Android6.0系统启动流程分析一:init进程
来源:互联网 发布:编程就业方向 编辑:程序博客网 时间:2024/05/20 08:25
文章来源:http://blog.csdn.net/u011913612/article/details/53204253?ref=myread
到了Android6.0,Init进程使用c++来写了,不过没有关系,它和c写的init没有太大的区别。
Init进程的入口代码是:system\core\init\init.cpp
main函数:
int main(int argc, char** argv) { if (!strcmp(basename(argv[0]), "ueventd")) { return ueventd_main(argc, argv); } if (!strcmp(basename(argv[0]), "watchdogd")) { return watchdogd_main(argc, argv); } // Clear the umask. umask(0); add_environment("PATH", _PATH_DEFPATH); bool is_first_stage = (argc == 1) || (strcmp(argv[1], "--second-stage") != 0); // Get the basic filesystem setup we need put together in the initramdisk // on / and then we'll let the rc file figure out the rest. if (is_first_stage) { mount("tmpfs", "/dev", "tmpfs", MS_NOSUID, "mode=0755"); mkdir("/dev/pts", 0755); mkdir("/dev/socket", 0755); mount("devpts", "/dev/pts", "devpts", 0, NULL); mount("proc", "/proc", "proc", 0, NULL); mount("sysfs", "/sys", "sysfs", 0, NULL); } // We must have some place other than / to create the device nodes for // kmsg and null, otherwise we won't be able to remount / read-only // later on. Now that tmpfs is mounted on /dev, we can actually talk // to the outside world. open_devnull_stdio(); klog_init(); klog_set_level(KLOG_NOTICE_LEVEL); NOTICE("init%s started!\n", is_first_stage ? "" : " second stage"); if (!is_first_stage) { // Indicate that booting is in progress to background fw loaders, etc. close(open("/dev/.booting", O_WRONLY | O_CREAT | O_CLOEXEC, 0000)); property_init(); // If arguments are passed both on the command line and in DT, // properties set in DT always have priority over the command-line ones. process_kernel_dt(); process_kernel_cmdline(); // Propogate the kernel variables to internal variables // used by init as well as the current required properties. export_kernel_boot_props(); } // Set up SELinux, including loading the SELinux policy if we're in the kernel domain. selinux_initialize(is_first_stage); // If we're in the kernel domain, re-exec init to transition to the init domain now // that the SELinux policy has been loaded. if (is_first_stage) { if (restorecon("/init") == -1) { ERROR("restorecon failed: %s\n", strerror(errno)); security_failure(); } char* path = argv[0]; char* args[] = { path, const_cast<char*>("--second-stage"), nullptr }; if (execv(path, args) == -1) { ERROR("execv(\"%s\") failed: %s\n", path, strerror(errno)); security_failure(); } } // These directories were necessarily created before initial policy load // and therefore need their security context restored to the proper value. // This must happen before /dev is populated by ueventd. INFO("Running restorecon...\n"); restorecon("/dev"); restorecon("/dev/socket"); restorecon("/dev/__properties__"); restorecon_recursive("/sys"); epoll_fd = epoll_create1(EPOLL_CLOEXEC); if (epoll_fd == -1) { ERROR("epoll_create1 failed: %s\n", strerror(errno)); exit(1); } signal_handler_init(); property_load_boot_defaults(); start_property_service(); init_parse_config_file("/init.rc"); action_for_each_trigger("early-init", action_add_queue_tail); // Queue an action that waits for coldboot done so we know ueventd has set up all of /dev... queue_builtin_action(wait_for_coldboot_done_action, "wait_for_coldboot_done"); // ... so that we can start queuing up actions that require stuff from /dev. queue_builtin_action(mix_hwrng_into_linux_rng_action, "mix_hwrng_into_linux_rng"); queue_builtin_action(keychord_init_action, "keychord_init"); queue_builtin_action(console_init_action, "console_init"); // Trigger all the boot actions to get us started. action_for_each_trigger("init", action_add_queue_tail); // Repeat mix_hwrng_into_linux_rng in case /dev/hw_random or /dev/random // wasn't ready immediately after wait_for_coldboot_done queue_builtin_action(mix_hwrng_into_linux_rng_action, "mix_hwrng_into_linux_rng"); // Don't mount filesystems or start core system services in charger mode. char bootmode[PROP_VALUE_MAX]; if (property_get("ro.bootmode", bootmode) > 0 && strcmp(bootmode, "charger") == 0) { action_for_each_trigger("charger", action_add_queue_tail); } else { action_for_each_trigger("late-init", action_add_queue_tail); } // Run all property triggers based on current state of the properties. queue_builtin_action(queue_property_triggers_action, "queue_property_triggers"); while (true) { if (!waiting_for_exec) { execute_one_command(); restart_processes(); } int timeout = -1; if (process_needs_restart) { timeout = (process_needs_restart - gettime()) * 1000; if (timeout < 0) timeout = 0; } if (!action_queue_empty() || cur_action) { timeout = 0; } bootchart_sample(&timeout); epoll_event ev; int nr = TEMP_FAILURE_RETRY(epoll_wait(epoll_fd, &ev, 1, timeout)); if (nr == -1) { ERROR("epoll_wait failed: %s\n", strerror(errno)); } else if (nr == 1) { ((void (*)()) ev.data.ptr)(); } } return 0;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
1.这个函数是否往下执行取决于传入的参数,如果第0个参数的basename为ueventd,则执行ueventd_main(argc, argv);如果basename为watchdogd_main,则执行watchdogd_main(argc, argv);只有basename不为这二者时,才会继续往下执行。
2.如果argv[1]不为”–second-stage”或者只有一个参数的话,那么is_first_stage就为true,就会创建/dev/pts和”/dev/socket”两个设备文件节点,并挂载一个文件系统。可以看出来init进程分两个阶段,不同的阶段有不同的行为。具体的内涵鄙人还没搞明白。
3.启动属性服务。创建一个socket,并在之后的死循环中监听这个socket返回的文件描述符。
3.解析init.rc。这个过程也是我最感兴趣的,也是最重要的复杂的。
4.对各个阶段的action排序。
5.进入死循环。
6.第一次进入死循环后,action_queue里面有很多时间,因此需要不断调用execute_one_command来执行命令。此时,action_queue_empty为假,timeout 为0,init线程不会在epoll_wait方法中休眠,因为设置的timeout=0哦,这一点曾一度困扰了我。
7.所有的命令执行完后,init进程进入休眠,监听property_set_fd和signal_read_fd两个文件描述符,一点他们有事件过来,立刻被唤醒,进而做事件处理。
init.rc梳理
在我们分析init.rc的解析过程之前,我们还需要先对init.rc有个基本的认识。
先看一张我根据理解绘制的图:
从图来看,init.rc主要有section组成,section由on,import,section三个关键字标示。其中on标示的section叫做action。
import就不用说了,和C语言中的include功能有点类似。
service格式如下
service <name> <pathname> [ <argument> ]* <option> <option> ...
