded as an unauthorized process. This makes it possible to easily identify the unauthorized process and its reason.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1) Overall Configuration FIG. 1 is a diagram showing an overall configuration of a system including an unauthorized process detection apparatus according to an embodiment of the present invention.
The system 1 includes a CPU 10 and a memory 20 connected to the CPU 10 via a bus 15. Since the system 1 is constituted by a one-chip microcomputer, the memory 20 includes a ROM of a nonvolatile memory and a RAM (none of which is shown) of a volatile memory. In this system 1, a program for executing a real-time OS is stored in the program area of the memory 20, and external interrupt processing and periodic interrupt processing are executed in real time.
The memory 20 is divided into areas such as a program area and a process stack area as shown in the memory map of FIG. 2, and a plurality of programs are stored in the program area for each area, and an interrupt process is executed. In some cases, information is received from a register written in the program saving area, and a corresponding program is processed by a request in this information. In addition, an unauthorized process information area (not shown) is also secured in the memory 20.
In the present embodiment, for example, the program area address is set to aaaa to nnnn, and the process save area address is set to yyyy to zzz.

The operation of the real-time OS will be described with reference to FIGS.
First, the CPU 10 executes the program from the upper address toward the lower side in accordance with the program sequence shown on the left side in FIG.
In the middle of the process, when an interrupt (execution request for another program) occurs as indicated by an arrow a, the process up to this address aaaa is divided into process 0 and the transition to address aaa + 1 as process 1 in the program being executed. Then, the data being executed, the return address, etc. are written in the process save area as indicated by the arrow b. For example, as shown in FIG. 3, when two register areas are set in the main memory, registers A and B are written to process 0. The interrupt signal includes information such as an address of a program to be requested next to the CPU 10 and various conditions.

More specifically, information (register) written in the process area is written in a structure as shown in FIG. That is, the register includes a program counter indicating the return address (address aaa + 1), a flag register (status register) indicating the operation state of the CPU 10, a stack register indicating the number of interrupt processing “1”, and other information (for example, a process) A general-purpose register indicating encoded data), and the above four registers.
When the CPU 10 finishes the processing of the other program, as shown by the arrow c, the return address of the program counter of the register is referred to return to the address aaa + 1, and this address transition processing is executed. At this time, based on each piece of information written in the register, the process that received the process 0 is executed again.

This process is repeated every time an interrupt occurs. If another program interrupt occurs while another program is being executed, the second register is written in the process save area. At this time, a return address corresponding to another program is written in the program counter in the register, and the interrupt processing count “2” is written in the stack register.
For example, since FIG. 4 shows a case where an 8-bit storage area is set, numbers up to 255 are written in decimal. When the processing of another program is completed, the processing returns to the other program based on the information in the second register, and the subsequent processing is executed. Thus, the register written in the process save area performs a FIFO (First In First Out) operation.

  In addition, when writing process information as a register, so-called task switching is performed to switch processes in order to rewrite data corresponding to the processing language of the process into binary numbers. The conversion of data by performing this task switch is also written in, for example, a flag register in the register.

(2) Unauthorized Process Detection Device Next, returning to FIG. 1, the unauthorized process detection device according to the present embodiment will be described.
The unauthorized process detection device 30 includes a storage device 31 and is disposed between the CPU 10 and the memory 20 via the bus 15. The illegal process detection device 30 monitors the signal on the bus 15 and is shown in the drawing for convenience, but is stored in the ROM constituting this system.
The storage device 31 temporarily stores information and is illustrated for convenience, but is secured in another area in the memory 20.

(3) Processing Operation The operation of the unauthorized process detection device 30 will be described with reference to the flowchart of FIG.
First, the apparatus 30 sets the address range of the process save area and the illegal address of the program area (step S1). In the present embodiment, as described above, the process save area address is set to yyyy to zzz, and the illegal address is set to an address other than the program area addresses aaaa to nnnn. Also, as shown in FIG. 4, when there are four registers corresponding to one process in the process save area, the data amount is 8 bits × 4 = 32 bits.

