On 10/31, Christian Brauner wrote:
>
> --- a/include/uapi/linux/sched.h
> +++ b/include/uapi/linux/sched.h
> @@ -51,6 +51,10 @@
> * sent when the child exits.
> * @stack: Specify the location of the stack for the
> * child process.
> + * Note, @stack is expected to point to the
> + * lowest address. The stack direction will be
> + * determined by the kernel and set up
> + * appropriately based on @stack_size.
I can't review this patch, I have no idea what does stack_size mean
if !arch/x86.
x86 doesn't use stack_size unless a kthread does kernel_thread(), so
this change is probably fine...
Hmm. Off-topic question, why did 7f192e3cd3 ("fork: add clone3") add
"& ~CSIGNAL" in kernel_thread() ? This looks pointless and confusing
to me...
> +static inline bool clone3_stack_valid(struct kernel_clone_args *kargs)
> +{
> + if (kargs->stack == 0) {
> + if (kargs->stack_size > 0)
> + return false;
> + } else {
> + if (kargs->stack_size == 0)
> + return false;
So to implement clone3_wrapper(void *bottom_of_stack) you need to do
clone3_wrapper(void *bottom_of_stack)
{
struct clone_args args = {
...
// make clone3_stack_valid() happy
.stack = bottom_of_stack - 1,
.stack_size = 1,
};
}
looks a bit strange. OK, I agree, this example is very artificial.
But why do you think clone3() should nack stack_size == 0 ?
> + if (!access_ok((void __user *)kargs->stack, kargs->stack_size))
> + return false;
Why?
Oleg.