- 1
- 2
- 3
- 4
- 1
- 2
- 3
- 4
action后面会跟一个触发器,然后另起一行开始放置命令(command),格式如下:
on <trigger> <command> <command> <command>
- 1
- 2
- 3
- 4
- 1
- 2
- 3
- 4
跟在service后面的是option,跟在action后面的是command.command都会对应一个处理函数,定义在keywords.h中:
... KEYWORD(loglevel, COMMAND, 1, do_loglevel) KEYWORD(mkdir, COMMAND, 1, do_mkdir) KEYWORD(mount_all, COMMAND, 1, do_mount_all) KEYWORD(mount, COMMAND, 3, do_mount) ...
- 1
- 2
- 3
- 4
- 5
- 6
- 1
- 2
- 3
- 4
- 5
- 6
命名也是很有规则的。比如mkdir,对应的函数就是do_mkdir。我们看看do_mkdir做了什么:
int do_mkdir(int nargs, char **args){ mode_t mode = 0755; int ret; /* mkdir <path> [mode] [owner] [group] */ if (nargs >= 3) { mode = strtoul(args[2], 0, 8); } ret = make_dir(args[1], mode); /* chmod in case the directory already exists */ if (ret == -1 && errno == EEXIST) { ret = fchmodat(AT_FDCWD, args[1], mode, AT_SYMLINK_NOFOLLOW); } if (ret == -1) { return -errno; } if (nargs >= 4) { uid_t uid = decode_uid(args[3]); gid_t gid = -1; if (nargs == 5) { gid = decode_uid(args[4]); } if (lchown(args[1], uid, gid) == -1) { return -errno; } /* chown may have cleared S_ISUID and S_ISGID, chmod again */ if (mode & (S_ISUID | S_ISGID)) { ret = fchmodat(AT_FDCWD, args[1], mode, AT_SYMLINK_NOFOLLOW); if (ret == -1) { return -errno; } } } return e4crypt_set_directory_policy(args[1]);}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
其实就是调用了make_dir并做了一些权限等方面的操作。所以,跟在action后面的命令并不能随随便便乱加,而是要确保这个命令被定义了,不然就会出错。
init.rc的解析过程(以import为例)
因为init.rc的第一行代码就是Import语句。万事开头难,只要我们理清了第一行的解析过程,后面行的解析分析起来就不怎么费劲了。所以下面我们主要看看init.rc中第一行的解析过程。
init.tc的解析函数为:init_parse_config_file
int init_parse_config_file(const char* path) { INFO("Parsing %s...\n", path); Timer t; std::string data; if (!read_file(path, &data)) { return -1; } data.push_back('\n'); // TODO: fix parse_config. parse_config(path, data); dump_parser_state(); // MStar Android Patch Begin INFO("(Parsing %s took %.2fs.)\n", path, t.duration()); // MStar Android Patch End return 0;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
这个函数把/init.rc中的内容读出来,并让data这个string类型的变量指向它。
把读出来的data传递给parse_config函数做真正的解析工作。parse_config函数如下:
static void parse_config(const char *fn, const std::string& data){ char *args[UEVENTD_PARSER_MAXARGS]; int nargs = 0; parse_state state; state.filename = fn; state.line = 1; state.ptr = strdup(data.c_str()); // TODO: fix this code! state.nexttoken = 0; state.parse_line = parse_line_no_op; for (;;) { int token = next_token(&state); switch (token) { case T_EOF: parse_line(&state, args, nargs); return; case T_NEWLINE: if (nargs) { parse_line(&state, args, nargs); nargs = 0; } state.line++; break; case T_TEXT: if (nargs < UEVENTD_PARSER_MAXARGS) { args[nargs++] = state.text; } break; } }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
我看到这个函数的时候,我想起了xml解析方法之一的pull解析,感觉挺像的。每次循环都会找到一个token,token就是一个特定的符号,然后根据这个toke做不同的处理。这里使用到了parse_state结构,启动以如下:
struct parse_state{ char *ptr; char *text; int line; int nexttoken; void *context; void (*parse_line)(struct parse_state *state, int nargs, char **args); const char *filename; void *priv;};
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
这个就够中:ptr执行init.rc字符流的,text后面会用到,用来保存参数,line当然就是行数了,nexttoken保存下一个token,filename保存init.rc的文件描述符,filename当然是/init.rc了.parse_line是一个函数指针。context暂时没明白…state.priv 指向Import的一个文件链表。
我们打开Init.rc看看,从头分析它的解析过程。
import /init.environ.rcimport /init.usb.rcimport /init.${ro.hardware}.rcimport /init.${ro.zygote}.rcimport /init.trace.rc...
- 1
- 2
- 3
- 4
- 5
- 6
- 1
- 2
- 3
- 4
- 5
- 6
init.rc前面几行都是import语句,我们看看一开始的解析流程。
这个时候,parse_satate的状态为:
state.filename = fn; state.line = 1; state.ptr = strdup(data.c_str()); // TODO: fix this code! state.nexttoken = 0; state.parse_line = parse_line_no_op; list_init(&import_list); state.priv = &import_list;
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 1
- 2
- 3
- 4
- 5
- 6
- 7
step 1.第一次循环
然后进入死循环,第一次调用next_token函数:
int next_token(struct parse_state *state){ char *x = state->ptr; char *s; if (state->nexttoken) { int t = state->nexttoken; state->nexttoken = 0; return t; } for (;;) { switch (*x) { case 0: state->ptr = x; return T_EOF; case '\n': x++; state->ptr = x; return T_NEWLINE; case ' ': case '\t': case '\r': x++; continue; case '#': while (*x && (*x != '\n')) x++; if (*x == '\n') { state->ptr = x+1; return T_NEWLINE; } else { state->ptr = x; return T_EOF; } default: goto text; } }textdone: state->ptr = x; *s = 0; return T_TEXT;text: state->text = s = x;textresume: for (;;) { switch (*x) { case 0: goto textdone; case ' ': case '\t': case '\r': x++; goto textdone; case '\n': state->nexttoken = T_NEWLINE; x++; goto textdone; case '"': x++; for (;;) { switch (*x) { case 0: /* unterminated quoted thing */ state->ptr = x; return T_EOF; case '"': x++; goto textresume; default: *s++ = *x++; } } break; case '\\': x++; switch (*x) { case 0: goto textdone; case 'n': *s++ = '\n'; break; case 'r': *s++ = '\r'; break; case 't': *s++ = '\t'; break; case '\\': *s++ = '\\'; break; case '\r': /* \ <cr> <lf> -> line continuation */ if (x[1] != '\n') { x++; continue; } case '\n': /* \ <lf> -> line continuation */ state->line++; x++; /* eat any extra whitespace */ while((*x == ' ') || (*x == '\t')) x++; continue; default: /* unknown escape -- just copy */ *s++ = *x++; } continue; default: *s++ = *x++; } } return T_EOF;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
