HongMeng kernel source code analysis editor (Shell) | two tasks, three stages OpenHarmony source | | best blog analysis v71.02

The Master said, “I was not born a man of knowledge. Analects of Confucius: A review

A hundred blog series. This is:

V71. Xx HongMeng kernel source code analysis (Shell editor) | two tasks, three stages

Process management:

• V02. Xx HongMeng kernel source code analysis (process management) | who in the management of core resources
• V24. Xx HongMeng kernel source code analysis concept (process) | process in which resources management
• V45. Xx HongMeng kernel source code analysis (Fork) | one call, return twice
• V46. Xx HongMeng kernel source code analysis (special) | mouse son can make hole
• V47. Xx HongMeng kernel source code analysis (process recycling) | how to entrust an orphan to ancestor dying
• V48. Xx HongMeng kernel source code analysis (signal) | the year lead half hundred, still energetic
• V49. Xx HongMeng kernel source code analysis (signal) | who let CPU run for four times in the stack
• V71. Xx HongMeng kernel source code analysis (Shell editor) | two tasks, three stages
• V72. Xx HongMeng kernel source code analysis (Shell) | watching the kernel of the application window

This series summarizes the underlying implementation of shell from the perspective of kernel in one sentence: two tasks, three stages. It is by nature an independent process, and therefore a process management module. Each time a shell process is created, two more tasks are created.

• Client task (ShellEntry) :Responsible for accepting character by character typed from the terminal (console), character pressVTSpecifications are assembled into sentences of commands.
• ShellTask: Parses and executes commands and outputs the results to the console.

The command life cycle can be divided into three phases.

• Editor:In this section, Hongmeng implements a simple editor function that handles every character input from the console, including control characters such as<ESC>.\t.\b.\n.\rFour arrow keys0x41 ~ 0x44Processing.
• Parsing: Parses the edited string, parses command items and parameter items, and finds the corresponding command items to execute the function.
• Execution: Commands can be registered with the kernel statically or dynamically. After the command is parsed, the corresponding function callback can be found in the registry. Output the results to the console.

The editing part is done by the client task, the last two parts are done by the server task, and command global registration is done by the kernel.

• This article focuses on client tasks and the editing process
• The server tasks and the parsing/execution process are explained in Shell parsing.

What is a Shell

From the perspective of users, shell is a window for users to peep and operate the kernel. The kernel is not monolithic, but opens two Windows on the application layer, one is system call and the other is shell. The kernel provides implementation functions and the user provides parameters to execute. The difference is that shell is completed by an independent task, which can be written into an independent and simple shell program by serializing shell commands. Therefore, shell is also a scripting language, and system call is attached to the task of the application program to complete, which can be limited. Through the shell window, you can see the running status of CPU, memory consumption, network link status and so on.

Where is the Hongmeng Shell code

The concept corresponding to shell is kernel. In hongmeng kernel, these two parts of code are separated. The shell code is viewed in the shell code, and the directory structure is as follows.

├ ─ the include │ dmesg. H │ dmesg_pri. H │ SHCMD. H │ shcmdparse. H │ shell. H │ shell_lk. H │ shell_pri. H │ SHMSG. H │ show. H │ └ ─ SRC ├ ─ base │ SHCMD. C │ shcmdparse. C │ shell_lk. C │ SHMSG. C │ show. C │ └ ─ CMDS date_shellcmd. C dmesg. C hwi_shellcmd. C shell_shellcmd.c watch_shellcmd.cCopy the code

Shell control block

Like process and task, behind each concept needs a main structure to support. The main structure of shell is ShellCB. If you master ShellCB, you can handle shell too tightly, but you can’t understand this structure and the kernel implementation of shell. So you can’t spend too much time on it.

typedef struct { UINT32 consoleID; // Console ID UINT32 shellTaskHandle; // Shell server task ID UINT32 shellEntryHandle; //shell client task ID VOID *cmdKeyLink; // List of shell commands to be processed VOID *cmdHistoryKeyLink; VOID *cmdMaskKeyLink; VOID *cmdMaskKeyLink; // Historically traversed by arrow keys. UINT32 shellBufOffset; // BUF offset UINT32 shellKeyType; // Button type EVENT_CB_S shellEvent; // The event type triggers pthread_mutex_t keyMutex; Pthread_mutex_t historyMutex; // Historical mutex CHAR shellBuf[SHOW_MAX_LEN]; // The shell command buf accepts input from the keyboard and needs to parse the input characters. CHAR shellWorkingDirectory[PATH_MAX]; } ShellCB; Typedef struct {UINT32 count; // The number of characters LOS_DL_LIST list; CHAR cmdString[0]; } CmdKeyLink;} CmdKeyLink; Enum {STAT_NOMAL_KEY, // Common key STAT_ESC_KEY, //<ESC> start key STAT_MULTI_KEY // combination key};Copy the code

