JPH0724030B2 - Debug device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a debug device, and more particularly to a debug device which is characterized in that an actual argument of a subroutine of a program or a local variable is accessed at high speed.

(Prior Art) Conventionally, in a debug device for performing debugging by connecting to an actual machine, an address of a program memory in the actual machine to be accessed is specified, and data is written to the address or the address from the address is written. I was reading data.

(Problems to be Solved by the Invention) In the conventional method described above, for example, in a program written in a high-level language, when a subroutine is called at the time of program execution, an actual argument, a local variable, A stack frame composed of the value of the frame pointer pointing to the frame of the subroutine and the return address is formed. At this time, the following problems occur when accessing the memory address corresponding to the actual argument and local variable of the specified subroutine.

First, the contents of the stack frame are examined by tracing the frame pointer in the stack frame from the stack frame of the most recently called subroutine in the runtime stack to the stack frame of the calling subroutine.

If the return address in the stack frame is included in the instruction area of the specified subroutine, the subroutine that called the subroutine corresponding to the stack frame is
It turns out that it is a designated subroutine. Therefore, the actual argument and local variable held in the stack frame of the subroutine are accessed.

At this time, if the host machine that holds the source file of the program and the symbol table and the debug device are connected by a line, and the host machine tries to access the actual arguments and local variables of the specified function, the instructions of the function Since the information about the area, the actual argument to be accessed, and the relative position in the frame of the local variable is only in the host machine, as described above, when the execution stack is traced, communication between the host machine and the debug device is performed. The number of times increases, the actual argument of the subroutine or the local variable is not accessed at high speed, and the efficiency of debugging work is reduced.

The present invention has solved such a conventional drawback, and an object thereof is to speed up access to an actual argument of a subroutine of a program or a local variable to improve efficiency of debugging work.

(Means for Solving the Problem) According to the present invention, in a debug device, a first register holding a subroutine start address of a program being executed on the real machine, a second register holding an end address of the subroutine, and the real machine. A third register that holds an offset from a frame pointer that points to a frame in which an argument of a subroutine to be executed or a local variable is stored, and a fourth register that holds data read from the frame or data written to the frame. Subroutine called from the register's register and the execution stack in the program memory in the actual machine, which is sandwiched between the start address of the subroutine held in the first register and the end address of the subroutine held in the second register. Frame is found, and the third frame from that frame is found. It has means for reading the contents of the actual argument or local variable of the subroutine designated by the offset value stored in the register and setting it to the contents of the fourth register, and means for writing the contents of the fourth register to the address.

(Example) Next, the Example of this invention is described with reference to drawings.

FIG. 1 is a block diagram of an embodiment of a debug device of the present invention, which is composed of a debug device 1 and an actual machine 2.

The debug device 1 stores a processor 10, a memory 14, a display 15, a keyboard 16, a control circuit 103 for controlling the actual processor 20, a register 17 for storing the start address of a designated subroutine, and an end address of the designated subroutine. Register 18, the local variable to be accessed in the specified subroutine, or register 1 that stores the offset value from the frame point to the actual argument
9. A data register 101 for storing the data to be set in the accessed local variable or actual argument, or data read from the local variable or actual argument, and an access register 102 for holding a read or write access method To do.

Processor 10, memory 14, display 15, keyboard
16, the register 17, the register 18, the register 19, and the data register 101 are connected by a data bus 11, an address bus 12, and a control bus 13. Real machine 2 is a processor
20 and a memory 24 are provided. Address bus 22, processor
20 and the memory 24 are connected by a data bus 21 and a control bus 23. In the memory 14 of the debug device 1,
By controlling the display 15 and the keyboard 16, the instruction start address of the designated subroutine is set in the register 17, the instruction end address of the subroutine is set in the register 18, and the local variable accessed by the subroutine or the frame pointer of the actual argument The offset value from is set in the register 19, the read or write access method to the local variable or the actual argument is set in the instruction register 102, and the data to be set in the local variable or the actual argument is set in the data register 101. However, a program for reading data from the data register 101 holding the data read from the local variable or the actual argument is included.

Next, the operation of the debug device shown in FIG. 1 will be described with reference to FIGS. 2 and 3.

