JPH08249206A - Computer with stack area destruction detection function - Google Patents

Abstract

PURPOSE: To detect the abnormality of a function at the time of return to a calling origin when the abnormal function for destructing the stack area of the calling origin is called. CONSTITUTION: This computer for performing operations while securing and releasing the stack area for performing a fixed processing by a program within a program memory, storing a base pointer for indicating the bottom part of the stack area in a register 5 inside a CPU and the program memory 8c and operating the program while changing the base painter inside the register 5 by using storage 8c inside the program memory is provided with auxiliary preservation means 13 and 11 different from the storage part 8c for preserving the base pointer and comparing and reporting means 10 and 12 for comparing register contents 8c and 5 with the contents 11 of the auxiliary preservation means when the operation of the program is returned from a new stack area 9 to a certain stack area 8 and reporting that effect when they do not match with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a computer with a stack area destruction detection function in a computer in which a program operation progresses in stack area units.

[0002]

2. Description of the Related Art In the operation of a computer, an operation area, that is, a stack area is secured in order from the lowest program memory (from the bottom), and data is input / output to / from each stack area to execute a function or the like. Is generally done.

Each stack area is released when the operation of the corresponding function or the like ends, and a new stack area is secured on the stack area when another function or the like is called from the stack area.

Among the computers that advance processing by securing / releasing the stack area in this way, in particular, a compiler that compiles a program so that the stack variable area in the function is processed in the form of "EBP register-offset" There is a calculator used.

In this computer, an EBP register as a base pointer register and an ESP register as a stack pointer register are prepared in the CPU (or MPU; microprocessor unit).
The EBP register and the ESP register guarantee the progress of the program operation. Then, when a new stack area is secured, the value of the EBP register or the like is saved in the upper portion of the calling side stack area.

FIG. 5 is a diagram for explaining the progress of program processing accompanied by securing / releasing a stack area in such a computer. 5A to 5D show the state of the program memory, the lower side of the figure is the lower side (lower) of the memory in the above description, and the upper side is the memory above. First, in FIG. 5A, the program is processing the function A on the stack 31 of the function A, and the input / output of calculation results and the like is also performed on the stack 31.

Therefore, at this time, the EBP in the CPU
The register stores the address A1 that points to the bottom of the stack 31 of the function A, while the ESP register stores the address A2 that points to the top of the stack area in operation.

That is, the content of the EBP register, which is the base pointer, always points to the bottom address (bottom of the stack area) of the stack corresponding to the processing,
The contents of the ESP register, which is the stack pointer, always indicates the top address of the corresponding stack (the top address when the parameters for the next stack are stacked on the stack). is there.

The computer can secure an address and the like necessary for operation from the contents of these two registers, thereby ensuring high-speed operation. Here, as shown in FIG.
If the function B is called from inside the function A, the parameter 32 for processing the function B, the function 32 on the address A2 at the top of the stack 31 of the function A, and the function B are allocated before the stack area for the function B is secured. Return address 33 to A, EBP of function A
The area 34 is saved in order. Each time a new memory area is secured in this way, the contents of the ESP register are
The addresses are changed to address A3, address A4, and address A5.

When the EBP area 34 of the function A is secured and the EBP register content, that is, the address A1 is stored in this area 34, the content of the ESP register, that is, the address A5 is stored in the EBP register and the stack of the function B is stored. Move to area reservation processing.

FIG. 5C shows a situation in which the stack 35 of the function B is secured and the function B is being processed. here,
The EBP register in the CPU has a stack 35 of the function B.
The address A5 pointing to the bottom of the stack is stored, while the ESP register stores the address A6 pointing to the top of the stack area in operation.

At this time, if a new function or the like is called, a new stack area is secured on the stack 35 of the function B through the same processing as in FIGS. 5A and 5B. Become.

On the other hand, when the processing for the function B is completed, the stack 35 is released and the processing target returns to the function A. That is, as shown in FIG. 5D, the content of the EBP area 34 of the function A storing the address A1 is E.
It is moved to the BP register, and the contents of the ESP register are changed to the address A2 indicating the top of the stack 31 of the function A. Further, the CPU sets the return address in the function A to
Upon receiving from the return address 33 to the function A, the processing for the function A is restarted from this address.

The above is the "EBP register-offset".
When a new stack area is secured in a program compiled to perform processing in the form of
This is the processing method when the value of a register or the like is saved in the upper part of the stack area of the calling side. Such a processing method is a method generally used in a computer using a CPU having registers corresponding to the EBP register and the ESP register. In particular, when the C language is used as the programming language, the above processing method is used.

[0015]

By the way, when a program is processed by the above processing method, if data is written in a certain stack area in excess of the capacity of the stack area, the data is written from the top of the memory. Since the data is written downward, the contents of the caller's stack area will be destroyed. in this case,
The caller's stack area is, for example, the function A
If so, it indicates an area composed of the EBP area 34 of the function A, the return address 33 to the function A, the parameter 32 for processing the function B, and the stack 31 of the function A.

