On Wed, Oct 17, 2012 at 05:07:03PM +0100, Al Viro wrote: > What happens during boot is this: > * init_task (not to be confused with init) is used as current during > infrastructure initializations. Once everything needed for scheduler and > for working fork is set, we spawn two threads - future init and future > kthreadd. The last thing we do with init_task is telling init that kthreadd > has been spawned. After that init_task turns itself into an idle thread. > * future init waits for kthreadd to be spawned (it would be more > natural to fork them in opposite order, but we want init to have PID 1 - > too much stuff in userland depends on that). Then it does the rest of > initialization, including setting up initramfs contents. And does > kernel_execve() on /init. Note that this is a task that had been created > by kernel_thread() and is currently in function called from > ret_from_kernel_thread(). Its kernel stack has been set up by copy_thread(). > That's where pt_regs need to be set up; note that they'll be passed to > start_thread() before you return to userland. If there are any magic bits > in pt_regs needed by return-from-syscall code, set them in kthread case of > copy_thread().
PS: I suspect that we end up with the wrong value in childregs->msr; start_thread() only add MSR_UMS there. I'd suggest running the kernel with these patches + printk childregs->msr the very first time start_thread() is called and see what it prints, then working kernel + such printk and compare the results... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