这时候,init.rc中的第一个符号应该是i(impor,省去空格),所以next_token直接进入到text:标签执行,执行的结果是state->text = s = ‘i’;然后继续执行textresume:标签后面的内容:
标签后面的for死循环中,发现第一个字符是i,于是执行default分支:*s++ = *x++;这样直到import的t被检测完以后,在下一次循环变得到一个空格,于是执行x++,并goto textdone.。textdown执行完后函数返回,返回后,state->ptr 指向’/’符号 。*s = 0;意味着state.text就是字符串“import”,因为0就是字符串结束符了。注意返回值为T_TEXT。这个时候执行parse_config函数中的case T_TEXT:分支。
case T_TEXT: if (nargs < INIT_PARSER_MAXARGS) { args[nargs++] = state.text; }
- 1
- 2
- 3
- 4
- 1
- 2
- 3
- 4
这个时候,nargs为0,state.text位import,于是args数组的第0项就存了”import”字符串了。然后nargs++,也就是等于1了。然后进入下次循环。
step 2.第二次循环
第二次循环再次调用next_token函数,这次state->ptr=’\’,这我们分析过了。因此next_token函数不断执行defaulty分支,最终state.text = “/init.environ.rc”,返回类型还是T_TEXT。于是和之前一样,args[1]=”/init.environ.rc”,nargs=2。
step 3.第三次循环
这个时候一行结束,parse_config函数进入case T_NEWLINE:分支。
这个分支中,首先执行lookup_keyword函数,从名字来看是查找关键字。肯定就是import了,它肯定是关键字。不信请看代码:
static int lookup_keyword(const char *s){ switch (*s++) { case 'b': if (!strcmp(s, "ootchart_init")) return K_bootchart_init; break; case 'c': if (!strcmp(s, "opy")) return K_copy; if (!strcmp(s, "lass")) return K_class; if (!strcmp(s, "lass_start")) return K_class_start; if (!strcmp(s, "lass_stop")) return K_class_stop; if (!strcmp(s, "lass_reset")) return K_class_reset; if (!strcmp(s, "onsole")) return K_console; if (!strcmp(s, "hown")) return K_chown; if (!strcmp(s, "hmod")) return K_chmod; if (!strcmp(s, "ritical")) return K_critical; break; case 'd': if (!strcmp(s, "isabled")) return K_disabled; if (!strcmp(s, "omainname")) return K_domainname; break; case 'e': if (!strcmp(s, "nable")) return K_enable; if (!strcmp(s, "xec")) return K_exec; if (!strcmp(s, "xport")) return K_export; break; case 'g': if (!strcmp(s, "roup")) return K_group; break; case 'h': if (!strcmp(s, "ostname")) return K_hostname; break; case 'i': if (!strcmp(s, "oprio")) return K_ioprio; if (!strcmp(s, "fup")) return K_ifup; if (!strcmp(s, "nsmod")) return K_insmod; if (!strcmp(s, "mport")) return K_import; if (!strcmp(s, "nstallkey")) return K_installkey; break; case 'k': if (!strcmp(s, "eycodes")) return K_keycodes; break; case 'l': if (!strcmp(s, "oglevel")) return K_loglevel; if (!strcmp(s, "oad_persist_props")) return K_load_persist_props; if (!strcmp(s, "oad_all_props")) return K_load_all_props; break; case 'm': if (!strcmp(s, "kdir")) return K_mkdir; if (!strcmp(s, "ount_all")) return K_mount_all; if (!strcmp(s, "ount")) return K_mount; break; case 'o': if (!strcmp(s, "n")) return K_on; if (!strcmp(s, "neshot")) return K_oneshot; if (!strcmp(s, "nrestart")) return K_onrestart; break; case 'p': if (!strcmp(s, "owerctl")) return K_powerctl; break; case 'r': if (!strcmp(s, "estart")) return K_restart; if (!strcmp(s, "estorecon")) return K_restorecon; if (!strcmp(s, "estorecon_recursive")) return K_restorecon_recursive; if (!strcmp(s, "mdir")) return K_rmdir; if (!strcmp(s, "m")) return K_rm; break; case 's': if (!strcmp(s, "eclabel")) return K_seclabel; if (!strcmp(s, "ervice")) return K_service; if (!strcmp(s, "etenv")) return K_setenv; if (!strcmp(s, "etprop")) return K_setprop; if (!strcmp(s, "etrlimit")) return K_setrlimit; if (!strcmp(s, "ocket")) return K_socket; if (!strcmp(s, "tart")) return K_start; if (!strcmp(s, "top")) return K_stop; if (!strcmp(s, "wapon_all")) return K_swapon_all; if (!strcmp(s, "ymlink")) return K_symlink; if (!strcmp(s, "ysclktz")) return K_sysclktz; break; case 't': if (!strcmp(s, "rigger")) return K_trigger; break; case 'u': if (!strcmp(s, "ser")) return K_user; break; case 'v': if (!strcmp(s, "erity_load_state")) return K_verity_load_state; if (!strcmp(s, "erity_update_state")) return K_verity_update_state; break; case 'w': if (!strcmp(s, "rite")) return K_write; if (!strcmp(s, "ritepid")) return K_writepid; if (!strcmp(s, "ait")) return K_wait; break; } return K_UNKNOWN;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
调用这个函数的时候,我们传入的参数args[0]=”import”.显而易见该函数返回K_import。它是一个整数。返回以后使用kw_is函数看他是不是一个Section。当然是一个section了,import也是一个section。不信看代码:
#define kw_is(kw, type) (keyword_info[kw].flags & (type))
- 1
- 1
keyword_info定义在system/core/init/keywords.h中:
... KEYWORD(group, OPTION, 0, 0) KEYWORD(hostname, COMMAND, 1, do_hostname) KEYWORD(ifup, COMMAND, 1, do_ifup) KEYWORD(import, SECTION, 1, 0) ...