In FIG. 6, the EBP area 34 of the function A is written to the stack 35 of the function B, and the return address 3 to the function A is 3.
FIG. 3 is an explanatory diagram showing a case where the content of the parameter 32 for processing the function B is destroyed.

In this case, since the return address 33 to the function A is lost, the CPU cannot receive the return address and tries to shift to an abnormal address as a return from the function B. Therefore, the occurrence of abnormality can be immediately detected. That is, in this case, it is immediately known that the function B has a defect.

On the other hand, even when writing is performed beyond the stack 35 of the function B, the return address 33 to the function A is returned.
May not be destroyed. FIG. 7 is an explanatory diagram showing a case where only the EBP area 34 of the function A is destroyed by writing the function B to the stack 35.

As shown in FIG. 7, for example, when only one byte is written over the stack 35 of the function B to the lower side of the memory, the content of the EBP area 34 of the function A becomes an abnormal value, but the function The contents of the return address 33 to A and the parameter 32 for processing the function B remain normal.

Therefore, when returning from the function B to the function A, an abnormal content is input to the EBP register, but the return itself to the function A is normally performed. Then, the processing in the function A continues normally, and when the EBP register is used next time, for example, when returning from the function A to the stack area of the calling source, a memory access error occurs for the first time, and the error occurs. Is detected.

Since the occurrence of the abnormality at this time occurs during the processing of the function A, it is difficult for the programmer to specify that the abnormality has occurred due to the function B. Therefore, it takes a considerable amount of time and labor to detect the cause of the abnormality, that is, the malfunction of the function B, and there is a problem that the cause of the abnormality cannot be known unless the programmer is a proficient programmer.

The present invention has been made in consideration of such a situation, and when an abnormal function or the like that destroys the stack area of the caller is called, the abnormality of the function or the like is detected when returning to the caller. It is an object of the present invention to provide a computer with a stack area destruction detection function that enables the above.

[0023]

In order to solve the above problems, the present invention secures a stack area in a program memory for performing a certain process in a computer program.
It operates while being released, and stores a base pointer that points to the bottom of the stack area in a register in the CPU to guarantee the operation of the program, and secures a new stack area during processing operation in a certain stack area. In this case, after saving the base pointer of the stack area near the boundary between a certain stack area and the new stack area in the program memory, a new stack area is secured, and a new stack area that indicates the bottom of the new stack area is created. Store the base pointer in a register to perform other constant processing in the program in the new stack area,
On the other hand, when a program operation returns from a new stack area to a certain stack area, the base pointer saved near the boundary is returned to the register and then the program operation continues Auxiliary saving means that saves the base pointer of a certain stack area, which is different from the above, and when the program operation returns from the new stack area to a certain stack area, compares the register contents at this time with the contents of the auxiliary saving means. Then, when these do not match, the computer with a stack area destruction detection function is provided with a comparison notifying means for notifying that effect.

[0024]

Therefore, first, in the computer with the stack area destruction detection function of the present invention, the stack area for performing a certain process in the computer program is secured and released in the program memory as necessary to operate. .

At this time, the stack area is used, for example, as a data input / output area for executing a function, and is secured / released in accordance with the function call, return, and the like. Then, at the time of securing / releasing the stack area, a base pointer pointing to the bottom of the stack area for guaranteeing the operation of the program is input to the register in the CPU.

For example, when a new stack area is secured during a processing operation in a certain stack area, that is, when another function is called, first, the boundary between the certain stack area and the new stack area in the program memory is first approached. At this time, the base pointer of the certain stack area stored in the register at this time is saved.

Next, a new stack area is secured, a new base pointer pointing to the bottom of the new stack area is stored in a register, and other constant processing in the program in the new stack area, that is, the target The function is executed.

On the other hand, when the execution of the function ends and the operation of the program returns from a new stack area to a certain stack area, the base pointer saved near the boundary is returned to the register and then the program at the calling source. Let the operation continue.

In the above computer, if there is an abnormality such as writing over the size of the secured stack area in a function that uses the new stack area on the called side, the data is saved near the boundary. The created base pointer will be destroyed.

Therefore, in the present invention, the base pointer of the certain stack area is stored by the auxiliary storage means different from that near the boundary in the program memory. Then, when the operation of the program returns from a new stack area to a certain stack area, the comparison and notification means compares the register contents at this time with the contents of the auxiliary storage means, and if they do not match, the fact is notified. To be done. Therefore, when the program is executed, it is possible to easily detect the stack area destruction of the caller due to the called function or the like.

[0031]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing an embodiment of a computer with a stack area destruction detection function according to the present invention.

