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  • Linux源码与编译出的目标文件汇编代码的一致性问题

    start_kernel是内核启动时比较重要的一个函数,然而我发现一个问题,我编译出来的目标文件中的汇编代码与C源码并不完全对应,这是怎么一回事呢?

    asmlinkage void __init start_kernel(void)
    {
            char * command_line;
            extern const struct kernel_param __start___param[], __stop___param[];
    
            /*
             * Need to run as early as possible, to initialize the
             * lockdep hash:
             */
            lockdep_init();
            smp_setup_processor_id();
            debug_objects_early_init();
    
            /*
             * Set up the the initial canary ASAP:
             */
            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_owner(&init_mm, &init_task);
            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 */
    objdump -d main.o
    
    00000337 <start_kernel>:
     337:	55                   	push   %ebp
     338:	89 e5                	mov    %esp,%ebp
     33a:	53                   	push   %ebx
     33b:	83 ec 14             	sub    $0x14,%esp
     33e:	e8 fc ff ff ff       	call   33f <start_kernel+0x8>
     343:	e8 fc ff ff ff       	call   344 <start_kernel+0xd>
     348:	ff 15 08 00 00 00    	call   *0x8
     34e:	64 8b 1d 00 00 00 00 	mov    %fs:0x0,%ebx
     355:	ba 01 00 00 00       	mov    $0x1,%edx
     35a:	89 d8                	mov    %ebx,%eax
     35c:	c6 05 00 00 00 00 01 	movb   $0x1,0x0
     363:	e8 fc ff ff ff       	call   364 <start_kernel+0x2d>
     368:	89 d8                	mov    %ebx,%eax
     36a:	ba 01 00 00 00       	mov    $0x1,%edx
     36f:	e8 fc ff ff ff       	call   370 <start_kernel+0x39>
     374:	89 d8                	mov    %ebx,%eax
     376:	ba 01 00 00 00       	mov    $0x1,%edx
     37b:	e8 fc ff ff ff       	call   37c <start_kernel+0x45>
     380:	ba 01 00 00 00       	mov    $0x1,%edx
     385:	89 d8                	mov    %ebx,%eax
     387:	e8 fc ff ff ff       	call   388 <start_kernel+0x51>
     38c:	e8 fc ff ff ff       	call   38d <start_kernel+0x56>
     391:	c7 44 24 04 00 00 00 	movl   $0x0,0x4(%esp)
    
    objdump -r main.o
    
    00000309 R_386_32          boot_command_line
    0000030e R_386_32          .init.data
    00000313 R_386_PC32        strlcpy
    00000318 R_386_32          .init.data
    0000031d R_386_PC32        parse_early_options
    00000324 R_386_32          .init.data
    0000033f R_386_PC32        smp_setup_processor_id
    00000344 R_386_PC32        cgroup_init_early
    0000034a R_386_32          pv_irq_ops
    00000351 R_386_32          cpu_number
    0000035e R_386_32          early_boot_irqs_disabled
    00000364 R_386_PC32        set_cpu_online
    00000370 R_386_PC32        set_cpu_active
    0000037c R_386_PC32        set_cpu_present
    00000388 R_386_PC32        set_cpu_possible
    0000038d R_386_PC32        page_address_init
    00000395 R_386_32          linux_banner
    0000039c R_386_32          .rodata.str1.1
    000003a1 R_386_PC32        printk
    000003a9 R_386_PC32        setup_arch
    000003ae R_386_32          init_task
    000003b3 R_386_32          init_mm
    000003b8 R_386_PC32        mm_init_owner
    000003bd R_386_32          boot_command_line
    

    那么,lockdep_init函数哪里去了呢,start_kernel究竟有没有调用到它呢。

    首先可以肯定的是,lockdep_init没有被内核导出,因为在System.map中找不到它。

    然后,在重定位信息中也找不到lockdep_init。

    lockdep_init是在哪个文件中定义的?

    kernel/locking/lockdep.c
    

     但是在kernel/locking目录下并没有生成lockdep.o,这又是为什么?

    void lockdep_init(void)
    {
            int i;
    
            /*
             * Some architectures have their own start_kernel()
             * code which calls lockdep_init(), while we also
             * call lockdep_init() from the start_kernel() itself,
             * and we want to initialize the hashes only once:
             */
            if (lockdep_initialized)
                    return;
    
            for (i = 0; i < CLASSHASH_SIZE; i++)
                    INIT_LIST_HEAD(classhash_table + i);
    
            for (i = 0; i < CHAINHASH_SIZE; i++)
                    INIT_LIST_HEAD(chainhash_table + i);
    
            lockdep_initialized = 1;
    }
    
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  • 原文地址:https://www.cnblogs.com/long123king/p/3577875.html
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