linux-kernel - RE: [PATCH v2 2/2] kfence: allow change number of object by early parameter

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Message-ID: <2ff11f959e78405088865c6d61535bfc@honor.com>
Date: Mon, 29 Dec 2025 04:01:45 +0000
From: yuanlinyu <yuanlinyu@...or.com>
To: Marco Elver <elver@...gle.com>
CC: Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov
	<dvyukov@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Huacai Chen
	<chenhuacai@...nel.org>, WANG Xuerui <kernel@...0n.name>,
	"kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>, "loongarch@...ts.linux.dev"
	<loongarch@...ts.linux.dev>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/2] kfence: allow change number of object by early
 parameter

> From: Marco Elver <elver@...gle.com>
> Sent: Thursday, December 18, 2025 6:24 PM
> To: yuanlinyu <yuanlinyu@...or.com>
> Cc: Alexander Potapenko <glider@...gle.com>; Dmitry Vyukov
> <dvyukov@...gle.com>; Andrew Morton <akpm@...ux-foundation.org>;
> Huacai Chen <chenhuacai@...nel.org>; WANG Xuerui <kernel@...0n.name>;
> kasan-dev@...glegroups.com; linux-mm@...ck.org; loongarch@...ts.linux.dev;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2 2/2] kfence: allow change number of object by early
> parameter


> > Could you share the better design idea ?
> 
> Hot-patchable constants, similar to static branches/jump labels. This
> had been discussed in the past (can't find the link now), but it's not
> trivial to implement unfortunately.
> 

Hi Marco,

If you have concern about one more global, 

how about below code ?

/* The pool of pages used for guard pages and objects with number of objects at lower bits . */
unsigned long __kfence_pool_objects __read_mostly;

static __always_inline bool is_kfence_address(const void *addr)
{
	return unlikely((unsigned long)((char *)addr - KFENCE_POOL_ADDR) < KFENCE_POOL_LEN && __kfence_pool_objects);
}

It may generate one or two more instruction when compare with original patch.