This computer with a stack area destruction detection function is a CPU that is connected to the system bus 1 and performs various processes.
2 and a memory 4 connected to the system bus 1 for storing at least a program memory 3 for program operation
And other peripheral elements (not shown).

Unless otherwise specified, the program for operating this computer is written in C language. The CPU 2 is provided with an EBP register 5 and an ESP register 6, and these registers 5 and 6 are provided.
Respectively function as a base pointer register and a stack pointer register, as described in the conventional example.

In the program memory 3, the stack unit 7 up to the stack A, the stack A unit 8 and the stack B unit 9 are stacked.
Are secured, and these areas are secured in order from the lower side of the memory.

As explained in the conventional example, each of these stack parts, and a stack part not shown in the figure, are secured and released according to the processing of the program. The stack A unit 8 includes a stack 8a for the function A, a return address / parameter unit 8b, and an EBP storage unit 8c for the stack A.

Here, the stack 8a of the function A corresponds to the stack 31 of the function A of the conventional example. Also,
The return address / parameter section 8b includes a parameter 32 for processing the function B of the conventional example and a return address 33 to the function A.
It has the same configuration as. Furthermore, stack A
The EBP saving unit 8c of the EBP area 3 of the function A of the conventional example also
It has the same configuration as that of No. 4.

Further, the stack B unit 9 also stores in the stack 9a of the function B the same storage / comparison / notification unit 1 as the stack A unit 8.
0, 11, 12, etc., and other stack parts not shown in the figure are stored and stored in the same manner as the stack A part 8 if necessary.
The comparison / notification units 10, 11, 12 and the like are provided. In addition,
The configuration status of each of these stacks depends on the operating status of the program.

Here, in the stack 8a of the function A, the EB
A P capture / comparison unit 10, a check EBP storage unit 11, and an abnormality notification unit 12 are provided. A similar configuration is provided when other stack parts such as the stack 9a of the function B exist.

On the other hand, the EBP register reading section 13 is provided in the stack section 7 up to the stack A section. EB
The P capture / comparison unit 10 captures the contents of the EBP register 5 at that time, specifically, the address A1 immediately before calling a function or the like that creates a new stack unit such as the function B, It is adapted to be stored in the check EBP storage unit 11. After the end of the function B processing, the contents of the check EBP storage unit 11 and the contents of the EBP register 5 are compared, and if they do not match, the abnormality notification unit 12 is notified.

FIG. 2 is a diagram showing a concrete program example of the EBP fetch / comparison section 10 in the function A. That is, as shown in FIG. 2, in the program line P1, EB
Using GetEBP () which is an example of the P register reading unit 13, Sa which is an example of the check EBP storage unit 11 is used.
The contents of the EBP register 5 are saved in veEBP.

In the next program line P2, the function B is executed, and after the function B is completed, that is, after the EBP register 5 receives the value of the EBP storage unit 8c of the stack A,
In the previous stage P3a of the program line P3, the contents of the EBP register 5 (GetEBP ()) and the check EB
The contents of the P storage unit 11 (SaveEBP) are compared. And SaveEBP! = GetE
BP (), that is, if they do not match, the abnormality notification unit 1
The second stage P3b, which is an example of the program line P3, is executed to output the abnormality notification.

On the other hand, the function GetEBP (), which is an example of the EBP register reading unit 13, is created in the assembler language and can read the contents of the EBP register 5. Here, what is written in assembler language is
This is because the value of the hardware register in the CPU is read as it is. Further, as an interface to the C language, by designing the return value of this function to indicate the EBP register, it can be used as a C language-like function.

FIG. 3 is a diagram showing a specific program example of the EBP register reading unit 13. Further, in FIG. 1, the EBP register reading unit 13 is provided in the stack unit 7 up to the stack A, but may be provided as a stack unit in another area, for example. That is, EB
The P register reading unit 13 may be provided in an area that is not destroyed by writing the function B or the like.

The EBP register reading unit 13 and the checking EBP storage unit 11 constitute an example of an auxiliary storage unit, and the EBP import / comparison unit 10 and the abnormality notification unit 12 constitute an example of a comparison notification unit. It is configured.

Next, the operation of the computer with the stack area destruction detection function of this embodiment constructed as described above will be explained. FIG. 4 is a flow chart showing the operation of this embodiment.

In FIG. 4, first, the function A is executed (ST1). Next, when it is desired to call the function B while the function A is being executed, the contents of the EBP register 5 are stored in the read check EBP storage unit 11 before the call (ST
2).

Then, the function B is executed (ST3).
When the stack 9a of the function B is secured, the return address to the function A and the EBP of the function A are provided on the stack 8a of the function A and the return address / parameter section 8b and the stack A, respectively, as described in the conventional example. Is stored in the EBP storage unit 8c.

