JPH06236300A - Microcomputer - Google Patents

Abstract

PURPOSE:To more facilitate the debugging of a system program and to protect a system with a hardware when the program is detected that it is accessed outside of a previously decided range. CONSTITUTION:This microcomputer is provided with a storage device 3 for storing information to specify each program positioned on a system resource 4 and occupied area information representing the range of the area of the system resource 4 occupied by each program while making both the pieces of information correspondent, program area detector/for detecting the occupied area information of the program in the case of storing the program in the system resource 4, storing that information in the storage device 3 while making it correspondent to the information to specify the program, specifying the program in the case of executing the program, and reading the occupied area information of that program from the storage device 3, and address comparator 2 for comparing the occupied area information with the address representing the position on the system resource 4 to be accessed in the case of executing the program.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer system using a microprocessor, and more particularly to a microcomputer effective for supporting program debugging.

[0002]

2. Description of the Related Art When a single computer program or a plurality of programs operate in parallel in a conventional computer system, a memory area managed by another software such as an operating system and a system resource itself do not exist. For example, a memory area that cannot be originally used for some reason, an area in which another program has already secured resources as an operation area, or an incorrect reference / change / branch to an I / O area (hereinafter referred to as access ) Could be done.

In the prior art, for example, when a program branches to another program that is completely unrelated, normal operation of the branched program and the branch destination program is not guaranteed, and one or both programs may run out of control. It was very good. In such a case, it is necessary to reset the system by some means, and it is difficult or impossible to manage such unauthorized access by the conventional technology, which causes the system to be destroyed or runaway.

[0004]

As described above, it is necessary to reset the system except when a dedicated debugging device such as an ICE (in-circuit emulator) is used when the system is destroyed or a runaway occurs. However, when such a system reset is performed, the inside of the system is once initialized, so it was difficult or impossible to determine which part of the program was the cause of the runaway.

The present invention has been made in order to avoid the inconvenience that it is impossible to specify the cause of system destruction or runaway in the conventional microcomputer as described above, and the program is out of a predetermined range. When an access is detected, it is detected by the hardware, the instruction is first invalidated, and then the system or program is debugged more appropriately by causing the system or program to perform appropriate exception handling due to the occurrence of a software interrupt. An object of the present invention is to provide a microcomputer capable of easily protecting the system by hardware without using system management software.

[0006]

A microcomputer of the present invention stores a memory, information for identifying each program located on the memory, and occupied area information indicating a range of an area of the memory occupied by each program. When a program is stored in a memory, a storage device that stores the program in association with each other detects the occupied area information of the program based on a control signal generated when the program is stored, and associates it with information that identifies the program. Area storing means for storing the data in a storage device, and when the program is executed, the program is specified based on a control signal generated when the program is executed, and the occupied area information of the program is read from the storage device. When the program is executed, the program area detection means reads it from the storage device. And occupied area information, compares the address representing the position of the memory accessed by the execution of the program, and a determining address comparator the appropriateness of access in accordance with the comparison result.

[0007]

In the microcomputer of the present invention, when the program is stored in the memory, the program area detecting means detects the occupied area information of the program based on the control signal generated when the program is stored, and the program is stored in the memory. When the program is stored in the storage device in association with the information to be specified, and the program is executed, the program area detection means specifies the program based on the control signal generated when the program is executed, and the occupied area of the program When the information is read from the storage device and the program is executed, the address comparator compares the occupied area information read by the program area detecting means from the storage device with the address representing the position on the memory accessed by the execution of the program, Determines whether access is appropriate according to the comparison result That.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments thereof.

FIG. 1 is a block diagram showing the configuration of the essential parts of an embodiment of a microcomputer according to the present invention.

In FIG. 1, reference numeral 4 is a system resource including a memory, and in this embodiment, areas A1 to A7 and other areas are prepared. The area A1 of the system resource 4 is allocated as a system area, the area A2 is allocated as a common area, the area A7 is allocated as an I / O area, and the areas A3, A4, A6 are allocated as areas for normal programs. A5 is an unused area where system resources are not prepared. Note that FIG. 1 shows a state in which the program A is already stored in the area A4.

Reference numeral 1 is a program area detector. The program area detector 1 is provided with a control signal CS output from a CPU (not shown),
By using this control signal CS, when the program accesses the system resource 4, it is detected which area on the system resource 4 the program (including a so-called operating system, initial diagnosis program, etc.) is assigned. .

That is, the program area detector 1 is a CPU required when a program is stored in the system resource 4.
By using a control signal CS output from, for example, an address signal, a write (write) signal, etc., the area in the system resource 4 in which the program is stored is detected, and the information (hereinafter referred to as occupied area information) is detected. ) And information specifying the program itself are stored in a plurality of storage devices SA1 to SAn.
It is stored in any one or a plurality of the storage devices 3 configured by.

Further, the program area detector 1 specifies a currently executing program by using a control signal CS generated from a CPU or the like (not shown) at the time of executing the program, and relates to the program. Storage device 3 in which occupied area information is stored
Information is read from any of (SA1 to SAn) and output to the address comparator 2.

Reference numeral 3 is a storage device as described above,
Multiple (n in the embodiment shown in FIG. 1) storage devices
It is composed of SA1 to SAn. Each of these storage devices SA
1 to SAn are areas A1 to 1 of the system resource 4, respectively.
Information for identifying a program stored in An and information in which area of each of the areas A1 to An of the system resource 4 the program is stored, that is, occupied area information, are stored in association with each other.

For example, when the program A is read in the memory, the main control signal CS is an address signal and a write signal, which makes it possible to detect in which area on the memory the program A is allocated and stored. Is. Therefore, the program area detector 1 detects the area on the memory to which the program A is assigned based on the control signal CS, and uses the information as occupied area information to configure the storage device 3 to store one or more storage devices SA1 to SA1. One of SAn is assigned and stored.