- 1
- 2
- 3
- 4
- 5
- 6
- 1
- 2
- 3
- 4
- 5
- 6
截取含有import的一部分代码,后面SECTION已经表明它是个Section了。KEYWORD自后一个参数是这个关键字对应的处理函数。比如这其中的hostname。如果你在init.rc中使用hostname 关键字,那么最终会调用do_hostname函数来处理。
既然import是一个section。那么parce_config就会调用state.parse_line函数,这里是一个函数指针,其实调用的是parse_line_no_op,不记得回去看下state的初始就知道了。
static void parse_line_no_op(struct parse_state*, int, char**) {}
- 1
- 2
- 1
- 2
这个函数是空的。接下来调用parse_new_section函数:
static void parse_new_section(struct parse_state *state, int kw, int nargs, char **args){ printf("[ %s %s ]\n", args[0], nargs > 1 ? args[1] : ""); switch(kw) { case K_service: state->context = parse_service(state, nargs, args); if (state->context) { state->parse_line = parse_line_service; return; } break; case K_on: state->context = parse_action(state, nargs, args); if (state->context) { state->parse_line = parse_line_action; return; } break; case K_import: parse_import(state, nargs, args); break; } state->parse_line = parse_line_no_op;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
我们当然是执行case K_import:分支了,想都不用想。所以接下来执行parse_import方法:
static void parse_import(struct parse_state *state, int nargs, char **args){ struct listnode *import_list = (listnode*) state->priv; char conf_file[PATH_MAX]; int ret; if (nargs != 2) { ERROR("single argument needed for import\n"); return; } ret = expand_props(conf_file, args[1], sizeof(conf_file)); if (ret) { ERROR("error while handling import on line '%d' in '%s'\n", state->line, state->filename); return; } struct import* import = (struct import*) calloc(1, sizeof(struct import)); import->filename = strdup(conf_file); list_add_tail(import_list, &import->list); INFO("Added '%s' to import list\n", import->filename);}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
这个函数首先使用expand_props方法对args[1]也就是“/init.environ.rc”做进一步处理。这个函数如下:
int expand_props(char *dst, const char *src, int dst_size){ char *dst_ptr = dst; const char *src_ptr = src; int ret = 0; int left = dst_size - 1; if (!src || !dst || dst_size == 0) return -1; /* - variables can either be $x.y or ${x.y}, in case they are only part * of the string. * - will accept $$ as a literal $. * - no nested property expansion, i.e. ${foo.${bar}} is not supported, * bad things will happen */ while (*src_ptr && left > 0) { char *c; char prop[PROP_NAME_MAX + 1]; char prop_val[PROP_VALUE_MAX]; int prop_len = 0; int prop_val_len; c = strchr(src_ptr, '$'); if (!c) { while (left-- > 0 && *src_ptr) *(dst_ptr++) = *(src_ptr++); break; } ...
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
可以看出,这个函数的作用是拓展args[1].这里不需要拓展,因为我们的args[1]=”/init.environ.rc”没有$符号,所以直接就跳出循环了。这里应该是对那些有包含变量的字符串,把变量的内容展开。
然后构建了一个import结构体。import中的filename项赋值为”/init.environ.rc”.并把它加入到import_list链表中。
import定义如下:
struct import { struct listnode list; const char *filename;};
- 1
- 2
- 3
- 4
- 1
- 2
- 3
- 4
这样,第一行就分析完了,从而我们也彻底明白了怎么解析一个import 的section。
只要能看懂一个,其他的就简单了。因为,他们都是类似的。
service的解析与启动
service的解析
和import解析过程类似,遇到service关键字后,service关键字和后面的参数会保存在args[]数组中。然后通过对args[0]提取关键字,发现args[0]=”service”,于是开始执行parse_new_section函数。此时这个函数必然会进入 case K_service:分支执行:
case K_service: state->context = parse_service(state, nargs, args); if (state->context) { state->parse_line = parse_line_service; return; } break;
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 1
- 2
- 3
- 4
- 5
- 6
- 7
这里做了两件事情非常重要,一件是调用parse_service解析service这个section。另一件事情是给state->parse_line赋值为parse_line_service。也就是service 关键字所在的行后面的那些options行都是使用parse_line_service函数来解析的。我们从parse_service看起:
static void *parse_service(struct parse_state *state, int nargs, char **args){ if (nargs < 3) { parse_error(state, "services must have a name and a program\n"); return 0; } if (!valid_name(args[1])) { parse_error(state, "invalid service name '%s'\n", args[1]); return 0; } service* svc = (service*) service_find_by_name(args[1]); if (svc) { parse_error(state, "ignored duplicate definition of service '%s'\n", args[1]); return 0; } nargs -= 2; svc = (service*) calloc(1, sizeof(*svc) + sizeof(char*) * nargs); if (!svc) { parse_error(state, "out of memory\n"); return 0; } svc->name = strdup(args[1]); svc->classname = "default"; memcpy(svc->args, args + 2, sizeof(char*) * nargs); trigger* cur_trigger = (trigger*) calloc(1, sizeof(*cur_trigger)); svc->args[nargs] = 0; svc->nargs = nargs; list_init(&svc->onrestart.triggers); cur_trigger->name = "onrestart"; list_add_tail(&svc->onrestart.triggers, &cur_trigger->nlist); list_init(&svc->onrestart.commands); list_add_tail(&service_list, &svc->slist); return svc;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
可以看到和import做的事情差不多。import解析的最后,会创建一个import结构体,并把它添加到import_list双向链表中。service解析从这里看,也是构建一个service结构体,然后把service结构体添加到service_list链表中。
我们看下service结构体:
struct service { void NotifyStateChange(const char* new_state); /* list of all services */ struct listnode slist; char *name; const char *classname; unsigned flags; pid_t pid; time_t time_started; /* time of last start */ time_t time_crashed; /* first crash within inspection window */ int nr_crashed; /* number of times crashed within window */ uid_t uid; gid_t gid; gid_t supp_gids[NR_SVC_SUPP_GIDS]; size_t nr_supp_gids; const char* seclabel; struct socketinfo *sockets; struct svcenvinfo *envvars; struct action onrestart; /* Actions to execute on restart. */ std::vector<std::string>* writepid_files_; /* keycodes for triggering this service via /dev/keychord */ int *keycodes; int nkeycodes; int keychord_id; IoSchedClass ioprio_class; int ioprio_pri; int nargs; /* "MUST BE AT THE END OF THE STRUCT" */ char *args[1];}; /*
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
