Messages in this thread Patch in this message | | | Date | Tue, 15 Aug 2017 17:30:36 +0100 | From | Mark Rutland <> | Subject | Re: [PATCHv2 02/14] fork: allow arch-override of VMAP stack alignment |
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On Tue, Aug 15, 2017 at 09:09:36AM -0700, Andy Lutomirski wrote: > On Tue, Aug 15, 2017 at 5:50 AM, Mark Rutland <mark.rutland@arm.com> wrote: > > In some cases, an architecture might wish its stacks to be aligned to a > > boundary larger than THREAD_SIZE. For example, using an alignment of > > double THREAD_SIZE can allow for stack overflows smaller than > > THREAD_SIZE to be detected by checking a single bit of the stack > > pointer. > > > > This patch allows architectures to override the alignment of VMAP'd > > stacks, by defining THREAD_ALIGN. Where not defined, this defaults to > > THREAD_SIZE, as is the case today. > > This looks okay, but it might make sense to move that to a header file > so THREAD_ALIGN is always available.
I was a little worried about breaking things, since arches don't define THREAD_SIZE in a consistent location.
Looking again, it looks like those are all transitiviely included into each arch's <asm/thread_info.h>, so I think I can move this into <linux/thread_info.h>, which'll have to be added to kernel.fork.c's includes.
Are you happy with the below fixup?
Thanks, Mark.
---->8---- diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 250a276..905d769 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -38,6 +38,10 @@ enum { #ifdef __KERNEL__ +#ifndef THREAD_ALIGN +#define THREAD_ALIGN THREAD_SIZE +#endif + #ifdef CONFIG_DEBUG_STACK_USAGE # define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_NOTRACK | \ __GFP_ZERO) diff --git a/kernel/fork.c b/kernel/fork.c index 696d692..f12882a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -88,6 +88,7 @@ #include <linux/sysctl.h> #include <linux/kcov.h> #include <linux/livepatch.h> +#include <linux/thread_info.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> @@ -217,9 +218,6 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) return s->addr; } -#ifndef THREAD_ALIGN -#define THREAD_ALIGN THREAD_SIZE -#endif stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN, VMALLOC_START, VMALLOC_END, THREADINFO_GFP,
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