When the execution of the function B ends, the stack A
The value of the EBP storage unit 8c is input to the EBP register 5. Therefore, the EBP fetching / comparing unit 10 in the function A reads the contents of the EBP register 5 at this time before restarting the processing of the function A (ST4), and saves the previously stored function A Check EBP storage unit 11 of stack 8a
(ST5).

Here, if the contents of the EBP register 5 and the contents of the check EBP storage unit 11 are different,
Since it can be determined that at least the contents of the EBP storage unit 8c of the stack A are destroyed, the function B notifies that it is an abnormal function that destroys the stack area of the caller (ST6).

On the other hand, if the above contents are the same, the stack area of the caller has not been destroyed, so the processing is continued (ST7). As described above, in the computer with the stack area destruction detection function according to the present embodiment, when the stack 9a of the function B is secured as a new stack unit, the EBP register reading unit 13 causes the EBP storage unit 8c of the stack A to The contents of the EBP register 5 are saved in another check EBP saving unit 11, and immediately after returning from the function B to the function A, the EBP fetching / comparing unit 10 causes the E of the stack A to be deleted.
The contents of the returned BP storage unit 8c are compared with the contents of the returned EBP register 5 and the contents of the check EBP storage unit 11, and when the two do not match, the abnormality notification unit 12 notifies the fact. When an abnormal function that destroys the original stack area is called, the abnormal function can be detected and the fact that the caller stack area has been destroyed can be notified.

Further, as shown in the program examples of FIGS. 2 and 3, each of the above means can be realized by a very short program, so that the above functions can be realized without reducing the program execution speed so much. In particular, the EBP register reading unit 13 is written in assembler language,
Since only two machine language instructions are required, there is almost no adverse effect on the program execution speed.

Therefore, it is possible to detect a function or the like that causes the above abnormality with a small labor and in a short time. Furthermore, by using the apparatus of the present embodiment, even a programmer with a low proficiency level can easily detect the abnormality.

Further, in this embodiment, the EBP register reading unit 13 is made in assembler language, but it may be made in C language for the convenience of the programmer. In this case, the entire program becomes easy for the programmer to handle.

Further, in the present embodiment, the abnormality notifying section 12 is provided in the stack A section 8. However, it may be provided in another storage area such as the stack section 7 up to the stack A, and the function You may process by calling. It should be noted that the present invention is not limited to the above-described embodiments, but can be variously modified without departing from the scope of the invention.

[0055]

As described above in detail, according to the present invention, E
The contents of the BP register are stored in another storage unit other than the EBP storage unit, and the two are compared when the function returns, so when an abnormal function that destroys the stack area of the calling source is called, Provided is a computer with a stack area destruction detection function capable of detecting an abnormality such as a function when returning to a caller.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a computer with a stack area destruction detection function according to the present invention.

FIG. 2 is a diagram showing a specific program example of an EBP import / comparison unit in a function A in the embodiment.

FIG. 3 is a diagram showing a specific program example of an EBP register reading unit in the embodiment.

FIG. 4 is a flowchart showing the operation of the embodiment.

FIG. 5 is a diagram for explaining the progress of program processing that involves securing and releasing a stack area in a conventional computer.

FIG. 6 is an explanatory diagram showing a case where a part of the stack area for the function A is destroyed by writing the function B to the stack in the conventional computer.

FIG. 7 is an explanatory diagram showing a case where only the EBP area of the function A is destroyed by writing the function B to the stack in the conventional computer.

[Explanation of symbols]

1 ... System bus, 2 ... CPU, 3 ... Program memory, 5 ... EBP register, 6 ... ESP register, 7 ... Stack part up to stack A, 8 ... Stack A part, 9 ... Stack B part, 10 ... EBP import -Comparison unit, 11 ... Check EBP storage unit, 12 ... Abnormality notification unit, 13 ... EBP register reading unit.

Claims (1)

[Claims] 1. A stack area is secured in a program memory for performing a certain process in a computer program.
It operates while being released, and stores a base pointer pointing to the bottom of the stack area in a register in the CPU in order to guarantee the operation of the program, and a new stack area is stored during a processing operation in a certain stack area. To secure the new stack area after storing the base pointer of the certain stack area near the boundary between the certain stack area and the new stack area in the program memory. A new base pointer pointing to the bottom of the stack area is stored in the register to perform some other constant processing in the program in the new stack area, while:
A computer which, when the operation of the program returns from the new stack area to the certain stack area, returns the base pointer stored near the boundary to the register and then continues the operation of the program, Auxiliary storage means for storing a base pointer of the certain stack area, which is different from the vicinity of the boundary in the memory, and when the operation of the program returns from the new stack area to the certain stack area. A computer with a stack area destruction detection function, comprising: a register notifying unit that compares the register contents with the contents of the auxiliary storage unit and, if they do not match, informs to that effect.