socketinfo 用来保存socket option的相关信息。
classname 给service定义一个类名,如果多个service使用相同的类型,可以方便进行批量操作。
nargs 保存参数的个数。
很多字段不理解,没关系,我们看看parse_service函数给service做了那些初始化:
1. svc->name = strdup(args[1]);名字就是service 关键字后面的第一个参数
2. svc->classname = “default”; 类别名是default
3. memcpy(svc->args, args + 2, sizeof(char*) * nargs); svc->args[nargs] = 0;
把所有参数保存在args数组中,并把最有一个成员只为0。
4. svc->nargs = nargs; nargs保存参数个数
5. trigger* cur_trigger = (trigger*) calloc(1, sizeof(*cur_trigger));
list_init(&svc->onrestart.triggers);
cur_trigger->name = “onrestart”;
list_add_tail(&svc->onrestart.triggers, &cur_trigger->nlist);
构建一个触发器,并把它添加到service中的onrestart.triger列表中。
因此,我们可以知道么一个service都会有一个onrestart的action,这个action有一个触发器。这个action用来重启service。
解析完service后,就会解析service后面的option了,这个时候会调用parse_line_service。
static void parse_line_service(struct parse_state *state, int nargs, char **args){ struct service *svc = (service*) state->context; struct command *cmd; int i, kw, kw_nargs; if (nargs == 0) { return; } svc->ioprio_class = IoSchedClass_NONE; kw = lookup_keyword(args[0]); switch (kw) { case K_class: if (nargs != 2) { parse_error(state, "class option requires a classname\n"); } else { svc->classname = args[1]; } break; case K_console: svc->flags |= SVC_CONSOLE; break; case K_disabled: svc->flags |= SVC_DISABLED; svc->flags |= SVC_RC_DISABLED; break; case K_ioprio: if (nargs != 3) { parse_error(state, "ioprio optin usage: ioprio <rt|be|idle> <ioprio 0-7>\n"); } else { svc->ioprio_pri = strtoul(args[2], 0, 8); if (svc->ioprio_pri < 0 || svc->ioprio_pri > 7) { parse_error(state, "priority value must be range 0 - 7\n"); break; } if (!strcmp(args[1], "rt")) { svc->ioprio_class = IoSchedClass_RT; } else if (!strcmp(args[1], "be")) { svc->ioprio_class = IoSchedClass_BE; } else if (!strcmp(args[1], "idle")) { svc->ioprio_class = IoSchedClass_IDLE; } else { parse_error(state, "ioprio option usage: ioprio <rt|be|idle> <0-7>\n"); } } break; case K_group: if (nargs < 2) { parse_error(state, "group option requires a group id\n"); } else if (nargs > NR_SVC_SUPP_GIDS + 2) { parse_error(state, "group option accepts at most %d supp. groups\n", NR_SVC_SUPP_GIDS); } else { int n; svc->gid = decode_uid(args[1]); for (n = 2; n < nargs; n++) { svc->supp_gids[n-2] = decode_uid(args[n]); } svc->nr_supp_gids = n - 2; } break; case K_keycodes: if (nargs < 2) { parse_error(state, "keycodes option requires atleast one keycode\n"); } else { svc->keycodes = (int*) malloc((nargs - 1) * sizeof(svc->keycodes[0])); if (!svc->keycodes) { parse_error(state, "could not allocate keycodes\n"); } else { svc->nkeycodes = nargs - 1; for (i = 1; i < nargs; i++) { svc->keycodes[i - 1] = atoi(args[i]); } } } break; case K_oneshot: svc->flags |= SVC_ONESHOT; break; case K_onrestart: nargs--; args++; kw = lookup_keyword(args[0]); if (!kw_is(kw, COMMAND)) { parse_error(state, "invalid command '%s'\n", args[0]); break; } kw_nargs = kw_nargs(kw); if (nargs < kw_nargs) { parse_error(state, "%s requires %d %s\n", args[0], kw_nargs - 1, kw_nargs > 2 ? "arguments" : "argument"); break; } cmd = (command*) malloc(sizeof(*cmd) + sizeof(char*) * nargs); cmd->func = kw_func(kw); cmd->nargs = nargs; memcpy(cmd->args, args, sizeof(char*) * nargs); list_add_tail(&svc->onrestart.commands, &cmd->clist); break; case K_critical: svc->flags |= SVC_CRITICAL; break; case K_setenv: { /* name value */ if (nargs < 3) { parse_error(state, "setenv option requires name and value arguments\n"); break; } svcenvinfo* ei = (svcenvinfo*) calloc(1, sizeof(*ei)); if (!ei) { parse_error(state, "out of memory\n"); break; } ei->name = args[1]; ei->value = args[2]; ei->next = svc->envvars; svc->envvars = ei; break; } case K_socket: {/* name type perm [ uid gid context ] */ if (nargs < 4) { parse_error(state, "socket option requires name, type, perm arguments\n"); break; } if (strcmp(args[2],"dgram") && strcmp(args[2],"stream") && strcmp(args[2],"seqpacket")) { parse_error(state, "socket type must be 'dgram', 'stream' or 'seqpacket'\n"); break; } socketinfo* si = (socketinfo*) calloc(1, sizeof(*si)); if (!si) { parse_error(state, "out of memory\n"); break; } si->name = args[1]; si->type = args[2]; si->perm = strtoul(args[3], 0, 8); if (nargs > 4) si->uid = decode_uid(args[4]); if (nargs > 5) si->gid = decode_uid(args[5]); if (nargs > 6) si->socketcon = args[6]; si->next = svc->sockets; svc->sockets = si; break; } case K_user: if (nargs != 2) { parse_error(state, "user option requires a user id\n"); } else { svc->uid = decode_uid(args[1]); } break; case K_seclabel: if (nargs != 2) { parse_error(state, "seclabel option requires a label string\n"); } else { svc->seclabel = args[1]; } break; case K_writepid: if (nargs < 2) { parse_error(state, "writepid option requires at least one filename\n"); break; } svc->writepid_files_ = new std::vector<std::string>; for (int i = 1; i < nargs; ++i) { svc->writepid_files_->push_back(args[i]); } break; default: parse_error(state, "invalid option '%s'\n", args[0]); }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
- 160
- 161
- 162
- 163
- 164
- 165
- 166
- 167
- 168
- 169
- 170
- 171
- 172
- 173
- 174
- 175
- 176
- 177
- 178
- 179
- 180
- 181
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
- 160
- 161
- 162
- 163
- 164
- 165
- 166
- 167
- 168
- 169
- 170
- 171
- 172
- 173
- 174
- 175
- 176
- 177
- 178
- 179
- 180
- 181
这个函数中定义了所有的option,每一个option处理方法都不相同,大家遇到感兴趣的option可以自行分析。
service解析完成后,是时候看看service的启动了。
service的启动
service解析完成以后,有了一个service_list的链表,可以service是在是么地方启动的呢?当然是在action中了,action中有个命名叫start,它对应的处理函数是do_start,着我们在前面已经说过了,do_start函数如下:
