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Re: [XEN v1] xen/Arm: Probe the entry point address of an uImage correctly
- To: Julien Grall <julien@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 8 Dec 2022 16:37:53 +0100
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- Cc: sstabellini@xxxxxxxxxx, stefanos@xxxxxxxxxx, Volodymyr_Babchuk@xxxxxxxx, bertrand.marquis@xxxxxxx, michal.orzel@xxxxxxx, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 08 Dec 2022 15:38:00 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.12.2022 14:51, Julien Grall wrote:
> On 08/12/2022 12:49, Ayan Kumar Halder wrote:
>> Currently, kernel_uimage_probe() does not set info->zimage.start. As a
>> result, it contains the default value (ie 0). This causes,
>> kernel_zimage_place() to treat the binary (contained within uImage) as
>> position independent executable. Thus, it loads it at an incorrect address.
>>
>> The correct approach would be to read "uimage.ep" and set
>> info->zimage.start. This will ensure that the binary is loaded at the
>> correct address.
>
> In non-statically allocated setup, a user doesn't know where the memory
> for dom0/domU will be allocated.
>
> So I think this was correct to ignore the address. In fact, I am worry
> that...
>
>> --- a/xen/arch/arm/kernel.c
>> +++ b/xen/arch/arm/kernel.c
>> @@ -222,6 +222,8 @@ static int __init kernel_uimage_probe(struct kernel_info
>> *info,
>> if ( len > size - sizeof(uimage) )
>> return -EINVAL;
>>
>> + info->zimage.start = be32_to_cpu(uimage.ep);
> ... this will now ended up to break anyone that may have set an address
> but didn't care where it should be loaded.
>
> I also understand your use case but now, we have contradictory
> approaches. I am not entirely sure how we can solve it. We may have to
> break those users (Cc some folks that may use it). But we should figure
> out what is the alternative for them.
I don't know anything about the uimage format, but is the ep field
required to be non-zero? If not, it being non-zero would retain
prior behavior.
Jan
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