Re: [PATCH 4/4] ptdump: add check_wx_pages debugfs attribute

From: Heiko Carstens <hca@linux.ibm.com>
To: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: linux-hardening@vger.kernel.org,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@kernel.org>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Kees Cook <keescook@chromium.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
	linux-mm@kvack.org, steven.price@arm.com,
	Phong Tran <tranmanphong@gmail.com>,
	mark.rutland@arm.com, Greg KH <greg@kroah.com>
Subject: Re: [PATCH 4/4] ptdump: add check_wx_pages debugfs attribute
Date: Tue, 9 Jan 2024 14:50:05 +0100	[thread overview]
Message-ID: <20240109135005.7302-A-hca@linux.ibm.com> (raw)
In-Reply-To: <2e8806da45a4b00249d5c449130b5f9ce78b3403.1704800524.git.christophe.leroy@csgroup.eu>

On Tue, Jan 09, 2024 at 01:14:38PM +0100, Christophe Leroy wrote:
> Add a writable attribute in debugfs to trigger a
> W^X pages check at any time.
> 
> To trigger the test, just echo any numeric value into
> /sys/kernel/debug/check_wx_pages
> 
> The result is provided into dmesg.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  mm/ptdump.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
...
> +static int check_wx_debugfs_set(void *data, u64 val)
> +{
> +	ptdump_check_wx();
> +
> +	return 0;
> +}
> +
> +DEFINE_SIMPLE_ATTRIBUTE(check_wx_fops, NULL, check_wx_debugfs_set, "%llu\n");
> +
> +static int ptdump_debugfs_init(void)
> +{
> +	debugfs_create_file("check_wx_pages", 0200, NULL, NULL, &check_wx_fops);
> +
> +	return 0;
> +}

Wouldn't it be better to have (only?) a readable attribute which triggers
this, and provides the result via this attribute?
That would allow for automated tests without having to parse dmesg.

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