Re: [PATCH v2 4/5] arm/efi: Simplify efi_arch_handle_cmdline()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 22/11/2023 1:31 am, Henry Wang wrote:
> Hi Both,
>
>> On Nov 22, 2023, at 04:41, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>
>> On 21/11/2023 8:33 pm, Luca Fancellu wrote:
>>> + CC henry
>>>
>>>> On 21 Nov 2023, at 20:15, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>>>
>>>> -Wwrite-strings is unhappy with assigning "xen" to a mutable pointer, but 
>>>> this
>>>> logic looks incorrect.  It was inherited from the x86 side, where the logic
>>>> was redundant and has now been removed.
>>>>
>>>> In the ARM case it inserts the image name into "xen,xen-bootargs" and 
>>>> there is
>>>> no logic at all to strip this before parsing it as the command line.
>>>>
>>>> The absence of any logic to strip an image name suggests that it shouldn't
>>>> exist there, or having a Xen image named e.g. "hmp-unsafe" in the 
>>>> filesystem
>>>> is going to lead to some unexpected behaviour on boot.
>>>>
>>>> No functional change.
>>>>
>>>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>> ---
>>>> CC: Jan Beulich <JBeulich@xxxxxxxx>
>>>> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>>>> CC: Wei Liu <wl@xxxxxxx>
>>>> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>>> CC: Julien Grall <julien@xxxxxxx>
>>>> CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
>>>> CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>>>> CC: Roberto Bagnara <roberto.bagnara@xxxxxxxxxxx>
>>>> CC: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx>
>>>>
>>>> v2:
>>>> * New.
>>>>
>>>> I'm afraid that all of this reasoning is based on reading the source code. 
>>>>  I
>>>> don't have any way to try this out in a real ARM UEFI environment.
>>> I will test this one tomorrow on an arm board
>> Thanks.  I have a sneaking suspicion that:
>>
>> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
>> index 9b9018574919..8bca5b9a1523 100644
>> --- a/xen/arch/arm/setup.c
>> +++ b/xen/arch/arm/setup.c
>> @@ -46,6 +46,12 @@
>>  #include <xsm/xsm.h>
>>  #include <asm/acpi.h>
>>  
>> +static int __init parse_ucode(const char *s)
>> +{
>> +    panic("Xen image name interpreted as a cmdline parameter\n");
>> +}
>> +custom_param("xen.efi", parse_xen);
>> +
>>  struct bootinfo __initdata bootinfo;
>>  
>>  /*
>>
>> will trigger.
> I saw I am CCed for this patch, so I think I am now going to throw this series
> to our CI and see if it explodes. Do you want me to also include above hunk?

Depends - up to you.  It needs tailoring for the name of the Xen binary
used, if it doesn't end up as a plain "xen.efi".

And to be more specific, it ought to trigger before this patch but cease
triggering after it.

It's probably better suited to a manual dev test in a real ARM UEFI
environment.

~Andrew