JPH04337847A - Program check method - Google Patents

Abstract

PURPOSE:To easily and detect the abnormal part of a program. CONSTITUTION:The address of a memory area which cannot possibly be accessed with an execution program 1 is previously registered in a memory address check table 21. An interruption processing is executed whenever an instruction in the execution program 1 is executed. Then, address check which is to compare an address designated by a subsequent instruction in the execution program 1 with the instruction registered in the memory address check table 21 is executed. When the both addresses do not coincide as the result of the address check, the subsequent instruction is executed. Then, the interruption processing is executed and the address of the subsequent instruction is checked. When the both addresses coincide in the middle of such a process, the execution of the instruction is stopped at that time. Thus, the abnormal part of the execution program 1 is detected.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a program checking method that uses software to detect memory corruption during program execution.

0002

2. Description of the Related Art Conventional program checking methods are as follows. That is, in a processor that does not have a memory protection function due to hardware, an abnormality in a program may destroy the contents of a memory that stores a program execution section (hereinafter referred to as a code section). In this case, the computer regards the contents of the destroyed memory as a code section and executes it. As a result, if an instruction error occurs, an exception interrupt occurs. Therefore, in this interrupt processing,
Program abnormalities were detected by performing error handling.

On the other hand, in a processor having a single-step interrupt function, a software debugger can be implemented using that function. That is, in such processors, a method has generally been adopted in which an instruction is executed step by step and a trace is taken to detect an abnormal location.

0004

[Problems to be Solved by the Invention] However, the above-mentioned conventional technology has the following problems. That is, in the method of detecting an abnormality using an exception interrupt, an instruction may be accidentally rewritten to an instruction with a different meaning due to destruction of the code section. In this case, no instruction error occurs and no exception interrupt occurs. As a result, the program runs out of control, making it difficult to detect abnormalities. Furthermore, even if an exception interrupt occurs, the location where the exception interrupt occurs does not match the abnormal location, making it difficult to analyze where the memory corruption that causes the abnormal operation occurred.

On the other hand, step-by-step tracing using single-step interrupts is effective for debugging local parts of a program, but it may require a large amount of trace information to detect memory corruption. is large and cannot necessarily be said to be effective. The present invention has been made with attention to the above points, and an object of the present invention is to provide a program checking method that can easily and quickly detect abnormalities in a program.

[0006]

[Means for Solving the Problems] The program check method of the present invention prepares a memory address check table in which addresses of memory areas that cannot be accessed by a program are registered in advance, and executes instructions in the program in one step. Each time the program is executed, interrupt processing is performed, and it is determined whether the next instruction in the program is an instruction related to memory access. An address check is performed to compare the address with the address registered in the memory address check table, and if the two addresses do not match as a result of the address check,
After executing the next instruction, the interrupt processing is performed, and the next instruction is determined and the address is checked.
Below, we will proceed with the process of executing an instruction while sequentially discriminating the instruction and checking the address. If the address check in the middle of these processes shows that both addresses match, the instruction will be executed at that point. This feature is characterized by detecting abnormalities in the program by stopping the program.

[0007]

[Operation] In the program checking method of the present invention,
First, a memory address check table is prepared in which addresses of memory areas that are unlikely to be accessed by a program are registered in advance. On the other hand, if the instructions in the program are
Interrupt processing is performed each time step execution is performed, and it is determined whether the next instruction in the program is an instruction related to memory access. When the next instruction is an instruction related to memory access, an address check is performed to compare the address specified by the next instruction with the address registered in the memory address check table. As a result of this address check, if the two addresses do not match, the next instruction is executed. Thereafter, the interrupt processing is performed, and the next instruction is determined and the address is checked. Hereinafter, the process of executing the instructions proceeds while sequentially discriminating the instructions and checking the addresses. As a result of address checking during these processes, if the two addresses match, execution of the instruction is stopped at that point. This allows detecting abnormalities in the program.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a computer to which the method of the present invention is applied. This figure shows a processor 10 and a memory 20, which are the main parts of the computer.

The processor 10 reads and executes the code portion of the program stored in the memory 20 step by step, and processes the data in the memory 20. This processor 10 has a single step interrupt function. A single step interrupt is an interrupt that occurs each time an instruction is executed one step. This interrupt is often used for trace execution functions of software debuggers. This interrupt function is used to check whether the memory is corrupted at each step.

Memory 20 is a main storage device consisting of a random access memory or the like. Alternatively, it may be a virtual storage device including an auxiliary storage device such as a magnetic disk. Execution programs 1 and 2 in the memory 20 are programs to be checked for memory corruption. In addition to execution programs 1 and 2, this memory 20 includes a memory address check table 21, a memory address check table registration program 22, and a single step interrupt processing program 23.
It stores programs such as and various data.

[0011] The execution program 1 is executed at 100 in the memory 20.
It is located at addresses 00H to 17FFFH, and divided within it, addresses 10000H to 12FFFH are the code section, and addresses 13000H to 17FFFH are the readable and writable data section. Similarly, execution program 2 runs from address 20000H of memory 20 to 25FF
It is located at address FH, from address 20000H to address 225FFH is the code section, and after that is the data section.