int do_start(int nargs, char **args){ struct service *svc; svc = service_find_by_name(args[1]); if (svc) { service_start(svc, NULL); } return 0;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
这个函数非常见到,找到服务,启动它。
查找service的过程:
struct service *service_find_by_name(const char *name){ struct listnode *node; struct service *svc; list_for_each(node, &service_list) { svc = node_to_item(node, struct service, slist); if (!strcmp(svc->name, name)) { return svc; } } return 0;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
遍历service_list,对比名字,相同就返回。
启动service过程:
void service_start(struct service *svc, const char *dynamic_args){ // Starting a service removes it from the disabled or reset state and // immediately takes it out of the restarting state if it was in there. svc->flags &= (~(SVC_DISABLED|SVC_RESTARTING|SVC_RESET|SVC_RESTART|SVC_DISABLED_START)); svc->time_started = 0; // Running processes require no additional work --- if they're in the // process of exiting, we've ensured that they will immediately restart // on exit, unless they are ONESHOT. if (svc->flags & SVC_RUNNING) { return; } bool needs_console = (svc->flags & SVC_CONSOLE); if (needs_console && !have_console) { ERROR("service '%s' requires console\n", svc->name); svc->flags |= SVC_DISABLED; return; } struct stat s; if (stat(svc->args[0], &s) != 0) { ERROR("cannot find '%s', disabling '%s'\n", svc->args[0], svc->name); svc->flags |= SVC_DISABLED; return; } if ((!(svc->flags & SVC_ONESHOT)) && dynamic_args) { ERROR("service '%s' must be one-shot to use dynamic args, disabling\n", svc->args[0]); svc->flags |= SVC_DISABLED; return; } char* scon = NULL; if (is_selinux_enabled() > 0) { if (svc->seclabel) { scon = strdup(svc->seclabel); if (!scon) { ERROR("Out of memory while starting '%s'\n", svc->name); return; } } else { char *mycon = NULL, *fcon = NULL; INFO("computing context for service '%s'\n", svc->args[0]); int rc = getcon(&mycon); if (rc < 0) { ERROR("could not get context while starting '%s'\n", svc->name); return; } rc = getfilecon(svc->args[0], &fcon); if (rc < 0) { ERROR("could not get context while starting '%s'\n", svc->name); freecon(mycon); return; } rc = security_compute_create(mycon, fcon, string_to_security_class("process"), &scon); if (rc == 0 && !strcmp(scon, mycon)) { ERROR("Warning! Service %s needs a SELinux domain defined; please fix!\n", svc->name); } freecon(mycon); freecon(fcon); if (rc < 0) { ERROR("could not get context while starting '%s'\n", svc->name); return; } } } NOTICE("Starting service '%s'...\n", svc->name); pid_t pid = fork(); if (pid == 0) { struct socketinfo *si; struct svcenvinfo *ei; char tmp[32]; int fd, sz; umask(077); if (properties_initialized()) { get_property_workspace(&fd, &sz); snprintf(tmp, sizeof(tmp), "%d,%d", dup(fd), sz); add_environment("ANDROID_PROPERTY_WORKSPACE", tmp); } for (ei = svc->envvars; ei; ei = ei->next) add_environment(ei->name, ei->value); for (si = svc->sockets; si; si = si->next) { int socket_type = ( !strcmp(si->type, "stream") ? SOCK_STREAM : (!strcmp(si->type, "dgram") ? SOCK_DGRAM : SOCK_SEQPACKET)); int s = create_socket(si->name, socket_type, si->perm, si->uid, si->gid, si->socketcon ?: scon); if (s >= 0) { publish_socket(si->name, s); } } freecon(scon); scon = NULL; if (svc->writepid_files_) { std::string pid_str = android::base::StringPrintf("%d", pid); for (auto& file : *svc->writepid_files_) { if (!android::base::WriteStringToFile(pid_str, file)) { ERROR("couldn't write %s to %s: %s\n", pid_str.c_str(), file.c_str(), strerror(errno)); } } } if (svc->ioprio_class != IoSchedClass_NONE) { if (android_set_ioprio(getpid(), svc->ioprio_class, svc->ioprio_pri)) { ERROR("Failed to set pid %d ioprio = %d,%d: %s\n", getpid(), svc->ioprio_class, svc->ioprio_pri, strerror(errno)); } } if (needs_console) { setsid(); open_console(); } else { zap_stdio(); } if (false) { for (size_t n = 0; svc->args[n]; n++) { INFO("args[%zu] = '%s'\n", n, svc->args[n]); } for (size_t n = 0; ENV[n]; n++) { INFO("env[%zu] = '%s'\n", n, ENV[n]); } } setpgid(0, getpid()); // As requested, set our gid, supplemental gids, and uid. if (svc->gid) { if (setgid(svc->gid) != 0) { ERROR("setgid failed: %s\n", strerror(errno)); _exit(127); } } if (svc->nr_supp_gids) { if (setgroups(svc->nr_supp_gids, svc->supp_gids) != 0) { ERROR("setgroups failed: %s\n", strerror(errno)); _exit(127); } } if (svc->uid) { if (setuid(svc->uid) != 0) { ERROR("setuid failed: %s\n", strerror(errno)); _exit(127); } } if (svc->seclabel) { if (is_selinux_enabled() > 0 && setexeccon(svc->seclabel) < 0) { ERROR("cannot setexeccon('%s'): %s\n", svc->seclabel, strerror(errno)); _exit(127); } } if (!dynamic_args) { if (execve(svc->args[0], (char**) svc->args, (char**) ENV) < 0) { ERROR("cannot execve('%s'): %s\n", svc->args[0], strerror(errno)); } } else { char *arg_ptrs[INIT_PARSER_MAXARGS+1]; int arg_idx = svc->nargs; char *tmp = strdup(dynamic_args); char *next = tmp; char *bword; /* Copy the static arguments */ memcpy(arg_ptrs, svc->args, (svc->nargs * sizeof(char *))); while((bword = strsep(&next, " "))) { arg_ptrs[arg_idx++] = bword; if (arg_idx == INIT_PARSER_MAXARGS) break; } arg_ptrs[arg_idx] = NULL; execve(svc->args[0], (char**) arg_ptrs, (char**) ENV); } _exit(127); } freecon(scon); if (pid < 0) { ERROR("failed to start '%s'\n", svc->name); svc->pid = 0; return; } svc->time_started = gettime(); svc->pid = pid; svc->flags |= SVC_RUNNING; if ((svc->flags & SVC_EXEC) != 0) { INFO("SVC_EXEC pid %d (uid %d gid %d+%zu context %s) started; waiting...\n", svc->pid, svc->uid, svc->gid, svc->nr_supp_gids, svc->seclabel ? : "default"); waiting_for_exec = true; } svc->NotifyStateChange("running");}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
