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Re: [PATCH v2] arm/xen: zero init memory region before returning to the heap
- To: Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>
- From: Luca Fancellu <Luca.Fancellu@xxxxxxx>
- Date: Wed, 12 Nov 2025 08:30:37 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Wed, 12 Nov 2025 08:31:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH v2] arm/xen: zero init memory region before returning to the heap
Hi Dmytro,
> On 31 Oct 2025, at 16:02, Dmytro Prokopchuk1 <dmytro_prokopchuk1@xxxxxxxx>
> wrote:
>
> The current implementation of 'free_init_memory()' fills the freed '__init'
> and '__initdata' memory regions with a faulting instruction before unmapping
> and returning them to the heap. However, after unmapping, any access to this
> region will result in a page fault, making the instruction fill redundant.
>
> Replace the instruction fill with a call to 'memset()', zeroing the entire
> region before it is unmapped and returned to the allocator.
>
> Additionally, this change resolves a violation of MISRA C:2012 Rule 11.3
> (cast between pointer to object type and pointer to a different object type),
> caused by performing a cast from a 'char *' to a 'uint32_t *' pointer to
> write instructions directly into memory, which is not compliant with MISRA
> guidelines.
>
> No functional changes.
>
> Signed-off-by: Dmytro Prokopchuk <dmytro_prokopchuk1@xxxxxxxx>
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
> ---
Looks good to me, I’ve also tested on Arm64 and Arm32 qemu.
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Tested-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Cheers,
Luca
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