Messages in this thread | | | Date | Mon, 2 Dec 2019 12:33:19 +0000 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64/kernel/entry: refine comment of stack overflow check |
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On Mon, Dec 02, 2019 at 07:37:02PM +0800, Heyi Guo wrote: > Stack overflow checking can be done by testing > sp & (1 << THREAD_SHIFT) > only for the stacks are aligned to (2 << THREAD_SHIFT) with size of > (1 << THREAD_SIZE), and this is the case when CONFIG_VMAP_STACK is > set.
Good point, I was sloppy with this comment.
> > Fix the code comment to avoid confusion. > > Signed-off-by: Heyi Guo <guoheyi@huawei.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > --- > arch/arm64/kernel/entry.S | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index cf3bd2976e57..9e8ba507090f 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -76,7 +76,8 @@ alternative_else_nop_endif > #ifdef CONFIG_VMAP_STACK > /* > * Test whether the SP has overflowed, without corrupting a GPR. > - * Task and IRQ stacks are aligned to (1 << THREAD_SHIFT). > + * Task and IRQ stacks are aligned to (2 << THREAD_SHIFT) with size of > + * (1 << THREAD_SHIFT). > */
Can we make that:
Task and IRQ stacks are aligned so that SP & (1 << THREAD_SHIFT) should always be zero.
... which I think is a bit clearer.
With that wording:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Mark.
> add sp, sp, x0 // sp' = sp + x0 > sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp > -- > 2.19.1 >
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