CN101894069A - Early serial printing debugging method and device in Linux - Google Patents

Abstract

The invention discloses an early serial port printing debugging method and device in Linux. The method comprises: reserving an information transmission space in the CPU address space of the embedded single board; realizing serial port driver and printing function in the Bootloader stage, and saving the address of the printing function into the reserved information transmission space; The address of the information transfer space is passed to Linux as a startup parameter; the address of the printing function implemented in the Bootloader is obtained from the information transfer space. The invention can realize instant printing of real debugging information at the earliest stage of Linux startup, and improves the efficiency of Linux development and transplantation.

Description

Early serial printing debugging method and device in Linux

technical field

The invention relates to an early printing debugging method of an embedded device, in particular to an early printing debugging method of an embedded device using a Linux operating system.

Background technique

At present, the application range of the Linux operating system is very wide, and there are more and more embedded devices using Linux. On new devices, the transplantation and development of the Linux kernel has become the first technical difficulty in using Linux.

For the transplantation and development of the Linux kernel, the first thing that needs to be solved is the problem of the debugging method. It is very difficult to do early debugging in Linux. Before the Printk function is enabled (including early_printk added after version 2.6.22), there is no intuitive and efficient way to output debugging information. Many technical developers use the method of lighting the indicator light on the device to obtain the working status of the current Linux system. This method is not only inconvenient to use, but also the information that can be displayed is quite limited.

Contents of the invention

The main purpose of the present invention is to provide an early serial port printing debugging method in Linux, which can improve the efficiency of Linux development and transplantation.

In order to achieve the above object, the present invention proposes an early serial port printing debugging method in Linux, comprising steps:

In the CPU address space of the embedded board, reserve a protected information transfer space for transferring information from Bootloader to Linux;

Realize the serial port driver and printing function in the Bootloader stage, and save the address of the printing function to the reserved information transmission space;

Pass the reserved information transfer space address to Linux as a startup parameter;

Obtain the address of the print function implemented in the Bootloader from the information transfer space.

Preferably, the information transfer space, Bootloader space, and Linux space do not overlap each other.

Preferably, the type of the printing function includes the printing without using the stack realized by the assembly code in the early stage of the Bootloader and the printing using the stack realized by the C code in the later stage of the Bootloader.

Preferably, the address of the printing function is stored in the information transfer space.

The present invention also proposes an early serial port printing debugging device in Linux, comprising:

The address planning module reserves a protected information transfer space for transferring information from Bootloader to Linux in the CPU address space of the embedded single board;

Implement the saving module, realize the serial port driver and printing function in the Bootloader stage, and save the address of the printing function to the reserved information transmission space;

The transmission module transmits the reserved information transmission space address to Linux as a startup parameter;

The acquisition module obtains the address of the printing function implemented in the Bootloader from the information transfer space.

Preferably, the information transfer space, the Bootloader space and the Linux space do not overlap each other.

Preferably, the types of the print function include:

In the early days of the Bootloader, the printing without using the stack was realized by assembly code, and the printing using the stack was realized by the C code in the later stage of the Bootloader.

Preferably, the address of the printing function is stored in the information transfer space.

The early serial port printing and debugging method in Linux described in the present invention enriches the debugging means of Linux, and can realize real-time printing of debugging information at the earliest stage of Linux startup, and improves the efficiency of Linux development and transplantation.

Description of drawings

Fig. 1 is the schematic flow sheet of an embodiment of the early serial port printing debugging method in Linux of the present invention;

Fig. 2 is the address space planning schematic diagram of an embodiment of the early serial port printing debugging method in Linux of the present invention;

Fig. 3 is the Bootloader implementation flow diagram of an embodiment of the early serial port printing debugging method in Linux of the present invention;

Fig. 4 is the Linux implementation flow schematic diagram of an embodiment of the early serial port printing debugging method in Linux of the present invention;

FIG. 5 is a schematic structural diagram of an embodiment of an early serial port printing debugging device in Linux of the present invention.

The realization of the purpose of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments and with reference to the accompanying drawings.

Detailed ways

In the present invention, Bootloader (bootloader) is a small program that runs before the operation of the operating system kernel. Through the Bootloader, hardware devices can be initialized and memory space mapping can be established, so as to bring the system's software and hardware environment to a suitable state, so as to prepare the correct environment for the final call of the operating system kernel.

