linux启动流程导读(arm为例)<二>

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http://blog.csdn.net/gdt_a20/article/details/7220389

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进入init/main.c

start_kernel

asmlinkage void __init start_kernel(void)

{

char * command_line;

extern const struct kernel_param __start___param[], __stop___param[];



smp_setup_processor_id();



/*

* Need to run as early as possible, to initialize the

* lockdep hash:

*/

lockdep_init();

debug_objects_early_init();



/*

* Set up the the initial canary ASAP:

*/

boot_init_stack_canary();



cgroup_init_early();

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第一个函数smp_setup_processor_id();

arch/arm/smp.c

================
int __cpu_logical_map[NR_CPUS];



void __init smp_setup_processor_id(void)

{

int i;

u32 cpu = is_smp() ? read_cpuid_mpidr() & 0xff : 0; //判断是否是smp系统，如果是读取当前cpuid，否则为0

//存在多cpu，判断哪个cpu是当前cpu

cpu_logical_map(0) = cpu; //当前cpu赋值给cpu第一个表项

for (i = 1; i < NR_CPUS; ++i)

cpu_logical_map(i) = i == cpu ? 0 : i; //当前cpu如果不是0，那么会把他安排到数组第一项，则原来位置要用0填充



printk(KERN_INFO "Booting Linux on physical CPU %d\n", cpu);

}

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arch/arm/include/asm/smp_plat.h

/*

* Return true if we are running on a SMP platform

*/

static inline bool is_smp(void)

{

#ifndef CONFIG_SMP

return false;

#elif defined(CONFIG_SMP_ON_UP)

extern unsigned int smp_on_up;

return !!smp_on_up;

#else

return true;

#endif

}

===============

可以配置是否为smp



===============

static inline unsigned int __attribute_const__ read_cpuid_mpidr(void)

{

return read_cpuid(CPUID_MPIDR);

}

arch/arm/include/asm/cputype.h

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#define read_cpuid(reg) \

({ \

unsigned int __val; \

asm("mrc p15, 0, %0, c0, c0, " __stringify(reg) \

: "=r" (__val) \

: \

: "cc"); \

__val; \

})

===============

1 /*
2  * Logical CPU mapping.
3  */
4 extern int __cpu_logical_map[NR_CPUS];
5 #define cpu_logical_map(cpu)    __cpu_logical_map[cpu]

Thanks