kernel_thread简析
1.3.100
static inline pid_t kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
long retval;
__asm__ __volatile__(
"movl %%esp,%%esi\n\t"
"int $0x80\n\t" /* Linux/i386 system call */
"cmpl %%esp,%%esi\n\t" /* child or parent? */
"je 1f\n\t" /* parent - jump */
"pushl %3\n\t" /* push argument */
"call *%4\n\t" /* call fn */
"movl %2,%0\n\t" /* exit */
"int $0x80\n"
"1:\t"
:"=a" (retval)
:"0" (__NR_clone), "i" (__NR_exit),
"r" (arg), "r" (fn),
"b" (flags | CLONE_VM)
:"si");
return retval;
}
1. 执行系统调用 __NR_clone
2. 父进程走1f,子进程调fn
3. fn完成后执行__NR_exit系统调用
4.注:%eax=__NR_clone, %ebx是参数,flags带上了CLONE_VM