The role of __SET_UP during the Linux kernel boot process!

__SET_UP is a macro

#define__setup (str, fn) \__setup_param (str, FN, FN,0)#define__setup_param (str, unique_id, FN, early)Static Char__setup_str_# #unique_id [] __initdata =str; Static structobs_kernel_param __setup_# #unique_id __attribute_used__ __attribute__ (__section__ ( ". Init.setup")) __attribute__ ((Aligned (sizeof(Long)))))            ={__setup_str_# #unique_id, FN, early}structObs_kernel_param {Const Char*str; int(*setup_func) (Char*); intearly;};#define__init __attribute__ ((__section__ (". Init.text")))#define__initdata __attribute__ ((__section__ (". Init.data")))#define__exitdata __attribute__ ((__section__ (". Exit.data")))

Example:

Static int__init Init_setup (Char*str) {unsignedinti; Execute_command=str;  for(i =1; i < Max_init_args; i++) Argv_init[i]=NULL; return 1;} __setup ("init=", init_setup);//converted to    Static Char__setup_str_init_setup[] __attribute__ (__section__ (". Init.data"))) ="init="; Static structobs_kernel_param __setup_init_setup __attribute_used__ __attribute__ (__section__ ( ". Init.setup")) __attribute__ ((Aligned (sizeof(Long)))))            = {__setup_str_init_setup, init_setup,0}

 /*vmlinux.lds in the. Init section
{
...
__setup_start =.;
* (. Init.setup)
__setup_end =.;
...
}*/
Static int__init Obsolete_checksetup (Char*line)/*Handle obsolete-style Parameters*/{    structObs_kernel_param *p; intHad_early_param =0; P=__setup_start; / * From the beginning of the. Init.setup section *  / Do {        intn = strlen (p->str); / * Calculates the length of the string in the. Init.setup *  /if(!STRNCMP (line, p->str, n)) {            if(p->early) {/ * Here is the early property of 0 *  //*already done in Parse_early_param?                 * (Needs exact match on param part). * Keep iterating, as we can have early * params and __setups of same names 8 (*/                if(Line[n] = =' /'|| Line[n] = ='=') Had_early_param=1; } Else if(!p->Setup_func) {PRINTK (kern_warning"Parameter%s is obsolete,"                       "ignored\n", p->str); return 1; } Else if(P->setup_func (line +N)) /* Call parameters in the corresponding function, the parameter is offset n (initialization is the length of the parameter) after the string */ return 1; } P++; / * Continue processing until the end * /}  while(P <__setup_end); returnHad_early_param;}

Static int__init Init_setup (Char*str) {unsignedinti; Execute_command=str; /** In case LILO was going to boot us with default command line, * it prepends "Auto" before the whole cmdline W     Hich makes * The shell think it should execute a script with such name. * So we ignore all arguments entered _before_ init= ... [MJ]*/     for(i =1; i < Max_init_args; i++) Argv_init[i]=NULL; return 1;}//The function is to pass "=" behind to the Execute_command. //For example, INIT=/LINUXRC is set to execute_command=& "/LINUXRC" is not correct that is the structure of the STR parameter offset n address

Static intNoinline Init_post (void){        ...    if(Ramdisk_execute_command) {run_init_process (Ramdisk_execute_command); PRINTK (kern_warning"Failed to execute%s\n", Ramdisk_execute_command); }        ...    if(Execute_command) {run_init_process (Execute_command); PRINTK (kern_warning"Failed to execute%s. Attempting"                    "defaults...\n", Execute_command); } run_init_process ("/sbin/init"); Run_init_process ("/etc/init"); Run_init_process ("/bin/init"); Run_init_process ("/bin/sh"); Panic ("No Init found. Try passing init= option to kernel.");} 

The role of __SET_UP during the Linux kernel boot process!