These execution programs 1 and 2 each access the address 100 during initial processing for setting the execution environment.
The addresses 00H to 12FFFH and 20000H to 225FFH are stored in the memory address check table 2 using the memory address check table registration program 22.
Register it in 1.

When the execution programs 1 and 2 are executed, the single step interrupt processing program 23 executes 10000H to 12FFFH and 20000H for each step.
Check whether a write operation is being performed on H to 225FFH. For example, execution program 1 is 21005
When attempting to write to address H, the single-step interrupt processing program 23 checks and execution of the instruction is stopped. At this time, the single-step interrupt processing program 23 performs processing to notify the user that the memory check has failed.

FIG. 2 is a diagram showing a software configuration according to the present invention. The illustrated software includes a memory address check table 21 necessary for memory checking.
, a program 22 to register it, and a program 23 to check the memory at the time of a single step interrupt. The memory address check table 21 consists of an area 11 for registering addresses that cannot be read or written, that is, cannot be accessed, and an area 12 for registering addresses that cannot be written to.

Area 1 for registering inaccessible addresses
1 registers a range of addresses (for example, a control program area) in which the execution programs 1 and 2 to be checked are prohibited from writing or reading. The area 12 for registering non-writable addresses registers a range of addresses (mainly addresses of code portions) to which the execution programs 1 and 2 to be checked are prohibited from writing.

The memory address check table registration program 22 executes the execution program 1 (
During the initialization process for setting the execution environment for execution program 2 (the same applies to execution program 2), or at the start of execution, the address range of the part that execution program 1 to be checked must not write to, and the part that must not be written to or read from. register. That is, the memory address check table registration program 22 knows this address range from the parameters passed from the control program. Then, the range of this address is stored in the memory address check table 21.
Register.

Single step interrupt processing program 2
3 is a program that checks whether or not the memory at the address registered in the memory address check table 21 is destroyed each time the execution program 1 to be checked is executed one step. An overview of the processing of this program will be explained with reference to FIG.

FIG. 3 is a flowchart showing a memory check procedure using a single step interrupt. first,
The next instruction scheduled to be executed when a single-step interrupt occurs is retrieved and decoded (step S
1). If the instruction is an instruction to write data to memory (step S2), the address to which the instruction is attempting to write is calculated and compared with the address registered on the memory address check table (step S3). . As a result of the comparison, if there is an address to be written within the range of inaccessible and non-writable addresses registered in the memory address check table 21 (step S4), it is regarded as abnormal and execution of the execution program 1 is stopped. to handle the abnormality (step S
5). This abnormality processing is, for example, abnormality display processing on a display.

On the other hand, if the address to which the instruction attempts to write is not within the range of inaccessible and non-writable addresses, it is assumed that the data will be written within a range that will not cause memory destruction, and the process ends normally. This completes the interrupt processing and executes the next step of the instruction.

On the other hand, if the next instruction scheduled to be executed in step S2 is an instruction to read data from memory,
Calculate the address that the instruction is trying to read,
It is compared with inaccessible addresses registered on the memory address check table (step S6). As a result of the comparison, if the address to be read is within the range of inaccessible addresses registered in the memory address check table 21 (step S4),
It is regarded as abnormal, and execution of the execution program 1 is stopped to handle the abnormality (step S5).

On the other hand, if the address that the instruction is trying to read is not within the inaccessible address range,
It is assumed that there is no risk that the data whose reading is prohibited will be read, and the process ends normally. This completes the interrupt processing and executes the next step of the instruction.

[0022]

As explained above, according to the program check method of the present invention, the program is executed step by step while checking the address using the memory address check table, so that the memory protection function is not implemented in hardware. memory corruption can be detected on processors that do not have That is, it is possible to detect an instruction immediately before destroying the memory and process the abnormality. This results in
Program failure analysis can be easily and quickly performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a computer to which the method of the present invention is applied.

FIG. 2 is a diagram showing a program configuration according to the present invention.

FIG. 3 is a flowchart showing a memory check procedure using a single step interrupt.

[Explanation of symbols]

1, 2 Execution program 10 Processor 11 Address registration area that cannot be accessed 12 Address registration area that cannot be written to 20 Memory

Claims (1)

[Claims] 1. A memory address check table is prepared in which addresses of memory areas that are unlikely to be accessed by a program are registered in advance, and interrupt processing is performed each time an instruction in the program is executed one step. Determine whether the next instruction is an instruction related to memory access or not, and if the next instruction is an instruction related to memory access, the address specified by the next instruction and the address registered in the memory address check table are determined. If the addresses do not match as a result of the address check, the next instruction is executed, the interrupt processing is performed, and the next instruction is determined and the address is checked. ,Then, the process of executing the instruction is proceeded by,discriminating the instruction and checking the address in order.,If the result of the address check in the middle of these processes is,that both addresses match, the instruction is executed at that,point. A program check method characterized by detecting an abnormal part of a program by stopping the program.