- 160
- 161
- 162
- 163
- 164
- 165
- 166
- 167
- 168
- 169
- 170
- 171
- 172
- 173
- 174
- 175
- 176
- 177
- 178
- 179
- 180
- 181
- 182
- 183
- 184
- 185
- 186
- 187
- 188
- 189
- 190
- 191
- 192
- 193
- 194
- 195
- 196
- 197
- 198
- 199
- 200
- 201
- 202
- 203
- 204
- 205
- 206
- 207
- 208
- 209
- 210
- 211
- 212
- 213
- 214
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
- 160
- 161
- 162
- 163
- 164
- 165
- 166
- 167
- 168
- 169
- 170
- 171
- 172
- 173
- 174
- 175
- 176
- 177
- 178
- 179
- 180
- 181
- 182
- 183
- 184
- 185
- 186
- 187
- 188
- 189
- 190
- 191
- 192
- 193
- 194
- 195
- 196
- 197
- 198
- 199
- 200
- 201
- 202
- 203
- 204
- 205
- 206
- 207
- 208
- 209
- 210
- 211
- 212
- 213
- 214
这个函数虽然长,但总结起来无非就做了这些事情:
1.解析参数
2.fork一个进程。
3.初始化子进程,主要是根据service结构体中的信息创建一个写东西。比如,根据sockets创建socket等。
4.执行execve,也就是加载可执行文件了。
也就是说,当init.rc等rc配置脚本解析完成后,开始执行action中的命令,并通过start命令来启动service。
action的解析与命令的执行
action的解析
对比service的解析来看,action的解析应该是调用parse_action函数:
static void *parse_action(struct parse_state *state, int nargs, char **args){ struct trigger *cur_trigger; int i; if (nargs < 2) { parse_error(state, "actions must have a trigger\n"); return 0; } action* act = (action*) calloc(1, sizeof(*act)); list_init(&act->triggers); for (i = 1; i < nargs; i++) { if (!(i % 2)) { if (strcmp(args[i], "&&")) { struct listnode *node; struct listnode *node2; parse_error(state, "& is the only symbol allowed to concatenate actions\n"); list_for_each_safe(node, node2, &act->triggers) { struct trigger *trigger = node_to_item(node, struct trigger, nlist); free(trigger); } free(act); return 0; } else continue; } cur_trigger = (trigger*) calloc(1, sizeof(*cur_trigger)); cur_trigger->name = args[i]; list_add_tail(&act->triggers, &cur_trigger->nlist); } list_init(&act->commands); list_init(&act->qlist); list_add_tail(&action_list, &act->alist); /* XXX add to hash */ return act;}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
action中命令的执行
可以看到所有的section解析都是类似的,构建一个结构体并添加到对应的链表中。
这里就不继续展开分析了。我们回到init.cpp的main函数中,看看action_list中存放的action是如何被执行的。
在解析init.rc结束后,会有如下函数:
action_for_each_trigger("early-init", action_add_queue_tail); action_for_each_trigger("init", action_add_queue_tail); action_for_each_trigger("charger", action_add_queue_tail); action_for_each_trigger("late-init", action_add_queue_tail);
- 1
- 2
- 3
- 4
- 1
- 2
- 3
- 4
action_for_each_trigger函数如下:
void action_for_each_trigger(const char *trigger, void (*func)(struct action *act)){ struct listnode *node, *node2; struct action *act; struct trigger *cur_trigger; list_for_each(node, &action_list) { act = node_to_item(node, struct action, alist); list_for_each(node2, &act->triggers) { cur_trigger = node_to_item(node2, struct trigger, nlist); if (!strcmp(cur_trigger->name, trigger)) { func(act); } } }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
也就是说,这个函数的作用是遍历action_list链表,找到对应名字的触发器,然后盗用传入的func函数,也就是action_add_queue_tail函数,这个函数如下:
void action_add_queue_tail(struct action *act){ if (list_empty(&act->qlist)) { list_add_tail(&action_queue, &act->qlist); }}
- 1
- 2
- 3
- 4
- 5
- 6
- 1
- 2
- 3
- 4
- 5
- 6
再把action添加到action_queuw中。这里是不是可以理解为给action排队呢?按照action的名字(early-init,init…)把action排好顺序。这个时候还是没有执行action中的命令。
继续往下看,看到execute_one_command函数,从名字来看是执行一个命令,我们看看是怎么执行的,execute_one_command函数如下:
void execute_one_command() { Timer t; char cmd_str[256] = ""; char name_str[256] = ""; if (!cur_action || !cur_command || is_last_command(cur_action, cur_command)) { cur_action = action_remove_queue_head(); cur_command = NULL; if (!cur_action) { return; } build_triggers_string(name_str, sizeof(name_str), cur_action); INFO("processing action %p (%s)\n", cur_action, name_str); cur_command = get_first_command(cur_action); } else { cur_command = get_next_command(cur_action, cur_command); } if (!cur_command) { return; } int result = cur_command->func(cur_command->nargs, cur_command->args); if (klog_get_level() >= KLOG_INFO_LEVEL) { for (int i = 0; i < cur_command->nargs; i++) { strlcat(cmd_str, cur_command->args[i], sizeof(cmd_str)); if (i < cur_command->nargs - 1) { strlcat(cmd_str, " ", sizeof(cmd_str)); } } char source[256]; if (cur_command->filename) { snprintf(source, sizeof(source), " (%s:%d)", cur_command->filename, cur_command->line); } else { *source = '\0'; } INFO("Command '%s' action=%s%s returned %d took %.2fs\n", cmd_str, cur_action ? name_str : "", source, result, t.duration()); }}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
这个函数就是从aciton_queue中取出头部的action,然后执行command中的函数。那这个函数是什么呢?我们在文章一开始就说过了,每一个command都对应一个do_xxxx的函数来处理该命令。是不是这样呢?
我们需要从command的解析说起。和解析service的option一样。解析command使用的是parse_line_action函数。这里不明白的可以返回去看看service的解析过程。
parse_line_action定义在system/core/init/init_parser.cpp中,该函数如下:
static void parse_line_action(struct parse_state* state, int nargs, char **args){ struct action *act = (action*) state->context; int kw, n; if (nargs == 0) { return; } kw = lookup_keyword(args[0]); if (!kw_is(kw, COMMAND)) { parse_error(state, "invalid command '%s'\n", args[0]); return; } n = kw_nargs(kw); if (nargs < n) { parse_error(state, "%s requires %d %s\n", args[0], n - 1, n > 2 ? "arguments" : "argument"); return; } command* cmd = (command*) malloc(sizeof(*cmd) + sizeof(char*) * nargs); cmd->func = kw_func(kw); cmd->line = state->line; cmd->filename = state->filename; cmd->nargs = nargs; memcpy(cmd->args, args, sizeof(char*) * nargs); list_add_tail(&act->commands, &cmd->clist);}
