From: Marco Elver <elver@google.com>
To: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Cc: catalin.marinas@arm.com, will@kernel.org, glider@google.com,
akpm@linux-foundation.org, linux-arm-kernel@lists.infradead.org,
linux-mm@kvack.org, Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] mm: kfence: export kfence_enabled as global variables
Date: Tue, 7 Feb 2023 08:19:00 +0100 [thread overview]
Message-ID: <CANpmjNP0tgPhCWS4dE4_VbvyTk-9qhQiM3oWDtJogAPQXtbXVA@mail.gmail.com> (raw)
In-Reply-To: <1675750519-1064-1-git-send-email-quic_zhenhuah@quicinc.com>
On Tue, 7 Feb 2023 at 07:15, Zhenhua Huang <quic_zhenhuah@quicinc.com> wrote:
>
> Export the variable to ease the judgement of whether kfence enabled
> at runtime. It should be more precise than through kernel config
> "CONFIG_KFENCE".
>
> For example We can disable kfence at runtime using bootargs
> "kfence.sample_interval=0" but CONFIG_KFENCE enabled.
> It was false positive.
>
> Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com>
> ---
> arch/arm64/mm/pageattr.c | 3 ++-
> include/linux/kfence.h | 2 ++
> mm/kfence/core.c | 2 +-
> 3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index 79dd201..208d780 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -7,6 +7,7 @@
> #include <linux/module.h>
> #include <linux/sched.h>
> #include <linux/vmalloc.h>
> +#include <linux/kfence.h>
>
> #include <asm/cacheflush.h>
> #include <asm/set_memory.h>
> @@ -27,7 +28,7 @@ bool can_set_direct_map(void)
> * protect/unprotect single pages.
> */
> return (rodata_enabled && rodata_full) || debug_pagealloc_enabled() ||
> - IS_ENABLED(CONFIG_KFENCE);
> + kfence_enabled;
Unfortunately this won't work, because it's possible to enable KFENCE
after the kernel has booted with e.g.: echo 100 >
/sys/module/kfence/parameters/sample_interval
What is the problem you have encountered? Is the page-granular direct
map causing issues?
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next prev parent reply other threads:[~2023-02-07 7:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-07 6:15 [PATCH] mm: kfence: export kfence_enabled as global variables Zhenhua Huang
2023-02-07 7:19 ` Marco Elver [this message]
2023-02-07 7:46 ` Zhenhua Huang
2023-02-07 10:28 ` Alexander Potapenko
2023-02-07 10:42 ` Zhenhua Huang
2023-02-07 10:48 ` Mark Rutland
2023-02-07 12:35 ` Zhenhua Huang
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