In FIG. 1, the detection result of the program A, that is, the occupied area information that the program A is stored in the area A4 of the system resource 4 is the third storage device SA3.
It is shown to be stored in. When executing the program, the program area detector 1 specifies the program based on the control signal CS generated by the program being executed, and stores the occupied area information of the program in any of the stored areas. The data is read from the devices SA1 to SAn and output to the address comparator 2.

The address comparator 2 has an address (hereinafter, referred to as an address of a memory to be accessed by a program being executed).
ADD is given. Therefore, the address comparator 2 stores the storage contents read from any of the storage devices SA1 to SAn that the program area detector 1 constitutes the storage device 3 as described above, that is, the occupied area information and the program being executed. Compare with the address ADD of the memory you are trying to access.

If the access target address ADD is in the occupied area of the program being executed, the access is correct, but if it is outside the occupied area, it is an illegal access. Therefore, when the program being executed accesses a certain area of the system resource 4, the address comparator 2 outputs the access target address ADD output by the execution of the program,
Whether the access is a correct access by comparing with the occupied area information given from the program area detector 1
Alternatively, it is determined whether the access is unauthorized.

For example, when the program A located in the area A4 of the system resource 4 accesses the first unused area A3, the address comparator 2 outputs the access target address ADD (in this case, output by the execution of the program A). The access target address ADD is the area A3 of the system resource 4.
Address) and the occupied area information of the program A, which is the contents of the third storage device SA3 given from the program area detector 1, are compared, and it is determined that the access is an unauthorized access. When the address comparator 2 recognizes an illegal access as described above, the address comparator 2 outputs the interrupt request signal INTREQ to the interrupt controller 5, so that the interrupt controller 5 is sent to a CPU (not shown). Give the interrupt signal INTS.

FIG. 2 is a schematic diagram showing the correspondence between the storage device 3 and the system resources 4 when the programs B and C other than the program A exist in the system resources 4.

Here, the program A is read by the system management program located in the system area which is the area A1 of the system resource 4, and the program B is the first program in the area A3 which is the subprogram of the program A.
It is assumed that the program C has been read into the unused area, and the program C has been read into the second unused area of the area A6 by the program B.

In FIG. 2, since the program B is the program read by the program A, the program B becomes a part of the program A and is subordinate to the program A. The reason is that the program B is required and read as a subprogram or data of the program A.

In such a case, the third storage device SA3 stores only the occupied area information of the program A in FIG. 1, but since the program A reads the program B, the program B also accesses the program B. As a possible occupied area, the occupied area information is stored again in the third storage device SA3 by the program area detector 1. That is, the area A4 as the occupied area information of the program A is stored in the third storage device SA3.
And A3 will be remembered.

By the way, regarding the occupied area information of the program B, the program B uses the system resource 4 by the program A.
Program area detector 1 when read into area A3
Is stored in the fifth storage device SA5. Further, the occupied area information of the program C is stored in the sixth storage device SA6 by the program area detector 1 when the program C is read into the area A6 of the system resource 4 by the program B.

In this case, the program A can access the program B, but on the contrary, the program B cannot access the program A because it is a program subordinate to the program A. That is, program B
When the program A accesses the program A, the address comparator 2 determines the access target address ADD given by the access of the program B and the occupied area information (the area A of the program A read by the program area detector 1 from the third storage device SA3). This is because it is detected that the former is outside the range of the latter by comparing with the area A4). Therefore, if program B accesses program A,
The address comparator 2 recognizes it as an unauthorized access.

Further, for example, the program C cannot access the program A or the program B read by the program A. That is, when the program C accesses the program A or the program B,
The address comparator 2 receives the access target address ADD given by the access of the program C and the occupied area information (area A4) of the program A read by the program area detector 1 from the third storage device SA3 or the fifth area SA5 or the program Compare the occupied area information of B (area A3),
This is because the former detects that it is out of the latter range.
Therefore, when the program C accesses the program A or the program B, the address comparator 2 recognizes it as an illegal access.

In this way, when the address comparator 2 recognizes an illegal access, the interrupt request signal INTREQ from the address comparator 2 to the interrupt controller 5 of FIG.
Is given.

In the above embodiment, the address comparator 2 supplies the interrupt request signal to the interrupt controller 5 so that the interrupt controller 5 generates the interrupt signal. ,
When the address comparator 2 and the like are built in the microprocessor, it is possible to directly generate an interrupt to the CPU.

[0029]

As described above in detail, according to the present invention, it is possible to prevent the system from being destroyed or runaway even if the system resource is illegally accessed, and to obtain a stable operating environment. Further, the system / program can be debugged more easily, and the system can be protected by hardware without using system management software.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of an embodiment of a microcomputer according to the present invention.

FIG. 2 is a schematic diagram showing a correspondence between a storage device and a program when a plurality of programs exist in a memory.

[Explanation of symbols]

 1 Program area detector 2 Address comparator 3 Storage device 4 System resource CS control signal

Claims (1)

[Claims] 1. A memory and information for identifying each program located on the memory,
Based on a storage device that stores, in association with each other, occupied area information indicating a range of the area of the memory occupied by each program, and a control signal generated when the program is stored when the program is stored in the memory. The occupancy area information of the program is detected and stored in the storage device in association with the information for specifying the program, and when the program is executed, the program is based on a control signal generated when the program is executed. A program area detecting means for identifying the occupied area information of the program from the storage device, and executing the program, the occupied area information read from the storage device by the program area detecting means, and Compare with the address that represents the location in the memory that is accessed Microcomputer, and is characterized in that a determining address comparator the appropriateness of access in accordance with the comparison result.