Uart (Universal Asynchronous Receiver/Transmitter), commonly known as serial port, is a universal serial data bus for asynchronous communication. The bus bidirectional communication, can realize full-duplex transmission and reception. In embedded designs, UARTs are used to communicate with PCs, including monitoring debuggers and other devices such as EEPROMs.

With reference to shown in Fig. 1, it is the schematic flow chart of an embodiment of the early serial port printing debugging method in Linux of the present invention, and this method comprises:

Step S10 , in the CPU address space of the embedded board, reserve a section of protected information transfer space for transferring information from Bootloader to Linux; wherein, the above information transfer space, Bootloader space, and Linux space do not overlap each other. Wherein, in the CPU address space of the above-mentioned embedded single board, the space of the Bootloader can also be planned.

Step S11, implement the serial port driver and printing function in the Bootloader stage, and save the address of the printing function to the reserved information transmission space; wherein, there are two types of the above-mentioned printing function, one is that the early stage of the Bootloader is implemented with assembly code and does not use The printing of the stack, the other is the printing of the stack implemented by the C code in the later stage of the Bootloader. Further, the addresses of both types of printing functions are stored in the information transfer space.

Step S12 , transfer the reserved information transfer space address to Linux as a startup parameter; wherein, the startup parameter is a parameter transfer method already implemented by Linux. This step can be performed when the Linux operating system is loaded.

Step S13, obtaining the address of the printing function implemented in the Bootloader from the information transmission space; and realizing the printing function under Linux on this basis. Among them, there are also two types of printing functions under Linux, one is the assembly printing function in the early assembly code stage of Linux startup, and the printing is realized by assembly code; the other is the C printing function in the early C code stage of Linux startup , the printing realized by C code. This step can be implemented by modifying the Linux code, and can be performed at the initial stage of startup.

In this embodiment, the printing method used in the Linux startup phase outputs debugging information through a serial port and a display device.

With reference to shown in Fig. 2, it is the address space planning schematic diagram of an embodiment of the early serial port printing debugging method in Linux of the present invention, and the embedded equipment adopts the processor of mips (Microprocessor without interlocked piped stages, without internal interlocking piped stages) framework, According to the requirements of the mips processor, the bootloader load address is 0x9fc0 0000. In the present embodiment, the code segment of the Bootloader is specified to be linked to the address 0x8c10 0000, and a total of 1M space from the address 0x8c0 0000 to 0x8c10 0000 is planned as the information delivery space for storing the boot_info information. The transplanted Linux code segment is linked to the address 0x8340 0000. As long as the Linux code segment does not exceed 140M after compiling, it will not overwrite the information transfer space and the Bootloader code segment space on it, thereby ensuring that the information transfer space, Bootloader space, and Linux space are consistent. cover each other.

Shown in Fig. 3 with reference to, it is the Bootloader implementation flowchart of an embodiment of the early serial port printing debugging method in Linux of the present invention, has provided the operating procedure relevant to the present invention in the Bootloader stage, comprises:

In step 201, the Bootloader is specified to be loaded at address 0x9fc 00000, and its code segment is linked to 0x8c10 0000.

Step 202, realize the driver of the serial port in the boot stage, and enable the serial port of the device.

Step 203, in the early assembly code stage, realize the serial port printing function of the assembly code version. The print function is used in the initial stage of boot, its function is limited, and because the stack is not maintained, the caller is limited in the use of registers. The printing function can be named a_print.

Step 204, implement the serial port printing function of the C language code version in the later stage of the C code. The print function is used for calling in C language. It has a powerful function and has a stack, and the caller does not need to consider the usage limit of registers; but the function at this time cannot be called in an assembly program without a stack. The printing function can be named c_print.

Step 205, save the addresses of a_print and c_print in boot_info.

Step 206, when Bootloader guides Linux, the address 0x8c00 0000 of boot_info is passed to Linux as a startup parameter.

Shown in Fig. 4 with reference to, it is the Linux implementation flow schematic diagram of an embodiment of the early stage serial port printing debugging method in Linux of the present invention, has provided the operational flow process relevant to the present invention at the operating system stage, including:

Step 301, load the code segment linking Linux to 0x8340 0000.