Interpretation of the

• Hongmeng supports two ways of input in the consoleShellCommand, about the console please see the console chapter.
  • Enter the value in the serial port toolShellThe commandCONSOLE_SERIAL.
  • intelnetTool inputShellThe commandCONSOLE_TELNET.
• shellTaskHandleandshellEntryHandleEdit/processshellCommand’s two task ids, the latter of which is the focus of this article.
• cmdKeyLink.cmdHistoryKeyLink.cmdMaskKeyLinkThere are three types ofCmdKeyLinkThe structure is essentially a bidirectional linked list, corresponding to editingshellThree functions in a command procedure.
  • cmdKeyLinkList of commands to be executed
  • cmdHistoryKeyLinkThe command history is stored, that is:historyCommand display
  • cmdMaskKeyLinkRecord up and down arrow keys output content, this is a bit difficult to understand, in their ownshellPress the up and down arrow keys to experience
• shellBufOffsetandshellBufIs a pair, which is stored in the user typed after the character.
• keyMutexandhistoryMutexThe kernel uses most of the mutex locks needed to manipulate linked lists.
• shellEventFor communication between tasks, for example.
  • SHELL_CMD_PARSE_EVENT: Edit completed notification parsing task started
  • CONSOLE_SHELL_KEY_EVENT: Received from the consoleCTRL + CSignal generation events.
• shellKeyTypeThere are three types of keys: normal keys and combination keys
• shellWorkingDirectoryWorkspace does not need to say, from which directory to entershellthe

Create a Shell

Int main(int argc, char **argv) {//... g_shellCB = shellCB; Return OsShellCreateTask(shellCB); } // Creating a shell task STATIC UINT32 OsShellCreateTask(ShellCB * ShellCB) {UINT32 RET = ShellTaskInit(ShellCB); // Execute shell command tasks to initialize if (ret! = LOS_OK) { return ret; } return ShellEntryInit(shellCB); LITE_OS_SEC_TEXT_MINOR UINT32 Initializes a task that receives shell commands through the console. This task is responsible for editing commands and processing command generation processes, such as the direction keys, backspace keys, and Enter keys ShellEntryInit(ShellCB *shellCB) { UINT32 ret; CHAR *name = NULL; TSK_INIT_PARAM_S initParam = {0}; if (shellCB->consoleID == CONSOLE_SERIAL) { name = SERIAL_ENTRY_TASK_NAME; } else if (shellCB->consoleID == CONSOLE_TELNET) { name = TELNET_ENTRY_TASK_NAME; } else { return LOS_NOK; } initParam.pfnTaskEntry = (TSK_ENTRY_FUNC)ShellEntry; // Task entry function initparam. usTaskPrio = 9; /* 9:shell task priority */ initParam.auwArgs[0] = (UINTPTR)shellCB; initParam.uwStackSize = 0x1000; initParam.pcName = name; initParam.uwResved = LOS_TASK_STATUS_DETACHED; ret = LOS_TaskCreate(&shellCB->shellEntryHandle, &initParam); #ifdef LOSCFG_PLATFORM_CONSOLE (VOID)ConsoleTaskReg(INT32)shellCB->consoleID, shellCB->shellEntryHandle); #endif return ret; }Copy the code

Interpretation of the

• mainforshellThe main task of a process. Each process creates a default thread (task), whose entry function is well knownmainFunction, not clear self-review task management has detailed instructions.
• bymainTasks create two more tasks, one of which is the focus of this articleShellEntry, the task priority is9“Is considered a higher priority.
• Specifies that the kernel stack size is0x1000 = 4K Since the task is only responsible for editing the characters entered by the console, the execution of the command is in other tasks, so 4K kernel space is enough to use.
• ShellEntryIs the entry function, the implementation of which is the focus of this article