Next, the unauthorized process detection device 30 temporarily stores the register information transmitted from the memory 20 to the CPU 10 in the storage device 31 (step S2).
Further, the unauthorized process detection device 30 determines the information of this signal. That is, in the case of a register in which a signal is transmitted from the process save area, the amount of data is 32 bits. Therefore, it is first determined whether or not the read register is within 32 bits, and the task switch It is determined whether or not the register information has been rewritten (step S3).
If “YES” in the determination process in step S 3, the process proceeds to the process after step S 4. If “NO”, the CPU 10 generates an interrupt process (step S 7) and stores it in the storage device 31. The read register is read and written in the illegal process information area of the memory 20 (step S8).

As described above, the register includes a program counter indicating the return address, a flag register (status register) indicating the operation state of the CPU 10, a stack register indicating the number of interrupt processing, and other information (for example, encoding a process) General-purpose register indicating the data). For this reason, the user and the operator can easily grasp the process and the unauthorized state when the trouble occurs by referring to the register information.
In addition, when a register is written to the illegal process information area, it is more accurate if it is coded and written to the register so that it can be seen what kind of fraud (judgment processing) has occurred. The situation is remembered. At this time, the binarized code may be written in the upper bits of the stack register, which uses only relatively lower bits.

  The fraud when the determination in step S3 is negative is specifically a bit in which an illegal signal such as noise is superimposed on the signal while the register read from the process save area transmits the bus 15. This is a malfunction due to a change in the number or another signal transmitted through the bus 15. This determination process prevents the CPU 10 from erroneously recognizing a correct register.

  On the other hand, the illegal process detection device 30 determines whether or not the return address stored in the program counter of the register is the address of the program area, and further the data amount of the register indicates the data amount (for example, 32 bits) of the register in the process save area. It is determined whether an overflow has occurred or not (step S4).

If “NO” in the determination process in step S4, the process proceeds to the process after step S5. If “YES”, the CPU 10 generates an interrupt process, and performs the process after step S7.
If the determination in step S4 is affirmative, the illegality is that the return address stored in the program counter of the register does not exist in the address range of the program area, or some noise is superimposed on the register and the data amount overflows. There are cases. In particular, when the return address is an address not in the program area, there is a possibility that the CPU 10 is hung.

Further, the unauthorized process detection device 30 determines register information transmitted from the memory 20 to the CPU 10. That is, when the signal is a register transmitted from the CPU 10, the amount of data is 32 bits. Therefore, first, it is determined whether or not the read register is within 32 bits, and the task switch sets the register value. It is determined whether or not the information has been rewritten (step S5).
If “YES” in the determination process in step S5, the process proceeds to step S6, the register information stored in the storage device 31 is deleted, and the processes after step S2 are repeated. On the other hand, in the case of “NO”, an interrupt process is generated for the CPU 10, and the processes after step S7 are performed.

(4) Effects of the Embodiment As described above, the unauthorized process detection device 30 according to the present embodiment detects the unauthorized process by monitoring the register between the CPU 10 and the memory 20 and making various determinations. Further, by determining the data amount of the register and the task switch, it can be determined whether or not an illegal register is generated due to external noise or the like. By determining whether or not the return address stored in the program count in the register points to an address within the program area range, it can be determined whether or not the resist has been falsified for some reason.
As described above, the unauthorized process detection device 30 not only identifies the unauthorized process but also knows the unauthorized information. Therefore, the unauthorized process detection apparatus 30 can be very useful for identifying the unauthorized process in the system debugging process and investigating the cause of the unauthorized process.

(5) Modification In the above embodiment, the unauthorized process detection device 30 is incorporated in a one-chip microcomputer comprising the CPU 10 and the memory 20, but a probe for monitoring signals is applied to the bus 15 portion. Then, the determination process may be executed by a personal computer externally connected to the signal via the probe.

  In the processing operation of the above-described embodiment, the determination processing in steps S3 and S5 is performed by determining whether or not the data amount of the register is within 32 bits and determining whether or not the register information has been rewritten by the task switch. This is exemplified by the AND condition, but it may be determined as illegal even if any of the determinations is “NO”. Further, this determination process may be performed separately.