Step 302, when Linux is started, the first stage is assembly code. At this stage, the parameters passed by the Bootloader can be obtained, and the address of boot_info is saved in the memory variable. This process can be carried out at the first time when mips Linux is started, and the parameters passed to Linux are stored in registers a0-a4, and the data can be read directly from the registers.

In step 303, the address of the a_print function is obtained by adding the offset value to the boot_info address. The address of a_print is specifically stored in the specific location in boot_info, which can be determined through the planning of the boot_info structure by the technical developer.

Step 304, implement the assembly function early_os_a_print based on a_print. In this function, pass the printed character string and other parameters to a_print to complete the Linux printing program of the assembly version. In this way, this function can be used to print debugging information during the initial assembly code stage of Linux. The usage guidelines for the early_os_a_print function are the same as a_print.

Step 305, after entering the C code stage, the address of the c_print function is obtained by adding the offset value to the boot_info address. The address of c_print is stored in the specific location in boot_info, which can be determined by the technical developer's planning of the boot_info structure.

Step 306, implement the C function early_os_c_print based on c_print. In this function, the c_print function address obtained in step 305 is assigned to a function pointer variable, and the c_print function can be directly called through the function pointer. In this way, debugging information can be printed when Linux initially enters the c code stage. The usage guidelines for the early_os_c_print function are the same as for c_print.

Step 307, after the Linux code is further executed, when the Printk function can be used, the print function provided by Linux can be used; at the same time, the early_os_c_print function can also continue to be used.

Referring to FIG. 5 , it is a structural schematic diagram of an early serial port printing debugging device in Linux of the present invention. The device includes an address planning module 51 , an implementation saving module 52 , a transfer module 53 and an acquisition module 54 . The address planning module 51, in the CPU address space of the embedded board, reserves a section of protected information transfer space for transferring information from the Bootloader to Linux; function, and save the print function address to the reserved information transmission space; the transmission module 53 passes the reserved information transmission space address to Linux as a startup parameter; the acquisition module 54 obtains the implementation in the Bootloader from the information transmission space The address of the print function.

The above information transmission space, Bootloader space and Linux space do not overlap each other.

The types of the above printing functions include the printing without using the stack realized by the assembly code in the early stage of the Bootloader and the printing using the stack realized by the C code in the later period of the Bootloader.

The address of the above printing function is stored in the information delivery space.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related All technical fields are equally included in the scope of patent protection of the present invention.

Claims (8)

1. an early serial port printing debugging method in Linux, is characterized in that, comprises steps: In the CPU address space of the embedded single board, reserve a section of protected information transmission space for transmitting information from the bootloader to Linux; Realize the serial port driver and printing function in the Bootloader stage, and save the address of the printing function to the reserved information transmission space; Pass the reserved information transfer space address to Linux as a startup parameter; Obtain the address of the print function implemented in the Bootloader from the information transfer space. 2. the early serial port printing debugging method in Linux according to claim 1, is characterized in that, described information transmission space, Bootloader space and Linux space do not cover each other. 3. according to claim 1 and 2 described early serial port printing debugging methods in Linux, it is characterized in that, the type of described printing function comprises: In the early days of the Bootloader, the printing without using the stack was realized by assembly code, and the printing using the stack was realized by the C code in the later stage of the Bootloader. 4. the early serial port printing debugging method in Linux according to claim 3 is characterized in that, the address of described printing function is stored in the information transfer space. 5. an early stage serial port printing debugging device in Linux, is characterized in that, comprises: The address planning module, in the CPU address space of the embedded board, reserves a protected information transfer space for transferring information from the bootloader to Linux; Implement the saving module, realize the serial port driver and printing function in the Bootloader stage, and save the address of the printing function to the reserved information transmission space; The transmission module transmits the reserved information transmission space address to Linux as a startup parameter; The acquisition module obtains the address of the printing function implemented in the Bootloader from the information transfer space. 6. The early serial port printing debugging device in Linux according to claim 5, characterized in that, the information transfer space, the Bootloader space and the Linux space do not cover each other. 7. according to claim 5 or 6 described early serial port printing debugging devices in Linux, it is characterized in that, the type of described printing function comprises: In the early days of the Bootloader, the printing without using the stack was realized by assembly code, and the printing using the stack was realized by the C code in the later stage of the Bootloader. 8. The early serial port printing debugging device in Linux according to claim 7, characterized in that, the address of the printing function is stored in the information transfer space.

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