ShellEntry | editing process

LITE_OS_SEC_TEXT_MINOR UINT32 ShellEntry(UINTPTR param) { CHAR ch; INT32 n = 0; ShellCB *shellCB = (ShellCB *)param; CONSOLE_CB *consoleCB = OsGetConsoleByID((INT32)shellCB->consoleID); If (consoleCB == NULL) {PRINT_ERR("Shell task init error! \n"); return 1; } (VOID)memset_s(shellCB->shellBuf, SHOW_MAX_LEN, 0, SHOW_MAX_LEN); // reset shell command buf while (1) {#ifdef LOSCFG_PLATFORM_CONSOLE if (! IsConsoleOccupied(consoleCB) {// Is console ready for shell? */ n = read(consoleCB->fd, &ch, 1); ShellCmdLineParse(ch, (pf_OUTPUT)dprintf, shellCB); if (n == 1) {ShellCmdLineParse(ch, (pf_OUTPUT)dprintf, shellCB); } if (is_nonblock(consoleCB)) {// Pause in non-blocking mode for 50ms LOS_Msleep(50); / * 50: LITE_OS_SEC_TEXT_MINOR VOID for sleep */ #ifdef LOSCFG_PLATFORM_CONSOLE} #endif} ShellCmdLineParse(CHAR c, pf_OUTPUT outputFunc, ShellCB *shellCB) { const CHAR ch = c; INT32 ret; If ((shellCB->shellBufOffset == 0) && (ch! = '\n') && (ch ! = '\0')) { (VOID)memset_s(shellCB->shellBuf, SHOW_MAX_LEN, 0, SHOW_MAX_LEN); / / reset buf} / / meet carriage return or line feed the if ((ch = = '\ r') | | (ch = = '\ n')) {if (shellCB - > shellBufOffset < (SHOW_MAX_LEN - 1)) { shellCB->shellBuf[shellCB->shellBufOffset] = '\0'; } shellCB->shellBufOffset = 0; (VOID)pthread_mutex_lock(&shellCB->keyMutex); OsShellCmdPush(shellCB->shellBuf, shellCB->cmdKeyLink); VOID pthread_mutex_unlock(&shellcb ->keyMutex); ShellNotify(shellCB); // Notify the task to parse shell command return; } else if ((ch = = '\ b') | | (ch = = 0 x7f)) {/ * backspace or delete (0 x7f) * / / / in the delete button if ((shellCB - > shellBufOffset > 0) && (shellCB->shellBufOffset < (SHOW_MAX_LEN - 1))) { shellCB->shellBuf[shellCB->shellBufOffset - 1] = '\0'; // fill '\0' shellCB->shellBufOffset--; //buf reduces outputFunc("\b \b"); } return; } else if (ch == 0x09) { /* 0x09: If (shellCB->shellBufOffset > 0) && (shellCB->shellBufOffset < (show_max_len-1))) {ret = OsTabCompletion(shellCB->shellBuf, &shellCB->shellBufOffset); If (ret > 1) {outputFunc("OHOS # %s", shellCB->shellBuf); }} return; } /* parse the up/down/right/left key */ ret = ShellCmdLineCheckUDRL(ch, shellCB); If (ret == LOS_OK) {return; } if ((ch ! = '\n') && (ch ! If (shellCB->shellBufOffset < (show_max_len-1)) {//buf range shellCB->shellBuf[shellCB->shellBufOffset] = ch; } else {shellCB->shellBuf[show_max_len-1] = '\0'; } shellCB->shellBufOffset++; // Offset increases outputFunc("%c", ch); ShellCB ->shellKeyType = STAT_NOMAL_KEY;} shellCB->shellKeyType = STAT_NOMAL_KEY; // Common characters}Copy the code

Interpretation of the

• ShellEntryInside is an infinite loop that reads every character typed by the console, note the character processing.
• Four directions, line feed, carriage return,tab.backspace.delete.escAnd other control keys, equivalent to a new understanding of the nextAsciiWatch. You can do itshellA terminal is understood as a simple editor.
  • Press Enter to complete the previous input and enter the parsing execution phase.
  • Press the arrow key to display the up/next command, and press continuously to display the up/down command.
  • According to thetabKey is to complete the content of the command, currently Hongmeng supports the following commands:

        arp           cat           cd            chgrp         chmod         chown         cp            cpup          
        date          dhclient      dmesg         dns           format        free          help          hwi           
        ifconfig      ipdebug       kill          log           ls            lsfd          memcheck      mkdir         
        mount         netstat       oom           partinfo      partition     ping          ping6         pwd           
        reset         rm            rmdir         sem           statfs        su            swtmr         sync          
        systeminfo    task          telnet        test          tftp          touch         umount        uname         
        watch         writeproc  
    Copy the code

    For example: when pressed in the consolechandtabThe following three outputs are generated after the key

    chgrp         chmod         chown
    Copy the code

    Content, these functions seem very common to users, but all need to be implemented by the kernel.

• shellBufStores the results of the edit and, when the Enter key is pressed, saves the results and delivers them to the next stage for use.

Intensive reading of the kernel source code

Four code stores synchronous annotation kernel source code, >> view the Gitee repository

Analysis of 100 blogs. Dig deep into the core

Add comments to hongmeng kernel source code process, sort out the following article. Content based on the source code, often in life scene analogy as much as possible into the kernel knowledge of a scene, with a pictorial sense, easy to understand memory. It’s important to speak in a way that others can understand! The 100 blogs are by no means a bunch of ridiculously difficult concepts being put forward by Baidu. That’s not interesting. More hope to make the kernel become lifelike, feel more intimate. It’s hard, it’s hard, but there’s no turning back. 😛 and code bugs need to be constantly debug, there will be many mistakes and omissions in the article and annotation content, please forgive, but will be repeatedly amended, continuous update. Xx represents the number of modifications, refined, concise and comprehensive, and strive to create high-quality content.

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