First, in the debug device 1, the program contained in the memory 14 is activated. The program is a keyboard
Instruction start address of the subroutine accessed from 16,
The offset value is input from the instruction end address, the local variable to be accessed, or the frame pointer of the actual argument, and set in register 17, register 18, and register 19, respectively.
The access method is set in the instruction register 102, and when the content of the instruction register 102 is a write instruction, the write data is set in the data register 101.

Next, in the execution suspended state of the actual machine 2, the control program contained in the memory 14 performs the processing shown in FIG. That is,
The control program sets the content of the frame pointer register of the processor 20 (FIG. 3) to the variable A in the memory 14 (201 of FIG. 2).

Next, the return address of the subroutine stored at the address offset by the offset value β from the address of the stack frame of the subroutine held in the variable A is obtained,
It is stored in the variable B in the memory 14 (202 in FIG. 2).

Next, it is judged whether or not the content of the variable B, that is, the return address is between the start address of the designated subroutine contained in the register 17 and the end address of the subroutine contained in the register 18 (FIG. 2, 203). ). If there is a gap, the subroutine that called the subroutine of interest is the designated subroutine.

If the return address of the subroutine is register 17 and register
If it is not between 18, the subroutine that called the subroutine of interest is not the designated subroutine.

Therefore, the address of the frame of the subroutine that called the subroutine, which is stored at the address offset by the offset value α from the address of the stack frame of the subroutine, is obtained and stored in the variable A (205 in FIG. 2).

In the determination 203 of the return address of the subroutine, when the designated subroutine is found, the pointer value of the stack frame of the designated subroutine is set to the variable A (204 in FIG. 2).

Next, referring to FIG. 206 in FIG. 2, the contents of the instruction register 102 are checked.
The contents of the data register 101 are written to the memory addresses separated by the offset value included in (2) in FIG.

In the case of a read instruction, the content of the address is set in the data register 101. This completes the operation of the control program contained in the memory 14 (FIG. 2, 208).

(Effect of the Invention) As described above, according to the present invention, when accessing a local variable or an actual argument of a subroutine that becomes a runtime stack formed when a program written in a high-level language or the like is executed in an actual machine, By providing a means for tracing the execution stack in the real machine in the debug device, it becomes possible to access at a higher speed than a debug device which allows only memory access by address only. Furthermore, when debugging is performed by connecting the debug device and the host machine with a line, the communication amount between the host machine and the debug device can be reduced, and the debug effect is improved as compared with the conventional debug device. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart showing an example of processing for accessing a local variable or an actual argument of a subroutine on an execution stack in an actual machine, and FIG. 3 is an explanation of FIG. Is an example of an execution stack in a real machine for. Subroutine i calls subroutine i + 1, and subroutine i + 1 calls the next function. The currently called subroutine is n. The stack frame of the subroutine n is stored in the frame pointer register. The frame pointer points to an address within the stack frame of subroutine n.
It is assumed that the return address of the subroutine i (0 ≦ i ≦ n) is stored at an address β away from the frame pointer, and the stack frame storage area of the subroutine i-1 is stored at an address α away. . 1 …… debug device, 10 …… data bus 11 …… address bus, 12 …… control bus 14 …… memory, 15 …… display 16 …… keyboard, 17 …… register 18 …… register, 19 …… register 101 ...... Data register 102 ...... Access register 103 ...... Control circuit, 2 …… Actual machine, 20 …… Processor 21 …… Data bus, 22 ...... Address bus 23 ...... Control bus, 24 ...... Memory

Claims (1)

[Claims] 1. A debug device for executing program debugging by extracting an address signal, a data signal and a control signal from a system bus or a terminal of the processor, which is an actual machine having a processor and a program memory in which a control program of the processor is recorded. The first register that holds the subroutine start address of the program being executed on the actual machine, the second register that holds the end address of the subroutine, and the arguments or local variables of the subroutine executed on the actual machine are stored. A third register that holds an offset from a frame pointer that points to a frame and a fourth register that holds the data read from the frame or the data to be written to the frame, and the execution stack in the program memory in the actual machine, Stored in the first register Found the frame of the subroutine called from the memory address sandwiched between the start address of the executed subroutine and the end address of the subroutine held in the second register, and designated from the frame by the offset value stored in the third register Means for reading the actual argument or the content of the local variable of the subroutine to be set to the content of the fourth register and the means for writing the fourth register content to the address, and the actual argument of the subroutine of the program or the local A debug device characterized by high-speed access to variables.