* [PATCH] arm64/kernel/entry: refine comment of stack overflow check
@ 2019-12-02 11:37 Heyi Guo
2019-12-02 12:33 ` Mark Rutland
2019-12-06 13:58 ` Catalin Marinas
0 siblings, 2 replies; 4+ messages in thread
From: Heyi Guo @ 2019-12-02 11:37 UTC (permalink / raw)
To: linux-arm-kernel, linux-kernel
Cc: wanghaibin.wang, Heyi Guo, Catalin Marinas, Will Deacon
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.
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).
*/
add sp, sp, x0 // sp' = sp + x0
sub x0, sp, x0 // x0' = sp' - x0 = (sp + x0) - x0 = sp
--
2.19.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/kernel/entry: refine comment of stack overflow check
2019-12-02 11:37 [PATCH] arm64/kernel/entry: refine comment of stack overflow check Heyi Guo
@ 2019-12-02 12:33 ` Mark Rutland
2019-12-03 0:55 ` Guoheyi
2019-12-06 13:58 ` Catalin Marinas
1 sibling, 1 reply; 4+ messages in thread
From: Mark Rutland @ 2019-12-02 12:33 UTC (permalink / raw)
To: Heyi Guo
Cc: linux-arm-kernel, linux-kernel, wanghaibin.wang, Catalin Marinas,
Will Deacon
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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/kernel/entry: refine comment of stack overflow check
2019-12-02 12:33 ` Mark Rutland
@ 2019-12-03 0:55 ` Guoheyi
0 siblings, 0 replies; 4+ messages in thread
From: Guoheyi @ 2019-12-03 0:55 UTC (permalink / raw)
To: Mark Rutland
Cc: linux-arm-kernel, linux-kernel, wanghaibin.wang, Catalin Marinas,
Will Deacon
在 2019/12/2 20:33, Mark Rutland 写道:
> 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.
Sure :)
Thanks,
Heyi
>
> 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
>>
> .
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] arm64/kernel/entry: refine comment of stack overflow check
2019-12-02 11:37 [PATCH] arm64/kernel/entry: refine comment of stack overflow check Heyi Guo
2019-12-02 12:33 ` Mark Rutland
@ 2019-12-06 13:58 ` Catalin Marinas
1 sibling, 0 replies; 4+ messages in thread
From: Catalin Marinas @ 2019-12-06 13:58 UTC (permalink / raw)
To: Heyi Guo
Cc: linux-arm-kernel, linux-kernel, wanghaibin.wang, Will Deacon,
Mark Rutland
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.
>
> 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>
Queued with Mark's suggested update.
--
Catalin
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-12-06 13:58 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2019-12-02 11:37 [PATCH] arm64/kernel/entry: refine comment of stack overflow check Heyi Guo
2019-12-02 12:33 ` Mark Rutland
2019-12-03 0:55 ` Guoheyi
2019-12-06 13:58 ` Catalin Marinas
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