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
关键的代码只有一行cmd->func = kw_func(kw),kw_func函数定义在相同文件下,是一个宏:
#define kw_func(kw) (keyword_info[kw].func)
- 1
- 1
这里keyword_info数组又出现了吧,这个数组也定义在system/core/init/init_parser.cpp中:
static struct { const char *name; int (*func)(int nargs, char **args); unsigned char nargs; unsigned char flags;} keyword_info[KEYWORD_COUNT] = { [ K_UNKNOWN ] = { "unknown", 0, 0, 0 },#include "keywords.h"};
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
可以看到数组的初始化使用的是#include “keywords.h”。这中写法我还是第一次见到。
keywords.h:
#ifndef KEYWORDint do_bootchart_init(int nargs, char **args);int do_class_start(int nargs, char **args);int do_class_stop(int nargs, char **args);int do_class_reset(int nargs, char **args);int do_domainname(int nargs, char **args);int do_enable(int nargs, char **args);int do_exec(int nargs, char **args);int do_export(int nargs, char **args);int do_hostname(int nargs, char **args);int do_ifup(int nargs, char **args);int do_insmod(int nargs, char **args);int do_installkey(int nargs, char **args);int do_mkdir(int nargs, char **args);int do_mount_all(int nargs, char **args);int do_mount(int nargs, char **args);int do_powerctl(int nargs, char **args);int do_restart(int nargs, char **args);int do_restorecon(int nargs, char **args);int do_restorecon_recursive(int nargs, char **args);int do_rm(int nargs, char **args);int do_rmdir(int nargs, char **args);int do_setprop(int nargs, char **args);int do_setrlimit(int nargs, char **args);int do_start(int nargs, char **args);int do_stop(int nargs, char **args);int do_swapon_all(int nargs, char **args);int do_trigger(int nargs, char **args);int do_symlink(int nargs, char **args);int do_sysclktz(int nargs, char **args);int do_write(int nargs, char **args);int do_copy(int nargs, char **args);int do_chown(int nargs, char **args);int do_chmod(int nargs, char **args);int do_loglevel(int nargs, char **args);int do_load_persist_props(int nargs, char **args);int do_load_all_props(int nargs, char **args);int do_verity_load_state(int nargs, char **args);int do_verity_update_state(int nargs, char **args);int do_wait(int nargs, char **args);#define __MAKE_KEYWORD_ENUM__#define KEYWORD(symbol, flags, nargs, func) K_##symbol,enum { K_UNKNOWN,#endif KEYWORD(bootchart_init, COMMAND, 0, do_bootchart_init) KEYWORD(chmod, COMMAND, 2, do_chmod) KEYWORD(chown, COMMAND, 2, do_chown) KEYWORD(class, OPTION, 0, 0) KEYWORD(class_reset, COMMAND, 1, do_class_reset) KEYWORD(class_start, COMMAND, 1, do_class_start) KEYWORD(class_stop, COMMAND, 1, do_class_stop) KEYWORD(console, OPTION, 0, 0) KEYWORD(copy, COMMAND, 2, do_copy) KEYWORD(critical, OPTION, 0, 0) KEYWORD(disabled, OPTION, 0, 0) KEYWORD(domainname, COMMAND, 1, do_domainname) KEYWORD(enable, COMMAND, 1, do_enable) KEYWORD(exec, COMMAND, 1, do_exec) KEYWORD(export, COMMAND, 2, do_export) KEYWORD(group, OPTION, 0, 0) KEYWORD(hostname, COMMAND, 1, do_hostname) KEYWORD(ifup, COMMAND, 1, do_ifup) KEYWORD(import, SECTION, 1, 0) KEYWORD(insmod, COMMAND, 1, do_insmod) KEYWORD(installkey, COMMAND, 1, do_installkey) KEYWORD(ioprio, OPTION, 0, 0) KEYWORD(keycodes, OPTION, 0, 0) KEYWORD(load_all_props, COMMAND, 0, do_load_all_props) KEYWORD(load_persist_props, COMMAND, 0, do_load_persist_props) KEYWORD(loglevel, COMMAND, 1, do_loglevel) KEYWORD(mkdir, COMMAND, 1, do_mkdir) KEYWORD(mount_all, COMMAND, 1, do_mount_all) KEYWORD(mount, COMMAND, 3, do_mount) KEYWORD(oneshot, OPTION, 0, 0) KEYWORD(onrestart, OPTION, 0, 0) KEYWORD(on, SECTION, 0, 0) KEYWORD(powerctl, COMMAND, 1, do_powerctl) KEYWORD(restart, COMMAND, 1, do_restart) KEYWORD(restorecon, COMMAND, 1, do_restorecon) KEYWORD(restorecon_recursive, COMMAND, 1, do_restorecon_recursive) KEYWORD(rm, COMMAND, 1, do_rm) KEYWORD(rmdir, COMMAND, 1, do_rmdir) KEYWORD(seclabel, OPTION, 0, 0) KEYWORD(service, SECTION, 0, 0) KEYWORD(setenv, OPTION, 2, 0) KEYWORD(setprop, COMMAND, 2, do_setprop) KEYWORD(setrlimit, COMMAND, 3, do_setrlimit) KEYWORD(socket, OPTION, 0, 0) KEYWORD(start, COMMAND, 1, do_start) KEYWORD(stop, COMMAND, 1, do_stop) KEYWORD(swapon_all, COMMAND, 1, do_swapon_all) KEYWORD(symlink, COMMAND, 1, do_symlink) KEYWORD(sysclktz, COMMAND, 1, do_sysclktz) KEYWORD(trigger, COMMAND, 1, do_trigger) KEYWORD(user, OPTION, 0, 0) KEYWORD(verity_load_state, COMMAND, 0, do_verity_load_state) KEYWORD(verity_update_state, COMMAND, 0, do_verity_update_state) KEYWORD(wait, COMMAND, 1, do_wait) KEYWORD(write, COMMAND, 2, do_write) KEYWORD(writepid, OPTION, 0, 0)#ifdef __MAKE_KEYWORD_ENUM__ KEYWORD_COUNT,};#undef __MAKE_KEYWORD_ENUM__#undef KEYWORD#endif
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
这其中定义了所有的init.rc中需要的关键字。从中可以知道哪些是命令,哪些是option,哪些是sercion。此外,也验证我们说的命令(command)都对应这一个do_xxxx的函数,执行这些命令其实就是执行这些函数。
- Android6.0系统启动流程分析一:init进程
- Android6.0系统启动流程分析一:init进程
- Android系统启动流程(一)解析init进程启动过程
- Android系统启动流程(一)解析init进程启动过程
- Android系统启动流程——init进程
- Android系统启动流程 四--init进程
- Android6.0 init 深入分析
- Android6.0 init 深入分析
- Android系统启动流程分析init.c和init.rc文件
- android系统启动流程之init.rc详细分析笔记
- android系统启动流程之init.rc详细分析笔记
- android系统启动流程之init.rc详细分析笔记
- Linux系统启动分析-从start_kernel到init进程的启动
- Android系统启动流程分析(一)
- android init进程分析 基本流程
- Android开机流程分析 -- init进程
- android init进程分析 基本流程
- android系统启动流程启动画面学习之init和init.rc分析
- href:Hypertext Reference的缩写。意思是超文本引用。
- 【NOI2001】聪明的打字员
- iterm2 mac 快捷键
- Zabbix的SNMPTrap监控配置
- AI 从业者该如何选择深度学习开源框架
- Android6.0系统启动流程分析一:init进程
- c++引用
- 关于char以及varchar2在实际使用时的一点经验
- cocopos 安装
- Python爬虫系列之----Scrapy(九)使用CrawlSpider完善豆瓣图书爬虫
- sort函数的用法
- Android开发实践:Java层与Jni层的数组传递
- 1050. String Subtraction (20)-PAT甲级
- 传统CDN加速不给力,来看适合GIS的Geo-CDN