It is a figure which shows the system configuration | structure containing the unauthorized process detection apparatus which concerns on embodiment of this invention. It is a figure which shows the program sequence and memory map in the embodiment. It is a figure which shows the structure of the memory map in the embodiment. It is a figure which shows the structure of the register | resistor in the embodiment. It is a flowchart which shows the unauthorized process detection operation | movement in the embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... System, 10 ... CPU, 15 ... Bus, 20 ... Memory, 30 ... Unauthorized process detection apparatus, 31 ... Storage device.

Claims (5)

A system in which a real-time OS for executing processing of a plurality of processes in real time by interrupt processing is mounted, a CPU that sequentially executes the plurality of processes, and a memory that sequentially saves and stores information on the processes And a task switch for switching process information, in the unauthorized process detection device of the system,
Save area range setting means for setting the save area range of the memory;
Storage means for temporarily storing information by the process written to and read from the save area;
When it is determined that the information has not been switched by the task switch and / or the data amount of the process is greater than or equal to the data amount corresponding to the range of the save area, the information is stored in the storage unit An unauthorized process detection apparatus comprising: a determination unit that sets the processed process as an unauthorized process. A system in which a real-time OS for executing processing of a plurality of processes by real-time interrupt processing is mounted, and a CPU that sequentially executes the plurality of processes, and an address of a process that is executed next by the CPU In an unauthorized process detection device of a system comprising a program counter for storing and a memory for sequentially saving and storing the information of the process,
Save area range setting means for setting the save area range of the memory;
Storage means for temporarily storing information by the process written to and read from the save area;
It is determined that information that does not match the next process to be executed corresponding to the address stored in the program counter is written to or read from the save area, and / or the data amount of the process is saved An unauthorized process detection apparatus comprising: a determination unit that determines that the process stored in the storage unit is an unauthorized process when it is determined that the amount of data is greater than or equal to the range of the area. A system in which a real-time OS for executing processing of a plurality of processes in real time by interrupt processing is mounted, a CPU that sequentially executes the plurality of processes, and a memory that sequentially saves and stores information on the processes And a program counter for storing an address of a process to be executed next by the CPU,
Unauthorized access range setting means for setting a range of unauthorized access of the memory;
Storage means for temporarily storing information by the process written to and read from the save area;
An unauthorized process detection apparatus comprising: a determination unit that determines that the process stored in the storage unit is an unauthorized process when the address stored in the program counter is determined to be an unauthorized access range. The unauthorized process detection device according to any one of claims 1 to 3,
An unauthorized process detection apparatus, comprising: a writing unit that writes information on a process stored in the storage unit into the memory when the determination unit determines that the process is an unauthorized process. A system in which a real-time OS for executing processing of a plurality of processes in real time by interrupt processing is mounted, a CPU that sequentially executes the plurality of processes, and a memory that sequentially saves and stores information on the processes And an unauthorized process detection device of a system comprising: a task switch for switching process information; and a program counter for storing an address of a process to be executed next by the CPU.
Save area range setting means for setting the range of the save area of the memory and the range of unauthorized access;
Storage means for temporarily storing information by the process written to and read from the save area;
When it is determined that the information has not been switched by the task switch and / or the data amount of the process is greater than or equal to the data amount corresponding to the range of the save area, the information is stored in the storage unit First determination means for setting the processed process as an unauthorized process;
It is determined that information that does not match the next process to be executed corresponding to the address stored in the program counter is written to or read from the save area, and / or the data amount of the process is saved If it is determined that the amount of data corresponding to the range of the area is greater than or equal to the second determination means for making the process stored in the storage means an unauthorized process;
If the address stored in the program counter is determined to be a range of unauthorized access, third determining means for setting the process stored in the storage means as an unauthorized process;
An unauthorized process detection apparatus comprising: a writing unit that writes information on a process stored in the storage unit into the memory when any of the determination units determines an unauthorized process.

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