2018-2019-1 20189221《Linux内核原理与分析》第四周作业
教材学习：《庖丁解牛Linux内核分析》
第 3 章 MenuOS的构造
计算机三大法宝：存储程序计算机，函数调用堆栈，中断
操作系统两把宝剑：中断上下文，进程上下文
Linux内核源代码：
Linux内核使用的是第二周时下载的Linux-2.6版本
Linux内核目录：
init目录下的main.c函数：
start_kernel()：
init_task()：
rest_init()：
随书学习很有收获，也算是为实验操作做了很多准备。
实验报告：实验 3 跟踪分析Linux内核的启动过程
实验流程
使用实验楼的虚拟机打开shell，内核启动完成后进入menu程序
使用gdb跟踪调试内核
gdb
（gdb）file linux-3.18.6/vmlinux # 在gdb界面中targe remote之前加载符号表
（gdb）target remote:1234 # 建立gdb和gdbserver之间的连接,按c 让qemu上的Linux继续运行
（gdb）break start_kernel # 断点的设置可以在target remote之前，也可以在之后
设置断点：
使用list查看断点临近代码：
调试过程中：
代码分析
start_kernel()代码：
asmlinkage __visible void __init start_kernel(void)
{
char *command_line;
char *after_dashes;
lockdep_init();
set_task_stack_end_magic(&init_task);
smp_setup_processor_id();
debug_objects_early_init();
boot_init_stack_canary();
cgroup_init_early();
local_irq_disable();
early_boot_irqs_disabled = true;
/*
* Interrupts are still disabled. Do necessary setups, then
* enable them
*/
boot_cpu_init();
page_address_init();
pr_notice("%s", linux_banner);
setup_arch(&command_line);
mm_init_cpumask(&init_mm);
setup_command_line(command_line);
setup_nr_cpu_ids();
setup_per_cpu_areas();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */
build_all_zonelists(NULL, NULL);
page_alloc_init();
pr_notice("Kernel command line: %s\n", boot_command_line);
parse_early_param();
after_dashes = parse_args("Booting kernel",
static_command_line, __start___param,
__stop___param - __start___param,
-1, -1, &unknown_bootoption);
if (!IS_ERR_OR_NULL(after_dashes))
parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
set_init_arg);
jump_label_init();
/*
* These use large bootmem allocations and must precede
* kmem_cache_init()
*/
setup_log_buf(0);
pidhash_init();
vfs_caches_init_early();
sort_main_extable();
trap_init();
mm_init();
/*
* Set up the scheduler prior starting any interrupts (such as the
* timer interrupt). Full topology setup happens at smp_init()
* time - but meanwhile we still have a functioning scheduler.
*/
sched_init();
* Disable preemption - early bootup scheduling is extremely
* fragile until we cpu_idle() for the first time.
*/
preempt_disable();
if (WARN(!irqs_disabled(),
"Interrupts were enabled *very* early, fixing it\n"))
local_irq_disable();
idr_init_cache();
rcu_init();
context_tracking_init();
radix_tree_init();
/*
init some links before init_ISA_irqs()
*/
early_irq_init();
init_IRQ();
tick_init();
rcu_init_nohz();
init_timers();
hrtimers_init();
softirq_init();
timekeeping_init();
time_init();
sched_clock_postinit();
perf_event_init();
profile_init();
call_function_init();
WARN(!irqs_disabled(), "Interrupts were enabled early\n");
early_boot_irqs_disabled = false;
local_irq_enable();
kmem_cache_init_late();
/*
* HACK ALERT! This is early. We're enabling the console before
* we've done PCI setups etc, and console_init() must be aware of
* this. But we do want output early, in case something goes wrong.
*/
console_init();
if (panic_later)
panic("Too many boot %s vars at `%s'", panic_later,
panic_param);
lockdep_info();
/*
* Need to run this when irqs are enabled, because it wants
* to self-test [hard/soft]-irqs on/off lock inversion bugs
* too:
*/
locking_selftest();
#ifdef CONFIG_BLK_DEV_INITRD
if (initrd_start && !initrd_below_start_ok &&
page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
pr_crit("initrd overwritten (0x%08lx < 0x%08lx) - disabling it.\n",
page_to_pfn(virt_to_page((void *)initrd_start)),
min_low_pfn);
initrd_start = 0;
}
#endif
page_cgroup_init();
debug_objects_mem_init();
kmemleak_init();
setup_per_cpu_pageset();
numa_policy_init();
if (late_time_init)
late_time_init();
sched_clock_init();
calibrate_delay();
pidmap_init();
anon_vma_init();
acpi_early_init();
#ifdef CONFIG_X86 /*与x86硬件相关代码 如果主板支持EFI的话*/
if (efi_enabled(EFI_RUNTIME_SERVICES))
efi_enter_virtual_mode();
#endif
#ifdef CONFIG_X86_ESPFIX64
/* Should be run before the first non-init thread is created */
init_espfix_bsp();
#endif
thread_info_cache_init();
cred_init();
fork_init(totalram_pages);
proc_caches_init();
buffer_init();
key_init();
security_init();
dbg_late_init();
vfs_caches_init(totalram_pages);
signals_init();
/* rootfs populating might need page-writeback */
page_writeback_init();
proc_root_init();
cgroup_init();
cpuset_init();
taskstats_init_early();
delayacct_init();
check_bugs();
sfi_init_late();
if (efi_enabled(EFI_RUNTIME_SERVICES)) {
efi_late_init();
efi_free_boot_services();
}
ftrace_init();
/* Do the rest non-__init'ed, we're now alive */
rest_init();
}
start_kernel()分析：
lockdep_init(); //死锁检测模块初始化
debug_objects_early_init(); //初始化堆栈 此堆栈有额外的越界保护功能
page_address_init(); //初始化页表地址
pidhash_init(); //给新进程分配进程号
mm_init(); //初始化内存管理
sched_init(); //启动调度器
radix_tree_init(); //init some links before init_ISA_irqs() //初始化中断
rest_init()函数：
static noinline void __init_refok rest_init(void)
{
int pid;
rcu_scheduler_starting();
/*
* We need to spawn init first so that it obtains pid 1, however
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
kernel_thread(kernel_init, NULL, CLONE_FS);
numa_default_policy();
pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
rcu_read_lock();
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
rcu_read_unlock();
complete(&kthreadd_done);
/*
* The boot idle thread must execute schedule()
* at least once to get things moving:
*/
init_idle_bootup_task(current); /*idle初始化*/
schedule_preempt_disabled();
/* Call into cpu_idle with preempt disabled */
cpu_startup_entry(CPUHP_ONLINE);
}
rest_init()分析：
int pid; //定义进程号
kernel_thread(kernel_init, NULL, CLONE_FS); //初始化内核线程
本周小结
- 这周学习时间上按照计划完成，较之之前两周都轻松许多
- 这周遇到的问题不确定是怎样的问题：
问题一：一开始实验时，QEMU窗口无反应，点击则实验楼的实验环境宕机
解决：个人认为是实验楼的原因，因为第二天我再次进行实验时：
两个小时之后再次尝试实验楼才恢复正常