From: Josh Cartwright <joshc@ni.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, Borislav Petkov <bp@alien8.de>,
linux-kernel@vger.kernel.org, Brian Gerst <brgerst@gmail.com>,
Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v6 1/3] fork: Add generic vmalloced stack support
Date: Wed, 24 Aug 2016 11:51:02 -0500 [thread overview]
Message-ID: <20160824165102.GB22613@jcartwri.amer.corp.natinst.com> (raw)
In-Reply-To: <14c07d4fd173a5b117f51e8b939f9f4323e39899.1470907718.git.luto@kernel.org>
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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 <oleg@redhat.com>
> Signed-off-by: Andy Lutomirski <luto@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
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next prev parent reply other threads:[~2016-08-24 17:19 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-11 9:35 [PATCH v6 0/3] virtually mapped stacks Andy Lutomirski
2016-08-11 9:35 ` [PATCH v6 1/3] fork: Add generic vmalloced stack support Andy Lutomirski
2016-08-15 11:55 ` Michal Hocko
2016-08-24 10:03 ` Ingo Molnar
2016-08-24 16:11 ` Dmitry Vyukov
2016-08-24 13:02 ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-08-24 16:51 ` Josh Cartwright [this message]
2016-08-30 22:01 ` [PATCH v6 1/3] " Andy Lutomirski
2016-08-30 22:26 ` Josh Cartwright
2016-08-11 9:35 ` [PATCH v6 2/3] dma-api: Teach the "DMA-from-stack" check about vmapped stacks Andy Lutomirski
2016-08-24 13:02 ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-08-11 9:35 ` [PATCH v6 3/3] x86/mm/64: Enable " Andy Lutomirski
2016-08-24 13:03 ` [tip:x86/asm] x86/mm/64: Enable vmapped stacks (CONFIG_HAVE_ARCH_VMAP_STACK=y) tip-bot for Andy Lutomirski
2016-10-21 12:32 ` Matt Fleming
2016-10-22 0:18 ` Andy Lutomirski
2016-10-24 13:09 ` Matt Fleming
2016-10-30 16:21 ` Andy Lutomirski
2016-11-07 12:32 ` Matt Fleming
2016-08-20 18:06 ` [PATCH v6 0/3] virtually mapped stacks Andy Lutomirski
2016-08-24 10:12 ` Ingo Molnar
2016-08-24 15:27 ` Andy Lutomirski
2016-08-24 17:16 ` Ingo Molnar
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