顾涛原创作品转载请注明出处《Linux内核分析》MOOC课程http://mooc.study.163.com/course/USTC-1000029000
如果我写的不好或者有误的地方请留言
- 题目自拟，内容围绕Linux内核的启动过程，即从start_kernel到init进程启动；
- 博客中需要使用实验截图
- 博客内容中需要仔细分析start_kernel函数的执行过程
- 总结部分需要阐明自己对“Linux系统启动过程”的理解，尤其是idle进程、1号进程是怎么来的。
实验报告：
在实验楼里跑了一下gdb 没有多大印象 印象就是卡 这是卡吗 下面分析换自己的虚拟机
先来个宏观认识：
从start_kernel()中可以看到最后一条语句是rest_init();
1 asmlinkage __visible void __init start_kernel(void)
2 {
3 char *command_line;
4 char *after_dashes;
5
6 /*
7 * Need to run as early as possible, to initialize the
8 * lockdep hash:
9 */
10 lockdep_init();
11 set_task_stack_end_magic(&init_task);
12 smp_setup_processor_id();
13 debug_objects_early_init();
14
15 /*
16 * Set up the the initial canary ASAP:
17 */
18 boot_init_stack_canary();
19
20 cgroup_init_early();
21
22 local_irq_disable();
23 early_boot_irqs_disabled = true;
24
25 /*
26 * Interrupts are still disabled. Do necessary setups, then
27 * enable them
28 */
29 boot_cpu_init();
30 page_address_init();
31 pr_notice("%s", linux_banner);
32 setup_arch(&command_line);
33 mm_init_cpumask(&init_mm);
34 setup_command_line(command_line);
35 setup_nr_cpu_ids();
36 setup_per_cpu_areas();
37 smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
38
39 build_all_zonelists(NULL, NULL);
40 page_alloc_init();
41
42 pr_notice("Kernel command line: %s\n", boot_command_line);
43 parse_early_param();
44 after_dashes = parse_args("Booting kernel",
45 static_command_line, __start___param,
46 __stop___param - __start___param,
47 -1, -1, &unknown_bootoption);
48 if (!IS_ERR_OR_NULL(after_dashes))
49 parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
50 set_init_arg);
51
52 jump_label_init();
53
54 /*
55 * These use large bootmem allocations and must precede
56 * kmem_cache_init()
57 */
58 setup_log_buf(0);
59 pidhash_init();
60 vfs_caches_init_early();
61 sort_main_extable();
62 trap_init();
63 mm_init();
64
65 /*
66 * Set up the scheduler prior starting any interrupts (such as the
67 * timer interrupt). Full topology setup happens at smp_init()
68 * time - but meanwhile we still have a functioning scheduler.
69 */
70 sched_init();
71 /*
72 * Disable preemption - early bootup scheduling is extremely
73 * fragile until we cpu_idle() for the first time.
74 */
75 preempt_disable();
76 if (WARN(!irqs_disabled(),
77 "Interrupts were enabled *very* early, fixing it\n"))
78 local_irq_disable();
79 idr_init_cache();
80 rcu_init();
81 context_tracking_init();
82 radix_tree_init();
83 /* init some links before init_ISA_irqs() */
84 early_irq_init();
85 init_IRQ();
86 tick_init();
87 rcu_init_nohz();
88 init_timers();
89 hrtimers_init();
90 softirq_init();
91 timekeeping_init();
92 time_init();
93 sched_clock_postinit();
94 perf_event_init();
95 profile_init();
96 call_function_init();
97 WARN(!irqs_disabled(), "Interrupts were enabled early\n");
98 early_boot_irqs_disabled = false;
99 local_irq_enable();
100
101 kmem_cache_init_late();
102
103 /*
104 * HACK ALERT! This is early. We‘re enabling the console before
105 * we‘ve done PCI setups etc, and console_init() must be aware of
106 * this. But we do want output early, in case something goes wrong.
107 */
108 console_init();
109 if (panic_later)
110 panic("Too many boot %s vars at `%s‘", panic_later,
111 panic_param);
112
113 lockdep_info();
114
115 /*
116 * Need to run this when irqs are enabled, because it wants
117 * to self-test [hard/soft]-irqs on/off lock inversion bugs
118 * too:
119 */
120 locking_selftest();
121
122 #ifdef CONFIG_BLK_DEV_INITRD
123 if (initrd_start && !initrd_below_start_ok &&
124 page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
125 pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
126 page_to_pfn(virt_to_page((void *)initrd_start)),
127 min_low_pfn);
128 initrd_start = 0;
129 }
130 #endif
131 page_cgroup_init();
132 debug_objects_mem_init();
133 kmemleak_init();
134 setup_per_cpu_pageset();
135 numa_policy_init();
136 if (late_time_init)
137 late_time_init();
138 sched_clock_init();
139 calibrate_delay();
140 pidmap_init();
141 anon_vma_init();
142 acpi_early_init();
143 #ifdef CONFIG_X86
144 if (efi_enabled(EFI_RUNTIME_SERVICES))
145 efi_enter_virtual_mode();
146 #endif
147 #ifdef CONFIG_X86_ESPFIX64
148 /* Should be run before the first non-init thread is created */
149 init_espfix_bsp();
150 #endif
151 thread_info_cache_init();
152 cred_init();
153 fork_init(totalram_pages);
154 proc_caches_init();
155 buffer_init();
156 key_init();
157 security_init();
158 dbg_late_init();
159 vfs_caches_init(totalram_pages);
160 signals_init();
161 /* rootfs populating might need page-writeback */
162 page_writeback_init();
163 proc_root_init();
164 cgroup_init();
165 cpuset_init();
166 taskstats_init_early();
167 delayacct_init();
168
169 check_bugs();
170
171 sfi_init_late();
172
173 if (efi_enabled(EFI_RUNTIME_SERVICES)) {
174 efi_late_init();
175 efi_free_boot_services();
176 }
177
178 ftrace_init();
179
180 /* Do the rest non-__init‘ed, we‘re now alive */
181 rest_init();
182 }
start_kernel
1 static noinline void __init_refok rest_init(void)
2 {
3 int pid;
4
5 rcu_scheduler_starting();
6 /*
7 * We need to spawn init first so that it obtains pid 1, however
8 * the init task will end up wanting to create kthreads, which, if
9 * we schedule it before we create kthreadd, will OOPS.
10 */
11 kernel_thread(kernel_init, NULL, CLONE_FS);
12 numa_default_policy();
13 pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
14 rcu_read_lock();
15 kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
16 rcu_read_unlock();
17 complete(&kthreadd_done);
18
19 /*
20 * The boot idle thread must execute schedule()
21 * at least once to get things moving:
22 */
23 init_idle_bootup_task(current);
24 schedule_preempt_disabled();
25 /* Call into cpu_idle with preempt disabled */
26 cpu_startup_entry(CPUHP_ONLINE);
27 }
rest_init
咱们需要知道的东西如下：
在start_kernel中：
init_task:手工创建的PCB 0号进程即最终的idle进程
trap_init:初始化中断管理模块
mm_init:初始化内存管理模块
sched_init:初始化调度模块
在rest_init中：
run_init_process:linux系统中的1号进程 第一个用户态进程
注意：
1.我们需要首先初始化获得pid=1的进程 如果初始化最终创建了ktheads
我们在创建kthreadd之前调度它 Linux系统将会OOPS
2.启动空闲线程必须至少执行一次schedule()
时间： 2024-10-01 03:42:51