linux-kernel - Re: Fix MAX_STACK_ENTRIES from 100 to 32

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Message-ID: <ZKpqpamE89nvgslC@debian.me>
Date:   Sun, 9 Jul 2023 15:07:01 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     wardenjohn <ydzhang@...ux.alibaba.com>
Cc:     jpoimboe <jpoimboe@...nel.org>, jikos <jikos@...nel.org>,
        mbenes <mbenes@...e.cz>, pmladek <pmladek@...e.com>,
        "joe.lawrence" <joe.lawrence@...hat.com>,
        Kernel Live Patching <live-patching@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Fix MAX_STACK_ENTRIES from 100 to 32

On Sat, Jul 08, 2023 at 09:56:34AM +0800, wardenjohn wrote:
> Thanks for reading my suggestion. I found that the array for task stack entries when
> doing livepatch function check is too large which seems to be unnecessary. Therefore,
> I suggest to fix the MAX_STACK_ENTRIES from 100 to 32.

Can you provide Link: to the discussion? Yet, I guess this is somehow
v2 patch.

> 
> The patch is as follows:
> 
> From ee27da5e64daced159257f54170a31141e943710 Mon Sep 17 00:00:00 2001
> From: Yongde Zhang <ydzhang@...ux.alibaba.com>
> Date: Sat, 8 Jul 2023 09:40:50 +0800
> Subject: [PATCH] Fix MAX_STACK_ENTRIES to 32
> 
> When checking the task stack, using an stack array of size 100 
> seems to be to large for a task stack. Therefore, I suggest to
> change the stack size from 100 to 32. 

Why is MAX_STACK_ENTRIES=100 overkill? And why do you reduce it?

> 
> Signed-off-by: Yongde Zhang <ydzhang@...ux.alibaba.com>
> ---
>  kernel/livepatch/transition.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c
> index e54c3d60a904..8d61c62b0c27 100644
> --- a/kernel/livepatch/transition.c
> +++ b/kernel/livepatch/transition.c
> @@ -14,7 +14,7 @@
>  #include "patch.h"
>  #include "transition.h"
>  
> -#define MAX_STACK_ENTRIES  100
> +#define MAX_STACK_ENTRIES  32
>  static DEFINE_PER_CPU(unsigned long[MAX_STACK_ENTRIES], klp_stack_entries);
>  
>  #define STACK_ERR_BUF_SIZE 128 

Your patch is MIME'd, please submit it with git-send-email(1) instead.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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