Re: [PATCH v2 1/2] arm64: Move .hyp.rodata outside of the _sdata.._edata range

From: Quentin Perret <qperret@google.com>
To: Marc Zyngier <maz@kernel.org>
Cc: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	kernel-team@android.com, stable@vger.kernel.org
Subject: Re: [PATCH v2 1/2] arm64: Move .hyp.rodata outside of the _sdata.._edata range
Date: Mon, 2 Aug 2021 14:11:07 +0100	[thread overview]
Message-ID: <YQfu6+3uo6qlxrpv@google.com> (raw)
In-Reply-To: <20210802123830.2195174-2-maz@kernel.org>

Hi Marc,

On Monday 02 Aug 2021 at 13:38:29 (+0100), Marc Zyngier wrote:
> The HYP rodata section is currently lumped together with the BSS,
> which isn't exactly what is expected (it gets registered with
> kmemleak, for example).
> 
> Move it away so that it is actually marked RO. As an added
> benefit, it isn't registered with kmemleak anymore.

2d7bf218ca73 ("KVM: arm64: Add .hyp.data..ro_after_init ELF section")
states explicitly that the hyp ro_after_init section should remain RW in
the host as it is expected to modify it before initializing EL2. But I
can't seem to trigger anything with this patch applied, so I'll look
into this a bit more.

> Fixes: 380e18ade4a5 ("KVM: arm64: Introduce a BSS section for use at Hyp")

Not sure this is the patch to blame?

> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Cc: stable@vger.kernel.org #5.13
> ---
>  arch/arm64/kernel/vmlinux.lds.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 709d2c433c5e..f6b1a88245db 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -181,6 +181,8 @@ SECTIONS
>  	/* everything from this point to __init_begin will be marked RO NX */
>  	RO_DATA(PAGE_SIZE)
>  
> +	HYPERVISOR_DATA_SECTIONS
> +
>  	idmap_pg_dir = .;
>  	. += IDMAP_DIR_SIZE;
>  	idmap_pg_end = .;
> @@ -260,8 +262,6 @@ SECTIONS
>  	_sdata = .;
>  	RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_ALIGN)
>  
> -	HYPERVISOR_DATA_SECTIONS
> -
>  	/*
>  	 * Data written with the MMU off but read with the MMU on requires
>  	 * cache lines to be invalidated, discarding up to a Cache Writeback
> -- 
> 2.30.2

Thanks,
Quentin