Hey Andy- Small non-critical/potential future optimization comment below:
On Thu, Aug 11, 2016 at 02:35:21AM -0700, Andy Lutomirski wrote:
> If CONFIG_VMAP_STACK is selected, kernel stacks are allocated with
> vmalloc_node.
>
> grsecurity has had a similar feature (called
> GRKERNSEC_KSTACKOVERFLOW) for a long time.
>
> Cc: Oleg Nesterov <o...@redhat.com>
> Signed-off-by: Andy Lutomirski <l...@kernel.org>
> ---
[..]
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 52e725d4a866..05f7ef796fb4 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -158,19 +158,39 @@ void __weak arch_release_thread_stack(unsigned long
> *stack)
> * Allocate pages if THREAD_SIZE is >= PAGE_SIZE, otherwise use a
> * kmemcache based allocator.
> */
> -# if THREAD_SIZE >= PAGE_SIZE
> -static unsigned long *alloc_thread_stack_node(struct task_struct *tsk,
> - int node)
> +# if THREAD_SIZE >= PAGE_SIZE || defined(CONFIG_VMAP_STACK)
> +static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int
> node)
> {
> +#ifdef CONFIG_VMAP_STACK
> + void *stack = __vmalloc_node_range(THREAD_SIZE, THREAD_SIZE,
> + VMALLOC_START, VMALLOC_END,
> + THREADINFO_GFP | __GFP_HIGHMEM,
> + PAGE_KERNEL,
> + 0, node,
> + __builtin_return_address(0));
> +
> + /*
> + * We can't call find_vm_area() in interrupt context, and
> + * free_thread_stack can be called in interrupt context, so cache
> + * the vm_struct.
> + */
> + if (stack)
> + tsk->stack_vm_area = find_vm_area(stack);
This is annoying, we end up having to walk the vm_area tree twice (once
for the allocation, then here to get a handle on area).
Perhaps it's time the vmalloc code learned an allocation API that
returned the vm_area handle as well.
Josh
signature.asc
Description: PGP signature
