On Thursday 29 April 2005, Blaisorblade wrote:
> What's kernel_thread_helper?
kernel_thread_helper and kernel_thread are defined in i386 as following:
-----------------------------------------------
/*
* This gets run with %ebx containing the
* function to call, and %edx containing
* the "args".
*/
extern void kernel_thread_helper(void);
__asm__(".section .text\n"
".align 4\n"
"kernel_thread_helper:\n\t"
"movl %edx,%eax\n\t"
"pushl %edx\n\t"
"call *%ebx\n\t"
"pushl %eax\n\t"
"call do_exit\n"
".previous");
/*
* Create a kernel thread
*/
int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
{
struct pt_regs regs;
/* BProc: (SLAVE) kernel forks are not subject to BProc's
* remote process management stuff. */
bproc_kcall();
memset(®s, 0, sizeof(regs));
regs.ebx = (unsigned long) fn;
regs.edx = (unsigned long) arg;
regs.xds = __USER_DS;
regs.xes = __USER_DS;
regs.orig_eax = -1;
regs.eip = (unsigned long) kernel_thread_helper;
regs.xcs = __KERNEL_CS;
regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2;
/* Ok, create the new process.. */
return do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0, ®s, 0, NULL,
NULL);
}
-----------------------------------------------
I think kernel_thread_helper make the new generated kernel thread to call the
function and then exit. But in UML there is no kernel_thread_helper. Then how
does UML make its kernel thread call the function and then exit? Thanks a lot!
Alex
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